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Neuroscience > Chapter 6 - Somatosensory > Flashcards

Chapter 6 - Somatosensory Flashcards

1
Q

muscle spindle

A

the sensory organ in muscle

- consists of muscle fibers, sensory endings, and motor endings

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2
Q

sensory endings of spindle

A
  • respond to stretch(changes in muscle length)
  • respond to velocity of length change
    Type 1a afferents(primary endings) = quick and tonic stretch of the spindle
    • wrap around the central region of each intrafusal fiber
      Type 2 afferents(secondary endings) = tonic stretch of the muscle
    • end on nuclear chain fibers
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3
Q

intrafusal fibers

A

fibers inside the spindle
- contractile only at their ends
Types: 1) nuclear bag fibers 2) nuclear chain fibers

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4
Q

nuclear bag fibers

A

intrafusal fibers

- have a clump of nuclei in the central region

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5
Q

nuclear chain fibers

A

intrafusal fibers

- have nuclei arranged in single file

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6
Q

primary endings

A

type 1a

  • wrap around the central region of the intrafusal fiber
  • also called annulospiral endings
  • discharge is phasic and tonic
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7
Q

secondary endings

A

type 2

  • end mainly on nuclear chain fibers adjacent to the primary endings
  • also called flower-spray endings
  • respond only tonically
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8
Q

phasic discharge

A

maximal during quick stretch and fades quickly

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9
Q

tonic discharge

A

sustained during constant stretch

- rate of firing is proportional to the stretch of spindle fibers

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10
Q

Golgi tendon organs

A

encapsulated nerve endings woven among the collagen strands of the tendon

  • relays tension in tendons(very sensitive)
  • responds to tension exerted by active contraction and passive stretch
  • type 1b afferents
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11
Q

joint receptors

A
  • respond to mechanical deformation of the capsule and ligaments
    Types:
    1) ligament receptors(type 1b)
    2) Ruffini’s and paciniform endings(type 2)
    3) free nerve endings
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12
Q

Ruffini’s endings

A

in the joint capsule

  • signal extremes of joint range
  • respond more to passive than active movement
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13
Q

paciniform corpuscles

A

respond to movement, but not when joint position is constant

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14
Q

ligament receptors

A

signal tension

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15
Q

free nerve endings

A

stimulated by inflammation

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16
Q

discriminative touch

A

localization of touch and vibration

- ability to discriminate between two closely spaced points touching the skin

17
Q

conscious proprioception

A

awareness of movements and of the relative position of body parts

18
Q

stereognosis

A

ability to use touch and proprioception to identify an object

19
Q

pathway for discriminative touch and conscious proprioception

A
  • dorsal column/medial lemniscus system
    1) 1st order = neuron conveys information from the receptors to the medulla
    2) 2nd order = neuron conveys information from the medulla to the thalamus
    3) 3rd order = neuron conveys information from the thalamus to the cerebral cortex
20
Q

Discriminative touch and conscious proprioceptive information pathways from the body

A

1st order = dorsal root ganglion —–> 2nd order = nucleus cuneatus or gracilis —–> VPL(ventral posterolateral) nucleus of thalamus

21
Q

Discriminative touch and conscious proprioceptive information pathways from the face

A

1st order = trigeminal ganglion —-> main sensory nucleus of trigeminal nerve ——> VPM(ventral posteromedial) nucleus of thalamus

22
Q

SPG

A

Stepping Pattern generator

  • adaptable networks of spinal interneurons that activate lower motor neurons to elicit alternating flexion and extension of the hips and knees
  • for walking
23
Q

H-reflex

A

monosynaptic reflex elicited by electrically stimulating a nerve

  • testing substitutes cutaneous electrical stimulation of a peripheral nerve for tendon percussion of the myotatic reflex
  • faster than the tendon tap reflex because it does not require activation of spindle receptors
24
Q

UMNs

A

upper motor neurons

  • provide all motor signals from the brain to the spinal cord and from the cerebrum to the cranial nerve lower motor neurons in the brainstem
  • ones projecting to the spinal cord are classified according to where they synapse: medially, laterally, or throughout the ventral horn
25
Q

Medial UMNs

A 
signal lower motor neurons that innervate postural and girdle muscle
3 tracts from the brainstem:
- reticulospinal
- medial and lateral vestibulospinal
- medial corticospinal
26
Q

Lateral UMN’s

A

signal lower motor neurons that innervate muscle used for fractionated movement and muscles in face and neck

27
Q

UMNs throughout the ventral horn

A

contributes to background levels of excitation in the cord and facilitates local reflex arcs

28
Q

reticulospinal tract

A

begins in the reticular formation

  • facilitate bilateral lower motor neurons innervating postural and gross limb movement muscles throughout the entire body
  • involved in anticipatory postural adjustments and reaching
  • for neck reflexes in response to visual and auditory input
29
Q

medial vestibulospinal tract

A

receive information about head movement and position from the vestibular apparatus in the inner ear
- project to cervical and thoracic levels and affect activity in lower motor neurons controlling neck and upper back muscle

30
Q

lateral vetibulospinal tract

A

respond to gravity information from the vestibular apparatus

  • facilitate lower motor neurons to extensors while inhibiting lower motor neurons to flexors
  • continuously active to maintain the center of gravity over the base of support, responding to destabilization
31
Q

medial corticospinal tract

A

direct connection from cerebral cortex to the spinal cord

  • project to the ipsilateral, contralateral, and bilateral spinal cord
  • synapse with lower motor neurons that control neck, shoulder and trunk muscles
32
Q

fractionation

A

the ability to activate individual muscles independently of other muscles

  • lateral spinal cord
    • 2 tracts: 1) rubrospinal(minimal contribution) 2) lateral corticospinal
33
Q

lateral corticospinal tract

A

most important in controlling voluntary movement

  • fractionates movement by activating inhibitory neurons to prevent unwanted muscles from contracting
  • arise in the primary motor, premotor, and supplementary motor cortex
34
Q

raphespinal tract

A

releases serotonin

  • modulates the activity of spinal lower motor neurons
  • part of the emotional motor system
35
Q

ceruleospinal tract

A

releases norepinephrine

  • produces tonic facilitation of spinal lower motor neurons
  • part of the emotional motor system

Neuroscience (14 decks)

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