Lecture CNS 1

  1. What does the CNS consist of?
    The Brain

    The Spinal Cord
  2. Cephalization
    Evolutionary development of the rostral (anterior) portion of the CNS

    Each evolutionary level has an increased number of neurons in the head

    Highest level is reached in human brain
  3. Adult brain Regions
    • 1. Cerebrum
    • 2. Diencephalon
    • 3. Brain stem (midbrain, pons, medulla)
    • 4. Cerebellum
  4. Regions of the spinal Cord
    central cavity is surrounded by gray matter core

    external white matter composed of myelinated fiber tracts
  5. Ventricles of the brain
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    They care connected to one another and to the central canal of the spinal cord

    Lines by ependymal cells

    • Contain Cerebrospinalfluid (CSF)
    • -two lateral C shaped ventricles in the cerebal hemispheres
    • -thies ventrucle in diencephalon
    • -fourth ventricle in hindbrain, dorsal to the pons, develops from lumen of the neural tube
    • -contains choroid plexus which creates CSF
  6. Cerebral Hemispheres
    Surface Markings
    Cerebral Hemispheres make up 83% of the brain

    • Gyri-ridges
    • Sulci-shallow grooves
    • Fissures- deep grooves

    Central sulcus: seperates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe

    Longitudinal Fissue: seperates the two hemispheres

    Transverse Cerebral Fissue: separates the cerebrum and the cerebellum
  7. Cerebral Hemispheres
    Five lobes
    • 1 .Frontal
    • 2. Parietal
    • 3. Temporal
    • 4. Occipital
    • 5. Insula: deep to lateral sulcus, covered by portions of the temporal, parietal, and frontal lobes
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  8. Cerebral cortex
    -Thin (2-4 mm) superficial layer of gray matter

    -40% of the brain mass

    -Site of concious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding

    -Each hemisphere connexts to the ctralateral side of body (left brain to right side of body)

    -There is a lateralization (specialization) of cortical function in the hemispheres
  9. Functional Areas of the Cerebral Cortex
    • The three types of functional areas are:
    • 1. Motor areas: control voluntary movment
    • 2. Sensory areas: conscious awareness of sensation
    • 3. Association areas: integrate diverse information

    • *conscious behavior involves the entire cortex
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  10. Motor Areas of the Cerebral Cortex
    1. Primary (somatic) motor cortex

    2. Premotor cortex

    3. Broca's area

    • 4. Frontal Eye Field
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  11. Primary (somatic) motor cortex
    -Large pyramidal cells (large neurons) of the precentral gyrus

    -Long axons--> pyramidal (corticospinal) tracts

    -Allows conscious control of precise, skilled, coluntary movements

    • -Motor homunculi: upside-down caricatures representing the motor innervation of body regions
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  12. Premotor Cortex
    -Anterior ot the precentral gyrus

    -Controls learned, repetitious, or patterns motor skills (such as typing)

    -Coordinated simultaneous or sequential actions

    -Involved in the planning of movments that depend on sensory feedback
  13. Broca's Area
    -Anterior to the inferior region of the premotor area

    -Present in one hemisphere (usually the left)

    -A motor speech area that directs the muscles of the tongue

    -Is active as one prepares to speak
  14. Frontal Eye Field
    Anterior ot the premotor cortex and superior to Broca's Area

    Controls coluntary eye movments
  15. Sensory Areas
    *Conscious awareness of sensation

    • -Primary somatosensory cortex
    • -Somatosensory association cortex
    • -Visual Areas
    • -Auditory Areas
    • -Olfactory cortex
    • -Gustatory Cortex
    • -Visceral Sensory Area
    • -Vestibular Cortex
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  16. Primary Somantosensory Cortex
    -In the postcentral gyri

    -Recieves sensory information from the skin, skeletal muscles, and joints

    -Capable of spatial discrimitation: identification of the body region being stimualted
  17. Somatasensory Association Cortex
    Posterior to the primary somatosensory cortex

    Integrates sensory input (such as pressure, temp, etc) from the primary somatosensory cortex

    Determines size, texture, and relationship of parts of objects being felt (based soley on touch, not sight)
  18. Visual Areas
    • Primary visual (striate) cortex
    • -extreme posterior tip of the occipital lobe
    • -most of it is buried in the calcarine sulcus
    • -receives visual information from the retinas

    • Visual Association Area
    • -surround the primary visual cortex
    • -uses past visual experiences to interpret visual stimuli (ex: color, form, and mvoement)
    • -complex processing involves entore posterior half of the hemispheres
  19. Auditory Areas
    • Primary Auditory Cortex
    • -superior margin of the temporal lobes
    • -interprets infomration from inner ear as pitch, loudness, and location

    • Auditory Association area
    • -located posterior to the primary auditory cortex
    • -stores memories of sounds and permits the perception of souns
  20. Olfactory Cortex
    Medial Aspect of temporal lobes (in piriform lobes)

    • Part of the primative rhinencephalon, along wotj tje p;factpry bulb and tracts
    • -remainder of the rhinencephalon in humans is part of the limbic system

    Region of concious awareness of odors
  21. Gustatory Cortex
    In the Insula (just deep to the temporal lobe)

    • Involved in the perception of taste
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  22. Visceral Sensory Area
    Posterior to the gustary cortex

    Concious perception of visceral snesation (such as an upset stomache or a full bladder)
  23. Vestibular Cortex (equilibrium)
    Posterior part of the insula nad adjacent parietal cortex

    responsible for conscious awareness of balance (position of the head in space)
  24. Multimodel Association Areas
    -recieves input from multiple sensory areas

    -sends output to multiple areas, including the premotor cortex

    -allows us to give meaning to information received, store it as memory, compare it to previous experiences, and decide on what actions to take

    • Three parts:
    • 1. Anterior association area (prefrontal cortex)
    • 2. Posterior association area
    • 3. Limbic Association Area
  25. Multimodel Association Areas
    Anterior association area (prefrontal cortex)
    -Most complicated cortical region

    -involved with intellect, cognition, recall, and personality

    -Contains working memory needed for judgement, reasoning, persistence, and conscience

    -development depends on feedback from social enviornment
  26. Multimodel Association Areas
    Posterior association area
    Large region in temporal, parietal, and occipital lobes

    Plays a role in recognizing patterns and face and localizing us in space

    Involved in understanding written and spoken language (Wernicke's area)
  27. Multimodel Association Areas
    Limbic Association Area
    Part of the limbic system

    Provides emotional impact that helps establish memories
  28. Embryonic Development tissue
    • 1. Neural plate form from ectoderm
    • 2. Neural Plate invaginates to form a neural groove and neural folds
    • 3. Neural groove fuses dorsally to form the neural tube
    • 4. The neural tube gives rise to the brain and spinal cord
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  29. Embryonic Development Brain Vesicles
    • Anterior end of the neural tube gives rise to three primary brain vesicles
    • 1. Proencephalon- forebrain
    • 2. Mesencephalon- midbrain
    • 3. Rhombencenphalon- hindbrain

    • These primary vesicles give rise to 5 secondary vesicles
    • 1. Telencephalon and diencephalon arise from the forebrain
    • 2. Mesencephalon remains undivided
    • 3. Metencephalon and myelencephalone arise from the hindbrain
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    • Telencephalon--> cerebrum (2 hemispheres with cortex, white matter, and basal nuclei)
    • Diencephalon--> thalamas, hypothalamus, epithalamus, and retina
    • Mesencephalon-->Brain stem (mid brain)
    • Metenchephalon--> brain stem (pons) and cerebellum
    • Myelencephalon--> brain stem (medulla)

    Central Canal of the neural tube enlarges to form fluid filled ventricles
  30. Effects of space restriction on brain development
    -Midbrain flexure and cervical flexure cause forebrain to move toward the brain stem

    - Cerebral hemispheres grow posteriorly and laterally

    -cerebral hemisphere surgaces crease and fold into convolutions
  31. Lateralization of Cortical Function
    Laterlization: division of labor between hemispheres

    Cerebral dominance: designates the hemispheres dominant for language (left hemispheres in 90% of people because most people are right handed)

    • Left hemisphere:
    • controls language, math, logic

    • Right Hemisphere:
    • insight, visual spatial skills, intuition, and artistic skills

    Right and Left hemispheres communicate bia fiber tracts in the cerebal white matter
  32. Cerebral white matter (internal)
    -Myelinated fober and their tracts

    • Responsible for communication
    • -Commisures (in corpis collosum)-- connect gray matter of two hemispheres
    • -Associated fibers- connect different parts of the same hemisphere
    • - Projection fibers (corona radiata)- connect the hemispheres with lower brain or spinal cord
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  33. Basal Nuclei (ganglia)
    Subcortical nuclei

    • consists of corpius striatus
    • -caudal nucleus
    • -lentiform nucleus (putamen + globus Pallidus)

    • Functionally associated with the subhtalamic nuclei (diencephalon) and the substantia nigra (midbrain)
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  34. Functions of the Basal Nuclei
    Though someone elusive, the folloiwng are though to be function of basal nuclei:

    • 1. influence muscular control
    • 2. help regulate attention and cognition
    • 3. regulate intensity of slow or sterotyped movement (too much movement, huntingtons. too little movement- parkinsons)
    • 4. Inhibit antagonistic and unnecessary movments
  35. Parts of the Diencephalon
    • Three paired structures:
    • 1. Thalamus
    • 2. Hypothalamus
    • 3. Epithalamus

    Diencephalon enlocses the third ventricle
  36. Thalamus
    80% of diencephalon

    Superplateral walls of third ventricle

    Connected by teh interthalamic adhesion (intermediate mass)

    Contains several nuclei, named for their location

    Nuclei project and recieve fibers from the cerebal cortex
  37. Thalamic functions
    Gateway to the cerebral cortex

    • Sorts, eduts, and relays information
    • -afferent impulses from all senses and all parts of body
    • -impulses from the hypothalamus for regulation of emotion and visceral function
    • *impulses from the cerebullum and basal nuclei to help direct motor cortices

    Mediates snesation, motor activities, cortical arousal, learning, and memory
  38. Hypothalamus
    Caps the brain stem, posterior and inferior to thalamus

    *lies at the heart of the limbic system

    Forms the inferolateral walls of the third ventricle

    • Contains many nuclei
    • -Example: mammilary bodies (paired anterior nuclei)-olfactory relay stations

    Infundibulum-- stalk that connects the pituitary gland to the hypothalamus
  39. Hypothalimic Function
    Autonomic control center for many visceral functions (main visceral control center) such as blood pressure, rate and force of heartbeat, digestive tract motility

    Center for emotional response: involved in perception of pleasure, fear, and rage and in biologicial rythms and drives

    Regulates body temperature, food intake, water balance, and thirst

    regulates sleep and the sleep cycle

    controls release of hormones by the anterior pituitary

    produces posterior pituitary hormones (ADH, Oxycotin)
  40. Epithalamus
    Most dorsal portion of the diencephalon; forms the roof of the third ventricle

    Pineal gland--extends from the posterior border and secretes melatonin (helps regulate the sleep-wake cycle)
  41. Brain stem
    each about 1 inch long-->Midbrain, pons, medulla oblongata

    Similar structure to spinal cord byt contains embedded nuclei (deep gray matter surrounded by whtie matter, but also nuclei of gray matter embedded in white matter)

    controld automatic behaviors necessary for survival

    Contains fiver tracts connecting higher and lower neural centers

    Associated with 10 of the 12 pairs of cranial nerves
  42. Midbrain
    located between the diencephalon and the pons

    Cerebral peducles (little verticle pillars seemingly holding up the cerebrum)

    Contain pyramidial motor tracts (descending toward the spinal cord)

    • Cerebral aqueduct
    • -channel between the third and fourth ventricles (surrounded by gray matter, involved in pain suppression and fight or flight response)
  43. Midbrain Nuclei
    Nuclei that control cranial nerves III (oculomotor) and IV (trochlear)

    • Corpora Quadrigemina - domelike dorsal protrusions
    • -superior colliculi: visual reflex centers
    • -inferior colliculi: auditory relay centers (also "startle" relex)

    Substantia nigra- functionally linked tot he basal nuclei (deep the cerebral peducle, dark in color, releases dopamine)

    • red nucleus- relay nuclei for some descending motor pathways and part of the reticular fomation (red dur to rich blood supply )
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  44. Pons (means bridge)
    Forms part of the anterior wall of the fourth ventricle

    • Fibers of the pons
    • -connect higher brain centers and the spinal cord
    • -relay impuses between the motor cortex and the cerebellum

    Origin of CN V (trigeminal), VI (abducens) and VII (facial)

    Some nuclei of the reticular formation

    Nuclei that help maintain normal rythm of breathing
  45. Medulla Oblongata
    Joins the spinal cord and the foramen magnum

    Forms part of the ventral wall of the forth ventricle

    Contains a choroid plexus of the fourt ventricle

    Pyramids--two ventral longitudinal ridged formed by the pyramidal tracts

    Decussation of the pyramids-- crossover and othe corticospinal tracts (how the hemisphere controld hte opposite side of the body)

    Inferior olivary nuclei- relay sensory information from msucles and joints to cerebellum

    CN VIII, X, and VII are associated with medulla

    Vestibular nuclear complex- mediates responses that maintain equilibrium

    Several nuclei (such as nucleus cuneatus and nucleus gracilis) relay sensory information
  46. Medula Oblongata Function
    **Medulla and Hypothalamus have many similar functions. This is b/c hypothalamus relays its instructions through the medulary reticular centers, which carry them out in the body**

    Autonomic Reflex centers

    • Cardiovasulcar Center
    • -cardiac center adjusts force and rate of heart contraction
    • -Vasomotor centers adjusts blood vessel diameter for blood pressure regulation

    • Respiratory Centers:
    • -generate respiratory rhytm
    • -control rate and depth of breathing, with pontine centers

    • Additional centers regulate
    • -vomiting
    • -hiccuping
    • -swallowing
    • -coughing
    • -sneezing
  47. The Cerebellum (called the small brain)
    11% of brain mass

    Dorsal to the pons and the medulla (protrudes under occipital lobe)

    Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction
  48. Anatomy of the Cerebellum
    Two hemispheres connected by vermis ((bilaterally symmetrical)

    • Each hemisphere has 3 lobs (divided by deep fissures)
    • 1. Anterior (both anterior and posterior coordinate body movemnets)
    • 2. Posterior
    • 3. Flocculonodular (maintains balance)

    Folia- transversely oriented gyri

    • Arbor vitae- distinctive treelike pattern of cerebellar white matter
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  49. Cerebellar Peduncles
    All fibers in the cerebellum are ipsilateral (to the same side of the body)

    • Three paired fiber tracts connect the cerebellum to the brain stem
    • 1. Superior peduncles connect the cerebellum to the midbrain
    • 2. Middle peduncles connecet the pons to the cerebellum (one way communication)
    • 3. Inferior peduncles connectt he medulla to the cerebellum (convey sensory information from muscle sensors, vestibular nucleu of the brain stem concerned with balance)
  50. Cerebellar Processing for Motor Activity
    Cerebellum recieves impulses from the cerebal cortex of the intent to initiate voluntary muscle contraction

    signals from proprioceptors and visual and equilibrium pathways continuously "inform" the cerebellum of the bodys position and momentum

    cerebellar cortex calculates the best way to smoothly coordinate a muscle contraction

    a "blue print" of coordinated movment is sent to the cerebal motor cortex and to the brain stem nuclei via superior peduncles
  51. Cognitive function of the Cerebellum
    Recognizes and predicts sequences of events during complex movments

    Plays a role in nonmotor functions such as word association and puzzle solving
Card Set
Lecture CNS 1
brain, development, CNS for LCCC BIO163