neurobio 917 ch 12 of Bear's book: the somatic sensory system part 1 (Pacinian corpuscle two-point

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mikepl103
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neurobio 917 ch 12 of Bear's book: the somatic sensory system part 1 (Pacinian corpuscle two-point
Updated:
2014-04-21 06:55:52
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neurobio 917 12 Bear book somatic sensory system part Pacinian corpuscle two point discrimination touch spinal segment dermatome dorsal column nociception spinothalamic pain pathway 21
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2014,biology,neurobiology
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neurobio 917 ch 12 of Bear's book: the somatic sensory system part 1 (Pacinian corpuscle, two-point discrimination, touch, spinal segment, dermatome, dorsal column, nociception, spinothalamic pain pathway) #21
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  1. what is the most abundant sensory receptor in the somatic sensory system? how do they function?
    mechanoreceptors. they are made up of unmyelinated axon branches. These axons have mechanosensitive ion channels; their gating depends on stretching or changes in tension of hte surrounding membrane
  2. why are fingertips better than other body parts at resolving the sensation of touch from two points?
    1) there is a much higher density of mechanoreceptors in the skin of the fingertip than on other parts of the body; (2) the fingertips are enriched in receptor types that have small receptive fields; (3) there is more brain tissue (and thus mire raw computing power) devoted to the sensory informatin of each square milimeter of fingertip than elswhere; and 4) there may be special neural mechanisms devoted to high-resolution discriminations
  3. what are primary afferent axons of the somatic sensory system>?
    primary afferent axons of the somatic sensory system are axons bringing info from the somatic sensory receptors to the spinal cord or brain stem
  4. where are the cell bodies of the primary afferent axons located?
    in the dorsal root ganglia
  5. what are the names of the types of axons from the skin?
    From thickest to thinnest:

    Aα, Aβ, Aδ, C
  6. what are the names of the types of axons from the muscles?
    From thickest to thinnest:

    I, II, III, IV
  7. Which type of axon isn't myleinated?
    C (IV)
  8. Which axon type conducts info the fastest?
  9. what type of sensory receptors are Aα (I) axons associated with?
    proprioceptors of skeletal muscle
  10. what type of sensory receptors are Aβ (II) axons associated with?
    mechanoreceptors of the skin
  11. what type of sensory receptors are Aδ (III) axons associated with?
    pain, temperature
  12. what type of sensory receptors are C (IV) axons associated with?
    temperature, pain, itch
  13. how many pairs of spinal nerves are there?
    30
  14. the spinal nerves are divided into what four groups?
    from top to bottom:

    cervical (8 pairs), thoracic (12), lumbar (5), and sacral (5)
  15. what is a dermatome?
    a dermatome is the area of skin innervated by the right and left dorsal roots of a single spinal segment. when mapped, the dermatomes delineate a set of bands on the body surface
  16. spinal gray matter is divided into what three zones?
    the dorsal horn, the intermediate zone, and the ventral horn
  17. what are second order sensory neurons and where are they located?
    the neurons that receive sensory input from primary afferents are called second order sensory neurons. Most of the second order sensory neurons of the spinal cord lie within the dorsal horns
  18. what is the dorsal column-medial lemniscal pathway
    the pathway serving touch is called the dorsal column-medial lemniscal pathway.
  19. which part of the spinal cord does sensory info enter?
    The ascending branch of the large sensory axons (Aβ) enters the ipsilateral dorsal column of the spinal cord, the white matter tract medial to the dorsal horn.
  20. describe the dorsal columns
    The dorsal columns carry info about tactile sensation toward the brain. They are composed of primary sensory axons, as well as second order axons from neurons in the spinal gray matter. The axons of the dorsal column terminate in the dorsal column nuclei, which lie at the junction of the spinal cord and medulla.
  21. does decussation occur for sensory info going to the brain?
    yes. axons of the dorsal column nuclei arch toward the ventral and medial medulla and decussate.
  22. at what point does info decussate in the dorsal column-medial lemniscal pathway?
    after info leaves the dorsal column nuclei, the info decussates (info is still ipsilateral when the info reaches the dorsal column nuclei)

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