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neurophys > reflexes > Flashcards

reflexes Flashcards

1
Q

what is a reflex action

A

involuntary response to a stimulus applied to the periphery & transmitted to CNS(spinal cord, medulla and/or cortex)

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2
Q

characteristics of reflex action

A

repeatable
directed and purposeful
rapid

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3
Q

definition of motor unit

A

one motor nerve and skeletal muscle fibers it innervates

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4
Q

each skeletal muscle bundle has mix of __ types of motor units

A

3

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5
Q

types of motor units

A

slow twitch-fatigue resistant
fast twitch-fatigable
fast twice-fatigue resistant

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6
Q

slow twitch fatigue resistant

A

S, type I, red
many mitochondria, much myoglobin
slow contraction, develops little tension, high endurance,

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7
Q

slow twitch fatigue resistant adapted for

A

posture maintenace

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8
Q

fast twitch fatigable

A

FF, type IIb, glycolytic, white
abundant glycogen
large fiber diameter, small to very large motor units
fast contraction, high tension, low endurance

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9
Q

fast twice fatigable mainly for

A

strong bursts of tension but some adapted for precision movements

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10
Q

fast twice fatigue resistant

A

FR, type IIAb, type IIa, oxidative-glycolytic
mitochondria glycogen&myoglobin
large fiber diameter
intermediate motor units
fast contraction, significant tension, moderate to high endurance

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11
Q

fast twice fatigue resistant adapted for

A

strong bursts of continuous activity like walking

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12
Q

FF fibers with training can develop into

A

FR
•Example; Compared to your initial efforts at jogging, the speed and distances you can jog without fatigue will increased.

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13
Q

what gives demand to move a limb

A

motor cortex

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14
Q

size principle

A

MUs receive common neural input and are recruited according to their sizes

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15
Q

there is progression from ___ motor units to ____ motor units as motion action is effected

A

small –> larger

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16
Q

during sustained activity, ___ motor units are activated and muscle fibers cycle in ____

A

larger IIb; rotation

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17
Q

what happens to precision of motor skills during prolonged task

A

degrades

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18
Q

reflexes are mediated using

A

hard wired pre-existing nerve circuits

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19
Q

reflexes generally integrated at

A

spinal cord level

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20
Q

modulation of reflex activity is

A

product of other circuits

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21
Q

control signals from higher centers are sent by ___

A

interneurons to motor nerves controlling reflex

22
Q

how are receptors located in monosynaptic reflex

A

parallel

23
Q

what kind of nerve enters cord in monosynaptic reflex

A

afferent nerve from spindle(1a fiber)

24
Q

what does efferent nerve do in monosynaptic reflex

A

goes from cord to affected motor units

25
Q

what is adequate stimulus of monosynaptic reflex

A

rapid stretch of motor unit

26
Q

types of length receptors in muscle spindle

A 
intrafusal fibers(nuclear bag fibers)
nuclear chain fibers
27
Q

what do intrafusal fibers mediate

A

phasic/dynamic response

28
Q

skeletal muscle derivatives have striations at ___

A

end of spindle

29
Q

ends of spindle innervated by

A

gamma efferent fibers
1a in center of nuclear bag fiber
1a fiber wrapped around nuclear bag fiber

30
Q

when muscle is stretched ___ tension on cytoskeletal strands pulls open ___ channels of 1a fiber

A

increased

ionic (Na)

31
Q

intrafusal fibers have __compliance

A

high
easily distorted
rapidly adapt to prolonged stretch

32
Q

what do low compliance nuclear bag fibers mediate

A 
dynamic and static response 
low compliance 
stimulate type II fibers
tonic 
give data on position of limb in space
33
Q

sequence of stimulation

A

muscle rapidly stretched and circuit activated
intrafusal fibers (muscle spindles) depolarize 1a nerves &AP results
activated 1a fibers enter cord in dorsal ramus
1a fibers stimulate alpha motor nerves in cord

34
Q

contraction of extrafusal fibers __ stretch on spindle

A

unloads
ia fibers stop firing
alpha motor nerves not stimulated

35
Q

reflex disadvantageous if

A

you want to hold precise position

36
Q

reflex resists rapid stretch but also establishes ___ in resting muscle

A

tension

to oppose gravity

37
Q

3 neural circuits that modulate monosynaptic reflex

A

reciprocal innervation
renshaw arc
gamma efferents

38
Q

what is reciprocal innervation important circuit for

A

monosynaptic and multisynaptic reflexes

39
Q

reciprocal innervation purpose

A

enhance action of agonist muscle by reducing resistance to movement from antagonist muscle

40
Q

where do gamma efferent nerves originate from

A

reticular activating system

41
Q

what do gamma efferent nerves innervate

A

polar ends of intrafusal fibers

42
Q

what is recurrent inhibition

A

•Twigs of motor nerves activate interneurons called Renshaw cells

43
Q

purpose of renshaw arc

A

confines reflex to one group of muscles w/o interference from other muscle groups

44
Q

renshaw arc inhibits other ___ motor nerves and ___ motor neuron

A

parallel

same

45
Q

in renshaw arc GABA and glycine increase ___ conductance through channel

A

Cl-

46
Q

renshaw arc modulates the reflex to avoid ____ response

A

over exuberant

47
Q

primary function of inverse myotatic reflex/golgi tendon reflex

A

equalize forces between agonist and antagonist muscles across a joint
stabilizes limb across other joints

48
Q

secondary function of inverse myotatic reflex

A

prevents muscle and or tendon tearing if muscle tendon is subjected to rapidly induced high levels of tension

49
Q

golgi tendon reflex senstive to force developed at the

A

tendons

50
Q

after stimulation of golgi tendon organ, agonist muscle is ____ by interneurons and antagonist muscle is ____

A

inhibited

stimulated

51
Q

flexor withdrawl reflex is the motor response to

A

sensory reception of pain

pain reflex

52
Q

once flexor withdrawal reflex stimulated, ipsilaterally motor nerves of flexor groups are ____
contralaterally motor nerves of flexor groups ___

A

stimulated to contract

inhibited

  • extensor groups stimulated to contract
  • double reciprocal inhibition/crossed extensor reflex

neurophys (8 decks)

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