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7303 Neuroanatomy > 2.24 Motor SC 3 > Flashcards

2.24 Motor SC 3 Flashcards

1
Q

reflexes

A

involuntary, relatively short-latency, and stereotyped response set into motion by an environmental stimulus

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2
Q

components of a reflex arc

A
  • receptor
  • afferent fiber
  • reflex center in CNS
  • efferent fiber
  • effector
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3
Q

polysynaptic reflex

A

if there’s an interneuron in the reflex arc (doesn’t have to be)

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4
Q

monosynaptic reflex

A

no interneuron

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5
Q

What are the 3 major reflexes?

A
  • Stretch (myotatic) reflex
  • Inverse myotatic reflex
  • Flexion and Crossed Extension Reflex
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6
Q

simplest and best studied reflex

A

stretch (myotatic)

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7
Q

stretch reflex (overall)

A
  • elicited by tapping tendon of the muscle with a reflex hammer
  • brief and brisk contraction of the stretched muscle
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8
Q

stretch reflex mediated by

A

muscle spindle

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9
Q

stretch reflex is (mono/poly)synaptic

A

monosynaptic

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10
Q

reciprocal inhibition

A
  • agonist contracts

- antagonist relaxes

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11
Q

What would happen without reciprocal inhibition?

A

the antagonist muscle would prevent the reflex from happening

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12
Q

process of reciprocal inhibition

A
  • tapping tendon stretches muscle
  • monosynaptic reflex sends out positive signal to quad to contract
  • polysynaptic mechanism sends negative signal to hamstring muscle telling it to relax
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13
Q

At agonist, the reflex is (mono/poly)synaptic

A

monosynaptic

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14
Q

At antagonist, the reflex is (mono/poly)synaptic

A

polysynaptic

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15
Q

purpose of stretch reflex

A

controls muscle directly by causing agonist contraction

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16
Q

inverse myotatic reflex is mediated by

A

Golgi Tendon Organs (GTOs) located in tendons that respond to muscle tension

17
Q

autogenic inhibition generally results in

A

relaxation of the agonist and contraction of the antagonist

18
Q

inverse myotatic reflex: mechanism

A
  • polysynaptic reflex (with interneuron) between afferent and efferent
  • targeted muscle gets a negative (relaxation) signal
  • antagonist gets a positive signal
19
Q

function of GTO

A
  • cause relaxation of the muscles
  • GTO helps with proprioception during movement
  • measures the amount of tension on the tendons
  • helps create proprioceptive schema so we know where all body parts are at any point in time
20
Q

Flexion and Crossed Extension Reflex is a response to

A

a suddenly applied noxious stimulus

21
Q

In the flexion and crossed extension reflex, adaptive withdrawal of limb from offending stimulus causes an excitatory discharge that spreads through many segments via

A

spinospinal system

22
Q

flexion and crossed extension reflex: ipsilateral limb

A
  • reciprocal inhibition of the antagonists

- flexion

23
Q

flexion and crossed extension reflex: contralateral limb

A

extends

24
Q

flexion and crossed extension reflex mediated by

A

interneurons that decussate

25
Q

flexion and crossed extension reflex: inteneuron activity

A
  • crossing pathways

- inhibit extensors, activating flexors

26
Q

Why do pathways cross for the flexion/crossed extension reflex?

A
  • opposite thing happens on the other side

- need to stabilize and bear weight on the other leg

27
Q

What are the other reflexes we talked about?

A
  • somatomotor reflex
  • viscerovisceral reflex
  • somatovisceral reflex
  • viscerosomatic reflex
28
Q

somatomor reflex

A

works via long descending tracts (pyramidal tracts)

29
Q

viscerovisceral reflex

A
  • ANS only
  • contribute to muscle tone of bladder, etc.
  • monosynaptic
30
Q

somatovisceral reflex

A
  • skin cooling: reflex activates muscles that give you chill bumps
  • monosynaptic
31
Q

viscerosomatic reflex

A
  • noxious stimulus activates muscle guarding
  • primal reflex of movement
  • works similarly to stretch reflex, except it’s polysynaptic
32
Q

clinical connection: evaluation

A
  • Is the reflex present?
  • If present, is status altered (grading)?
  • Are pathological reflexes present?
33
Q

hyporeflexia indicates damage to:

What happens?

A
  • LMN

- LMN isn’t adequately stimulating the muscle

34
Q

hyporeflexia is a (PNS/CNS) problem

A

PNS

35
Q

hyperreflexia is a (PNS/CNS) problem

A

CNS

36
Q

hyperreflexia indicates

A

UMN is not properly modulating activity of LMN in long descending motor tracts

37
Q

UMN is typically (excitatory/inhibitory) in reflexes

A

inhibitory

38
Q

reflexes and knee stability if knee is moderately hyperextended

A

hamstring stretch reflexes will cause contraction of hamstrings and relieve strain on ACL

7303 Neuroanatomy (69 decks)

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