lecture 3 Flashcards

1
Q

sensory input lost, control affected
- 5 general receptors
3 specific skin receptors

A
  1. skin - pressure
  2. viscera - stretch of tissue
  3. proprioception - in muscle joints
  4. thermoreceptors in skin
  5. nociceptors in skin,viscera
    a. bare nerve ending - temp
    b. hair receptor: flow of air, change in position
    c. pacinian corpuscle - respond rapidly, adapt quickly.
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2
Q

measuring nerve conduction velocity

A

electrode pairs at 2 stimulating points. measure time it takes for each to get to recording electrode. measure distance btw points and distance in time

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3
Q

sensory axon types - myelin? conduction velocity? associated sensory endings?
1a
IV
A

A
Ia = Aa, yes, 80-120 m/s, muscle spindle primary endings
IV = C, no, 0.5-2.0 m/s, nociceptors, warmth thermoreceptors
A = Aa, yes, 80-120 m/s, extrafusal muscle fibers
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4
Q

spinal cord anatomy
central grey matter =
white matter =
spinal nerves =

A

c: motoneurons, interneurons
w: axonal tracts from brain or ascending to brain
s: dorsal root (sensory), ventral root (motor)

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5
Q

interface between PNS and CNS

  • sensory afferents enter spinal cord where?
  • sensory afferents bifurcate discuss.
  • descending axons travel how far?
  • how many segments of axons synapse on what?
  • motoneuron cell bodies where?
  • motor efferent axons leave from where?
A
  • dorsal root.
  • one ascending, one descending branch. carry sensory info to brain.
  • 2-3 spinal segments
  • 2-3 segments of azons synapse on motoneurons and interneurons
  • cell bodies = ventral horn
  • axons leave from ventral roots
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6
Q

pathway from peripheral mechanoreceptors to somatosensory cortex

A

mechanoreception, ascend in dorsal columns. synapse on 2nd-order neurons and decussate in dorsal column nuclei, cross to contralateral thalamus and S1

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7
Q

neural coding - based on 3 things

A

frequency code - rate of firing
population code - pressure causes more receptors fired
temporal pattern code: variability of firing rate mayencode sensory info.

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8
Q

divergence - neuron

convergence

A

d: each interneuron gets and gives various inputs
C: inputs from multiple receptors to 1 interneuron

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9
Q

coincidence detection

hypothesis?

A

2nd order neurons in Dorsal column nuclei, detect coincidence of AP from tactile afferents.

  • activated at different times, depending on shape touched.
  • time of arrival of afferent AP vary w conductio velocity
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10
Q

lateral inhibition:

A

sharpen contrast by focussing activation of CNS neurons. enhance highest activated, inhibited adjacent - lower firing.

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11
Q

2 -point discrimination

- depends on 3 things

A
  1. receptor density in skin
  2. contrast enhancement by lateral inhibition
  3. number of receiving neurons in CNS
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12
Q

proprioception
kinesthesia
mediated by?

A

position sense
movement sense
by skin afferents and muscle spindle afferents

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13
Q

goodwin experiment on muscle spindles

A

vibrate one arm, subject indicates with left arm where perception of right arm is.
= muscle spindle activity elicited illusions of movement and changes in position.

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14
Q

gelfan & carter - pulled surgically exposed tendons of finger flexor
moberg’s repitition

A

moberg - said yes, but when skin anesthetized, couldnt feel anything.

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15
Q

mccloskey: reproduce moberg and gelfan

A

tendon in toe exposed & cut - felt it move.

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16
Q

collins - finger flexion controlled by ?

A

stretching of skin

17
Q

edin - human skin afferents signal?

A

joint movement

18
Q

somatosensory cortex

  • dorsal column ?
  • “private lines” to S1
  • alternating columns of neurons
  • receptive fields of single neurons from S1 to S2 (etc)
  • feature detecting in S2 respond to specific features of stimuli. ie?
A
  • DC mediate touch, pressure, vibration, kinesthesia.
  • private line from skin to S1 respond in mocality-specific way.
  • alternating, receive input from Merkel’s, Meissner’s
  • become pregressily larger
  • ie directional tuning - neuron attune to specific direction of stimulus firing
19
Q

multisensory object recognition

A

if hand is holding object, and when hand is in the same position without object = same tactile and proprioceptive respoonses.

20
Q

perception of touch in bodily areas not involved in task reduced during movement.

A
  • reduction of responses when not involved in muscle activty. progressive, greated reduction at S1 - when not relevant.
    BUT augments behaviourally important.
21
Q

peripheral nerve injury and repair
5 steps
3 facts

A
  1. nerve severed, wallerian degeneration (myein in distal nerve degenerates
  2. schwann and macrophage clean up
  3. chromatolysis : nucleus migrate
  4. more molecules for growth and repair.
  5. schwann grow, proliferate. growth cone forms, send axons along phyllopodia - attracted toguidance molecules
    - rate = 2-5 mm/day
    - more proximal = worse re-innervation
    - surgical reconnection may help