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PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community Ninth Edition College Human Anatomy & Physiology CHAPTER 12 The Central Nervous System: Part A © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. Central Nervous System (CNS) • CNS consists of brain and spinal cord • Cephalization – Evolutionary development of rostral (anterior) portion of CNS – Increased number of neurons in head – Highest level reached in human brain © 2013 Pearson Education, Inc. Embryonic Development • Brain and spinal cord begin as neural tube • 3 primary vesicles form at anterior end – Prosencephalon or forebrain – Mesencephalon or midbrain – Rhombencephalon or hindbrain • Posterior end becomes spinal cord © 2013 Pearson Education, Inc. Embryonic Development • Primary vesicles 5 secondary brain vesicles – Forebrain telencephalon and diencephalon – Midbrain remains undivided – Hindbrain metencephalon and myelencephalon © 2013 Pearson Education, Inc. Figure 12.1 Embryonic development of the human brain. Neural tube (contains neural canal) Anterior (rostral) Primary brain vesicles Secondary brain vesicles Adult brain structures Cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei) Lateral ventricles Telencephalon Prosencephalon (forebrain) Diencephalon (thalamus, hypothalamus, epithalamus), retina Third ventricle Diencephalon Mesencephalon (midbrain) Mesencephalon Brain stem: midbrain Cerebral aqueduct Metencephalon Brain stem: pons Rhombencephalon (hindbrain) Cerebellum Myelencephalon Posterior (caudal) © 2013 Pearson Education, Inc. Adult neural canal regions Fourth ventricle Brain stem: medulla oblongata Spinal cord Central canal Figure 12.2a Brain development. Anterior (rostral) Metencephalon Mesencephalon Diencephalon Telencephalon Myelencephalon Posterior (caudal) Midbrain Cervical Flexures Spinal cord Week 5: Two major flexures form, causing the telencephalon and diencephalon to angle toward the brain stem. © 2013 Pearson Education, Inc. Figure 12.2b Brain development. Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Pons Medulla oblongata Spinal cord Week 13: Cerebral hemispheres develop and grow posterolaterally to enclose the diencephalon and the rostral brain stem. © 2013 Pearson Education, Inc. Regions and Organization • Adult brain regions 1. 2. 3. 4. Cerebral hemispheres Diencephalon Brain stem (midbrain, pons, and medulla) Cerebellum © 2013 Pearson Education, Inc. Figure 12.2c Brain development. Cerebral hemisphere Diencephalon Cerebellum Brain stem • Midbrain • Pons • Medulla oblongata Birth: Shows adult pattern of structures and convolutions. © 2013 Pearson Education, Inc. Regions and Organization of the CNS • Spinal cord – Central cavity surrounded by gray matter – External white matter composed of myelinated fiber tracts © 2013 Pearson Education, Inc. Regions and Organization of the CNS • Brain – Similar pattern – Additional areas of gray matter in brain – Cerebral hemispheres and cerebellum • Outer gray matter called cortex – Cortex disappears in brain stem • Scattered gray matter nuclei amid white matter © 2013 Pearson Education, Inc. Ventricles of the Brain • Filled with cerebrospinal fluid (CSF) • Lined by ependymal cells • Connected to one another and to central canal of spinal cord – Lateral ventricles third ventricle via interventricular foramen – Third ventricle fourth ventricle via cerebral aqueduct © 2013 Pearson Education, Inc. Ventricles of the Brain • Paired, C-shaped lateral ventricles in cerebral hemispheres – Separated anteriorly by septum pellucidum • Third ventricle in diencephalon • Fourth ventricle in hindbrain – Three openings: paired lateral apertures in side walls; median aperture in roof • Connect ventricles to subarachnoid space © 2013 Pearson Education, Inc. Figure 12.3 Ventricles of the brain. Lateral ventricle Anterior horn Interventricular foramen Septum pellucidum Inferior horn Posterior horn Third ventricle Inferior horn Median aperture Cerebral aqueduct Lateral aperture Fourth ventricle Lateral aperture Central canal Anterior view © 2013 Pearson Education, Inc. Left lateral view Cerebral Hemispheres • Surface markings – Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) – Longitudinal fissure • Separates two hemispheres – Transverse cerebral fissure • Separates cerebrum and cerebellum © 2013 Pearson Education, Inc. Cerebral Hemispheres • Five lobes – Frontal – Parietal – Temporal – Occipital – Insula PLAY Animation: Rotatable brain © 2013 Pearson Education, Inc. Cerebral Hemispheres • Central sulcus – Separates precentral gyrus of frontal lobe and postcentral gyrus of parietal lobe • Parieto-occipital sulcus – Separates occipital and parietal lobes • Lateral sulcus outlines temporal lobes © 2013 Pearson Education, Inc. Cerebral Hemispheres • Three basic regions – Cerebral cortex of gray matter superficially – White matter internally – Basal nuclei deep within white matter © 2013 Pearson Education, Inc. Figure 12.4c Lobes, sulci, and fissures of the cerebral hemispheres. Precentral gyrus Frontal lobe Central sulcus Postcentral gyrus Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Fissure (a deep sulcus) Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Medulla oblongata Spinal cord Gyrus Cortex (gray matter) Sulcus White matter Lobes and sulci of the cerebrum © 2013 Pearson Education, Inc. Figure 12.4d Lobes, sulci, and fissures of the cerebral hemispheres. Frontal lobe Central sulcus Gyri of insula Temporal lobe (pulled down) Location of the insula lobe © 2013 Pearson Education, Inc. Figure 12.4a Lobes, sulci, and fissures of the cerebral hemispheres. Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Left cerebral hemisphere Right cerebral hemisphere Occipital lobe Posterior Superior view © 2013 Pearson Education, Inc. Figure 12.4b Lobes, sulci, and fissures of the cerebral hemispheres. Left cerebral hemisphere Brain stem Transverse cerebral fissure Cerebellum Left lateral view © 2013 Pearson Education, Inc. Cerebral Cortex • Thin (2–4 mm) superficial layer of gray matter • 40% mass of brain • Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding © 2013 Pearson Education, Inc. 4 General Considerations of Cerebral Cortex 1. Three types of functional areas – Motor areas—control voluntary movement – Sensory areas—conscious awareness of sensation – Association areas—integrate diverse information 2. Each hemisphere concerned with contralateral side of body © 2013 Pearson Education, Inc. 4 General Considerations of Cerebral Cortex 3. Lateralization of cortical function in hemispheres 4. Conscious behavior involves entire cortex in some way © 2013 Pearson Education, Inc. Figure 12.5 Functional neuroimaging (fMRI) of the cerebral cortex. Longitudinal fissure © 2013 Pearson Education, Inc. Left frontal lobe Left temporal lobe Central sulcus Areas active in speech and hearing (fMRI) Motor Areas of Cerebral Cortex • In frontal lobe; control voluntary movement • Primary (somatic) motor cortex in precentral gyrus • Premotor cortex anterior to precentral gyrus • Broca's area anterior to inferior premotor area • Frontal eye field within and anterior to premotor cortex; superior to Broca's area © 2013 Pearson Education, Inc. Figure 12.6a Functional and structural areas of the cerebral cortex. Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca's area (outlined by dashes) Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Gustatory cortex (in insula) Prefrontal cortex Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems Wernicke's area (outlined by dashes) Primary visual cortex Visual association area Auditory association area Primary auditory cortex Lateral view, left cerebral hemisphere Primary motor cortex © 2013 Pearson Education, Inc. Taste Motor association cortex Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Figure 12.7 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum. Posterior Motor Sensory Anterior Hip Trunk Neck Motor map in precentral gyrus Sensory map in postcentral gyrus Foot Knee Toes Genitals Jaw Tongue Swallowing © 2013 Pearson Education, Inc. Primary motor cortex (precentral gyrus) Primary somatosensory cortex (postcentral gyrus) Intraabdominal Broca's Area • Present in one hemisphere (usually the left) • Motor speech area that directs muscles of speech production • Active in planning speech and voluntary motor activities © 2013 Pearson Education, Inc. Frontal Eye Field • Controls voluntary eye movements © 2013 Pearson Education, Inc. Figure 12.6a Functional and structural areas of the cerebral cortex. Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca's area (outlined by dashes) Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Gustatory cortex (in insula) Prefrontal cortex Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems Wernicke's area (outlined by dashes) Primary visual cortex Visual association area Auditory association area Primary auditory cortex Lateral view, left cerebral hemisphere Primary motor cortex © 2013 Pearson Education, Inc. Taste Motor association cortex Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Figure 12.6b Functional and structural areas of the cerebral cortex. Premotor cortex Cingulate Primary gyrus motor cortex Corpus callosum Central sulcus Primary somatosensory cortex Frontal eye field Parietal lobe Somatosensory association cortex Parieto-occipital sulcus Prefrontal cortex Occipital lobe Processes emotions related to personal and social interactions Visual association area Orbitofrontal cortex Olfactory bulb Olfactory tract Fornix Temporal lobe Primary olfactory cortex Parasagittal view, right cerebral hemisphere Primary motor cortex © 2013 Pearson Education, Inc. Motor association cortex Primary sensory cortex Uncus Calcarine sulcus Parahippocampal gyrus Sensory association cortex Primary visual cortex Multimodal association cortex Sensory Areas of Cerebral Cortex • Conscious awareness of sensation • Occur in parietal, insular, temporal, and occipital lobes • Primary somatosensory cortex • Somatosensory association cortex • Visual areas • Auditory areas © 2013 Pearson Education, Inc. • • • • Vestibular cortex Olfactory cortex Gustatory cortex Visceral sensory area Figure 12.7b Body maps in the primary motor cortex and somatosensory cortex of the cerebrum. Posterior Sensory Neck Hip Trunk Anterior Sensory map in postcentral gyrus Foot Genitals Primary somatosensory cortex (postcentral gyrus) © 2013 Pearson Education, Inc. Intraabdominal Visual Areas • Primary visual (striate) cortex – Extreme posterior tip of occipital lobe – Most buried in calcarine sulcus of occipital lobe – Receives visual information from retinas © 2013 Pearson Education, Inc. Visual Areas • Visual association area – Surrounds primary visual cortex – Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement) • E.g., ability to recognize faces – Complex processing involves entire posterior half of cerebral hemispheres © 2013 Pearson Education, Inc. Auditory Areas • Primary auditory cortex – Superior margin of temporal lobes – Interprets information from inner ear as pitch, loudness, and location • Auditory association area – Located posterior to primary auditory cortex – Stores memories of sounds and permits perception of sound stimulus © 2013 Pearson Education, Inc. PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community Ninth Edition College Human Anatomy & Physiology CHAPTER 12 The Central Nervous System: Part B © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. Lateralization of Cortical Function • Hemispheres almost identical • Lateralization - division of labor between hemispheres • Cerebral dominance - hemisphere dominant for language (left hemisphere 90% people) © 2013 Pearson Education, Inc. Lateralization of Cortical Function • Left hemisphere – Controls language, math, and logic • Right hemisphere – Visual-spatial skills, intuition, emotion, and artistic and musical skills • Hemispheres communicate almost instantaneously via fiber tracts and functional integration © 2013 Pearson Education, Inc. Diencephalon • Three paired structures – Thalamus – Hypothalamus – Epithalamus • Encloses third ventricle PLAY Animation: Rotatable brain (sectioned) © 2013 Pearson Education, Inc. Figure 12.10a Midsagittal section of the brain. Cerebral hemisphere Corpus callosum Fornix Choroid plexus Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Thalamus (encloses third ventricle) Posterior commissure Pineal gland Interventricular foramen Anterior commissure Hypothalamus Optic chiasma Corpora quadrigemina Midbrain Cerebral aqueduct Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord © 2013 Pearson Education, Inc. Epithalamus Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Thalamic Function • Gateway to cerebral cortex • Sorts, edits, and relays ascending input – Impulses from hypothalamus for regulation of emotion and visceral function – Impulses from cerebellum and basal nuclei to help direct motor cortices – Impulses for memory or sensory integration • Mediates sensation, motor activities, cortical arousal, learning, and memory © 2013 Pearson Education, Inc. Hypothalamic Function • Controls autonomic nervous system (e.g., blood pressure, rate and force of heartbeat, digestive tract motility, pupil size) • Physical responses to emotions (limbic system) – Perception of pleasure, fear, and rage, and in biological rhythms and drives © 2013 Pearson Education, Inc. Hypothalamic Function • Regulates body temperature – sweating/shivering • Regulates hunger and satiety in response to nutrient blood levels or hormones • Regulates water balance and thirst © 2013 Pearson Education, Inc. Hypothalamic Function • Regulates sleep-wake cycles – Suprachiasmatic nucleus (biological clock) • Controls endocrine system – Controls secretions of anterior pituitary gland – Produces posterior pituitary hormones © 2013 Pearson Education, Inc. Epithalamus • Most dorsal portion of diencephalon; forms roof of third ventricle • Pineal gland (body)—extends from posterior border and secretes melatonin – Melatonin—helps regulate sleep-wake cycle © 2013 Pearson Education, Inc. Brain Stem • Three regions – Midbrain – Pons – Medulla oblongata © 2013 Pearson Education, Inc. Brain Stem • Similar structure to spinal cord but contains nuclei embedded in white matter • Controls automatic behaviors necessary for survival • Contains fiber tracts connecting higher and lower neural centers • Nuclei associated with 10 of the 12 pairs of cranial nerves © 2013 Pearson Education, Inc. Figure 12.12 Inferior view of the brain, showing the three parts of the brain stem: midbrain, pons, and medulla oblongata. Frontal lobe Olfactory bulb (synapse point of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Mammillary body Midbrain Pons Temporal lobe Medulla oblongata Cerebellum Spinal cord © 2013 Pearson Education, Inc. Cerebellum • 11% of brain mass • Dorsal to pons and medulla • Input from cortex, brain stem and sensory receptors • Allows smooth, coordinated movements © 2013 Pearson Education, Inc. Anatomy of Cerebellum • Cerebellar hemispheres connected by vermis • Folia—transversely oriented gyri • Each hemisphere has three lobes – Anterior, posterior, and flocculonodular • Arbor vitae—treelike pattern of cerebellar white matter © 2013 Pearson Education, Inc. Figure 12.15a Cerebellum. Anterior lobe Arbor vitae Cerebellar cortex Pons Fourth ventricle Medulla oblongata © 2013 Pearson Education, Inc. Posterior lobe Flocculonodular lobe Choroid plexus PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community Ninth Edition College Human Anatomy & Physiology CHAPTER 12 The Central Nervous System: Part C © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. Functional Brain Systems • Networks of neurons that work together but span wide areas of brain – Limbic system – Reticular formation © 2013 Pearson Education, Inc. Brain Wave Patterns and the EEG • EEG = electroencephalogram • Records electrical activity that accompanies brain function • Measures electrical potential differences between various cortical areas © 2013 Pearson Education, Inc. Figure 12.18 Electroencephalography (EEG) and brain waves. 1-second interval Alpha waves—awake but relaxed Beta waves—awake, alert Theta waves—common in children Delta waves—deep sleep Scalp electrodes are used to record brain wave activity. © 2013 Pearson Education, Inc. Brain waves shown in EEGs fall into four general classes. Brain Waves • • • • Patterns of neuronal electrical activity Generated by synaptic activity in cortex Each person's brain waves are unique Can be grouped into four classes based on frequency measured as hertz (Hz) – Alpha, beta, theta, and delta waves © 2013 Pearson Education, Inc. Epilepsy • Victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking • Epilepsy not associated with intellectual impairments • Epilepsy occurs in 1% of population • Aura (sensory hallucination) may precede seizure © 2013 Pearson Education, Inc. Epileptic Seizures • Absence seizures (formerly petit mal) – Mild seizures of young children - expression goes blank for few seconds • Tonic-clonic (formerly grand mal) seizures – Most severe; last few minutes – Victim loses consciousness, bones broken during intense convulsions, loss of bowel and bladder control, and severe biting of tongue © 2013 Pearson Education, Inc. Consciousness • Conscious perception of sensation • Voluntary initiation and control of movement • Capabilities associated with higher mental processing (memory, logic, judgment, etc.) • Loss of consciousness signal that brain function impaired – Fainting or syncopy – brief – Coma – extended period © 2013 Pearson Education, Inc. Sleep and Sleep-Wake Cycles • State of partial unconsciousness from which person can be aroused by stimulation • Two major types of sleep (defined by EEG patterns) – Non-rapid eye movement (NREM) sleep – Rapid eye movement (REM) sleep © 2013 Pearson Education, Inc. Importance of Sleep • Slow-wave sleep (NREM stages 3 and 4) presumed to be restorative stage • People deprived of REM sleep become moody and depressed • REM sleep may be reverse learning process where superfluous information purged from brain • Daily sleep requirements decline with age • Stage 4 sleep declines steadily and may disappear after age 60 © 2013 Pearson Education, Inc. Sleep Disorders • Narcolepsy – Abrupt lapse into sleep from awake state – Often have cataplexy • Sudden loss of voluntary muscle control – Orexins ("wake-up" chemicals from hypothalamus) destroyed by immune system • Key to possible treatment © 2013 Pearson Education, Inc. Sleep Disorders • Insomnia – Chronic inability to obtain amount or quality of sleep needed – May be treated by blocking orexin action • Sleep apnea – Temporary cessation of breathing during sleep – Causes hypoxia © 2013 Pearson Education, Inc. Memory • Storage and retrieval of information • Two stages of storage – Short-term memory (STM, or working memory)—temporary holding of information; limited to seven or eight pieces of information – Long-term memory (LTM) has limitless capacity © 2013 Pearson Education, Inc. Protection of the Brain • • • • Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood brain barrier © 2013 Pearson Education, Inc. Meninges • Cover and protect CNS • Protect blood vessels and enclose venous sinuses • Contain cerebrospinal fluid (CSF) • Form partitions in skull © 2013 Pearson Education, Inc. Meninges • Three layers – Dura mater – Arachnoid mater – Pia mater • Meningitis – Inflammation of meninges © 2013 Pearson Education, Inc. Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater. Skin of scalp Periosteum Superior sagittal sinus Subdural space Subarachnoid space © 2013 Pearson Education, Inc. Bone of skull Dura mater • Periosteal layer • Meningeal layer Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) Dura Mater • Strongest meninx • Two layers of fibrous connective tissue (around brain) separate to form dural venous sinuses © 2013 Pearson Education, Inc. Figure 12.23b Dural septa and dural venous sinuses. Superior sagittal sinus Falx cerebri Parietal bone Scalp Occipital lobe Tentorium cerebelli Falx cerebelli Cerebellum Arachnoid mater over medulla oblongata Posterior dissection © 2013 Pearson Education, Inc. Dura mater Transverse sinus Temporal bone Arachnoid Mater • Middle layer with weblike extensions • Separated from dura mater by subdural space • Subarachnoid space contains CSF and largest blood vessels of brain • Arachnoid villi protrude into superior sagittal sinus and permit CSF reabsorption © 2013 Pearson Education, Inc. Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater. Skin of scalp Periosteum Superior sagittal sinus Subdural space Subarachnoid space © 2013 Pearson Education, Inc. Bone of skull Dura mater • Periosteal layer • Meningeal layer Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) Pia Mater • Delicate vascularized connective tissue that clings tightly to brain © 2013 Pearson Education, Inc. Cerebrospinal Fluid (CSF) • Composition – Watery solution formed from blood plasma • Less protein and different ion concentrations than plasma – Constant volume © 2013 Pearson Education, Inc. Cerebrospinal Fluid (CSF) • Functions – Gives buoyancy to CNS structures • Reduces weight by 97% – Protects CNS from blows and other trauma – Nourishes brain and carries chemical signals © 2013 Pearson Education, Inc. Figure 12.24a Formation, location, and circulation of CSF. Slide 1 4 Superior sagittal sinus Arachnoid villus Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Interventricular foramen Third ventricle Right lateral ventricle (deep to cut) 3 Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord (a) CSF circulation © 2013 Pearson Education, Inc. Choroid plexus of fourth ventricle 2 1 The choroid plexus of each Ventricle produces CSF. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. Choroid Plexuses • Hang from roof of each ventricle; produce CSF at constant rate; keep in motion – Clusters of capillaries enclosed by pia mater and layer of ependymal cells • Ependymal cells use ion pumps to control composition of CSF and help cleanse CSF by removing wastes • Normal volume ~ 150 ml; replaced every 8 hours © 2013 Pearson Education, Inc. Hydrocephalus • Obstruction blocks CSF circulation or drainage • Unfused skull bones of newborn allow enlargement of head • Brain damage in adult due to rigid adult skull • Treated by draining with ventricular shunt to abdominal cavity © 2013 Pearson Education, Inc. Figure 12.25 Hydrocephalus in a newborn. © 2013 Pearson Education, Inc. Blood Brain Barrier • Helps maintain stable environment for brain • Separates neurons from some bloodborne substances © 2013 Pearson Education, Inc. Blood Brain Barrier: Functions • Selective barrier – Allows nutrients to move by facilitated diffusion – Metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, K+ denied – Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics • Absent in some areas, e.g., vomiting center and hypothalamus, where necessary to monitor chemical composition of blood © 2013 Pearson Education, Inc. Homeostatic Imbalances of the Brain • Traumatic brain injuries – Concussion—temporary alteration in function – Contusion—permanent damage – Subdural or subarachnoid hemorrhage— may force brain stem through foramen magnum, resulting in death – Cerebral edema—swelling of brain associated with traumatic head injury © 2013 Pearson Education, Inc. Homeostatic Imbalances of the Brain • Cerebrovascular accidents (CVAs or strokes) – Ischemia • Tissue deprived of blood supply; brain tissue dies, e.g., blockage of cerebral artery by blood clot – Hemiplegia (paralysis on one side), or sensory and speech deficits – Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia – Tissue plasminogen activator (TPA) is only approved treatment for stroke © 2013 Pearson Education, Inc. Homeostatic Imbalances of the Brain • Degenerative brain disorders – Alzheimer's disease (AD): a progressive degenerative disease of brain that results in dementia • Memory loss, short attention span, disorientation, eventual language loss, irritable, moody, confused, hallucinations • Plaques of beta-amyloid peptide form in brain – Toxic effects may involve prion proteins • Neurofibrillary tangles inside neurons kill them • Brain shrinks © 2013 Pearson Education, Inc. Homeostatic Imbalances of the Brain • Parkinson's disease – Degeneration of dopamine-releasing neurons of substantia nigra – Basal nuclei deprived of dopamine become overactive tremors at rest – Cause unknown • Mitochondrial abnormalities or protein degradation pathways? – Treatment with L-dopa; deep brain stimulation; gene therapy; research into stem cell transplants promising © 2013 Pearson Education, Inc. Homeostatic Imbalances of the Brain • Huntington's disease – Fatal hereditary disorder – Caused by accumulation of protein huntingtin • Leads to degeneration of basal nuclei and cerebral cortex • Initial symptoms wild, jerky "flapping" movements • Later marked mental deterioration • Treated with drugs that block dopamine effects • Stem cell implant research promising © 2013 Pearson Education, Inc. PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community Ninth Edition College Human Anatomy & Physiology CHAPTER 12 The Central Nervous System: Part D © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. Spinal Cord: Gross Anatomy and Protection • Location – Begins at the foramen magnum – Ends at L1 or L2 vertebra • Functions – Provides two-way communication to and from brain – Contains spinal reflex centers © 2013 Pearson Education, Inc. Spinal Cord: Gross Anatomy and Protection • Bone, meninges, and CSF • Epidural space – Cushion of fat and network of veins in space between vertebrae and spinal dura mater • CSF in subarachnoid space • Dural and arachnoid membranes extend to sacrum, beyond end of cord at L1 or L2 – Site of lumbar puncture or tap © 2013 Pearson Education, Inc. Spinal Cord: Gross Anatomy and Protection • Terminates in conus medullaris • Filum terminale extends to coccyx – Fibrous extension of conus covered with pia mater – Anchors spinal cord • Denticulate ligaments – Extensions of pia mater that secure cord to dura mater © 2013 Pearson Education, Inc. Figure 12.27 Diagram of a lumbar tap. T12 L5 Ligamentum flavum Lumbar puncture needle entering subarachnoid space L4 Supraspinous ligament Filum terminale L5 S1 Intervertebral disc © 2013 Pearson Education, Inc. Arachnoid mater Dura mater Cauda equina in subarachnoid space Figure 12.26a Gross structure of the spinal cord, dorsal view. Cervical enlargement Dura and arachnoid mater Lumbar enlargement Conus medullaris Cauda equina Filum terminale © 2013 Pearson Education, Inc. Cervical spinal nerves Thoracic spinal nerves Lumbar spinal nerves Sacral spinal nerves The spinal cord and its nerve roots, with the bony vertebral arches removed. The dura mater and arachnoid mater are cut open and reflected laterally. Figure 12.26b Gross structure of the spinal cord, dorsal view. Cranial dura mater Terminus of medulla oblongata of brain Sectioned pedicles of cervical vertebrae Spinal nerve rootlets Dorsal median sulcus of spinal cord Cervical spinal cord. © 2013 Pearson Education, Inc. Figure 12.26c Gross structure of the spinal cord, dorsal view. Spinal cord Vertebral arch Denticulate ligament Denticulate ligament Dorsal median sulcus Arachnoid mater Dorsal root Spinal dura mater Thoracic spinal cord, showing denticulate ligaments. © 2013 Pearson Education, Inc. Spinal Cord • Spinal nerves (Part of PNS) – 31 pairs • Cervical and lumbosacral enlargements – Nerves serving upper and lower limbs emerge here • Cauda equina – Collection of nerve roots at inferior end of vertebral canal © 2013 Pearson Education, Inc. Cross-sectional Anatomy • Two lengthwise grooves partially divide cord into right and left halves – Ventral (anterior) median fissure – Dorsal (posterior) median sulcus • Gray commissure—connects masses of gray matter; encloses central canal © 2013 Pearson Education, Inc. Figure 12.28a Anatomy of the spinal cord. Epidural space (contains fat) Subdural space Subarachnoid space (contains CSF) Pia mater Arachnoid mater Dura mater Spinal meninges Bone of vertebra Dorsal root ganglion Body of vertebra Cross section of spinal cord and vertebra © 2013 Pearson Education, Inc. Figure 12.28b Anatomy of the spinal cord. Dorsal funiculus White columns Ventral funiculus Lateral funiculus Dorsal median sulcus Gray commissure Dorsal horn Gray Ventral horn matter Lateral horn Dorsal root ganglion Spinal nerve Dorsal root (fans out into dorsal rootlets) Central canal Ventral median fissure Pia mater Ventral root (derived from several ventral rootlets) Arachnoid mater Spinal dura mater The spinal cord and its meningeal coverings © 2013 Pearson Education, Inc. Gray Matter • Dorsal horns - interneurons that receive somatic and visceral sensory input • Ventral horns - some interneurons; somatic motor neurons; axons exit cord via ventral roots • Lateral horns (only in thoracic and superior lumbar regions) - sympathetic neurons • Dorsal roots – sensory input to cord • Dorsal root (spinal) ganglia—cell bodies of sensory neurons © 2013 Pearson Education, Inc. White Matter • Divided into three white columns (funiculi) on each side – Dorsal (posterior), lateral, and ventral (anterior) • Each spinal tract composed of axons with similar destinations and functions © 2013 Pearson Education, Inc. Spinal Cord Trauma • Functional losses – Paresthesias • Sensory loss – Paralysis • Loss of motor function © 2013 Pearson Education, Inc. Spinal Cord Trauma • Flaccid paralysis—severe damage to ventral root or ventral horn cells – Impulses do not reach muscles; there is no voluntary or involuntary control of muscles – Muscles atrophy © 2013 Pearson Education, Inc. Spinal Cord Trauma • Spastic paralysis—damage to upper motor neurons of primary motor cortex – Spinal neurons remain intact; muscles are stimulated by reflex activity – No voluntary control of muscles – Muscles often shorten permanently © 2013 Pearson Education, Inc. Spinal Cord Trauma • Transection – Cross sectioning of spinal cord at any level – Results in total motor and sensory loss in regions inferior to cut – Paraplegia—transection between T1 and L1 – Quadriplegia—transection in cervical region • Spinal shock – transient period of functional loss caudal to lesion © 2013 Pearson Education, Inc. Assessing CNS Dysfunction • Reflex tests • Imaging techniques – CT, MRI, PET, radiotracer dyes for Alzheimer's, ultrasound, cerebral angiography © 2013 Pearson Education, Inc.