Human Anatomy & Physiology
Chapter 12
The Central Nervous System
PowerPoint® Lectures created by Suzanne Pundt, University of Texas at Tyler
Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved
Second Edition
Module 12.1 Overview of the Central Nervous System
Central Nervous System
•	Central nervous system (CNS) – includes brain and spinal cord; involved in movement, interpreting sensory information, maintaining homeostasis, and functions relating to mind
Overview of CNS Functions
•	Functions of nervous system can be broken down into three categories: motor, sensory, and integrative
•	Motor functions – include stimulation of a muscle cell contraction or a gland secretion; performed by peripheral nervous system (PNS)
•	Sensory functions – detection of sensations within and outside body; also performed by PNS
Overview of CNS Functions
•	Functions of nervous system (continued):
•	Integrative functions – includes decision-making processes; carried out exclusively by CNS; includes a wide variety of functions:
•	Interpretation of sensory information
•	Planning and monitoring movement
•	Maintenance of homeostasis
•	Higher mental functions such as language and learning
Basic Structure of the Brain and Spinal Cord 
•	Brain – soft, whitish-gray organ, anatomically continuous with spinal cord; resides in cranial cavity and directly or indirectly controls most of body’s functions
•	Weighs between 1250 and 1450 grams; made of mostly nervous tissue; contains epithelial and connective tissues as well
•	Internal cavities called ventricles; filled with cerebrospinal fluid
•	Receives about 20% of total blood flow during periods of rest; reflects its requirements for large amounts of oxygen, glucose, and nutrients
Basic Structure of the Brain and Spinal Cord 
•	Brain consists of four divisions, each distinct in type of input it receives and where it sends its output:
•	Cerebrum
•	Diencephalon
•	Cerebellum
•	Brainstem
Basic Structure of the Brain and Spinal Cord 
•	Cerebrum – enlarged superior portion of brain; divided into left and right cerebral hemispheres
•	Each cerebral hemisphere is further divided into five lobes containing groups of neurons that perform specific tasks
•	Responsible for higher mental functions such as learning, memory, personality, cognition (thinking), language, and conscience
•	Performs major roles in sensation and movement as well
Basic Structure of the Brain and Spinal Cord 
•	Diencephalon – beneath cerebral hemispheres; central core of brain
•	Consists of four distinct structural parts
•	Responsible for processing, integrating, and relaying information to different parts of brain, homeostatic functions, regulation of movement, and biological rhythms
Basic Structure of the Brain and Spinal Cord 
•	Cerebellum – posterior and inferior portion of brain
•	Divided into left and right hemispheres 
•	Heavily involved in planning and coordination of movement, especially complex activities such as playing a sport or an instrument
Basic Structure of the Brain and Spinal Cord 
•	Brainstem – oldest part of brain from evolutionary standpoint, connects brain and spinal cord
•	Functions include basic involuntary homeostatic functions
•	Control of certain reflexes
•	Monitoring movement
•	Integrating and relaying information to other parts of nervous system
Basic Structure of the Brain and Spinal Cord 
Basic Structure of the Brain and Spinal Cord 
•	Spinal cord – long tubular organ enclosed within protective vertebral cavity; begins at foramen magnum and blends with inferior portion of brainstem; ends between first and second lumbar vertebrae
•	43–46 cm (17–18 inches) in length and only ranges from 0.65–1.25 cm (0.25–0.5 inches) in diameter
•	Like the brain, the spinal cord has an internal cavity filled with cerebrospinal fluid (CSF), the cavity is called the central canal, which is continuous with the ventricles in the brain.
Basic Structure of the Brain and Spinal Cord 
•	White matter – found in both brain and spinal cord; consists of myelinated axons 
•	Each lobe of cerebrum contains bundles of white matter called tracts; receives input from and sends output to clusters of cell bodies and dendrites in cerebral gray matter called nuclei, this communication connects different parts of brain and spinal cord 
•	Spinal cord contains gray matter internally containing nuclei that process information, as well as tracts of white matter that shuttle this information to and from the brain. 
Basic Structure of the Brain and Spinal Cord 
•	Gray matter – found in both brain and spinal cord; consists of neuron cell bodies, dendrites, and unmyelinated axons
•	Outer few millimeters of cerebrum is gray matter; also scattered throughout deeper portions, remainder of cerebrum is white matter
•	Spinal cord contains gray matter internally containing nuclei that process information

Basic Structure of the Brain and Spinal Cord 
•	Make note – organization of gray and white matter in brain and spinal cord is reversed; spinal white matter is superficial while it is deep in brain
Basic Structure of the Brain and Spinal Cord 
Myth of Brain Differences between the Sexes
•	Humans are sexually dimorphic creatures; differences in physical characteristics between males and females; extends beyond reproductive system to essentially every system 
•	Scientists have been trying to prove existence of “male brain” and “female brain”; researchers have found differences between brains of men and women; men, on average, have higher visual-spatial intelligence, whereas women, on average, have higher verbal-emotional intelligence
•	Evidence strongly suggests this is due to neuroplasticity
•	Socialization influences development of neural networks; engaging in sports or building activities encourages development of visual-spatial skills; participating in imaginative play fosters verbal-emotional skills
•	When we test very young children, sex differences in visual-spatial and verbal-emotional intelligence become statistically insignificant

Myth of Brain Differences between the Sexes  
•	Other data used to support hypothesis of brain sex include MRI studies appearing to show vastly dissimilar “brain maps” in males and females; when maps are corrected for size discrepancies in male and female brains, differences virtually disappear
•	Long been held that hippocampus is larger in females than in males, accounting for women’s higher “emotional intelligence”; recent analysis of over 80 studies found no significant size difference between male and female hippocampus
Overview of CNS Development
•	The CNS structure is complicated but can think of it as a tube with an enlarged end. 
•	Nervous tissue develops from a hollow structure called the Neural tube (completely formed by the 4th week). Just after the neural tube forms, its caudal end goes on to become the spinal cord and the cranial end rapidly enlarges and forms three saclike structures: forebrain, midbrain, and hindbrain which continue to enlarge and give rise to 5 secondary brain vesicles (about 5th week of development). These eventually become the four divisions of the mature brain.
•	Cavity within hollow neural tube becomes ventricles in brain and central canal in spinal cord
Overview of CNS Development
Module 12.2 The Brain
The Cerebrum 
•	Cerebrum – structure responsible for higher mental functions 
•	Gross anatomical features of cerebrum include: 
•	Sulci – shallow grooves on surface of cerebrum; gyri – elevated ridges found between sulci; together increase surface area of brain; maximizing limited space within confines of skull; example of Structure-Function Core Principle
The Cerebrum 
•	Gross anatomical features (continued):
•	Fissures – deep grooves found on surface of cerebrum
•	Longitudinal fissure – long deep groove that separates left and right cerebral hemispheres
•	The cerebral hemispheres house two ventricles, the right and left lateral ventricles
The Cerebrum 
The Cerebrum 
•	Five lobes are found in each hemisphere of cerebrum:
•	Frontal lobe
•	Parietal lobe 
•	Temporal lobe 
•	Occipital lobe 
•	Insula
The Cerebrum 
The Cerebrum 
•	Five lobes of cerebrum (continued):
•	Frontal lobes – most anterior lobes
•	Posterior border – called central sulcus; sits behind precentral gyrus 
•	Neurons in these lobes are responsible for planning and executing movement and complex mental functions such as behavior, conscience, and personality
The Cerebrum 
•	Five lobes of cerebrum (continued):
•	Parietal lobes –posterior to frontal lobes
•	Contains postcentral gyrus posterior to central sulcus
•	Neurons in these lobes are responsible for processing and integrating sensory information and function in attention
The Cerebrum 
•	Five lobes of cerebrum (continued):
•	Temporal lobes – form lateral surfaces of each cerebral hemisphere 
•	Separated from parietal and frontal lobes by lateral fissure
•	Neurons in these lobes are involved in hearing, language, memory, and emotions 
The Cerebrum 
•	Five lobes of cerebrum (continued):
•	Occipital lobes make up posterior aspect of each cerebral hemisphere 
•	Separated from parietal lobe by parieto-occipital sulcus
•	Neurons in these lobes process all information related to vision
The Cerebrum 
•	Five lobes of cerebrum (continued):
•	Insulas – only visible when you pry the frontal, parietal, and temporal lobes apart at the lateral fissure (think the insula is “insulated” by the other lobes) 
•	Neurons of insulas are currently thought to have functions relating to taste and to our viscera (internal organs)
The Cerebrum 
The Cerebrum-Gray Matter 
•	Gray Matter: Cerebral Cortex – functionally most complex part of brain; covers cerebral hemispheres (like bark covers a tree)
•	Most of cerebral cortex is neocortex (most recently evolved region of brain); has a large surface area
•	Composed of 6 layers (of neurons and neuroglia) of variable thickness 
The Cerebrum-Gray Matter 
•	Gray Matter: Cerebral Cortex (continued):
•	Functions of neocortex revolve around conscious processes such as planning movement, interpreting incoming sensory information, and complex higher functions
•	Neocortex has three areas: primary motor cortex, primary sensory cortices, and association areas (next slide)
The Cerebrum-Gray Matter 
•	Gray Matter: Cerebral Cortex (continued): 
•	Neocortex three areas: primary motor cortex, primary sensory cortices, and association areas (continued):
•	Primary motor cortex – plans and executes movement
•	Primary sensory cortices – first to receive and process sensory input
•	Association areas integrate different types of information: 
•	Unimodal areas integrate one specific type of information 
•	Multimodal areas integrate information from multiple different sources and carry out many higher mental functions
The Cerebrum-Gray Matter 
The Cerebrum-Gray Matter 
Motor areas – most are located in frontal lobe; contain upper motor neurons which are interneurons that connect to other neurons (not skeletal muscle)
•	Primary motor cortex; involved in conscious planning of movement; located in precentral gyrus of frontal lobe
•	Upper motor neurons of each cerebral hemisphere control motor activity of opposite side of body via PNS neurons called lower motor neurons (responsible for executing movements)
The Cerebrum-Gray Matter 
•	Movement requires input from several motor association areas such as large premotor cortex located anterior to primary motor cortex in the frontal lobe
•	Motor association areas are unimodal areas involved in planning, guidance, coordination, and execution of movement
•	Another motor association area consists of the paired frontal eye fields – one on each side of the brain anterior to premotor cortex, fields are required for back-and-forth eye movements, may in fact be multimodal association area
The Cerebrum-Gray Matter 
Sensory Cortices 
Each of  the 5 classic senses-touch, vision, hearing, smell, and taste is represented by BOTH a primary and a unimodal association area in the cerebral cortex.
•	Two main areas of the cerebral cortex deal with the somatic senses, those pertaining to touch or temperature, including vibration, pressure, stretch, and joint position. 
•	Primary somatosensory cortex (S1) – in postcentral gyrus of parietal lobe 
•	Somatosensory association cortex (S2) – posterior to S1
The Cerebrum-Gray Matter 
Sensory Cortices (continued): 
•	Special senses 
•	Primary visual cortex – at posterior end of occipital lobe; first area to receive visual input; feeds this information to visual association areas which process color, object movement, and depth
The Cerebrum-Gray Matter 
Sensory Cortices (continued): 
•	Special senses (continued):
•	Primary auditory cortex – in superior temporal lobe; first to receive auditory information; input is transferred to nearby auditory association cortex and other multimodal association areas for further processing
The Cerebrum-Gray Matter 
Sensory Cortices (continued): 
•	Special senses (continued):
•	Gustatory cortex – taste information processing; in insula and part of parietal lobe
•	Vestibular areas – information pertaining to equilibrium and positional sense processing; located in parietal and temporal lobes
The Cerebrum-Gray Matter 
Sensory Cortices (continued): 
•	Special senses (continued):
•	Olfactory cortex – processes sense of smell; consists of several areas in limbic and medial temporal lobes
The Cerebrum-Gray Matter 
The Cerebrum-Gray Matter 
Multimodal association areas –allow us to perform complex mental functions:
•	Language areas– two areas of the cortex are directly involved in language: 
•	Broca’s area – in anterolateral frontal lobe; premotor area responsible for ability to produce language
•	Wernicke’s area (integrative speech area) – in temporal and parietal lobes; responsible for ability to understand language
Videos
•	https://www.youtube.com/watch?v=3oef68YabD0

•	https://www.youtube.com/watch?v=JWC-cVQmEmY
The Cerebrum-Gray Matter 
Multimodal association areas (continued):
•	Prefrontal cortex occupies most of frontal lobe; communicates with parts of diencephalon, other cerebral gray matter, and association cortices located in other lobes; many functions including modulating behavior, personality, learning, memory, and an individual’s psychological state
The Cerebrum-Gray Matter 
Multimodal association areas (continued):
•	Parietal and temporal association areas – occupy most of their respective lobes; perform multiple functions including integration of sensory information, language, maintaining attention, recognition, and spatial awareness
The Cerebrum-Gray Matter
The Cerebrum-Gray Matter 
•	Basal nuclei, found deep within each cerebral hemisphere; clusters of neuron cell bodies, primarily associated with movement, however disorders involving basal nuclei also cause problems with behavior, cognition, and perception (these nuclei have multiple functional roles in the brain):
•	Caudate nuclei 
•	Putamen
•	Globus pallidus 
The Cerebrum-Gray Matter 
•	Basal nuclei (continued):
•	Caudate nuclei – C-shaped rings of gray matter; lateral to lateral ventricle of each hemisphere with anteriorly oriented tail
•	Putamen – posterior and inferior to caudate nucleus; connected to caudate nucleus by small bridges of gray matter; combination of putamen and caudate are sometimes called corpus striatum
•	Globus pallidus sits medial to putamen; contains more myelinated fibers than other basal nuclei
The Cerebrum-Gray Matter 
The Cerebrum-White Matter 
•	Cerebral white matter can be classified as one of three types:
•	Commissural fibers – connect right and left hemispheres; corpus callosum, largest of four groups in this category, lies in middle of brain at base of longitudinal fissure
•	Projection fibers – connect cerebral cortex of one hemisphere with other areas of same hemisphere, other parts of brain, and spinal cord; cerebral projection fibers in each hemisphere form a radiating pattern called corona radiata; condense around diencephalon to form two V-shaped bands called internal capsules
•	Association fibers – restricted to a single hemisphere; connect gray matter of cortical gyri with one another
The Cerebrum-White Matter 
The Cerebrum-Limbic System
•	Possible pathway for information transfer by conduction of an action potential from one region of brain to another:
•	Action potential originates in gray matter
•	Action potential is sent to another area of gray matter by projection fibers
•	 New action potential sent to neighboring gray matter by association fibers 
•	Another action potential is generated and sent to the other cerebral hemisphere by commissural fibers
The Cerebrum-Limbic System
The Cerebrum-Limbic System
•	Limbic system – important functional brain system, includes limbic lobe (region of medial cerebrum), hippocampus, amygdala, and pathways; connect these regions of gray matter with each other and with other parts of brain
•	Found only within mammalian brains 
•	Involved in memory, learning, emotion, and behavior
•	When you are nervous and have “butterflies in your stomach” or are scared and have a racing heart, that reaction is partially a product of your limbic system.
The Cerebrum-Limbic System
•	Limbic system (continued):
•	Limbic lobe and associated structures form a ring on medial side of cerebral hemisphere; contain two main gyri: cingulate gyrus and parahippocampal gyrus
•	Hippocampus – in temporal lobe; connected to a prominent C-shaped ring of white matter (fornix) which is its main output tract; involved in memory and learning
•	Amygdala – anterior to hippocampus; involved in behavioral expression of emotion, particularly fear
The Cerebrum-Limbic System
The Diencephalon
Diencephalon – at physical center of brain; has four components, each consists of various nuclei that receive specific input and send output to other brain regions:
•	Thalamus
•	Hypothalamus
•	Epithalamus
•	Subthalamus
The Diencephalon
•	Thalamus – Literally the “main entrance” into the cerebral cortex
•	Consists of two egg-shaped masses of gray matter; make up about 80% of diencephalon
•	Third ventricle is found between these two masses 
The Diencephalon
The Diencephalon
•	Thalamus (continued):
•	Nearly all information destined for the cerebral cortex must first pass through the thalamus
•	Ultimately thalamus regulates cortical activity
•	Each half of thalamus has three main groups of nuclei separated by thin layers of white matter
•	Thalamic nuclei receive input from multiple sources including cerebral cortex, cerebellum, basal nuclei, structures of limbic system and sensory system (except smell)
The Diencephalon
•	Thalamus (continued):
•	Specific relay nuclei function as relay stations that receive incoming information, process and integrate it, and then send to specific motor or sensory areas of the cerebral cortex
•	Association nuclei 
•	Receive input from variety of sources
•	Process information related to emotions, memory, and integration of sensory information
•	Processed information is mainly sent on to association areas of cerebral cortex
The Diencephalon
•	Thalamus (continued):
•	Nonspecific nuclei  
•	Receive information from basal nuclei, cerebellum, and motor cortex
•	Send information to broad areas of cerebral cortex and rest of the brain 
•	Involved in controlling arousal, consciousness, and level of responsiveness and excitability of cerebral cortex
The Diencephalon
•	Hypothalamus – collection of nuclei anterior and inferior to thalamus
•	Performs several vital functions critical to survival; some include regulating much of autonomic nervous system, sleep/wake cycle, thirst and hunger, and body temperature
The Diencephalon
•	Hypothalamus (continued):
•	Anatomically and functionally linked to pituitary gland, connected by infundibulum; hypothalamic tissue makes up posterior portion of this pituitary gland
•	Hypothalamus secretes a variety of hormones that affect the pituitary gland, hypothalamic releasing or inhibiting hormones increase or decrease the secretion of other hormones from the pituitary gland. The pituitary gland, in turn, secretes hormones that influence secretion from other glands throughout the body. 
The Diencephalon
•	Hypothalamus (continued):
•	Hypothalamus also produces two additional hormones that do not act on the pituitary gland:
•	Antidiuretic hormone (ADH) which influences water balance and oxytocin which in women stimulates contraction of the uterus during childbirth and in both sexes may promote emotional bonding. 
•	Hypothalamus receives input from a variety of sources, including cerebral cortex and basal nuclei
The Diencephalon
•	Hypothalamus (continued):
•	Mammillary bodies – connect hypothalamus with limbic system; receive input from hippocampus; involved in memory regulation and behavior
•	Input from outside nervous system; endocrine system, receptors that detect changes in body temperature, and receptors that detect blood’s osmotic concentration
The Diencephalon
•	Epithalamus – superior to thalamus; major part is the pineal gland; secretes melatonin; hormone involved in sleep/wake cycle
•	Subthalamus – inferior to thalamus; functionally connected with basal nuclei; together, they control movement
The Diencephalon
Cerebellum 
Cerebellum – makes up posterior and inferior portion of brain; functions with cerebral cortex, basal nuclei, brainstem, and spinal cord in coordination of movement 
•	Anatomically, divided into two cerebellar hemispheres connected by structure called vermis 
•	Ridges called folia; separated by shallow sulci; increases surface area
Cerebellum 
Cerebellum 
Cerebellum (continued):
•	Divided into three lobes: anterior, posterior, and flocculonodular lobes
•	Cerebellar cortex – outer layer of gray matter
•	Cortex is extremely folded, the branching white matter resembles tree branches, called arbor vitae
Cerebellum 
Cerebellum  (continued):
•	Inner white matter has clusters of gray matter embedded (deep cerebellar nuclei)
•	White matter converges into three large tracts called cerebellar peduncles; connect cerebellum to brainstem, form the only route by which information flows into and out of the cerebellum
Cerebellum
Cerebellum 
Cerebellum
The Brainstem
Brainstem – one of oldest components of brain; vital to our immediate survival as its nuclei control many basic homeostatic functions such as maintenance of heart rate and breathing rhythms 
•	Controls many reflexes (programmed, automatic responses to stimuli); functions in movement, sensation, and maintaining alertness
The Brainstem
Brainstem (continued):
•	Located inferior to diencephalon, anterior to cerebellum, and superior to spinal cord, on midsagittal section of brain 
•	Extends to level of foramen magnum after which it becomes the spinal cord; contains fourth ventricle which is continuous with central canal of spinal cord
The Brainstem
The Brainstem
The Brainstem
Brainstem (continued):
•	Three subdivisions
•	1. midbrain
•	2. pons
•	3. medulla oblongata
The Brainstem
Brainstem (continued):
Fibers of cerebellum and related nuclei –cerebellar fibers travel through parts of brainstem, some synapse on brainstem nuclei, others are destined for cerebral cortex or spinal cord
•	Nuclei of reticular formation – group of connected nuclei throughout brainstem called reticular formation, many functions including regulation of respiration, blood pressure, sleep/wake cycle, pain perception, and consciousness
•	Tracts of white matter between spinal cord and brain – nearly all pathways to and from brain and spinal cord travel through brainstem
•	Cranial nerve nuclei – many cranial nerves originate from brainstem; their nuclei have many sensory, motor, and autonomic responsibilities
The Brainstem
The Brainstem
•	Midbrain 
•	Inferior to diencephalon; surrounds cerebral aqueduct (connects third and fourth ventricles)
•	Also known as mesencephalon; shortest and most superior brainstem region
•	If you have ever been startled by a loud noise or an unexpected sight, your midbrain can take the blame for it.
The Brainstem
•	Midbrain (continued):
•	Includes following structures:
•	Superior and inferior colliculi, protrude from posterior surface; two paired rounded projections that form part of roof of midbrain (tectum); involved in visual and auditory functions; project to thalamus
•	Descending tracts – white matter tracts that originate in cerebrum located in anteriormost portion of midbrain; area called crus cerebri
The Brainstem
•	Midbrain (continued):
•	Includes following structures (continued):
•	Substantia nigra – posterior to crus cerebri, is a darkly pigmented region whose neurons work closely with basal nuclei to control movement
•	Red nucleus – posterior to substantia nigra; communicates with cerebellum, spinal cord, and other structures regulating movement; role in humans not yet understood
The Brainstem
•	Midbrain (continued):
•	Includes following structures (continued):
•	Many cranial nerve nuclei are found in midbrain
•	Midbrain tegmentum – tegmentum is a generic term for the area of the midbrain between the cerebral aquaduct and substantia nigra. It contains numerous nuclei, many of which are part of the reticular formation as well as ascending and descending white matter tracts. 
The Brainstem
•	Pons – inferior to midbrain; has a rounded and prominent anterior surface, anterior pons contains descending motor tracts from crus cerebri, some of which pass through pons en route to spinal cord
•	Others enter cerebellum by way of middle cerebellar peduncle
•	Posterior to these tracts is an area that contains reticular formation nuclei and cranial nerve nuclei. 
The Brainstem
•	Pons (continued):
•	Pontine nuclei have diverse roles including: regulation of movements including those required for breathing, participate in reflexes, and complex functions such as sleep and arousal
The Brainstem
•	Medulla oblongata – most inferior structure of brainstem; continuous with spinal cord after it passes through foramen magnum 
•	Pyramids – elevated ridges on anterior surface of medulla, contain upper motor neuron fibers of corticospinal tract (also called the pyramidal tract) that come from motor areas of cerebral cortex
The Brainstem
•	Medulla oblongata (continued):
•	Within the pyramids most fibers of the right and left corticospinal tracts  CROSS OVER (decussate) and switch sides
•	Motor fibers originating from right side of cerebral cortex descend through left side of spinal cord and vice versa
•	On posterior surface of medulla are posterior columns, carry sensory information from spinal cord, some also decussate in the medulla, so sensory fibers from the right side of the spinal cord are processed by the left side of the brain and vice versa.
The Brainstem
•	Medulla oblongata (continued):
•	Olive – lateral to each pyramid; protuberance that contains inferior olivary nucleus; receives sensory fibers from spinal cord and passes them to cerebellum
•	Several cranial nerve and reticular formation nuclei are found in medulla
The Brainstem
•	Medulla oblongata (continued):
Medulla Oblongata contains three important vital centers that regulate internal activities of the body.
•	1. Respiratory center-controls muscles of respiration in response to chemicals or other stimuli
•	2. Cardiac Center-slows the heart rate when the heart is beating too rapidly
•	3. Vasomotor Center- constricts or dilates the muscles in the walls of blood vessels, thus influencing blood pressure.
•	The part of the brain just above the spinal cord; controls breathing, heartbeat, and size of blood vessels

The Brainstem
Locked-In Syndrome
•	Patients who have sustained damage to motor tracts of pons may develop locked-in syndrome; cerebral cortex is unable to communicate with spinal cord; no purposeful movement is possible, but sensory pathways between brain and spinal cord remain intact (as do other cortical functions)
•	Patients are therefore literally “locked in” their bodies; yet fully aware of everything going on around them; some can communicate using eye movements controlled by midbrain
•	Small number of patients recover some motor functions but most do not; overall prognosis is poor; most succumb to infections or other paralytic complications
The Brainstem
•	Reticular formation – collection of over 100 nuclei found in central core of three brainstem subdivisions, one of most complex regions of brain
•	Input is received from multiple sources including: cerebral cortex, limbic system, and sensory stimuli
•	 It sends output to essentially entire brain as well as just about every part of the spinal cord. 
The Brainstem
•	Reticular formation (continued):
•	Like many structures of the limbic system, it is one of the more ancient parts of the mammalian brain from an evolutionary perspective. It shares many of the functions of the limbic system.
•	Central nuclei (center of reticular formation) function in sleep, pain transmission, and mood
•	Nuclei surrounding central nuclei serve motor functions for both skeletal muscles and autonomic nervous system
•	Several nuclei are intimately involved in maintenance of homeostasis, such as regulation of breathing and blood pressure
•	Lateral nuclei play a role in sensation and in level of alertness and activity of cerebral cortex
The Brainstem
The Big Picture of Major Brain Structures and Their Functions
The Big Picture of Major Brain Structures and Their
The Big Picture of Major Brain Structures and Their
Module 12.3 Homeostasis Part I: Role of the CNS in Maintenance of Homeostasis 
Role of CNS in Maintenance of Homeostasis
Homeostasis is defined as maintenance of a relatively stable internal environment in face of ever-changing conditions
•	Homeostatic functions include maintaining fluid, electrolyte, and acid-base balance; blood pressure; blood glucose and oxygen concentrations; biological rhythms; and body temperature
Role of CNS in Maintenance of Homeostasis
•	Nervous system and endocrine system are main systems dedicated to maintaining homeostasis; work together to accomplish this function, but do so in different ways
•	Endocrine system secretes hormones into blood; regulates functions of other cells
•	Nervous system sends action potentials; excite or inhibit target cells
•	Actions of endocrine system are typically slow (take several hours or even days to have an effect) whereas actions of nervous system are generally immediate
Role of CNS in Maintenance of Homeostasis
•	Two structures of CNS are concerned directly with maintenance of homeostasis: 
•	Reticular formation – controls functions of many internal organs as well as aspects of behavior
•	Hypothalamus – closely associated (anatomically and functionally) with pituitary gland; reflects close relationship between these vital systems
•	Reticular formation and hypothalamus have many connections with one another that enable them to coordinate many homeostatic functions
Homeostasis of Vital Functions
•	Maintenance of vital functions (heart pumping, blood pressure, and digestion) is largely controlled by autonomic nervous system (ANS); regulates function of body’s viscera 
•	Although ANS is a component of PNS, it is controlled by structures of CNS, the main “boss” of the ANS is the hypothalamus
Homeostasis of Vital Functions
•	(continued):
•	Hypothalamus receives sensory input from viscera, components of the limbic system, and the cerebral cortex
•	Allows hypothalamus to respond to both normal physiological changes and emotional changes and to adjust ANS output to maintain homeostasis
•	The hypothalamus accomplishes this task largely by relaying instructions to nuclei in the reticular formation of medulla-See next slide
Homeostasis of Vital Functions
•	The hypothalamus accomplishes this task largely by relaying instructions to nuclei in the reticular formation of medulla, including the following:
•	Vasopressor center – neurons of vasopressor center located in anterolateral medulla; when stimulated by hypothalamus, this center increases rate and force of cardiac contractions and causes blood vessels to narrow; all of these effects raise blood pressure
Homeostasis of Vital Functions
•	The hypothalamus accomplishes this task largely by relaying instructions to nuclei in the reticular formation of medulla, including the following (continued):
•	Vasodepressor center – located inferior and medial to vasopressor center; effects on heart and blood vessels are opposite of those of vasopressor center, decreases rate and force of heart contractions and opens blood vessels; these effects decrease blood pressure
•	Other centers- many nuclei in reticular formation participate in regulation of digestive processes and control of urination
Homeostasis of Vital Functions
•	Respiration is one of few vital functions not under direct control of ANS
•	Rate and depth of breathing are regulated by group of neurons in anterior medullary reticular formation
•	Several factors influence neuron firing rates: input from cerebral cortex, limbic system, hypothalamus, certain sensory receptors, and nuclei in pons
Body Temperature Homeostasis
•	Hypothalamus regulates body temperature
•	Acts as body’s thermostat; creates a set point/normal body temperature, about 37 C or 98.6 F
•	Input is received from temperature-sensitive neurons located in several places (skin and areas deeper in body) and from neurons in hypothalamus itself
Body Temperature Homeostasis
•	Hypothalamus regulates body temperature (continued):
•	When body temperature increases above set point, a negative feedback loop is initiated whereby certain hypothalamic nuclei induce changes that cool body (such as sweating)
•	When body temperature decreases below set point, a different feedback loop is initiated that conserves heat
•	Both are examples of Feedback Loops Core Principle
•	Fever-when set point for body temperature is temporarily set higher than normal
Fever
•	Elevation of normal body temperature can accompany variety of infectious and noninfectious conditions
•	Caused by pyrogens (chemicals) secreted by cells of immune system and by certain bacteria that cross blood-brain barrier and interact with temperature-controlling nuclei of hypothalamus
•	Pyrogens increase hypothalamic set point to higher temperature; which makes hypothalamus initiate feedback loop to raise body temperature, shivering and muscle aches due to increased muscle tone; constricts blood vessels serving skin
Fever
•	Treatment is not always necessary; often more important to address underlying cause
•	Antipyretics – used to treat fever; include acetaminophen and aspirin; work by blocking formation of pyrogens; permits hypothalamus to return to normal set point
Regulation of Feeding
•	Hypothalamus also regulates feeding
•	Stimulation of certain hypothalamic nuclei induces hunger and feeding behaviors; indirectly preserves homeostasis of glucose
•	These effects are believed to be due, in part, to neurotransmitters called orexins, which are secreted in high amounts by hypothalamic neurons during periods of fasting and appear to induce eating.
•	orexis=“appetite”
Regulation of Feeding
•	Hypothalamus also regulates feeding (continued):
•	Stimulation of different hypothalamic nuclei seems to inhibit feeding; mechanisms controlling food intake are complex and involve hormones, several hypothalamic nuclei, and other regions of brain
Sleep and Wakefulness 
•	Sleep- defined as a reversible and normal suspension of consciousness; one of most fundamental homeostatic processes carried out by humans and most other animals
•	Information is known pertaining to how we sleep, how sleep is regulated, and brain activity during sleep, but why most animals sleep is yet unknown
•	Physiologically, sleep appears to serve an energy restoration function; allows brain to replenish its glycogen supply
Sleep and Wakefulness 
•	Sleep (continued):
•	Sleep is required for survival; deprivation can cause imbalances in temperature homeostasis, weight loss, a decrease in cognitive abilities, hallucinations, and even death
•	Most adults require 7–8 hours of sleep per night while infants require about 17 hours per day
Sleep and Wakefulness 
•	Sleep (continued):
•	Circadian Rhythms and Biological “Clock”: Human sleep generally follows a circadian rhythm (circa=“around”, dia=“day”)
•	Meaning that we spend a period of 24-hour cycle awake and another period of cycle asleep
•	This rhythm is controlled by the hypothalamus; causes changes in level of wakefulness in response to day and night cycles
Sleep and Wakefulness 
•	Sleep occurs in following sequence of events:
•	Nerves from eye signal suprachiasmatic nucleus (SCN) of hypothalamus that light level is decreasing
•	SCN stimulates ventrolateral preoptic nucleus (in hypothalamus); SCN also sends signals to pineal gland that stimulate secretion of melatonin
•	Ventrolateral preoptic nucleus decreases activity of reticular formation
Sleep and Wakefulness 
•	Sleep (continued):
•	Decreased activity of reticular formation “disconnects” thalamus from cerebral cortex; in turn decreases level of consciousness
•	Arousal from sleep is mediated by a different group of hypothalamic neurons (not those regulating satiety); secrete neurotransmitter orexin
Sleep and Wakefulness 
Sleep and Wakefulness 
•	Brain Waves and Stages of Sleep – stages of sleep can be monitored using electroencephalogram (EEG); measures electrical activity of brain using electrodes attached to skin
•	Tracings of electrical activity (brain waves) show characteristic patterns during wakefulness and different stages of sleep
•	Waves differ in height (amplitude) and speed at which they are generated (frequency)
Sleep and Wakefulness 
•	Brain Waves and Stages of Sleep (continued):
•	Beta waves – low amplitude and high frequency; occur when we are awake and engaged in mental activity
•	When we fall asleep and progress thought its stages, the amplitude of the waves progressively increases and frequency progressively decreases, see stages of sleep next slide
Sleep and Wakefulness 
•	Brain Waves and Stages of Sleep (continued):
•	Stages I–III sleep are characterized by drowsiness progressing to moderately deep sleep; beta waves slow to theta waves. The amplitude of the theta waves increases and their frequency decreases as we move from stage I to III.  
•	State IV sleep -deepest sleep occurs in this stage, delta waves become lower frequency and higher amplitude. Delta waves are also seen during general anesthesia and in awake adults with significant brain damage. 
•	REM sleep (rapid eye movement)- As a person emerges from stage IV sleep he/she enters REM sleep, named for the rapid back–and-forth eye movements that occur during this stage, REM sleep is when majority of dreams occur, brain waves resemble beta waves of an awake adult, although clearly the two brain states are not equivalent, generally lasts about 10-15 minutes before cycling back into stage I sleep.
Sleep and Wakefulness 
States of Altered Consciousness Mimicking Sleep
•	Altered consciousness can indicate serious problems with brain function; examples include:
•	Stupor – diminished level of cortical activity; often arousable to strong or painful stimuli; common causes are infections, mental illnesses, and brain conditions (such as brain tumors)
•	Coma – unarousable unconsciousness; no purposeful responses to any stimuli (even pain); underlying defect is damage to reticular activating system or related component that prohibits normal arousal of cerebral cortex
States of Altered Consciousness Mimicking Sleep
•	Altered consciousness can indicate serious problems with brain function; examples include (continued):
•	Coma (continued):
•	EEG demonstrates slow, fixed pattern with no observable sleep/wake cycles
•	Brainstem reflexes remain intact; patients may exhibit certain involuntary movements
•	May result from head trauma, certain drugs, disturbances in acid-base homeostasis and various neurological conditions
States of Altered Consciousness Mimicking Sleep
•	Altered consciousness can indicate serious problems with brain function; examples include (continued):
•	Persistent vegetative state – sometimes patients with head trauma or neurological injury will move from coma state into persistent vegetative state, the patient is awake but unaware because of damage to cerebral cortex; also lacks voluntary movements
•	Sleep/wake cycles do occur; brainstem reflexes remain intact, leading to involuntary movements (such as head turning and grunt-like vocalizations)
•	Can be misinterpreted as meaningful interaction but not mediated by cerebral cortex, thus do not imply conscious awareness
States of Altered Consciousness Mimicking Sleep
•	People in these states may occasionally regain consciousness, depending on cause of state
•	Brain death – most extreme altered state of consciousness; EEG shows no activity; brainstem reflexes are absent; cerebral blood flow and metabolism are reduced to essentially zero; consciousness will not be regained
Module 12.4 Higher Mental Functions
Cognition and Language 
•	Cognition – collective term for diverse group of tasks; performed by association areas of cerebral cortex 
•	Cognitive functions – include processing and responding to complex external stimuli, recognizing related stimuli, processing internal stimuli, and planning appropriate responses to stimuli
•	Cognitive processes – responsible for social and moral behavior, intelligence, thoughts, problem-solving skills, language, and personality 
Cognition and Language 
•	Aspects of cognition have been localized to different multimodal association areas which include:
•	Parietal association cortex – responsible for spatial awareness and attention; allows us to focus on distinct aspects of a specific object and recognize position of object in space
•	Temporal association cortex – primarily responsible for recognizing stimuli, especially complex stimuli such as faces
Cognition and Language 
•	Localization of Cognitive Function (continued):
•	Prefrontal cortex – largest and most complex of association cortices
•	Responsible for majority of cognitive functions that make up a person’s “character” or “personality”
•	Receives information from other association cortices and from other sensory and motor cortices, allows for integration of complex sensory and motor information that creates an awareness of “self” in the world, which leads to planning and execution of behaviors appropriate for given circumstances.
Cognition and Language 
•	Cerebral lateralization – phenomenon in which many cognitive functions are unequally represented in right and left hemispheres 
•	Represents a division of labor between hemispheres to maximize a limited amount of brain space
Cognition and Language 
•	Cerebral lateralization (continued):
•	The functions that appear to be lateralized, although this is not an absolute
•	Emotional functions – left frontal cortex is mostly responsible for “positive” emotions while right cortex for “negative” emotions
•	Attention is lateralized to right parietal cortex while facial recognition tends to be performed by right temporal cortex
•	Language-related recognition, including ability to identify an object with its proper name, is lateralized to left temporal cortex
Dementia
•	Patients with dementia exhibit a progressive loss of recent memory, degeneration of cognitive functions, and changes in personality
•	No proven method for prevention or cure of dementia exists; some drugs may slow progression of Alzheimer’s disease in certain patients but do not reverse changes that already have taken place; ineffective in other forms of dementia
Dementia
•	Common (most to least) forms of dementia include:
•	Alzheimer’s disease (AD)
•	Most common form of dementia
•	Some characteristic findings in the brain tissue are neurofibrillary tangles (aggregates of proteins in neurons), senile plaques (extracellular deposits of specific protein around neurons), and degeneration of cortical neurons and synaptic connections, these changes found throughout brain; especially numerous in cortical association areas and hippocampus
•	Earliest signs typically involve recent memory loss and forgetfulness; progresses to impairment of attention, language skills, critical thinking and visual-spatial abilities, and changes in personality; eventually motor skills, sensory perception, and long-term memory are affected
Dementia
•	Common (most to least) forms of dementia include (continued):
•	Vascular dementia
•	Group of disorders that share common feature of a disruption in blood flow to parts of brain, particularly cerebral cortex
•	Signs and symptoms are highly variable because of range of brain regions affected
•	Significant overlap with AD; patients often have both forms; known as mixed dementia
Dementia
•	Common (most to least) forms of dementia include (continued):
•	Lewy body dementia
•	Cytoplasmic inclusions (Lewy bodies) in neurons in certain brain parts
•	Fluctuations in cognitive functions, less profound impact on memory formation, hallucinations, delusions, sleep disorders, and often have motor features of Parkinson’s disease
Dementia
•	Common (most to least) forms of dementia include (continued):
•	Pick’s disease
•	Cerebral cortex of frontal and temporal lobes progressively degenerates
•	Results in severe atrophy due to loss of neurons with excess neuroglia
•	Unusual, in that younger population affected (typically around age 55–65)
•	Patients deteriorate rapidly; dramatic personality changes and behavioral problems common because of prefrontal cortex involvement
Cognition and Language 
•	Language, arguably one of most important cognitive functions of brain; refers to ability to comprehend and produce words through speaking, writing, and/or signing, and to assign and recognize symbolic meaning of a word correctly
Cognition and Language 
•	Multiple parts of the brain are required for successful communication but two multimodal association areas are critical:
•	Broca’s area – in frontal lobe; responsible for production of language, including planning and ordering of words with proper grammar and syntax
•	Wernicke’s area – in temporal lobe; responsible for understanding language and linking a word with its correct symbolic meaning
•	Aphasia – language deficit; occurs when either of these two critical areas is damaged
Cognition and Language 
Aphasias
•	Aphasia (language deficits), two major types:
•	Broca’s aphasia– inability to produce speech because the patient is unable to correctly plan and order grammar and syntax of a statement; speech is not fluent, words and phrases tend to be repeated; grammar, syntax, and structure of individual words are disordered; frustrating for patients because language comprehension is intact
•	Wernicke’s – inability to understand language; speak fluently with adequate grammar and syntax but words and meanings are not correctly linked; language comprehension is not intact, so patients cannot fully understand what is being said to them and cannot realize that what they’re saying makes no sense. 

•	Nonfluent aphasia. Damage to the language network near the left frontal area of the brain usually results in Broca aphasia, which is also called nonfluent aphasia. People with this disorder struggle to get words out, speak in very short sentences and omit words. A person might say "Want food" or "Walk park today." A listener can usually understand the meaning.
•	People with Broca aphasia may understand what other people say better than they can speak. They're often aware of their difficulty communicating and may get frustrated. People with Broca aphasia may also have right-sided paralysis or weakness.
•	Fluent aphasia. People with this form of aphasia may speak easily and fluently in long, complex sentences that don't make sense or include unrecognizable, incorrect or unnecessary words. They usually don't understand spoken language well and often don't realize that others can't understand them. Also known as Wernicke aphasia, this type of aphasia is the result of damage to the language network in the middle left side of the brain. 
•	Global aphasia. Global aphasia results from extensive damage to the brain's language networks. People with global aphasia have severe disabilities with expression and comprehension.

•	If the brain damage is mild, a person may recover language skills without treatment. However, most people undergo speech and language therapy to rehabilitate their language skills and supplement their communication experiences. Researchers are currently investigating the use of medications, alone or in combination with speech therapy, to help people with aphasia.
•	Speech and language rehabilitation
•	Recovery of language skills is usually a relatively slow process. Although most people make significant progress, few people regain full pre-injury communication levels.
•	For aphasia, speech and language therapy tries to improve the person's ability to communicate by restoring as much language as possible, teaching how to compensate for lost language skills and finding other methods of communicating.
•	Therapy:
•	Starts early. Some studies have found that therapy is most effective when it begins soon after the brain injury.
•	Often works in groups. In a group setting, people with aphasia can try out their communication skills in a safe environment. Participants can practice initiating conversations, speaking in turn, clarifying misunderstandings and fixing conversations that have completely broken down.
•	May include use of computers. Using computer-assisted therapy can be especially helpful for relearning verbs and word sounds (phonemes).

Learning and Memory
•	Two basic types of memory: declarative (fact) memory – defined as memory of things that are readily available to consciousness; could in principle be expressed aloud (hence term “declarative”), and nondeclarative memory (procedural or skills memory); tends to include skills and associations that are largely unconscious
•	Declarative memory examples – phone number or a quote
•	Nondeclarative examples – how to enter phone number on a phone and how to move your mouth to speak the quote
Learning and Memory
•	Declarative and nondeclarative memory can be classified by length of time in which they are stored:
•	Immediate memory – stored only for a few seconds; is critical for carrying out normal conversation, reading, and daily tasks (like remembering the areas of the floor you just swept)
•	Short-term (working) memory – stored for several minutes; allows you to remember and manipulate information with a general behavioral goal in mind
•	Long-term memory – a more permanent form of storage for days, weeks, or even a lifetime
Learning and Memory
•	Some of the information in immediate and working memory is transferred into long-term memory, a process called consolidation
•	Formation and storage of declarative memory-formation of new declarative memories appears to require involvement of hippocampus (component of limbic system); immediate and short-term memories are likely stored here
Learning and Memory
•	Long-term potentiation (LTP) – mechanism by which hippocampal neurons encode long-term declarative memories, seems to involve an increase in synaptic activity between associated neurons 
•	Current evidence indicates that LTP in the hippocampus is required for new declarative memories to form, but it is clear from patients with damage to hippocampus that long-term declarative memories are NOT stored here. Instead, memories appear to be stored in different areas of the cerebral cortex that correlate with their function. 
•	Ex, image of a cat is stored in the visual association area, the sound of the cat in the auditory association area, and the feel of a cat’s fur in the somatosensory association area
Learning and Memory
•	Formation and storage of nondeclarative memory- Damage to the hippocampus and associated structures does not seem to impact the ability to form new nondeclarative memories. Instead, it appears from studies of patients with certain brain diseases that the motor cortices, cerebellum, and basal nuclei are required for the formation and storage of nondeclarative memories.
Learning and Memory
Learning and Memory
•	Emotion – complex combination of three separate phenomena:
•	Visceral motor responses – blushing or heart racing 
•	Somatic motor responses – smiling, laughing, frowning, and crying
•	Highly subjective “feelings” that respond to and are integrated with sensory and/or cognitive stimuli, such as feeling sad when remembering a lost pet, a key player in this aspect of emotion is the amygdala
Module 12.5 Protection of the Brain
Brain Protection
Three features within protective shell of skull provide additional shelter for delicate brain tissue:
•	Cranial meninges – three layers of membranes that surround brain
•	Cerebrospinal fluid (CSF) – fluid that bathes brain and fills cavities
•	Blood-brain barrier – prevents many substances in the blood from gaining access to the cells of the brain
Brain Protection
•	Cranial meninges – three of them, are protective membranes of mostly dense irregular collagenous tissue
•	Structural arrangement from superficial to deep: dura mater, arachnoid mater, and pia mater
Brain Protection
•	Cranial meninges (continued):
•	Epidural space – between inner surface of cranial bones and outer surface of dura mater; only a potential space as dura is normally tightly bound to bone only allowing for passage of blood vessels
•	Dura mater (dura) – outermost meninx; thickest and toughest of three meningeal layers; tough, leathery membrane with abundant collagen fibers and very few elastic fibers
Brain Protection
•	Cranial meninges (continued):
•	Dura mater (dura) (continued):
•	Has two layers:
•	Periosteal dura – outer layer; attached to inner surface of bones of cranial cavity; functions as periosteum with extensive blood supply in epidural space 
•	Meningeal dura – inner layer; avascular and lies superficial to arachnoid mater
•	Mostly fused, creating a single inelastic membrane except in regions where cavities called dural sinuses are found
Brain Protection
•	Cranial meninges (continued):
•	Dura mater (dura) (continued):
•	Dural sinuses – venous channels; drain CSF and deoxygenated blood from brain’s many veins; may also be found where meningeal dura folds over itself and courses between structures in brain
Brain Protection
•	Cranial meninges (continued):
•	Dura mater (dura) (continued):
•	Dural folds include falx cerebri, tentorium cerebelli, and falx cerebelli 
•	Falx cerebri – within longitudinal fissure; partition between left and right cerebral hemispheres; superior sagittal sinus (large dural sinus) found superior to falx cerebri
•	Tentorium cerebelli – partition between cerebellum and occipital lobe of cerebrum
•	Falx cerebelli – partition between left and right hemispheres of cerebellum
Brain Protection
•	Cranial meninges (continued):
•	Subdural space – found deep to dura, thin serous fluid-filled space; houses veins that drain blood from brain
•	Arachnoid mater – middle meninx, deep to subdural space; named for its resemblance to a spider web, composed of dense irregular collagenous tissue, thinner and somewhat more elastic than dura 
Brain Protection
•	Cranial meninges (continued):
•	Arachnoid mater (continued):
•	Arachnoid trabeculae – inward extensions, composed of collagen fiber bundles and fibroblasts; anchor arachnoid to deep pia mater
•	Arachnoid granulations (villi) – small bundles of arachnoid; project superficially through meningeal dura into the dural sinuses; play important role in the return of CSF to bloodstream
Brain Protection
•	Cranial meninges (continued):
•	Subarachnoid space – found deep to arachnoid mater and superficial to pia mater; contains CSF and the major blood vessels of brain
•	Pia mater – deepest meningeal layer; only meninx in physical contact with brain tissue
Brain Protection
•	Cranial meninges (continued):
•	Pia mater (continued):
•	Follows contour of brain, dives into sulci and fissures
•	Permeable to substances in brain extracellular fluid and CSF; allows substances to move between these two fluids; helps to balance concentration of different solutes in them
Brain Protection
	Brain Protection
The Ventricles and Cerebrospinal Fluid
•	Four ventricles within brain are linked cavities that are continuous with central canal of spinal cord  
•	Lined with ependymal cells
•	Filled with cerebrospinal fluid
The Ventricles and Cerebrospinal Fluid
•	Right and left lateral ventricles (first and second ventricles); within their respective cerebral hemisphere:
•	Resemble ram’s horns when observed in anterior view; horseshoe-shaped appearance in lateral view
•	Three regions: anterior horn, inferior horn, and posterior horn
The Ventricles and Cerebrospinal Fluid
•	Third ventricle – narrow cavity found between two lobes of diencephalon; continuous with lateral ventricles by interventricular foramen
•	Fourth ventricle – between pons and cerebellum; connected to third ventricle by cerebral aqueduct (small passageway through midbrain)
•	Continuous with central canal of spinal cord
•	Contains several posterior openings that allow CSF in ventricles to flow into subarachnoid space 
The Ventricles and Cerebrospinal Fluid
The Ventricles and Cerebrospinal Fluid
•	Cerebrospinal fluid (CSF) – clear, colorless liquid similar in composition to blood plasma; protects brain in following ways:
•	Cushions brain and maintains a constant temperature within cranial cavity
•	Removes wastes and increases buoyancy of brain; keeps brain from collapsing under its own weight
The Ventricles and Cerebrospinal Fluid
•	Most CSF is formed within each of the four ventricles by structures called choroid plexuses, located where blood capillaries come into direct contact with ependymal cells (which also produce some CSF) lining the ventricles. 
•	The capillaries within the choroid plexuses are fenestrated, cells have small gaps between them and within their membranes that allow fluid and electrolytes to escape the blood and enter the ECF.  
The Ventricles and Cerebrospinal Fluid
•	Choroid plexuses (continued): 
•	About 150 ml (about 2/3 cup) of CSF circulates through brain and spinal cord
•	750–800 ml of CSF is produced daily so old CSF must be removed as choroid plexuses make new CSF
•	Process of CSF production and removal occurs constantly; roughly 50% of total CSF is completely replaced every 5–6 hours
The Ventricles and Cerebrospinal Fluid
•	Pathway for formation, circulation, and reabsorption of CSF:
•	Fluid and electrolytes leak out of capillaries of choroid plexuses into ECF of ventricles
•	Taken up into ependymal cells; then secreted into ventricles as CSF
•	Circulated through and around brain and spinal cord in subarachnoid space; CSF circulates through ventricles with the help of the ciliated ependymal cells, some of this CSF then flows into the subarachnoid space around the spinal cord.
•	Some CSF is reabsorbed into blood in dural sinuses via arachnoid granulations
The Ventricles and Cerebrospinal Fluid
The Blood-Brain Barrier 
The brain is protects not only from outside threats, but also from inside. Most chemicals and disease-causing organisms (like bacteria and viruses) are denied access to the cells of the brain by the blood-brain barrier – keeps CSF and brain ECF separate from the blood
•	Consists mainly of simple squamous epithelial cells (endothelial cells) of blood capillaries, their basal laminae, and astrocytes
The Blood-Brain Barrier 
•	Unique features of endothelial cells found in barrier:
•	More tight junctions than cells of most capillaries
•	Limit endocytosis and exocytosis- many molecules in the blood cannot enter ECF of brain, the opposite is true as well, many substances in the ECF of brain cannot enter the blood.
The Blood-Brain Barrier 
•	Substances that easily pass through plasma membranes are able to pass through blood-brain barrier; include water, oxygen, carbon dioxide, and nonpolar, lipid-based molecules
•	Protein channels or carriers allow for passage of other molecules, include glucose, amino acids, and ions
•	Most large, polar molecules are effectively prevented from crossing blood-brain barrier in any significant amount; while barrier is protective, it can hinder access of medications into brain
The Blood-Brain Barrier 
Concept Boost: Where Exactly Is Blood-Brain Barrier? 
•	No single structure is labeled “blood-brain barrier” on any figure because blood-brain barrier isn’t around brain; it’s within brain
•	Not located in one distinct place but found throughout entire brain
•	To understand this, we must first understand body’s tiniest blood vessels; capillaries are vessels that deliver oxygen and nutrients to body’s cells and remove any wastes produced by cells
Concept Boost: Where Exactly Is Blood-Brain Barrier? 
•	Capillaries found in most organs and tissues are fairly leaky; allow a wide variety of substances to move from blood to extracellular fluid (and vice versa)
•	Capillaries of brain are specialized to allow only selected substances to enter its extracellular fluid; effectively act as a “barrier”; prevents other substances from doing so 
•	Blood-brain barrier, therefore, is actually a property of capillaries found throughout brain rather than a distinct physical barrier
Infectious Meningitis
•	Potentially life-threatening infection of meninges in subarachnoid space; inflammation occurs, causing classic signs: headache, lethargy, stiff neck, fever
•	Diagnosis – examination of CSF for infectious agents and white blood cells (cells of immune system); bacteria and certain viruses are most common causative agents:
•	Viral – generally mild; resolves in 1–2 weeks
•	Bacterial – can rapidly progress to brain involvement and death; aggressive antibiotic treatment necessary; some most common forms are preventable with vaccines
Module 12.6 The Spinal Cord
The Spinal Cord 
•	Spinal cord – composed primarily of nervous tissue; responsible for both relaying and processing information; less structurally complex than brain but still vitally important to normal nervous system function; two primary roles:
•	Serves as a relay station and as an intermediate point between body and brain; only means by which brain can interact with body below head and neck
•	Processing station for some less complex activities such as spinal reflexes; do not require higher level processing
Protection of the Spinal Cord
Brain’s meninges pass through foramen magnum to provide a continuous protective covering of spinal cord and distal nerves at base 
•	Three spinal meninges include dura, arachnoid, and pia mater; structurally similar to brain meninges except that spinal cord dura has only one layer and pia mater has some structural enhancements, helps to anchor the spinal cord in the vertebral cavity, thin pieces of spinal pia called denticulate ligaments extend outward through the arachnoid and attach to the spinal dura 
Protection of the Spinal Cord
•	Actual or potential spaces between spinal meninges are same as those found between cranial meninges with following features:
•	Epidural space – actual space due to absence of a periosteal dura; found between meningeal dura and walls of vertebral foramina; space is filled with veins and adipose tissue; cushions and protects spinal cord
•	Subdural space – only a potential space; normally dura and arachnoid adhere to one another
•	Subarachnoid space – found between arachnoid and pia mater; filled with thin layer of CSF; area inferior to the base of the spinal cord contains a larger volume of CSF, making it a useful place from which to sample CSF if needed. 

Protection of the Spinal Cord
Protection of the Spinal Cord
Epidural Anesthesia and Lumbar Punctures
•	Epidural (spinal) anesthesia – local anesthetic medication is injected into epidural space through an inserted needle
•	Causes “numbing” (inability to transmit motor or sensory impulses) of nerves extending off spinal cord below level of injection
•	Commonly given during childbirth and other surgical procedures
Epidural Anesthesia and Lumbar Punctures
•	Lumbar puncture (spinal tap) – needle inserted into subarachnoid space generally between fourth and fifth lumbar vertebrae; avoids possibility of injuring spinal cord
•	CSF is withdrawn for 
analysis; used to assess 
conditions like 
meningitis, encephalitis
and multiple sclerosis
External Spinal Cord Anatomy
Spinal cord extends proximally from foramen magnum to region between first and second lumbar vertebrae; following structural features can be seen on spinal cord:
•	Narrow posterior median sulcus on posterior side entire length of cord
•	Wider anterior median fissure can be seen on entire length of anterior side of cord
•	Conus medullaris is cone-shaped distal end of cord
External Spinal Cord Anatomy
•	At the level of first and second lumbar vertebrae;  spinal pia gathers into a very thin structure known as the filum terminale, which continues through the vertebral cavity and anchors into the first coccygeal vertebra
•	Spinal cord has two enlarged regions (cervical and lumbar enlargements); the nerve roots that fuse to form spinal nerves (serve upper and lower extremities) attach to these enlargements 
External Spinal Cord Anatomy
•	Spinal nerves are components of PNS; carry sensory and motor impulses to and from spinal cord
•	Projections off each side of spinal cord between vertebrae are posterior and anterior nerve roots
•	Roots of spinal nerves extend inferiorly from conus medullaris and fill remainder of vertebral cavity; this bundle of spinal nerve roots is called cauda equina due to its horsetail-like appearance
External Spinal Cord Anatomy
Internal Spinal Cord Anatomy
Butterfly-shaped spinal gray matter is surrounded by tracts of white matter; following features are seen on cross section of spinal cord:
•	Central canal – filled with CSF; seen in center of spinal cord; surrounded by thin strip of gray matter (gray commissure); connects each “butterfly” wing
Internal Spinal Cord Anatomy
•	Can tell anterior and posterior sides of spinal cord by different shapes of the wings
•	Anterior wings are broader while thinner posterior wings extend almost to outer surface of spinal cord
Internal Spinal Cord Anatomy
Internal Spinal Cord Anatomy
•	Spinal gray matter makes up three distinct regions found within spinal cord; houses neurons with specific functions and includes:
•	Anterior horn (ventral horn) makes up anterior wing of gray matter and gives rise to anterior motor nerve roots; neurons of anterior horn are concerned with somatic motor functions (those of skeletal muscles)
Internal Spinal Cord Anatomy
•	Spinal gray matter (continued):
•	Posterior horn (or dorsal horn) makes up posterior wing of gray matter, contains cell bodies of neurons that are involved in processing both somatic and visceral incoming sensory information. 
•	Lateral horn- found only in spinal cord between first thoracic vertebra and lumbar region; contains cell bodies of neurons responsible for motor control of viscera via the autonomic nervous system. 
Internal Spinal Cord Anatomy
Internal Spinal Cord Anatomy
•	Spinal White Matter: Ascending and Descending Tracts
•	Recall that one of the main functions of the spinal cord is to act as a relay station. This function is carried out by its white matter, which contains the axons of neurons that travel to and from the brain. 
•	Spinal white matter is organized into regions, each general region of spinal white matter is called a funiculus and three funiculi lie on each side of the spinal cord: posterior funiculus, lateral funiculus, and anterior funiculus

Internal Spinal Cord Anatomy
•	Spinal White Matter (continued):
•	The white matter within each funiculus is further organized into tracts (columns)
•	Ascending and descending tracts bring information to and from a specific part of brain
•	Sensory pathways travel in posterior and lateral funiculi while motor pathways travel in anterior and lateral funiculi
Internal Spinal Cord Anatomy
•	Spinal White Matter (continued):
•	Several ascending tracts carry various kinds of sensory information
•	Major tracts include:
•	Posterior columns –carry somatosensory information, such as proprioception and touch; nucleus gracilis transmits signals from lower limbs and lower trunk while nucleus cuneatus transmits stimuli from upper limbs and upper trunk
Internal Spinal Cord Anatomy
•	Spinal White Matter (continued):
•	Ascending tracts (continued):
•	Spinocerebellar tracts- carry information about joint position and muscle stretch from entire body to cerebellum
•	Anterolateral system includes spinothalamic tracts- send pain and temperature information from entire body to brain
Internal Spinal Cord Anatomy
Internal Spinal Cord Anatomy
•	Spinal White Matter (continued):
•	Descending tracts (Motor) 
•	Corticospinal tracts – largest of descending tracts; help control skeletal muscles below head and neck
•	Originate primarily from motor areas of cerebral cortex; descend as part of internal capsule then through brainstem where a majority of them decussate
•	Travel through lateral funiculi of spinal cord; bring motor information to appropriate places in the anterior horn
Internal Spinal Cord Anatomy
Module 12.7 Sensation Part I: Role of the CNS in Sensation
Sensory Stimuli
•	 We as humans have ability not only to perceive diferent sensory stimuli (things that cause senses to respond) but also to assemble multiple sensory stimuli into a single mental picture/idea 
•	Each of these disparate stimuli reaches brain in two-part process:
•	Stimulus is detected by neurons in PNS and sent as sensory input to CNS
•	In CNS, sensory input is sent to cerebral cortex for interpretation
Sensory Stimuli
•	Sensory stimuli (continued):
•	When CNS has received all different sensory inputs, it integrates them into a single perception (a conscious awareness of sensation)
•	 Sensations can be grouped into two basic types:
•	Special senses – detected by special sense organs and include vision, hearing, equilibrium, smell, and taste
•	General senses – detected by sensory neurons in skin, muscles, or walls of organs; can be further subdivided into general somatic senses that involve skin, muscles, and joints and general visceral senses that involve internal organs
General Somatic Senses 
General somatic senses pertain to touch, stretch, joint position, pain, and temperature 
•	Two types of touch stimuli are delivered to appropriate part of cerebral cortex by different pathways:
•	Tactile senses – (fine or discriminative touch) include vibration, two-point discrimination, and light touch.  Tactile senses allow you to discriminate between different shapes/textures without visual input.
•	Nondiscriminative touch (crude touch) lacks fine spatial resolution of tactile senses
General Somatic Senses 
•	Most of general somatic senses are considered mechanical senses; neurons that detect them are responsive to mechanical deformation in the skin, joint, and/or organ (temperature sensation is exception)
•	Two major ascending tracts in spinal cord carry somatic sensory information to brain: posterior columns/medial lemniscal system and anterolateral system 
General Somatic Senses 
•	Basic pathway consists of following:
•	First-order neuron –the sensory neuron that detects initial stimulus in PNS; axon of this neuron then synapses on a second-order neuron
•	Second-order neuron – interneuron located in posterior horn of spinal cord or in brainstem; generally synapses on third-order neuron 
•	Third-order neuron –interneurons in thalamus; delivers impulses to cerebral cortex
General Somatic Senses 
General Somatic Senses 
•	Posterior columns/medial lemniscal system -axons of neurons that transmit tactile sensory information about discriminative touch travel with axons that convey information regarding proprioception (joint position)  
General Somatic Senses 
General Somatic Senses 
•	Anterolateral system –As with the tactile senses and proprioception, the fibers that carry the stimuli of pain, temperature, and nondiscriminative touch enter the posterior spinal cord. However, these stimuli ascend via pathways in the anterolateral spinal cord, referred to as the anterolateral system. 
•	First-order neurons synapse on second-order neurons in posterior horn; then decussate
•	Several tracts lie within the anterolateral system, the largest are right and left spinothalamic tract –send signals through the spinal cord to the sensory relay nuclei of the thalamus; third-order neurons from the thalamus then carry information to cerebral cortex
General Somatic Senses 
General Somatic Senses 
•	Role of Cerebral Cortex in Sensation, S1 and Somatotopy: 
•	Thalamus relays most incoming information to primary somatosensory cortex (S1) in postcentral gyrus
•	Each part of body is represented by a specific region of S1, a type of organization called somatotopy 
General Somatic Senses 
•	Role of Cerebral Cortex (continued):
•	Map of S1 illustrates that different parts of body are unequally represented 
•	A disproportionate amount of space is dedicated to the hands and face; reflects importance of manual dexterity, facial expression, and speech to humans
•	This unequal representation of body parts in S1 is exemplified by the sensory homunculus (literally “little man”) 
General Somatic Senses 
General Somatic Senses 
•	Role of the Cerebral Cortex in Sensation –  Processing of Touch Stimuli: 
•	Thalamic nuclei relay touch information from spinothalamic tracts and posterior columns primarily to S1 for conscious perception
•	Once sensory information has reached S1, it is processed/perceived, and passed along to cortical association areas
General Somatic Senses 
•	Role of the Cerebral Cortex in Sensation – Processing of Touch Stimuli (continued):
•	One of main areas to which S1 axons send output is the somatosensory association cortex (S2), S2 in turn processes and sends information to structures of the limbic system (play a role in tactile learning and memory)
•	Neurons in S1 also send output to parietal and temporal association areas which integrate and relay information to motor areas of frontal lobe
General Somatic Senses 
•	Role of the Cerebral Cortex in Sensation – Processing of Pain Stimuli: perception of pain stimuli is called nociception
•	Thalamus relays pain stimuli to multiple parts of the brain, including S1 and S2, where the sensory discriminative (localization, intensity, and quality) aspects of pain are perceived and analyzed
•	Such stimuli are also sent to basal nuclei, structures of limbic system, hypothalamus, and prefrontal cortex, where emotional, behavioral, and other aspects of pain are processed
General Somatic Senses 
•	Role of the Cerebral Cortex in Sensation – Processing of Pain Stimuli (continued):
•	Cerebral cortex appears to have a significant influence over how pain is perceived; evident by a phenomenon called placebo effect, in which a patient is given a placebo “dummy treatment” with no actual therapeutic value, use of a placebo as an analgesic (pain reliever) can be surprisingly effective, in most studies, up to 30% of patients report relief from pain when a placebo is administered. 
•	This does NOT mean the patient is “crazy” or that the pain is imagined, instead, it reflects the very real ability of the brain to modulate the PERCEPTION of pain. 
General Somatic Senses 
•	Role of the Cerebral Cortex in Sensation – Processing of Pain Stimuli (continued):
•	The explanation for the placebo effect appears to involve a descending pathway originating mostly in S1, amygdala, and a region of midbrain called periaqueductal gray matter 
•	Neurons of the periaqueductal gray matter release neurotransmitters called endorphins, render the neurons of the posterior horn in the spinal cord less sensitive to pain input. 
•	Thus, the stimulus causing the pain is still present and its intensity has not decreased, but the CNS neurons perceive it as being less intense or even absent. 
•	Painkillers, like morphine, work by binding to the same receptors as endorphins.
Phantom Limb Pain
•	Phantom limb – occurs after amputation of limb, digit, or even breast; patients perceive body part is still present and functional in absence of sensory input; small percentage develop phantom pain (burning, tingling, or severe pain) in missing part
•	Very difficult to treat due to complex way CNS processes pain; supports idea that S1 has “map” of body that exists independently of PNS
•	Over time, map generally rearranges itself so body is represented accurately; phantom sensations decrease
Introduction to Special Senses
•	Special senses include vision, hearing (audition), taste (gustation), smell (olfaction), and balance (vestibular sensation)
•	Each involves neurons that detect a stimulus and send it to CNS for processing and integration
•	Thalamus – gateway for entry of most special sensory stimuli into cerebral cortex; interprets majority of this information
Introduction to Special Senses
•	Usual pathway for processing each type of special sensory stimuli:
•	Visual 
•	Most stimuli are sent directly to thalamus; then relayed to primary visual cortex (processes stimuli and perceives an object’s depth, color, and detects rapidly changing stimuli) 
•	Information is shared with association areas in temporal and parietal lobes; crucial for object recognition and spatial awareness, respectively
Introduction to Special Senses
•	Usual pathway for processing each type of special sensory stimuli (continued):
•	Auditory 
•	Stimuli from sound waves first go to nuclei in brainstem where some stimuli processing occurs
•	Remainder of stimuli are routed to thalamus and then primary auditory cortex (superior temporal lobe), for processing sounds with complex tempos such as speed and music
•	Information is relayed to many association areas such as Wernicke’s area for language comprehension
Introduction to Special Senses
•	Usual pathway for processing each type of special sensory stimuli (continued):
•	Gustatory 
•	Stimuli are sent to nucleus in medulla and relayed to thalamus
•	Then sent to gustatory cortices (insula and parietal lobes) to analyze different components of taste
•	Information is sent to hypothalamus and limbic system which presumably influence taste preferences and food-seeking behavior
Introduction to Special Senses
•	Usual pathway for processing each type of special sensory stimuli(continued):
•	Olfactory 
•	Stimuli enter cerebral cortex of limbic system for initial processing, bypassing thalamus
•	Then sent to several regions of brain including thalamus (which then transmits them to prefrontal cortex), hypothalamus, and other limbic system components
•	Allows smell stimuli to influence a number of behaviors including those relating to feeding, emotion, and cognition.  
Introduction to Special Senses
•	Usual pathway for processing each type of special sensory stimuli(continued):

•	Balance
•	Processing vestibular stimuli involves multiple brainstem nuclei, cerebellum, descending pathways through spinal cord, and pathways through thalamus to cerebral cortex
Module 12.8 Movement Part I: Role of the CNS in Voluntary Movement 
Voluntary Movement
•	Planning and coordination of voluntary movement are carried out within CNS; involve motor areas of cerebral cortex, basal nuclei, cerebellum, and spinal cord
•	Three types of neurons are directly involved in eliciting a muscle contraction (next slide)
Voluntary Movement
•	 Upper motor neurons with cell bodies in motor area 
	of cerebral cortex (most) or brainstem (some) – axons 
	descend through cerebral white matter to brainstem 
	and spinal cord; synapse with local interneurons
•	Interneurons – pass messages from upper motor 
	neurons to neighboring lower motor neurons
•	 Cell bodies of lower motor neurons reside in anterior 
	horn of spinal gray matter; axons exit spinal cord to innervate skeletal muscles (lower motor neurons are part of the PNS)
Motor Pathways from Brain through Spinal Cord 
•	Axons from cortical motor areas unite to form several white matter tracts; largest of these tracts are:
•	Corticospinal tracts – controls muscles below head and neck via lower motor neurons of spinal nerves
•	Corticonuclear tracts– controls muscles of head and neck via lower motor neurons of cranial nerves
Motor Pathways from Brain through Spinal Cord 
Motor Pathways from Brain through Spinal Cord 
•	Corticonuclear tracts originate from cell bodies of upper motor neurons; travel with corticospinal tracts through corona radiata and internal capsule to brainstem 
•	Fibers of corticonuclear tracts do not enter spinal cord; instead synapse on interneurons that communicate with cranial nerve nuclei at various levels of brainstem, whose lower motor neurons innervate muscles of the head and neck
Motor Pathways from Brain through Spinal Cord 
•	Corticonuclear tracts (continued):
•	Fibers do not decussate, but most cranial nerve nuclei communicate with upper motor neurons from both cerebral hemispheres; damage to upper motor neurons on one side of cerebrum does not lead to noticeable deficits from many cranial nerves
Role of Brain in Voluntary Movement 
Even simple movements require simultaneous firing of countless neurons as part of a selected group of actions called a motor program
•	Execution of motor program requires firing of neurons in motor association areas, firing of upper motor neurons, and input from basal nuclei, cerebellum, spinal cord, and multimodal association areas (such as prefrontal cortex and various sensory areas)
•	Also, firing of lower motor neurons in PNS is necessary
Role of Brain in Voluntary Movement 
•	Role of Cerebral Cortex – majority of upper motor neurons that control complex movements reside in primary motor cortex and premotor and motor association areas
•	Plan and initiate voluntary movement by selecting an appropriate motor program and coordinating sequence of skilled movements
The Cerebrum-Gray Matter 
Role of Brain in Voluntary Movement 
•	Role of Cerebral Cortex (continued):
•	Upper motor neurons are also located in certain nuclei of brainstem; work to maintain posture, balance, and body position especially during locomotion; also produce motor responses to sensory stimuli (such as turning head towards source of a loud noise)
•	Map of upper motor neurons in primary motor cortex and motor homunculus resemble somatosensory map and sensory homunculus 
Role of Brain in Voluntary Movement 
•	Role of Cerebral Cortex (continued):
•	Primary motor cortex is organized somatotopically; certain areas have disproportionately more cortical area devoted to them (especially lips, tongue, and hands); signifies importance of vocalization and manual dexterity to human survival
•	Upper motor neurons in cortical motor areas do not act alone when delivering commands to lower motor neurons; smooth, fluid motion requires input from basal nuclei and cerebellum 
Role of Brain in Voluntary Movement 
Role of Brain in Voluntary Movement 
•	Role of Basal Nuclei – three collections of cell bodies make up basal nuclei: caudate nucleus, globus pallidus, and putamen, complicated interconnections form a circuit between the basal nuclei and other structures of the brain:
•	Substantia nigra of midbrain works very closely with basal nuclei and often grouped with them because of shared functions
•	Basal nuclei modify activity of upper motor neurons to produce voluntary movements and inhibit involuntary, unintentional ones
Role of Brain in Voluntary Movement 
•	Role of Basal Nuclei (continued):
•	A critical function of basal nuclei is to inhibit inappropriate movements:
•	In absence of voluntary movement neurons in globus pallidus fire continuously to inhibit motor nuclei of thalamus
•	This in turn, inhibits upper motor neurons of cortical motor areas from firing at inappropriate times
Role of Brain in Voluntary Movement 
Role of Brain in Voluntary Movement 
•	Role of Basal Nuclei (continued):
•	Initiation of voluntary movement is another critical function of basal nuclei
•	If voluntary movement has been initiated, neurons of caudate nucleus and putamen receive input from cerebral cortex, with which they form excitatory synapses
•	These neurons inhibit globus pallidus neurons from firing; inhibitory effect is enhanced by substantia nigra (increases output of caudate nucleus and putamen) 
•	Overall effect – inhibitor (globus pallidus) is inhibited; allows motor nuclei of thalamus to fire and stimulate upper motor neurons of cerebral cortex; enables motion to begin
Role of Brain in Voluntary Movement 
•	Role of Basal Nuclei (continued):
•	Neurons of substantia nigra are dopaminergic (secrete dopamine); project to caudate nucleus and putamen, and when dopamine binds their receptors, their inhibitory output to the globus pallidus is enhanced. OVERALL EFFECT-  an increase in the eventual activation of the upper motor neurons that will stimulate the desired motor activity
•	Input of substantia nigra is vital for initiating movement
Role of Brain in Voluntary Movement 
Role of Brain in Voluntary Movement 
•	Role of Basal Nuclei (continued):
•	Damage to any component of basal nuclei system results in a movement disorder; two main forms:
•	Inability to initiate voluntary movement, making simple activities such as walking or talking difficult
•	Inability to inhibit inappropriate, involuntary movements; some of which are mild (throat clearing or blinking); others may be severe enough to cause disability
•	One of the more common movement disorders is Parkinson’s disease which we will soon discuss
Role of Brain in Voluntary Movement 
Role of Brain in Voluntary Movement 
•	Role of the Cerebellum – cerebellum monitors ongoing movement and integrates information about contraction and relaxation of muscles, positions of joints, and direction, force, and type of movement that is going to occur next 
•	Once information is integrated, cerebellum determines motor error – difference between intended movement and actual movement that is taking place
Role of Brain in Voluntary Movement 
•	Role of the Cerebellum (continued):
•	Cerebellum then influences different parts of brain to minimize this error; can occur over both short and long term by a process called motor learning
•	Corrections for motor error are added to the motor program over time; more repetition of specific action  more corrections for motor error added to program  more fluid and error-free motion becomes
•	“Practice makes perfect”
Role of Brain in Voluntary Movement 
•	Role of the Cerebellum (continued):
•	Cerebellum receives input from three sources simultaneously: 
•	motor areas of cerebral cortex via upper motor neurons
•	vestibular nuclei of pons
•	 ascending sensory tracts from spinal cord
Role of Brain in Voluntary Movement 
•	Motor areas provide information on intended movement, and vestibular nuclei and ascending tracts supply data on actual movement performed
•	Cerebellar neurons process and integrate input from these sources
•	Cerebellar neurons send output to correct motor error, primarily to upper motor neurons via premotor cortex and primary motor cortex
Role of Brain in Voluntary Movement 
•	Like basal nuclei, cerebellum affects movement by modifying activity of upper motor neurons; cerebellum does not have direct connections with lower motor neurons
•	Damage to cerebellum makes fluid, well-coordinated movements nearly impossible; movements become jerky and inaccurate; called cerebellar ataxia, typically features a wide, staggering gait, difficulty with rapid, alternating motions, overreaching or underreaching for an object, and/or intention tremor (shaking that occurs when attempting to move a body part with accuracy, like reaching for a glass)
Role of Brain in Voluntary Movement 
Parkinson’s Disease
•	One of most common movement disorders; termed hypokinetic (“low movement”) movement disorder, meaning that movement is difficult to initiate and once started, difficult to terminate
•	Symptoms – minimal facial expression, shuffling gait with no arm swing, resting tremor (uncontrollable shaking movements), difficulty swallowing, and rigid movements of arms and legs
Parkinson’s Disease
•	One of most common movement disorders (continued):
•	Cause – degeneration of dopamine-secreting neurons of substantia nigra; degeneration tends to progress slowly over 10–20 years; underlying cause is unknown, but genetics suspected in ~10% of cases
•	Treatment – generally treated by medications that increase level of dopamine in brain; compensate for decreased level
•	https://www.youtube.com/watch?v=sJqKvajUC3k

The Big Picture of CNS Control of Voluntary Movement