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Neuro I > Motor Control - Reflexes > Flashcards

Motor Control - Reflexes Flashcards

1
Q

Placing reaction and hopping reaction are examples of

A

cortical reflexes

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2
Q

Stretch (myotactic), golgi tendon, and crossed extensor ar examples of

A

spinal reflexes

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3
Q

vestibular, righting, suckle, yawn, eye/head movements are examples of

A

Brainstem/midbrain reflexes

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4
Q

Reflexes in oder to be effective must be very precise. This “precision” can

A

make reflexes look like volitional movement

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5
Q

difference between reflex and volitional movement

A

a reflex movement occurs faster than the fastest voluntary motion

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6
Q

reflex activity characteristics

A

precis motions in response to afferent stimuli
mediated at all levels of the CNS
rapid initiation
many elicited even during unconsciousneess

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7
Q

volitional activity characteristics

A

originates in cortical areas associated with judgement, initiative, and motor control
longer onset, latency due to processing
require conscious awareness

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8
Q

myotactic reflex (stretch) - appearance

A

shortening/contraction of a stretched muscle

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9
Q

myotactic reflex - purpose

A

protect mm from tearing due to strain

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10
Q

myotactic reflex - characteristics

A

initiated by muscle spindle

monosynaptic, segmental reflex

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11
Q

the muscle spindle is ____ to extra fusel fibers

A

parallel

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12
Q

There are ______ types of fibers with in the muscle____

A

several

spindle

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13
Q

muscle contains _____ and _____ parts

A

afferent (sensory)

efferent (muscle)

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14
Q

intrafual fibers of the muscle spindle have _______ components

A

both motor and sensory

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15
Q

Characeristics of the sensory fiber of a muscle spindle

A 
not contractile
it's the portion sensitive to length
two sensors with different afferents
1. nuclear bag fiber
2. nuclear chain fiber
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16
Q

Primary afferent of myotactic reflex

A

1a fiber

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17
Q

characteristics of 1a fiber

A

large, myelinated

sensitive to both length of mm and how fast that length is changing

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18
Q

1a fiber innervates

A

nuclear bag and nuclear change

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19
Q

at resting lenth, the 1a fiber fires

A

less frequently

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20
Q

with stretch, the 1a fiber fires

A

more frequently

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21
Q

with fast stretch, the 1a fiber fires

A

most frequently

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22
Q

The secondary afferent is a ____ fiber

A

Group II fiber

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23
Q

secondary afferent characteristics

A

smaller, myelinated,

sensitive only to the length of the muscle

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24
Q

the secondary afferent innervates

A

only the nuclear chain

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25
Q

Primary Afferent associated with the muscle spindle - summary

A

large 1a fiber (heavily myelinated, fast velocity, low threshold)
innervates both nuclear bag and nuclear chain fiber
detects length and speed of change of length

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26
Q

Secondary Afferent associated with the muscle spindle - summary

A

group II fiber (smaller, less myelin, still pretty fast)
innervates nuclear chain only
detects only lenth

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27
Q

Motor portion of the muscle spindle consists of

A

intrafusal contractile elements

28
Q

characteristics of motor portion of muscle spindle

A

same as skeletal muscle

control length of the sensory portion

29
Q

motor portion of the muscle spindle innervated by

A

gamma motor neuron

30
Q

By contracting intrafual muscles, we

A

stretch the sensory portion

this renders the sensory portion more sensitive to a superimposed stretch

31
Q

gamma motor neurons are important in

A

controlling sensitivity

32
Q

alpa motor neurons - summary

A

large, heavily myelinated fiber
innervates via NMJ the skeletal muscle
responsible for activating muscle
activity directly leads to motion

33
Q

Gamma motor neuron - summary

A

slightly smaller, slower than alpha, still fast overall
innervates the contractile component of the muscle spindle via nmj
activity causes contraction - controls sensitivity of muscle spindle , does NOT directly lead to motion

34
Q

path of myotactic reflex at spinal level

A

motor neuron is excited by activation of Ia afferent ==> contraction releives the stretch, returning the Ia discharge rate back to normal

35
Q

stretch reflex - we contract the agonist muscle, what happens to the antagonist muscle? why

A

it gets stretched

there;s more than just a single synapse, the Ia afferent can also act on interneurons

36
Q

with the stretch reflex, there is a ______ in the activity of the _____ innervating the antagonist allowing____

A

decrease
alpha motorneuron
relax and lenthen

37
Q

Golgi tendon reflex - aka

A

invers myotactic, autogenic inhibition

38
Q

Golgi tendon reflex - appearance

A

sudden relaxation of a contracted muscle

39
Q

Golgi tendon reflex - purpose

A

to protect muscle from damage due to excessive force

40
Q

Golgi tendon reflex - characteristics

A

initiated by golgi tendon organ

polysynaptic, segmental reflez

41
Q

Golgi tendon organs

A

innervate tendon
bare nerve ending with lots of branches
action potentials increase with tension

42
Q

golgi tendon organs use ___ fibers

A

Ib

43
Q

Golgi tendon reflex - mechanism

A

Ib afferent is + on the interneurin, which inhibits the motor neuron
result = abrupt relaxation of the muscle occurs, returning golgi tendon organ discharge rate back to normal

44
Q

Myotatic reflex - summary

A

initiated by muscle spindle
passive stretch of muscle
monosynaptic reflex
contraction of stretched muscle back to normal leng

45
Q

Golgi tendon reflex - summary

A

reverse myotactic
active contraction of muscle
polysynaptic refles
abrupt relaxation of contracted muscle to prevent damage

46
Q

Motor control - modification of reflexes (general types)

A

spinal shock
decerebrate posturing
spasticity

47
Q

Spinal shock

A

even though neurons producing the reflex are below the level of transection, (therefore intact) the reflex fails to occur

48
Q

spinal shock - recovery

A

results from axonal sprouting below the level of transection

expression of receptor phenotypes that are self activating (5HT-C)

49
Q

Decerebrate posturing results from

A

loss of all structures rostral to the pons

50
Q

Rigidity

A

resists motion in all directions
results from maintained mm contraction
continual activation of alpha motor neurons - not due to reflexes, brainstem is activating alpha motor neurons, but why is not clear

51
Q

Spasticity

A

resists motion in a given direction
myotatic reflex hyperactive
continual activation of gamma motor neurons - contracts nitrafual muscle, lenthens nuclear bag/chain fibers,
brainstem

52
Q

spasticity - brainstem facilitory region

A

by actuating the gamma motror neurons, makes muscle spindle more sensitive,
this region is spontaneously active

53
Q

Spasticity - brainstem inhibitory region

A

inhibits gamma motor neurons, making muscle spindle les sensitive
this region requires activation from cortical regions.

54
Q

Spasticity- why the loss the the cortex, the _____ region is not activated, leaving the _____ region to dominate

A

brainstem inhibitory
brainstem facilitory
the end result of the uncontrolled brainstem facility region is stretch reflexes that fight any passive motion - spasticity

55
Q

patient resists a passive stretch of their muscles
the contraction doesn’t start until the stretch occurs
hyperactie myotactic reflex due to increased gamma motor neuron firing

A

spasticity

56
Q

cause of spasticity

A

damage to cortex that abolishes activation of the brainstem inhibitory region (brain arousal systems0

57
Q

contraction of muscle in the absence of other stimuli

alpha motor neurons continually active

A

rigidity

58
Q

cause of rigidity

A

loss of cortical influence that inhibits a medullary input to the alpha motor neurons.

59
Q

decorticate posturing =

A

rigidity

60
Q

decorticate posturing - pt position

A

flexion of upper limb joints
extension of lower limbs
dependant on head position

61
Q

unlike the decerebrate posturing, decorticate posturing is dependent on

A

head position and while change as the head is moved passively

62
Q

you are extremely likely to see its with unilateral ____ posturing, which commonly results from

A

decorticate

strokes in the vicinity of the internal capsule

63
Q

Transection of the spinal cord
all reflexes abolished, even if circuit is intact.

Cause>

A

spinal shock

hyper polarization of spinal neurons due to loss of excitatory input from cortex

64
Q

internal rotation of legs in extended position, flexion of arms, dependent on head position
may be unilateral or bilateral
cause?

A

Decorticate posturing

loss of cortical inputs - most commonly caused by lesion of internal capsule

65
Q

contraction of all antigravity mm (arms in extension)
usually bilateral and indicative of severe brain injury
cause?

A

Decerebrate Posture

loss of input from all structures rostral to the pons.

Neuro I (30 decks)

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