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1/1/2016 Introduction The Nervous System The Brain Organization of Neural Tissue • White matter versus gray matter Gray matter: short, non-myelinated neurons and neuron cell bodies White matter: myelinated and non-myelinated axons Integration Memory Learning Sensation and perception Organization of Neural Tissue • Fiber bundles – Nerve fibers = axon + myelin – Bundles of nerve fibers CNS tracts CNS = tracts PNS = nerves Gray matter White matter PNS nerves Organization of Neural Tissue Organization of Neural Tissue • Nerve cell bodies – Collections of nerve cell bodies CNS = nucleus Largely in gray matter PNS = ganglion Exception: basal ganglia in the brain 1 1/1/2016 Organization of Neural Tissue – Generally • Central cavity surrounded by a gray matter core – External white matter • Composed of myelinated fiber tracts – Brain has additional areas of gray matter • Not present in spinal cord Cortex of gray matter Inner gray matter Central cavity Migratory pattern of neurons Cerebrum Cerebellum Outer white matter Gray matter Region of cerebellum Central cavity Inner gray matter Outer white matter Brain stem Gray matter Central cavity Outer white matter Inner gray matter Spinal cord Figure 12.4 Organization of Neural Tissue Similar pattern with additional areas of gray matter The Brain • Functions – Conscious perception – Internal regulation • Average adult male 3.5 lbs • Average adult female 3.2 lbs The Brain • Same brain mass to body mass ratio! The Brain 4 Adult brain regions 1. 2. 3. 4. Cerebral hemispheres (cerebrum) Diencephalon Cerebellum Brain stem (midbrain, pons, and medulla) 2 1/1/2016 The Brain • Four major regions are connected by ventricles and aqueducts The Brain • Ventricles – Filled with cerebrospinal fluid – Lined by ependymal cells – Continuous with one another, the subarachnoid space, and the central canal of the spinal cord Anterior The Cerebrum • Cerebral hemispheres form superior part of brain • About 80% of brain mass • 3 tissue layers – Superficial cortex = gray matter – Internal white matter – Basal nuclei = islands of gray matter Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Right cerebral hemisphere Occipital lobe Left cerebral hemisphere (c) Posterior Figure 12.6c The Cerebrum • Cerebral cortex – Surface layer of cerebrum – Gray matter – “Executive Suite” – where the conscious mind is found – Self-awareness, communication, memory, understanding, voluntary movements The Cerebrum • Cerebral cortex – Convolutions • Gyri – elevated ridges • Sulci – shallow grooves • Fissures – deep grooves, separate larger regions of the brain – May look random, but are actually fairly consistent between people • Important landmarks FISSURES 3 1/1/2016 The Cerebrum • Fissures divide cerebral hemispheres into 4 lobes The Cerebrum • 3 types of functional areas in the cerebral cortex 1. Motor areas* • Control voluntary movement 2. Sensory areas* • Conscious awareness of sensation 3. Association areas • Integrate diverse information * Do not confuse these areas with motor and sensory neurons. All neurons in the cerebral cortex are interneurons The Cerebrum • Functional areas of the cerebral cortex – Contralateral orientation • Each hemisphere is primarily concerned with functions on the opposite side of the body – Hemispheres are functionally specialized • Language on left, attention on the right Cerebral Motor Activity Motor areas Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area (outlined by dashes) 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 Primary visual cortex Visual association area Auditory association area Primary auditory cortex – Conscious behavior involves the entire cortex • We are grossly oversimplifying (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Taste Wernicke’s area (outlined by dashes) Vision Hearing Motor association cortex Primary sensory cortex Multimodal association cortex Figure 12.8a Cerebral Motor Activity • Primary motor cortex Posterior Motor Homunculus Somatotopy of precentral gyrus (primary motor cortex) Motor Anterior Motor map in precentral gyrus – Large pyramidal cells of the precentral gyrus – Long axons → pyramidal (corticospinal) tracts • Project all the way to the spinal cord • All other descending motor tracts are chains of neurons Toes – Allows conscious control • Precise, skilled, voluntary movements Motor homunculi: upside-down caricatures representing the motor innervation of body regions Jaw Tongue Swallowing Primary motor cortex (precentral gyrus) Figure 12.9 4 1/1/2016 Cerebral Motor Activity • Primary motor cortex – Most of the neurons here control muscles with the most precise motor control – the face, tongue, and hands – Individual neurons must work together to coordinate movement – Neurons that control related movements intermingle Cerebral Motor Activity • Premotor cortex – Anterior to the precentral gyrus – Controls learned, repetitious or patterned motor skills • “Muscle memory” • Example: reaching the arm forward involves muscles in the shoulder and elbow – Neurons controlling unrelated movements do not cooperate • Example: hand and foot Cerebral Motor Activity • Premotor cortex – Coordinates simultaneous or sequential actions • Examples: playing an instrument, typing – Involved in the planning of movements that depend on sensory feedback • Example: Feeling for a light switch in the dark Cerebral Motor Activity • Broca’s area – Anterior to the inferior region of the premotor area – Present in one hemisphere (usually the left) – Motor speech area that directs muscles of the tongue • Active as one prepares to speak, and as one plans other voluntary motor activities Cerebral Motor Activity Cerebral Motor Activity • Frontal eye field – Anterior to the premotor cortex and superior to Broca’s area – Controls voluntary eye movements Motor areas Central sulcus Primary motor cortex Premotor cortex Frontal eye field Broca’s area (outlined by dashes) 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 Taste Wernicke’s area (outlined by dashes) (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Sensory areas and related association areas Primary somatosensory cortex Somatic Somatosensory sensation association cortex Primary visual cortex Visual association area Auditory association area Primary auditory cortex Vision Hearing Motor association cortex Primary sensory cortex Multimodal association cortex Figure 12.8a 5 1/1/2016 Cerebral Vascular Accident (Stroke) Stroke • Types – Ischemic stroke – Hemorrhagic stroke • Result – Tissue death called an infarct – Effects are determined by • Where it occurs • How large the area involved Stroke Cerebral Vascular Accident (Stroke) • Damage to the primary motor cortex – Paralyzes muscles controlled by those areas – Only voluntary control is lost – muscles still contract reflexively • Damage to the premotor cortex – Loss of motor skills, but not of muscle strength or movement – Reprogramming the skill to another set of premotor neurons is possible Cerebral Sensory Activity Central sulcus Motor areas Primary motor cortex Premotor cortex Frontal eye field Sensory areas & related association areas Primary somatosensory cortex Somatosensory association cortex Broca’s area (outlined by dashes) 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 Taste Primary visual cortex Visual association area Auditory association area Primary auditory cortex • Widely dispersed – Parietal, temporal & occipital lobes • Concerned with conscious awareness of sensation Wernicke’s area (outlined by dashes) (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Somatic sensation Cerebral Sensory Activity Vision Hearing Motor association cortex Primary sensory cortex Multimodal association cortex Figure 12.8a 6 1/1/2016 Cerebral Sensory Activity • Primary somatosensory cortex Posterior Sensory Anterior Sensory map in postcentral gyrus – In the postcentral gyri, parietal lobe – Stimuli from skin, skeletal muscles, and joints – Capable of spatial discrimination • Identification of body region being stimulated • Ability to perceive separate points of contact on the same body part Genitals Primary somatosensory cortex (postcentral gyrus) Intraabdominal Figure 12.9 Cerebral Sensory Activity • Primary somatosensory cortex – The amount of sensory cortex devoted to a body region depends on that region’s sensitivity, not its size – Most sensitive regions in humans: face (especially lips) and fingertips Cerebral Sensory Activity • Somatosensory association cortex – Posterior to the primary somatosensory cortex – Integrates sensory input from primary somatosensory cortex – Integrates and analyzes inputs • Temperature, size, texture • Recalls past sensory experiences with objects being felt • Relationship of parts of objects being felt – Example: reaching into pocket and discerning keys from coins without looking Cerebral Sensory Activity • Visual areas – Primary visual cortex • Occipital lobe • Receives visual information from the retinas – Visual association area • Surrounds the primary visual cortex • Uses past visual experiences to interpret visual stimuli – Example: color, form and movement • Complex processing involves entire posterior half of the hemispheres • (Brain Games) 7 1/1/2016 Cerebral Sensory Activity • Auditory areas – Primary auditory cortex • Temporal lobes • Interprets information from inner ear – Pitch, loudness and location – Auditory association area • Posterior to the primary auditory cortex • Stores memories of sounds and permits perception of sounds – Allows us to differentiate between a scream, a song, thunder, speech, etc. Cerebral Sensory Activity Central sulcus Motor areas Primary motor cortex Premotor cortex Frontal eye field Primary somatosensory cortex Somatosensory association cortex Broca’s area (outlined by dashes) 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 Somatic sensation Taste Wernicke’s area (outlined by dashes) (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Association Areas Sensory areas and related association areas Primary visual cortex Visual association area Auditory association area Primary auditory cortex • Receive inputs from multiple sensory areas • Send outputs to multiple areas – Including the premotor cortex Vision Hearing Motor association cortex Primary sensory cortex Multimodal association cortex • Function – Allows us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take – Damage to association areas leads to functional deficits Figure 12.8a Association Areas • Multimodal association areas (most of the cortex) – Seems to be where sensations, thoughts, and emotions become conscious – Where complex sensory input coordinates with memory and the primary motor cortex to drive action Association Areas • Example: You’re watching a volleyball match, and the ball is flying at your face Primary visual cortex: Ball is getting bigger, shadow is moving across the floor. Primary auditory cortex: Someone yells, “Look out!” Visual association area: That means the ball is moving closer to me. Auditory association area: That means danger. Multimodal association area: If I don’t move, I am going to get hit. I should move! Premotor cortex: I should duck and put my hands in front of my face. Primary motor cortex: Neck, shoulders, elbows, and arms, MOVE!! 8 1/1/2016 Cerebral Association Activity Association Activity Central sulcus Motor areas • Three areas – Prefrontal cortex – Posterior association area (not discussed here) – Limbic association area Primary motor cortex Premotor cortex Frontal eye field Sensory areas and related association areas Primary somatosensory cortex Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Prefrontal cortex Taste Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Somatic sensation Primary visual cortex Visual association area Auditory association area Primary auditory cortex Vision Hearing Motor association cortex Primary sensory cortex Multimodal association cortex Figure 12.8a Association Activity • Prefrontal cortex – Most complicated cortical region – Involved with intellect, cognition, recall and personality – Contains working memory (needed for abstract ideas), judgment, reasoning and conscience – Development depends on feedback from social environment and develops slowly Association Activity • Prefrontal Labotomy – Popular treatment for “delusions, obsessions, nervous tensions, and the like” in the 1940s and 50s – Involves cutting or scraping away most of the connections to and from the prefrontal cortex – Some patients died on the table or later committed suicide – Some were severely brain damaged or developed seizures – Some patients saw improvement of symptoms, but not without impairments to personality, intellect, and empathy – “Surgically induced childhood” Association Activity • Limbic association area – Part of the limbic system – Provides emotional impact that helps establish memories – Connections with prefrontal cortex regulate emotional expression Association Activity • Walter Freeman and James Watt – 1945 – developed the transorbital method of lobotomy – Required no surgery or anesthesia – Initially pushed an ice pick (later a leukotome) through the back of the eye socket 9 1/1/2016 Cerebral Association Activity Central sulcus Motor areas Primary motor cortex Premotor cortex Frontal eye field Cerebral Lateralization Sensory areas and related association areas Primary somatosensory cortex Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Prefrontal cortex Somatic sensation Taste Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Primary motor cortex Sensory association cortex Primary visual cortex Visual association area Auditory association area Primary auditory cortex Left hemisphere Math Logic Language Controls right side of body Vision • Right hemisphere – – – – – Visual-spatial skills Intuition Emotion Art and music Controls left side of body Hearing Motor association cortex Primary sensory cortex Multimodal association cortex Figure 12.8a Cerebral White Matter • Responsible for communication between areas of the brain and the spinal cord • Consists largely of myelinated fibers bundled into large tracts • Tracts are classified by the direction in which they run White Matter Tracts Cerebral White Matter • Projection tracts – Connect cerebrum w/other body locations – Run vertically • Association tracts – Connect different parts of the same heisphere – Adjacent gyri or different cortical lobes • Commissural tracts – Connect corresponding gray matter areas in the two hemispheres – Allows the brain to function as a whole – Largest: corpus callosum (severed in some medical experiments) Cerebral Gray Matter • Basal Nuclei – Association of gray matter deep in cerebral hemispheres – Exact components controversial – Contribute to muscle coordination and control by excitatory innervation • Examples: Determine intensity of movements, disorders include Parkinson’s and Huntington’s 10 1/1/2016 Basal Nuclei Cerebral Gray Matter • Special notes… • Your text refers to the putamen and the globus pallidus – together, these structures make up the lentiform nucleus • Your study guide refers to the amygdaloid nucleus, which requires a different plane of section… Review • • • • • White versus grey matter Ventricles 4 brain regions 4 lobes of cerebral hemispheres 3 layers of cerebrum – Cortex • Motor • Sensory • Association Copyright 2009 John Wiley & Sons, Inc. Brain Regions 4 Adult brain regions 1. Cerebral hemispheres (cerebrum) 2. Diencephalon 3. Cerebellum 4. Brain stem (midbrain, pons, and medulla) – White matter tracts – Gray matter Diencephalon • Three paired structures – Thalamus – Hypothalamus – Epithalamus • Encloses the third ventricle • Surrounded by cerebral hemispheres 11 1/1/2016 Diencephalon Cerebral hemisphere Septum pellucidum Corpus callosum Fornix Choroid plexus Thalamus (encloses third ventricle) Posterior commissure Pineal gland Interthalamic adhesion (intermediate mass of thalamus) Interventricular foramen Anterior commissure Hypothalamus Epithalamus Corpora quadrigemina MidCerebral brain aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Optic chiasma Pituitary gland Mammillary body Pons Medulla oblongata Spinal cord • Thalamus – Several nuclei – Gateway of the cerebral cortex – Major relay station for most sensory impulses – Information is sorted, edited, bundled, and sent to the correct place Figure 12.12 Diencephalon • Thalamus – Relay center for cerebral activation – Associated with reticular formation • Neural pathways in the brain stem mediating consciousness – Relay center for somatosensory information • Except olfaction Diencephalon • Hypothalamus – Inferior to the thalamus – Forms portions of walls of the third ventricle – Caps the brain stem – Consists of a number of nuclei – Coma is associated with thalamic injury • Vegetative state = damage to cortical pathways Refer to diagram on CNS 8 Diencephalon • Hypothalamus – Infundibulum • Connects pituitary to hypothalamus – Mammillary bodies • Relay stations for olfactory pathways – Responsible for most neurogenic homeostasis of the body 12 1/1/2016 Diencephalon • Hypothalamic function – Autonomic control center for many visceral functions • Examples – Blood pressure, rate and force of heartbeat – Regulates body temperature – Hunger and G.I tract regulation Diencephalon • Hypothalamic Function – Water balance and thirst – Controls release of hormones by the anterior pituitary and produces posterior pituitary hormones – Regulation of sleep-wake cycles – Center for physical response to emotions • Examples: Fear = pounding heart, dry mouth, high blood pressure, sweating, paleness – Tactile sexual response, not psychological/emotional response Diencephalon Brain Regions 4 Adult brain regions • Epithalamus – Forms roof of third ventricle – Pineal gland, choroid plexus – Melatonin – We’ll discuss it’s endocrine function later…. 1. Cerebral hemispheres (cerebrum) 2. Diencephalon 3. Brain stem (midbrain, pons and medulla) 4. Cerebellum The Brain Stem • Functions – Supports most of the automatic basic life functions – Pathway for fiber tracts – Origin for most cranial nerves 13 1/1/2016 The Brain Stem Frontal lobe Olfactory bulb (synapse point of cranial nerve I) Optic chiasma Optic nerve (II) Optic tract Mammillary body Midbrain Pons • Midbrain – Associated with visual and auditory reflexes • Pupillary reflex, startle reflex – Cranial nerves III and IV – Red nucleus Temporal lobe Medulla oblongata Cerebellum Spinal cord • Descending motor pathways involved in voluntary movement Figure 12.14 View (a) Optic chiasma Optic nerve (II) Crus cerebri of cerebral peduncles (midbrain) Diencephalon • Thalamus • Hypothalamus Mammillary body Crus cerebri of cerebral peduncles (midbrain) Hypothalamus Diencephalon Midbrain Oculomotor nerve (III) Trochlear nerve (IV) Pons Vestibulocochlear nerve (VIII) Pyramid Superior colliculus Inferior colliculus Trochlear nerve (IV) Superior cerebellar peduncle Trigeminal nerve (V) Pons Middle cerebellar peduncle Facial nerve (VII) Abducens nerve (VI) Glossopharyngeal nerve (IX) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Inferior cerebellar peduncle Vestibulocochlear nerve (VIII) Olive Hypoglossal nerve (XII) Thalamus Vagus nerve (X) Vagus nerve (X) Ventral root of first cervical nerve Decussation of pyramids Infundibulum Pituitary gland Brainstem Medulla oblongata Trigeminal nerve (V) Pons Facial nerve (VII) Middle cerebellar peduncle Abducens nerve (VI) Thalamus View (b) Thalamus Hypothalamus Diencephalon Midbrain Accessory nerve (XI) Accessory nerve (XI) Pons Brainstem Medulla oblongata Spinal cord (a) Ventral view (b) Left lateral view Figure 12.15a The Brain Stem • Pons – Bridge between midbrain and medulla oblongata – Consists chiefly of tracts connecting different parts of the CNS • Longitudinal tracts connect the cerebellum to the cerebrum and spinal cord • Transverse tracts connect the two sides of the cerebellum – Cranial nerves V- VIII (vestibular branch) Figure 12.15b 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 Figure 12.14 14 1/1/2016 The Brain Stem Crus cerebri of cerebral peduncles (midbrain) Thalamus • Medulla oblongata View (b) Infundibulum Pituitary gland Superior colliculus Inferior colliculus Trochlear nerve (IV) Trigeminal nerve (V) Pons Superior cerebellar peduncle • Passage of motor & sensory impulses between brain & spinal cord Middle cerebellar peduncle Facial nerve (VII) Abducens nerve (VI) Glossopharyngeal nerve (IX) – Decussation of tracts in pyramids Inferior cerebellar peduncle Vestibulocochlear nerve (VIII) Olive Hypoglossal nerve (XII) Thalamus Vagus nerve (X) Hypothalamus Diencephalon Midbrain Accessory nerve (XI) – Continuous with spinal cord Pons Brainstem Medulla oblongata • Pyraminds: large corticospinal tracts descending from motor cortex • Reason that each cerebral hemisphere controls voluntary movements of muscles on the opposite side of the body (b) Left lateral view Figure 12.15b Longitudinal fissure Superior Commissural fibers (corpus callosum) The Brain Center Lateral ventricle Association fibers Basal nuclei • Caudate • Putamen • Globus pallidus Corona radiata Thalamus Internal capsule Fornix White matter Pons Projection fibers Cardiac – force and rate of heart contraction Vasomotor – changes blood vessel diameter Respiratory – rate and depth of breathing Swallowing Vomiting – Cranial nerves VIII (cochlear branch) -XII Decussation of pyramids Medulla oblongata (a) – Synapses with neurons in the hypothalamus give rise to several vital centers • • • • • Gray matter Third ventricle • Medulla Figure 12.10a Brain Regions 4 Adult brain regions 1. Cerebral hemispheres (cerebrum) 2. Diencephalon 3. Brain stem (midbrain, pons, and medulla) 4. Cerebellum The Cerebellum • Dorsal to the pons & medulla • Subconsciously provides precise timing & appropriate patterns of skeletal muscle contraction • Contains both white & gray matter 15 1/1/2016 The Cerebellum • Functions – Proprioception Anterior lobe Cerebellar cortex Arbor vitae (white matter) • Sensing body position, motion, equilibrium – Prime mover inhibition and antagonist activation • Controls strength, direction, and extent of movements – Progression Cerebellar peduncles • Superior • Middle • Inferior Medulla oblongata (b) Flocculonodular lobe Posterior lobe Choroid plexus of fourth ventricle • Smooth transition from one body movement to another • Dysfunction – Dysmetria – Dysarthria Figure 12.17b Functional Brain Systems Functional Brain Systems • Networks of neurons that work together & span wide areas of the brain – Limbic system – Reticular formation • Limbic system – Structures on the medial aspects of cerebral hemispheres and diencephalon – Includes parts of the diencephalon and some cerebral structures that encircle the brain stem Functional Brain Systems Septum pellucidum Diencephalic structures of the limbic system •Anterior thalamic nuclei (flanking 3rd ventricle) •Hypothalamus •Mammillary body Olfactory bulb Corpus callosum Fiber tracts connecting limbic system structures •Fornix •Anterior commissure Cerebral structures of the limbic system •Cingulate gyrus •Septal nuclei •Amygdala •Hippocampus •Dentate gyrus •Parahippocampal gyrus • Limbic system – Emotional brain • Recognizes angry or fearful facial expressions • Assesses danger & elicits the fear response • Plays a role in expressing emotions via gestures and resolves mental conflict • Connection to pre-frontal cortex allows us to “count to ten” – Puts emotional responses to odors • Example: skunks = smell bad – Alcohol and other depressants affect limbic system control • Person is subject to exaggerated states of emotion Figure 12.18 16 1/1/2016 Radiations to cerebral cortex Functional Brain Systems • Reticular formation – Broad columns of nuclei along the length of the brain stem – Far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum & spinal cord – Governs stimulation of the brain as a whole Visual impulses Auditory impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) Descending motor projections to spinal cord Figure 12.19 Functional Brain Systems • Functions of the reticular formation 1. Somatic motor control Reticulospinal tract = improves smoothness of movement • 2. Autonomic control Respiratory and cardiovascular centers • 3. Arousal Reticular Activating System • – – Keeps cortex alert and conscious Filters incoming sensory information and discards 99% of it 4. Pain modulation • Can block pain transmission 17