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13 PART 1 The Central Nervous System The Central Nervous System • Central nervous system • The brain and spinal cord • Directional terms unique to the CNS • Rostral—toward the nose • Caudal—toward the tail The Brain • Brain controls: • Heart rate, respiratory rate, blood pressure • Autonomic nervous system • Endocrine system • Is involved in innervation of the head through cranial nerves The Brain • Performs the most complex neural functions • Intelligence • Consciousness • Memory • Sensory-motor integration • Emotion • Behavior • Socialization Embryonic Development of the Brain • Brain arises from rostral part of the neural tube • Three primary brain vesicles in 4-week-old embryo • Prosencephalon—the forebrain • Mesencephalon—the midbrain • Rhombencephalon—the hindbrain Embryonic Development of the Brain • Secondary brain vesicles • Prosencephalon • Divides into telencephalon and diencephalon • Mesencephalon—remains undivided • Rhombencephalon • Divides into metencephalon and myelencephalon Embryonic Development of the Brain • Structures of the adult brain • Develop from secondary brain vesicles • • • • Telencephalon the cerebral hemispheres Diencephalon thalamus, hypothalamus, and epithalamus Metencephalon pons and cerebellum Myelencephalon medulla oblongata Embryonic Development of the Brain • Brain stem includes • The midbrain, pons, and medulla oblongata • Ventricles • Central cavity of the neural tube enlarges Embryonic Development of the Brain • Brain grows rapidly • Changes occur in the relative position of its parts • Cerebral hemispheres envelop the diencephalon and midbrain • Wrinkling of the cerebral hemispheres • More neurons fit within limited space Basic Parts and Organization of the Brain • Classified into four regions • Brain stem • Midbrain, pons, and medulla • Cerebellum • Diencephalon • Cerebral hemispheres Basic Parts and Organization of the Brain • Organization • Centrally located gray matter • Externally located white matter • Additional layer of gray matter external to white matter • Due to groups of neurons migrating externally • Cortex—outer layer of gray matter • Formed from neuronal cell bodies • Located in cerebrum and cerebellum Ventricles of the Brain • Expansions of the brain’s central cavity • Filled with cerebrospinal fluid • Lined with ependymal cells • Continuous with each other • Continuous with the central canal of the spinal cord Ventricles of the Brain • Lateral ventricles—located in cerebral hemispheres • Horseshoe-shaped from bending of the cerebral hemispheres • Third ventricle—lies in diencephalon • Connected with lateral ventricles by interventricular foramen Ventricles of the Brain • Cerebral aqueduct—connects 3rd and 4th ventricles • Fourth ventricle—lies in hindbrain • Connects to the central canal of the spinal cord The Brain Stem • Includes the • Midbrain • Pons • Medulla oblongata The Brain Stem • Several general functions • Passageway for all fiber tracts running between the cerebrum and spinal cord • Heavily involved with the innervation of the face and head • 10 of the 12 pairs of cranial nerves attach to it The Brain Stem • General functions, continued • Produces automatic behaviors necessary for survival • Integrates auditory and visual reflexes The Brain Stem—The Medulla Oblongata • Most of the caudal level of the brain stem • Is continuous with the spinal cord • Choroid plexus lies in the roof of the fourth ventricle The Brain Stem—The Medulla Oblongata • External landmarks of medulla • Pyramids of the medulla • Lie on its ventral surface • Decussation of the pyramids • Crossing over of motor tracts • Inferior cerebellar peduncles • Fiber tracts connecting medulla and cerebellum • Olive (olive of the medulla) • Contains inferior olivary nucleus The Brain Stem—The Medulla Oblongata • Four pairs of cranial nerves attach to the medulla oblongata • VIII—vestibulocochlear nerve • IX—glossopharyngeal nerve • X—vagus nerve • XII—hypoglossal nerve The Brain Stem—The Medulla Oblongata • The core of the medulla contains • Much of the reticular formation • Nuclei influence autonomic functions • Visceral centers of the reticular formation include • Cardiac center • Vasomotor center • The medullary respiratory center • Centers for hiccupping, sneezing, swallowing, and coughing The Brain Stem—The Pons • A “bridge” between the midbrain and medulla oblongata • Pons contains the nuclei of cranial nerves • V—trigeminal nerve • VI—abducens nerve • VII—facial nerve The Brain Stem—The Pons • The pons contains • Motor tracts coming from the cerebral cortex • Pontine nuclei • Connect portions of the cerebral cortex and cerebellum • Send axons to cerebellum through the middle cerebellar peduncles The Brain Stem—The Midbrain • Lies between the diencephalon and the pons • Cerebral aqueduct • The central cavity of the midbrain • Cerebral peduncles located on the ventral surface of the brain • Contain pyramidal (corticospinal) tracts • Superior cerebellar peduncles • Connect midbrain to the cerebellum The Brain Stem—The Midbrain • Periaqueductal gray matter surrounds the cerebral aqueduct • Involved in two related functions • Fight-or-flight reaction • Mediates response to visceral pain The Brain Stem—The Midbrain • Corpora quadrigemina • The largest nuclei • Divided into the superior and inferior colliculi • Superior colliculi—nuclei that act in visual reflexes • Inferior colliculi—nuclei that act in reflexive response to sound The Brain Stem—The Midbrain • Embedded in the white matter of the midbrain • Two pigmented nuclei • Substantia nigra—neuronal cell bodies containing melanin • Functionally linked to the basal nuclei • Red nucleus—lies deep to the substantia nigra • Largest nucleus of the reticular formation The Cerebellum • Located dorsal to the pons and medulla • Smoothing and coordinating body movements • Helps maintain equilibrium The Cerebellum • Consists of two cerebellar hemispheres • Surface folded into ridges called folia • Separated by fissures • Hemispheres each subdivided into • Anterior lobe • Posterior lobe • Flocculonodular lobe (tiny) The Cerebellum • Composed of three regions • Cortex—gray matter • Arbor vitae • Internal white matter • Deep cerebellar nuclei—deeply situated gray matter The Cerebellum • To coordinate body movements, the cerebellar cortex receives three types of information • Information on equilibrium • Information on current movements of the limbs, neck, and trunk • Information from the cerebral cortex The Cerebellum • Coordinating movement • The cerebellum receives information on movement from the motor cortex of the cerebrum • The cerebellum compares intended movement with body position • The cerebellum sends instructions back to the cerebral cortex to continuously adjust and fine-tune motor commands The Cerebellum • Higher cognitive functions of the cerebellum • Learning a new motor skill • Participates in cognition • Language, problem solving, task planning The Cerebellum—Cerebellar Peduncles • Thick tracts connecting the cerebellum to the brain stem are • Superior cerebellar peduncles • Middle cerebellar peduncles • Inferior cerebellar peduncles • Fibers to and from the cerebellum are ipsilateral 13 PART 2 The Central Nervous System The Diencephalon • Forms the central core of the forebrain • Surrounded by the cerebral hemispheres • Composed of three paired structures • Thalamus • Hypothalamus • Epithalamus • Border the third ventricle • Primarily composed of gray matter The Diencephalon—The Thalamus • Makes up 80% of the diencephalon • Contains approximately a dozen major nuclei • Act as relay stations for incoming sensory message • Every part of brain communicating with cerebral cortex relays signals through thalamic nuclei! • Send axons to regions of the cerebral cortex The Diencephalon—The Thalamus • Afferent impulses converge on the thalamus • Synapse in at least one of its nuclei • Is the “gateway” to the cerebral cortex • Nuclei organize and amplify or tone down signals The Diencephalon—The Hypothalamus • Lies between the optic chiasm and the mammillary bodies • Pituitary gland projects inferiorly • Contains approximately a dozen nuclei • Main visceral control center of the body The Diencephalon—The Hypothalamus • Functions include the following • Control of the ANS • Control of emotional responses • Regulation of body temperature • Regulation of hunger and thirst sensations • Control of behavior • Regulation of sleep-wake cycles • Control of the endocrine system • Formation of memory The Diencephalon—The Epithalamus • Forms part of the “roof” (top) of the third ventricle • Consists of a tiny group of nuclei • Includes the pineal gland (pineal body) • Secretes the hormone melatonin • Under influence of the hypothalamus • Aids in control of circadian rhythm The Cerebral Hemispheres • Account for 83% of brain mass • Fissures—deep grooves that separate major regions of the brain • Transverse fissure—separates cerebrum and cerebellum • Longitudinal fissure—separates cerebral hemispheres The Cerebral Hemispheres • Sulci • Grooves on the surface of the cerebral hemispheres • Gyri • Twisted ridges between sulci • Prominent gyri and sulci are similar in all people The Cerebral Hemispheres • Deeper sulci divide cerebrum into lobes • Lobes are named for the skull bones overlying them • Central sulcus separates frontal and parietal lobes • Bordered by two gyri • Precentral gyrus • Postcentral gyrus The Cerebral Hemispheres • Parieto-occipital sulcus • Separates the occipital from the parietal lobe • Lateral sulcus • Separates temporal lobe from parietal and frontal lobes • Insula—deep within the lateral sulcus Lobes of the Cerebral Cortex • Frontal lobe • Parietal lobe • Occipital lobe • Temporal lobe • Insula The Cerebral Cortex • Home of our conscious mind • Enables us to • Be aware of ourselves and our sensations • Initiate and control voluntary movements • Communicate, remember, and understand The Cerebral Cortex • Composed of gray matter • Neuronal cell bodies, dendrites, and short axons • Folds in cortex—triples its size • Approximately 40% of brain’s mass • Brodmann areas • 47 structurally distinct areas The Cerebral Cortex • Functional regions • Traditionally studied brain-injured people and animals • New discoveries—PET and fMRI • Regions of the cerebral cortex • Perform distinct motor and sensory functions • Memory and language spread over wide area 13 PART 3 The Central Nervous System The Cerebral Cortex • Three general kinds of functional areas • Sensory areas • Association areas • Motor areas The Cerebral Cortex • There is a sensory area for each of the major senses • A “primary sensory cortex” • Each primary sensory cortex • Has an association area that processes sensory information • Sensory association areas The Cerebral Cortex • Multimodal association areas • Receive and integrate input from multiple regions of the cerebral cortex The Cerebral Cortex • Motor cortex • Plans and initiates voluntary motor functions The Cerebral Cortex—Information Processing • Sensory information received by primary sensory cortex • Information relayed to sensory association area • Multimodal association areas receive input in parallel from sensory areas • Motor plan enacted Sensory Areas • Cortical areas involved in conscious awareness of sensation • Located in • Parietal lobes • Temporal lobes • Occipital lobes • Distinct regions of each lobe interpret each of the major senses Sensory Areas—Primary Somatosensory Cortex • Located along the postcentral gyrus • Involved with conscious awareness of general somatic senses • Spatial discrimination • Precisely locates a stimulus • Certain regions are more adept at distinguishing precise stimuli Sensory Areas—Primary Somatosensory Cortex • Projection is contralateral • Cerebral hemispheres • Receive sensory input from the opposite side of the body • Sensory homunculus • A body map of the sensory cortex Sensory Areas—Somatosensory Association Cortex • Lies posterior to the primary somatosensory cortex • Integrates different sensory inputs • Touch • Pressure • Draws upon stored memories of past sensory experiences • You are able to recognize keys or coins in your pocket without looking at them Sensory Areas—Visual Areas • Primary visual cortex • Location is deep within the calcarine sulcus • On medial part of the occipital lobe • Largest of all sensory areas • Receives visual information that originates on the retina • Exhibits contralateral function • First of a series of areas processing visual input Sensory Areas—Visual Areas • Visual association area • Surrounds the primary visual area • Continues the processing of visual information • Analyzes color, form, and movement • Complex visual processing extends into • Temporal and parietal lobes Sensory Areas—Auditory Areas • Primary auditory cortex • Function • Conscious awareness of sound • Sound waves excite receptors in the inner ear • Impulses transmitted to primary auditory cortex • Location • Superior edge of the temporal lobe Sensory Areas—Auditory Areas • Auditory association area • Lies posterior to the primary auditory cortex • Permits evaluation of different sounds • Processes auditory stimuli serially and in parallel • Posterolateral— “where” pathway • Anterolateral— “what” pathway • Lies in the center of Wernicke’s area • Involved in recognizing and understanding speech Sensory Areas—Vestibular Cortex • Responsible for • Conscious awareness of sense of balance • Located in the posterior part of the insula • Deep to the lateral sulcus Sensory Areas—Gustatory Cortex • Function • Involved in the conscious awareness of taste stimuli • Location • On the “roof” of the lateral sulcus Sensory Areas—Olfactory Cortex • Lies on the medial aspect of the cerebrum • Located in the piriform lobe • Olfactory nerves transmit impulses to the olfactory cortex • Provides conscious awareness of smells Sensory Areas—Olfactory Cortex • Part of the rhinencephalon—“nose brain” • Includes • The piriform lobe, olfactory tracts, and olfactory bulbs • Connects the brain to the limbic system • Explains why smells trigger emotions • Involved with consciously identifying and recalling specific smells Visceral Sensory Areas • Location • Within the lateral sulcus • On the insula lobe • Receives general sensory input • Pain • Pressure • Hunger Motor Areas • Cortical areas controlling motor function • Premotor cortex • Primary motor cortex • Frontal eye field • Broca’s area • All localized in posterior frontal lobe Motor Areas—Premotor Cortex • Located anterior to the precentral gyrus • Controls more complex movements • Receives processed sensory information • Visual, auditory, and general somatic sensory • Controls voluntary actions dependent on sensory feedback • Involved in planning movements Motor Areas—Primary Motor Cortex • Controls motor functions • Primary motor cortex (somatic motor area) • Located in precentral gyrus • Pyramidal cells • Large neurons of primary motor cortex Motor Areas—Primary Motor Cortex • Corticospinal tracts descend through brain stem and spinal cord • Axons signal motor neurons to control skilled movements • Contralateral • Pyramidal axons cross over to opposite side of the brain Motor Areas • Specific pyramidal cells control specific areas of the body • Face and hand muscles are controlled by many pyramidal cells • Somatotopy • Body is represented spatially in the primary motor cortex Motor Areas—Frontal Eye Field • Lies anterior to the premotor cortex • Controls voluntary movement of the eyes • Especially when moving eyes to follow a moving target Motor Areas—Broca’s Area • Located in left cerebral hemisphere • Manages speech production • Connected to language comprehension areas in posterior association area • A corresponding region in the right cerebral hemisphere controls emotional overtones to spoken words Multimodal Association Areas • Large areas of the cerebral cortex • Receive sensory input from • Multiple sensory modalities • Sensory association areas • Make associations between kinds of sensory information Multimodal Association Areas • Three multimodal association areas • Posterior association area • Anterior association area • Limbic association area Posterior Association Area • Located at interface of visual, auditory, and somatosensory association areas • Integrates sensory information into unified perception • Allows awareness of spatial location of body • “Body sense” • Related to language comprehension and speech Posterior Association Area • Dorsal stream • Extends to the postcentral gyrus • Perceives information about spatial relationships • “Where” pathway—location of objects • Ventral stream • Passes information into inferior part of the temporal lobe • Responsible for recognizing objects, words, and faces • “What” pathway—identifies objects Auditory Pathways • Auditory stimuli processed in two streams • From auditory association area through multimodal association areas • Parietal lobe and lateral part of frontal lobe—evaluate location of sound stimulus • “Where” pathway • Anterior region of temporal lobe and inferior region of frontal lobe—process sound identification • “What” pathway Posterior Association Area • Multiple language areas in left cerebral cortex • Wernicke’s area functions in • Speech comprehension • Coordination of auditory and visual aspects of language • Initiation of word articulation • Recognition of sound sequences Posterior Association Area • Areas in right cerebral hemisphere act in • Creative interpretation of words • Emotional overtones of speech Anterior Association Area • A large region of the frontal lobe • The prefrontal cortex • Receives information from posterior association area • Integrates information with past experience • Initiates and plans motor movements • Has links to the limbic system Anterior Association Areas • More complex functions include all aspects of • Thinking, perceiving, intentionally remembering • Processing abstract ideas, reasoning, judgment • Impulse control, mental flexibility, social skills • Humor, empathy, conscience Anterior Association Area • Functional neuroimaging techniques • Reveal functions of specific parts of the prefrontal cortex • Anterior pole of frontal cortex • Active in solving the most complex problems • More complex problems, emotions, cognition at anterior part of frontal lobe Anterior Association Area • Additional functions • Stores information for less than 30 seconds • Three working memory areas • Visual working memory • Auditory working memory • Executive area Limbic Association Areas • Located on medial side of frontal lobe • Involved with memory and emotions • Integrates sensory and motor behaviors • Aids in the formation of memory • Processes emotions Lateralization of Cortical Functioning • The two hemispheres control opposite sides of the body • Contralateral opposite side • Hemispheres are specialized for different cognitive functions Lateralization of Cortical Functioning • Left cerebral hemisphere—control over • Language abilities, math, and logic • Right cerebral hemisphere—involved with • Visual-spatial skills • Reading facial expressions • Intuition, emotion, artistic and musical skills 13 PART 4 The Central Nervous System Cerebral White Matter • Different areas of the cerebral cortex • Communicate with each other • Communicate with the brain stem and spinal cord • Fibers communicating are • Usually myelinated and bundled into tracts Cerebral White Matter • Types of tracts • Commissures—composed of commissural fibers • Allows communication between cerebral hemispheres • Corpus callosum—the largest commissure • Association fibers • Connect different parts of the same hemisphere • Parts of Wernike’s and Broca’s areas are connected by association fibers Cerebral White Matter • Types of tracts (continued) • Projection fibers—run vertically • Descend from the cerebral cortex • Ascend to the cortex from lower regions • Corticospinal tracts begin with pyramidal cells Projection Tracts • Internal capsule—projection fibers form a compact bundle • Passes between the thalamus and basal nuclei • Corona radiata—superior to the internal capsule • Fibers run to and from the cerebral cortex 13 PART 5 The Central Nervous System Deep Gray Matter of the Cerebrum • Consists of • Basal nuclei (basal ganglia) • Involved in motor control • Basal forebrain nuclei • Associated with memory • Claustrum • A nucleus of unknown function • Amygdaloid body • Located in cerebrum but is considered part of the of the limbic system Basal Nuclei • A group of nuclei deep within the cerebral white matter • Formed from • Caudate nucleus—arches over thalamus • Putamen • Globus pallidus Basal Ganglia • • • Complex neural calculators • Cooperate with the cerebral cortex in controlling movement Receive input from many cortical areas Substantia nigra also influences basal ganglia Basal Nuclei • Evidence shows that they • Start, stop, and regulate intensity of voluntary movements • Select appropriate muscles for a task and inhibit others • In some way estimate the passage of time Basal Forebrain Nuclei • Structures composing basal forebrain nuclei • Septum • Diagonal band of Broca • Horizontal band of Broca • Basal nucleus of Meynert Basal Forebrain Nuclei • Part of cholinergic system • That is, they synthesize and release acetylcholine • Location • Anterior and dorsal to hypothalamus • Functions related to • Arousal • Learning • Memory • Motor control • Degeneration of basal forebrain nuclei • Associated with Alzheimer’s disease 13 PART 6 The Central Nervous System Functional Brain Systems • Networks of neurons functioning together • Limbic system • Spread widely in the forebrain • The reticular formation • Spans the brain stem Functional Brain Systems—The Limbic System • Location • Medial aspect of cerebral hemispheres • Also within the diencephalon • • Composed of • Septal nuclei, cingulate gyrus, and hippocampal formation • Part of the amygdaloid body The fornix and other tracts link the limbic system together Functional Brain Systems—The Limbic System • The “emotional brain” • Cingulate gyrus • Allows us to shift between thoughts • Interprets pain as unpleasant • Hippocampal formation • Hippocampus and the parahippocampal gyrus Functional Brain Systems—The Reticular Formation • Runs through the central core of the medulla, pons, and midbrain • Forms three columns • Midline raphe nuclei • Medial nuclear group • Lateral nuclear group Functional Brain Systems—The Reticular Formation • Widespread connections • Ideal for arousal of the brain as a whole • Reticular activating system (RAS) • Maintains consciousness and alertness • Functions in sleep and arousal from sleep • Malfunctions in people with narcolepsy Protection of the Brain • The brain is protected from injury by • The skull • Meninges • Cerebrospinal fluid • Blood brain barrier Protection of the Brain—Meninges • Functions of meninges • Cover and protect the CNS • Enclose and protect the vessels that supply the CNS • Contain the cerebrospinal fluid • Between pia and arachnoid maters The Dura Mater • Strongest of the meninges • Composed of two layers • Periosteal layer • Meningeal layer • Two layers are fused except to enclose the dural sinuses The Dura Mater • Largest sinus—the superior sagittal sinus • Dura mater extends inward to subdivide the cranial cavity The Arachnoid Mater • Located beneath the dura mater • Arachnoid villi • Project through the dura mater • Allow CSF to pass into the dural blood sinuses The Pia Mater • Delicate connective tissue • Clings tightly to the surface of the brain • Follows all convolutions of the cortex 13 PART 7 The Central Nervous System Cerebrospinal Fluid (CSF) • Formed in choroid plexuses in the brain ventricles • Choroid plexus is • Located in all four ventricles • Composed of ependymal cells and capillaries • Arises from blood • 500 ml produced per day • Only 100–160 ml present at any one time Blood-Brain Barrier • Prevents most blood borne toxins from entering the brain • Impermeable capillaries • Not an absolute barrier • Nutrients such as oxygen pass through • Allows passage of alcohol, nicotine, and anesthetics The Spinal Cord • Functions of • Spinal nerves attach to it • Provides two-way conduction pathway • Major center for reflexes • Location • Runs through the vertebral canal • Extends from the foramen magnum to the level of the vertebra L1 or L2 The Spinal Cord • Conus medullaris • The inferior end of the spinal cord • Filum terminale • Long filament of connective tissue • Attaches to the coccyx inferiorly • Cervical and lumbar enlargements • Where nerves for upper and lower limbs arise • Cauda equina • Collection of spinal nerve roots The Spinal Cord • Spinal cord segments • Indicate the region of the spinal cord from which spinal nerves emerge • Designated by the spinal nerve that issues from it • T1 is the region where the first thoracic nerve emerges The Spinal Cord • Two deep grooves run the length of the cord • Posterior median sulcus • Anterior median fissure White Matter of the Spinal Cord • Outer region of the spinal cord • Composed of myelinated and nonmyelinated axons • Allow communication between spinal cord and brain • Fibers classified by type • Ascending fibers • Descending fibers • Commissural fibers Gray Matter of the Spinal Cord and Spinal Roots • Shaped like the letter “H” • Gray commissure—contains the central canal • Dorsal horns • Consist of interneurons • Ventral and lateral horns • Contain cell bodies of motor neurons Gray Matter of the Spinal Cord • Gray matter is primarily neuronal cell bodies and some nonmyelinated axons • Regions of gray matter • Gray commissure • Dorsal horns • Ventral horns • Lateral horns Gray Matter of the Spinal Cord • Gray matter • Divided according to somatic and visceral regions • SS—somatic sensory • VS—visceral sensory • VM—visceral motor • SM—somatic motor Protection of the Spinal Cord • Protected by vertebrae, meninges, and CSF • Meninges • Dura mater—a single layer surrounding spinal cord • Arachnoid mater—lies deep to the dura mater • Pia mater—innermost layer • Delicate layer of connective tissue • Extends to the coccyx • Denticulate ligaments—lateral extensions of pia mater Cerebrospinal Fluid • Fills the hollow cavities of the brain and spinal cord • Provides a liquid cushion for the spinal cord and brain • Other functions • Nourishes brain and spinal cord • Removes wastes • Carries chemical signals between parts of the CNS Sensory and Motor Pathways in the CNS • Multineuron pathways connect brain and body periphery • Pathways are composed of tracts • Ascending pathways—carry information to more rostral areas of the CNS • Descending pathways—carry information to more caudal regions of the CNS Ascending Pathways • Conduct general somatic sensory impulses • Chains of neurons composed of • First-, second-, and third-order neurons • Four main ascending pathways • Dorsal column pathway • Spinothalamic pathway • Posterior spinocerebellar pathway • Anterior spinocerebellar pathway Descending Pathways • Most motor pathways • Decussate at some point along their course • • • Consist of a chain of two or three neurons Exhibit somatotopy • Tracts arranged according to the body region they supply All pathways are paired • One of each on each side of the body Descending Pathways • Deliver motor instructions from the brain to the spinal cord • Divided into two groups • Pyramidal (corticospinal) tracts • Other motor pathways • Tectospinal tracts • Vestibulospinal tract • Rubrospinal tract • Reticulospinal tract Disorders of the Central Nervous System • Spinal cord damage • Paralysis—loss of motor function • Parasthesia—loss of sensation • Paraplegia—injury to the spinal cord is between T1 and L2 • Paralysis of the lower limbs • Quadriplegia—injury to the spinal cord in the cervical region • Paralysis of all four limbs Disorders of the Central Nervous System • Brain dysfunction • Degenerative brain diseases • Cerebrovascular accident (stroke) • Blockage or interruption of blood flow to a brain region • Alzheimer’s disease • Progressive degenerative disease leading to dementias Disorders of the Central Nervous System • Congenital malformations • Hydrocephalus • Neural tube defects • Anencephaly—cerebrum and cerebellum are absent • Spina bifida—absence of vertebral lamina • Cerebral palsy—voluntary muscles are poorly controlled • Results from damage to the motor cortex Postnatal Changes in the Brain • Brain structures complete development at different times • Critical periods in learning • Language • • Some development occurs into early 20s Decline with age attributed to changes • In neural circuitry • Amount of neurotransmitters being released