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Transcript
Anatomy & Physiology I Lecture 11 Chapter 12: The Central Nervous System The Central Nervous System • The Brain and Spinal Cord • Brain has four adult regions: – Cerebral hemispheres – Diencephalon – Brain stem (midbrain, pons, and medulla) – Cerebellum 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. Ventricles of the Brain • Filled with cerebrospinal fluid (CSF) – Lined by ependymal cells – Continuous with one another • Paired Lateral ventricles – cerebral hemisphere • Third ventricle – diencephalon • Fourth ventricle – hindbrain Communication Among Ventricles • Lateral ventricles communicates to third ventricle via interventricular foramen • Third ventricle communicates to fourth ventricle via cerebral aqueduct • Fourth ventricle is continuous with the central canal of the spinal cord 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 Hemisphere • Forms the Superior part of the brain • Surface markings – Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) • Longitudinal fissure – Separates two hemispheres • Transverse cerebral fissure – Separates cerebrum and cerebellum The Lobes • Five lobes – Frontal – Parietal – Temporal – Occipital – Insula • Each lobe is separated by several sulci Major Sulci • 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 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. Central Hemisphere • Three basic regions – Cerebral cortex of gray matter superficially – White matter internally – Basal nuclei deep within white matter 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 Four Generalizations of Cerebral Cortex • Functional areas – Motor areas—control voluntary movement – Sensory areas—conscious awareness of sensation – Association areas—integrate diverse information • Each hemisphere concerned with contralateral (opposite) side of body Four Generalizations of Cerebral Cortex • Two hemispheres are not equal in function – Lateral specialization of cortical function • Conscious behavior involves entire cortex in some way 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 Taste Motor association cortex © 2013 Pearson Education, Inc. Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Motor Areas • • • • Primary Motor cortex Premotor cortex Frontal eyelid field Broca’s area Primary Motor Cortex • Allows conscious control of precise, skilled, skeletal muscle movements 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 Premotor Cortex • Helps plan movements; staging area for skilled motor activities • Controls learned, repetitious, or patterned motor skills • Coordinates simultaneous or sequential actions • Controls voluntary actions that depend on sensory feedback 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 Frontal Eye Field • Controls voluntary eye movements Sensory Areas of Cerebral Cortex • Conscious awareness of sensation • Occur in parietal, insular, temporal, and occipital lobes 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 Taste Motor association cortex © 2013 Pearson Education, Inc. Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Primary Somatosensory Cortex • Receives general sensory information from skin, and proprioceptors of skeletal muscle, joints, and tendons • Capable of spatial discrimination: identification of body region being stimulated 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 Somatosensory Association Cortex • Integrates sensory input from primary somatosensory cortex for understanding of object • Determines size, texture, and relationship of parts of objects being felt Visual Areas • Primary visual (striate) cortex – Extreme posterior tip of occipital lobe – Receives visual information from retinas • Visual association area – Surrounds primary visual cortex – Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement) • ability to recognize faces Audio 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 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 Taste Motor association cortex © 2013 Pearson Education, Inc. Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Olfactory cortex • Primary olfactory (smell) cortex • Medial aspect of temporal • Region of conscious awareness of odors Gustatory cortex • In insula just deep to temporal lobe • Involved in perception of taste 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 Taste Motor association cortex © 2013 Pearson Education, Inc. 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 Motor association cortex © 2013 Pearson Education, Inc. Primary sensory cortex Uncus Calcarine sulcus Parahippocampal gyrus Sensory association cortex Primary visual cortex Multimodal association cortex Multimodal Association Areas • Most of cortex works together via complex connections – Receive inputs from multiple sensory areas – Send outputs to multiple areas, including premotor cortex • Allows meaning to information received, store in memory, tying to previous experience, and deciding on actions • Sensations, thoughts, emotions become conscious – makes us who we are Multimodal Association Areas • Three broad parts: – Anterior association area (prefrontal cortex) – Posterior association area – Limbic association area Anterior Association Area (Prefrontal Cortex) • Most complicated cortical region – Involved with intellect, cognition, recall, and personality • Contains working memory needed for abstract ideas, judgment, reasoning, persistence, and planning – Development depends on feedback from social environment 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 Taste Motor association cortex © 2013 Pearson Education, Inc. Primary sensory cortex Sensory association cortex Vision Hearing Multimodal association cortex Posterior Association Area • Large region in temporal, parietal, and occipital lobes • Plays role in recognizing patterns and faces and localizing us in space • Involved in understanding written and spoken language (Wernicke's area) Limbic Association Area • Part of limbic system • Provides emotional impact that makes scene important and helps establish memories Lateralization of Cortical Function • Lateralization of hemisperes – division of labor between hemispheres • Left hemisphere – Controls language, math, and logic • Right hemisphere – Visual-spatial skills, intuition, emotion, and artistic and musical skills Cerebral White Matter • Myelinated fibers and tracts • Communication between cerebral areas, and between cortex and lower CNS Cerebral White Matter • Association fibers – horizontal; connect different parts of same hemisphere • Commissural fibers – horizontal; connect gray matter of two hemispheres • Projection fibers – vertical; connect hemispheres with lower brain or spinal cord Figure 12.8a White fiber tracts of the cerebral hemispheres. Longitudinal fissure Superior Lateral ventricle Basal nuclei • Caudate • Putamen • Globus pallidus Thalamus Third ventricle Association fibers (within hemisphere) Commissural fibers (between hemispheres) • Corpus callosum Projection fibers (cerebral cortex to lower area) • Corona radiata • Internal capsule Gray matter White matter Pons Medulla oblongata Frontal section © 2013 Pearson Education, Inc. Decussation (cross-over) of pyramids Figure 12.8b White fiber tracts of the cerebral hemispheres. Association fibers Commissural fibers • Corpus callosum Projection fibers • Corona radiata • Internal capsule Parasagittal section and dissection © 2013 Pearson Education, Inc. Gray matter Basal Nuclei • Precise structure is controversial • Precise role elusive – Influence muscle movement – Role in cognition and emotion – Filter out incorrect or inappropriate responses (movements) Diencephalon • Three paired structures – Thalamus – Hypothalamus – Epithalamus 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 Epithalamus Corpora quadrigemina Midbrain Cerebral aqueduct Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord © 2013 Pearson Education, Inc. Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Thalamus • 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 Hypothalamus • Controls autonomic nervous system – 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 Hypothalamus (Ch 16) • Regulates body temperature – sweating/shivering • Regulates hunger and satiety in response to nutrient blood levels or hormones • Regulates water balance and thirst • Regulates sleep-wake cycles – biological clock • Controls endocrine system – Controls secretions of anterior pituitary gland – Produces posterior pituitary hormones Epithalamus • Pineal gland (body)—extends from posterior border and secretes melatonin – Melatonin—helps regulate sleep-wake cycle The Brain Stem • Three regions – Midbrain – Pons – Medulla oblongata Brain Stem • Similar structure to spinal cord • Controls automatic behaviors necessary for survival • Nuclei associated with 10 of the 12 pairs of cranial nerves Figure 12.10b Midsagittal section of the brain. Corpus callosum Fornix Thalamus Lateral ventricle (covered by septum pellucidum) Posterior commissure Pineal gland Third ventricle Epithalamus Corpora quadrigemina Cerebral aqueduct Anterior commissure Hypothalamus Arbor vitae Fourth ventricle Optic chiasma Cerebellum Mammillary body Pons Medulla oblongata © 2013 Pearson Education, Inc. Midbrain Pons • Connect higher brain centers and spinal cord • Relay impulses between motor cortex and cerebellum Medulla Oblongata • Autonomic reflex center – Functions overlap with hypothalamus – Hypothalamus relays instructions via medulla • Cardiovascular center (Ch 19) – Cardiac center adjusts force and rate of heart contraction – Vasomotor center adjusts blood vessel diameter for blood pressure regulation Medulla Oblongata • Respiratory centers (Ch. 22) – Generate respiratory rhythm – Control rate and depth of breathing (with pontine centers) • Additional centers regulate – – – – – Vomiting Hiccuping Swallowing Coughing Sneezing Cerebellum • Input from cortex, brain stem and sensory receptors • Allows smooth, coordinated movements Cerebellar Processing of Motor Activity • Cerebellum receives impulses from cerebral cortex of intent to initiate voluntary muscle contraction • Inform body's position and momentum – calculates the best way to smoothly coordinate muscle contraction Cognitive Function of Cerebellum • Role in thinking, language, and emotion Functional Brain Systems • Networks of neurons that work together but span wide areas of brain – Limbic system – Reticular formation Limbic System • Emotional or affective brain – recognizes angry or fearful facial expressions, assesses danger, and elicits fear response – role in expressing emotions via gestures, and resolves mental conflict – Puts emotional responses to odors Reticular Formation • Sends impulses to cerebral cortex to keep it conscious and alert • Reticular autonomic centers regulate visceral motor functions – Vasomotor centers – Cardiac center – Respiratory centers Protection of the Brain • Meninges • Consists of three connective tissue membranes that: – Cover and protect CNS – Protect blood vessels and enclose venous system – Contain cerbrospinal fluid – Form partitions in the skull Cerebrospinal Fluid (CSF) • Watery solution formed from blood plasma • Produced by the choroid plexus of each ventricle • Gives buoyancy to CNS structures • Reduces weight by 97% • Protects CNS from blows and other trauma • Nourishes brain and carries chemical signals Figure 12.24a Formation, location, and circulation of CSF. Superior sagittal sinus Slide 1 Arachnoid villus Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Interventricular foramen Third ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord (a) CSF circulation © 2013 Pearson Education, Inc. Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle Blood Brain Barrier • Helps maintain stable environment for brain • Separates neurons from some bloodborne substances • Astrocytes support function • Selective barrier – Allows nutrients to move by 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 The Spinal Cord • Travels via the vertebral column via vertebral foramen – Protected by bone, meninges, and CSF • Function – Provides two-way communication to and from brain 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 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 © 2013 Pearson Education, Inc. arachnoid mater are cut open and reflected laterally. The Spinal cord • Terminates in conus medullaris (~L1) • Filum terminale extends to coccyx – Fibrous nerve extension that continue down the legs – Anchors spinal cord • Spinal nerves (Part of PNS) – 31 pairs 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. Nerves Serving Gray Matter • Named by relative involvement in innervating somatic and visceral regions of body – Somatic sensory (SS) – Visceral sensory (VS) – Visceral (autonomic) motor (VM) – Somatic motor (SM) Figure 12.29 Organization of the gray matter of the spinal cord. Dorsal root (sensory) Dorsal horn (interneurons) Dorsal root ganglion SS VS Somatic sensory neuron VM Visceral sensory neuron SM Visceral motor neuron Somatic motor neuron Spinal nerve Ventral horn (motor neurons) Ventral root (motor) © 2013 Pearson Education, Inc. SS Interneurons receiving input from somatic sensory neurons VS Interneurons receiving input from visceral sensory neurons VM Visceral motor (autonomic) neurons SM Somatic motor neurons White Matter • Nerve fibers allow communication between parts of spinal cord, and spinal cord and brain • Run in three directions – Ascending – up to higher centers (sensory inputs) – Descending – from brain to cord or lower cord levels (motor outputs) – Transverse – from one side to other (commissural fibers) Figure 12.30 Major ascending (sensory) and descending (motor) tracts of the spinal cord, cross-sectional view. Ascending tracts Dorsal Fasciculus gracilis white Fasciculus cuneatus column Dorsal spinocerebellar tract Ventral spinocerebellar tract Lateral spinothalamic tract Ventral spinothalamic tract Descending tracts Ventral white commissure Lateral reticulospinal tract Lateral corticospinal tract Rubrospinal tract Medial reticulospinal tract Ventral corticospinal tract Vestibulospinal tract Tectospinal tract © 2013 Pearson Education, Inc. Summary of Spinal Cord Nerves • White matter – contain nerves that move up and down the column to relay signals to brain the organ systems • Gray matter – contain nerves that move outward to the PNS for sensory and motor function Lab Exercise • Lab Exercise 19 – Parts of the Brain – Cranial Nerves (Wednesday’s lecture)
