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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
Primary Afferent associated with the muscle spindle - summary
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
26
Secondary Afferent associated with the muscle spindle - summary
group II fiber (smaller, less myelin, still pretty fast) innervates nuclear chain only detects only lenth
27
Motor portion of the muscle spindle consists of
intrafusal contractile elements
28
characteristics of motor portion of muscle spindle
same as skeletal muscle | control length of the sensory portion
29
motor portion of the muscle spindle innervated by
gamma motor neuron
30
By contracting intrafual muscles, we
stretch the sensory portion | this renders the sensory portion more sensitive to a superimposed stretch
31
gamma motor neurons are important in
controlling sensitivity
32
alpa motor neurons - summary
large, heavily myelinated fiber innervates via NMJ the skeletal muscle responsible for activating muscle activity directly leads to motion
33
Gamma motor neuron - summary
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
path of myotactic reflex at spinal level
motor neuron is excited by activation of Ia afferent ==> contraction releives the stretch, returning the Ia discharge rate back to normal
35
stretch reflex - we contract the agonist muscle, what happens to the antagonist muscle? why
it gets stretched | there;s more than just a single synapse, the Ia afferent can also act on interneurons
36
with the stretch reflex, there is a ______ in the activity of the _____ innervating the antagonist allowing____
decrease alpha motorneuron relax and lenthen
37
Golgi tendon reflex - aka
invers myotactic, autogenic inhibition
38
Golgi tendon reflex - appearance
sudden relaxation of a contracted muscle
39
Golgi tendon reflex - purpose
to protect muscle from damage due to excessive force
40
Golgi tendon reflex - characteristics
initiated by golgi tendon organ | polysynaptic, segmental reflez
41
Golgi tendon organs
innervate tendon bare nerve ending with lots of branches action potentials increase with tension
42
golgi tendon organs use ___ fibers
Ib
43
Golgi tendon reflex - mechanism
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
Myotatic reflex - summary
initiated by muscle spindle passive stretch of muscle monosynaptic reflex contraction of stretched muscle back to normal leng
45
Golgi tendon reflex - summary
reverse myotactic active contraction of muscle polysynaptic refles abrupt relaxation of contracted muscle to prevent damage
46
Motor control - modification of reflexes (general types)
spinal shock decerebrate posturing spasticity
47
Spinal shock
even though neurons producing the reflex are below the level of transection, (therefore intact) the reflex fails to occur
48
spinal shock - recovery
results from axonal sprouting below the level of transection | expression of receptor phenotypes that are self activating (5HT-C)
49
Decerebrate posturing results from
loss of all structures rostral to the pons
50
Rigidity
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
Spasticity
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
spasticity - brainstem facilitory region
by actuating the gamma motror neurons, makes muscle spindle more sensitive, this region is spontaneously active
53
Spasticity - brainstem inhibitory region
inhibits gamma motor neurons, making muscle spindle les sensitive this region requires activation from cortical regions.
54
Spasticity- why the loss the the cortex, the _____ region is not activated, leaving the _____ region to dominate
brainstem inhibitory brainstem facilitory the end result of the uncontrolled brainstem facility region is stretch reflexes that fight any passive motion - spasticity
55
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
spasticity
56
cause of spasticity
damage to cortex that abolishes activation of the brainstem inhibitory region (brain arousal systems0
57
contraction of muscle in the absence of other stimuli | alpha motor neurons continually active
rigidity
58
cause of rigidity
loss of cortical influence that inhibits a medullary input to the alpha motor neurons.
59
decorticate posturing =
rigidity
60
decorticate posturing - pt position
flexion of upper limb joints extension of lower limbs dependant on head position
61
unlike the decerebrate posturing, decorticate posturing is dependent on
head position and while change as the head is moved passively
62
you are extremely likely to see its with unilateral ____ posturing, which commonly results from
decorticate | strokes in the vicinity of the internal capsule
63
Transection of the spinal cord all reflexes abolished, even if circuit is intact. Cause>
spinal shock hyper polarization of spinal neurons due to loss of excitatory input from cortex
64
internal rotation of legs in extended position, flexion of arms, dependent on head position may be unilateral or bilateral cause?
Decorticate posturing loss of cortical inputs - most commonly caused by lesion of internal capsule
65
contraction of all antigravity mm (arms in extension) usually bilateral and indicative of severe brain injury cause?
Decerebrate Posture loss of input from all structures rostral to the pons.

Neuro I (30 decks)

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