Ch 12 - CNS (1)

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KellyM
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Ch 12 - CNS (1)
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2013-04-09 23:26:49
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  1. Regions and organization of CNS
    • Brain regions:
    • cerebral hemispheres; diencephalon; brain stem (midbrain, pons, and medulla); cerebullum (outer gray matter called cortex.... cortex disappears in brain stem)

    • Spinal cord:
    • central cavity surrounded by gray matter; external white matter composed of myelinated fiber tracts
  2. ventricles of the brain
    • brain and spinal cord are a hollow organ (tube)
    • lined by ependymal cells
    • filled with cerebrospinal fluid (CSF)
    • ventricles are connected to one another and to central canal of spinal cord (lateral ventricles --> 3rd ventricle via internectricular foramen; 3rd ventricle --> 4th ventricle via cerebral aqueduct)
    • paired, C-shaped lateral ventricles in cerebral hemishperes (separated anteriorly by septum pellucidum)
    • 3rd ventricle in diencephalon
    • 4th ventricle in hindbrain
    • **ventricles are connected to the subarachnoid space**
  3. central hemispheres
    • surface markings:
    • ridges (gyri), shallow grooves (sulci), and deep grooves (fissures)
    • longitudal fissure (separates 2 hemispheres)
    • transverse cerebral fissure (sparates cerebrum and cerebellum)

    • 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 bones
  4. cerebral hemispheres: 5 lobes
    • frontal
    • parietal
    • temporal
    • occipital
    • insula
  5. cerebral hemispheres: 3 basic regions
    • cerebral cortex of gray matter superficially
    • white matter internally
    • basal nuclei deep within white matter
  6. 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
    • 3) lateralization of cortical function in hemispheres
    • 4) conscious behavior involves entire cortex in some way
  7. motor areas of cerebral cortex
    in frontal lobe: control voluntary movement

    • primary (somatic) motor cortex in precentral gyrus
    • Broca's area (speech formation) anterior to inferior premotor area
    • frontal eye field within and anterior to premotor cortex; superior to Broca's area
  8. primary motor cortex
    • large pyramidal cells of precentral gyri
    • long axons --> pyramidal (corticospinal) tracts of spinal cord
    • allows conscious control of precise, skilled, skeletal muscle movements
    • motor homunculi - upside down caricatures represent contralateral motor innervation of body regions
  9. 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
  10. 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
    • vestibular cortex
    • olfactory cortex
    • gustatory cortex
    • visceral sensory area
  11. primary somatosensory cortex
    • located in postcentral gyri of parietal lobe
    • receives general sensory info from skin, and proprioceptors of skeletal muscle, joints, and tendons
    • capable of spatial discrimination: identification of body region being stimulated
    • somatosensory homunculus upside down caricatures represent contralateral sensory input from body regions
  12. visual areas
    • primary visual (stiate) cortex:
    • extreme posterior tip of occipital lobe
    • most buried in calcarine sulcus of occipital lobe
    • receives visual info from retinas
    • surrounded by visual association area (uses past visual experiences to interpret visual stimuli -- ex: color, form, movement; complex processing involves entire posterior half of cerebral hemispheres)
  13. somatosensory association cortex
    • located posterior to primary somatosensory cortex
    • integrates sensory input from primary somatosensory cortex for understanding of object
    • determines size, texture, and relationship of parts of objects being felt
  14. auditory areas
    • Primary auditory cortex:
    • superior margin of temporal lobes
    • interprets info 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
  15. vestibular cortex
    • posterior part of insula and adjacent parietal cortex
    • responsible for conscious awareness of balance (position of head in space)
  16. olfactory cortex
    • primary olfactory (smell) cortex:
    • medial aspect of temporal lobes (in piriform lobes)
    • part of primitive rhinencephalon, along with olfactory bulbs and tracts
    • remainder of rhinencephalon in humans part of limbic system
    • region of conscious awareness of odors
  17. gustatory cortex
    • in insula just deep to temporal lobe
    • involved in perception of taste
  18. multimodal association areas
    • receive inputs from multiple sensory areas
    • send outputs to multiple areas, including premotor cortex
    • allows meaning to info received, store in memory, tying to previous experience, and deciding on actions
    • sensations, thoughts, emotions become conscious - makes up who we are
    • 3 broad parts: anterior association area (prefontal cortex); posterior association area; limbic association area)
  19. 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
  20. 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)
  21. limbic association area (limbic system)
    • involves cingulate gyrus, parahippocampal gyrus, and hippocampus
    • provides emotional impact that makes scene important and helps establish memories
  22. lateralization of cortical function
    • hemispheres almost identical
    • lateralization - division of labor between hemispheres
    • cerebral dominance - hemisphere dominant for language (90% people left hemisphere)
    • 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
  23. cerebral white matter
    • formed by myelinated fibers and tracts
    • communication between cerebral areas, and between cortex and lower CNS

    • association fibers - horizontal; connect different parts of same hemisphere
    • commissural fibers - horizontal; connect gray matter of 2 hemispheres
    • projection fibers - vertical; connect hemispheres with lower brain or spinal cord
  24. thalamus
    • 80% of diencephalon
    • superolateral walls of third ventricle
    • bilateral nuclei connected by interthalamic adhesion (intermediate mass) -- contains several nuclei, named for location; nuclei project and receive fibers from cerebral cortex
    • Function:
    • gateway to cerebral cortex
    • sorts, edits, and relays ascending input
    • mediates sensation, motor activities, cortical arousal, learning, and memory
  25. hypothalamus
    • forms inferolateral walls of third ventricle
    • contains many nuclei (ex: mammillary bodies, paired anterior nuclei, olfactory relay stations)
    • Function:
    • controls autonomic nervous system (ex: blood pressure, rate/force of heartbeat, digestive tract motility, pupil size)
    • physical responses to emotions (limbic system)
    • regulates body temp (sweating/shivering)
    • regulates hunger and satiety in response to nutrient blood levels or hormones
    • regulates water balance and thirst
  26. brain stem: 3 regions
    • midbrain
    • pons
    • medulla oblongata
  27. 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
  28. midbrain
    • between diencephalon and pons
    • cerebral peduncles ventrally (contain pyramidal motor tracts)
    • cerebral aqueduct (channel connecting third and fourth ventricles)
  29. midbrain nuclei - FYI
    • periaqueductal gray matter: pain suppression; links amygdaloid body and ANS; controls cranial nerves III (oculomotor) and IV (trochlear)
    • corpora quadrigemina: dorsal protrusions = superior colliculi (visual reflex centers) and inferior colliculi (auditory relay centers)
    • substantia nigra: functionally linked to basal nuclei
    • red nucleus: relay nuclei for some descending motor pathways; part of reticular formation
  30. pons
    • 4th ventricle separates pons and cerebellum
    • fibers of pons: connect higher brain centers and spinal cord; relay impulses between motor cortex and cerebellum
    • origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial)
    • some nuclei of reticular formation
    • nuclei help maintain normal rhythm of breathing
  31. medulla oblongata (medulla)
    • joins spinal cord at foramen magnum
    • forms part of ventral wall of 4th ventricle
    • contains choroid plexus (ependymal cells that produce CSF) of 4th ventricle

    • Functions as autonomic reflex center:
    • respiratory centers = generate respiratory rhythm, controls breathing rate
    • cardiovascular center = cardiac center adjusts force and rate of heart contraction; vasomotor center adjusts blood vessel diameter for blood pressure regulation
  32. medulla oblongata - additional centers regulate...
    • vomiting
    • hiccuping
    • swallowing
    • coughing
    • sneezing
  33. cerebellum
    • 11% of brain mass
    • dorsal to pons and medulla
    • input from cortex, brain stem and sensory receptors
    • allows smooth, coordinated movements
  34. anatomy of cerebellum
    • cerebellar hemispheres connected by vermis
    • folia - transversely oriented gyri
    • each hemisphere has 3 lobes: anterior, posterior, and flocculonodular
    • arbor vitae - treelike pattern of cerebellar white matter
  35. cerebellar peduncles
    all fibers in cerebullum are ipsilateral

    • three paired fiber tracts connect cerebellum to brain stem:
    • superior cerebellar peduncles connect cerebellum to midbrain
    • middle cerebellar peduncles connect pons to cerebellum
    • inferior cerebellar peduncles connect medulla to cerebellum
  36. cerebellar processing of motor activity
    • cerebellum receives impulses from cerebral cortex of intent to initiate voluntary muscle contraction
    • signals from proprioceptors and visual and equilibrium pathways continuously "inform" cerebellum of body's position and momentum
    • cerebullar cortex calulates the best way to smoothly coordinate muscle contraction
    • "blueprint" of coordinated movement sent to cerebral motor cortex and brain stem nuclei
  37. cognitive function of cerebellum
    • role in thinking, language, and emotion
    • may compare actual with expected output and adjust accordingly

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