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Neuroendocrine Exam 2 > Motor Control: reflexes > Flashcards

Motor Control: reflexes Flashcards

1
Q

In order to be effective, reflexes must be what?

A

precise

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2
Q

how can you tell the difference between a reflex and volitional movement?

A

speed (a reflex is much faster than the fastest volitional movement)

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3
Q

what is the purpose of a reflex?

A

direct and rapid response to sensory stimuli

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4
Q

what is the purpose of a volitional movement?

A

response to stimuli; but also need and desire

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5
Q

what is the initiation of a reflex?

A

sensory input

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6
Q

what is the initiation of a volitional movement?

A

higher cognition; sensory input

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7
Q

what is the appearance of the myotatic (stretch) reflex?

A

contraction (shortening) of a stretched muscle *most prominent during a passive stretch

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8
Q

what is the purpose of the myotatic (stretch) reflex?

A

to protect the muscle from tearing due to stretch (passive)

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9
Q

what is the myotatic (stretch) reflex initiated by?

A

muscle spindle

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10
Q

is the myotatic (stretch) reflex monosynaptic or polysynaptic?

A

monosynaptic

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11
Q

what does it mean to say that the myotatic (stretch) reflex is monosynaptic?

A

the sensory axon arising from the muscle spindle synapses directly onto the alpha-motor neuron

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12
Q

where is the muscle spindle found?

A

within the skeletal muscle, embedded in a fusiform capsule

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13
Q

what is the sensory element that detects muscle stretch?

A

the muscle spindle

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14
Q

what two sensors make up the sensory portion of the muscle spindle?

A

nuclear bag fiber and nuclear chain fiber

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15
Q

what is the primary afferent of the muscle spindle that innervates both the nuclear bag fiber and the nuclear chain fiber?

A

the Ia fiber

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16
Q

the Ia fiber changes its firing rate to what two things?

A

the length of the muscle and how fast the length is changing

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17
Q

What does the secondary afferent of the muscle spindle innervate?

A

only the nuclear chain fiber

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18
Q

what is the secondary afferent fiber?

A

group II fiber

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19
Q

what is the group II fiber sensitive to/ what will it change its firing rate to?

A

sensitive only to the length of the muscle (not to the speed it took to get there)

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20
Q

What is the motor portion of the muscle spindle (the intrafusal fibers) innervated by?

A

gamma motor neuron

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21
Q

what is the purpose of the motor portion of the muscle spindle?

A

it controls the length of the sensory portion of the muscle spindle

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22
Q

What happens when you contract the intrafusal muscles (the motor portion) of the muscle spindle?

A

it is going to lengthen/ stretch the sensory portion

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23
Q

What happens when the sensory portion of the muscle spindle is stretched?

A

it is going to be more sensitive to a superimposed stretch (increases the sensitivity of the Ia and II fibers to stretch)

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24
Q

What innervates the extrafusal fibers?

A

an alpha-motor neuron

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25
Q

What controls sensitivity of the muscle spindle?

A

the gamma motor neuron

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26
Q

Which motor neuron activity directly leads to motion?

A

alpha-motor neuron

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27
Q

within the spinal cord, the Ia afferent from the muscle spindle synapses where?

A

directly onto the alpha-motor neuron innervating the stretched muscle

28
Q

what is the NT released when the Ia afferent synapses onto the alpha motor neuron?

A

EAA

29
Q

what does the released EAA cause the alpha motor neuron to do?

A

contract the stretched muscle

30
Q

What does contraction of the stretched muscle do?

A

it relieves the stretch, returning the Ia discharge rate back to normal

31
Q

What happens to the antagonist muscle during the myotatic (stretched) muscle reflex?

A

it is actually getting stretched

32
Q

Besides the alpha motor neuron, what else does the Ia afferent fiber branch to synpase onto?

A

an interneuron

33
Q

Is the interneuron excitatory or inhibitory and what does it release?

A

inhibitory and releases GABA or glycine

34
Q

what does the GABA/glycine have its inhibitory effects on?

A

the alpha motor neuron of the antagonist muscle

35
Q

What happens to the antagonist muscle when exposed to GABA/glycine?

A

it will have fewer action potentials and therefore relax

36
Q

what does the relaxation of the antagonist muscle allow it to do?

A

it allows it to stretch and go along with the reflex

37
Q

what is the appearance of the golgi tendon reflex?

A

sudden (abrupt) relaxation of a contracted muscle

38
Q

what is the purpose of the golgi tendon reflex?

A

to protect the muscle from damage due to excessive force

39
Q

what is the golgi tendon reflex initiated by?

A

the golgi tendon organ

40
Q

is the golgi tendon reflex monosynpatic or polysynaptic?

A

polysynaptic

41
Q

What innervates tendons?

A

golgi tendon organ

42
Q

What is the golgi tendon organ?

A

it is a bare nerve ending with multiple branches

43
Q

As contraction of a muscle increases, what happens to the action potentials in the golgi tendon organ that is innervating the tendon of that muscle?

A

they increase as tension increases

44
Q

what carries the information from the tendon to the spinal cord?

A

Ib fiber

45
Q

what is the Ib afferent from the golgi tendon going to synapse onto?

A

an interneuron

46
Q

what does the Ib afferent release when it synapses onto the interneuron?

A

EAA

47
Q

is the interneuron excitatory or inhibitory?

A

inhibitory

48
Q

what does the inhibitory interneuron release when it synapses onto the alpha motor neuron of the contracted muscle?

A

GABA

49
Q

What happens when the alpha-motor neuron is inhibited by the activation of the spinal interneuron?

A

abrupt relaxation of the contracted muscle- returning the golgi tendon organ discharge rate back to normal

50
Q

What is spinal shock?

A

loss of reflex below the level of the transection (lesion of the spinal cord)

51
Q

recovery of reflexes are believed to be result from what?

A

axonal sprouting below the level of the transection and expression of receptor phenotypes that are self activating

52
Q

is the brainstem facilitatory region spontaneously active or does it require activation?

A

it is spontaneously active

53
Q

Normal reflexes depend on the balance of what two regions?

A

the brainstem facilitatory region and the brainstem inhibitory region

54
Q

what does the brainstem inhibitory region require activation from?

A

cortical regions

55
Q

in a patient with damage to the cortex, is the brainstem facilitatory region or the brainstem inhibitory region most affected?

A

the brainstem inhibitory region

56
Q

what would uncontrolled brainstem facilitatory region result in?

A

hyperactive reflexes as well as stretch reflexes that fight any passive motion aka spasticity

57
Q

What causes decerebrate posturing?

A

it results from loss of all structures rostral to the pons

58
Q

What is true about all of the muscles in a patient with decerebrate posturing?

A

all of their muscles are extended

59
Q

What is rigidity?

A

it is maintained muscle contraction; continual activation of the alpha-motor neurons

60
Q

You have to apply what to see spasticity?

A

a passive motion

61
Q

What is spasticity?

A

myotatic reflex is hyperactive and you have continual activation of the gamma motor neurons

62
Q

what is the cause of rigidity?

A

there is a loss of cortical influence that inhibits a medullary input to the alpha-motor neurons

63
Q

What does decorticate posturing look like?

A

flexion of the upper limb joints and extension of the lower limbs

64
Q

what causes the flexion of the upper limb joints as seen in decorticate posturing?

A

disinhibition of the red nucleus and its control of the UE flexors

65
Q

what causes the extension of the lower limbs seen in decorticate posturing?

A

disinhibition of reticulospinal and vestibulospinal pathways

66
Q

What is decorticate posturing dependent on?

A

head position

67
Q

What would cause unilateral decorticate posturing?

A

strokes in the vicinity of the internal capsule

Neuroendocrine Exam 2 (17 decks)

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