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Neuroantomy > Reflexes > Flashcards

Reflexes Flashcards

1
Q

what 3 sources provides us with sensory information about our movement?

A

proprioception
visual information
vestibular information

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2
Q

what is interdependent?

A

sensory input and movement

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3
Q

where are the cell bodies of our sensory neurons located?

A

in the dorsal root ganglia

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4
Q

how do sensory neurons send their messages to the spinal cord?

A

via the posterior roots

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5
Q

are peripheral nerves typically sensory or motor?

A

both, they are mixed

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6
Q

what information does the somatosensory system provide?

A

touch
proprioception
pain
temp

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7
Q

what are intrafusal muscle fibres encapsulated in?

A

connective tissue

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8
Q

what do intramural muscle fibres detect?

A

muscle length and velocity

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9
Q

what are the 2 types of sensory axons?

A

Type 1a
Type 2

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10
Q

what are type 1 axons wrapped around?

A

nuclear bag fibres

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11
Q

what are type 1a axons sensitive to?

A

changes in muscle length and velocity

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12
Q

what are type 2 axons wrapped around?

A

nuclear chain fibres

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13
Q

what do type 2 axons measure?

A

muscle length

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14
Q

what do alpha motor neurons innervate?

A

extrafusal muscle fibers

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15
Q

what are gamma motor neurons responsible for?

A

innervating the intramural muscle fibres

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16
Q

do alpha or gamma motor neurons have a lower threshold for activation?

A

gamma

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17
Q

what can gamma motor neurons be modulated by?

A

descending pathways

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18
Q

during active muscle contraction, which muscle fibres contract first?

A

gamma motor neurons cause the intramural fibres to contract at the same time as the extrafusal fibres

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19
Q

when does alpha-gamma co-activation only occur?

A

in movements initiated by the CNS (so it doesn’t happen during a reflex)

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20
Q

where are Golgi tendon organs found?

A

near the musculotendinous junction

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21
Q

what are Golgi tendon organs designed to measure?

A

muscle tension/force

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22
Q

what are the simplest form of movement?

A

reflexes

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23
Q

what does it mean that reflexes are stereotype?

A

evrytim you do an action you should see the sam response (tapping patellar tendon with reflex hammer)

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24
Q

what are reflexes largely controlled by?

A

local circuitry in the spinal cord

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25
Q

what happens if the input of the stimulus is increased?

A

larger amplitude

26
Q

how do our descending pathways influence our reflexes?

A

reflexes can be excited or inhibited via descending control

27
Q

why is the stretch reflex homonymous?

A

because the same muscle that stretched, is excited and contracts

28
Q

what can both our reflexes and spindle sensitivity be modulated by?

A

UMNs

29
Q

what is the purpose of the stretch reflex?

A

to maintain our muscle length or return the muscle to the desired position

30
Q

what happens at the same time as the stretch reflex?

A

reciprocal inhibition

31
Q

what is reciprocal inhibition?

A

the antagonist alpha motor neuron is inhibited while we get contraction of our agonist muscle

32
Q

what type of sensory neurons go from he GTO tot her spinal cord in the GTO reflex?

A

sensory afferent 1B

33
Q

what is the function of the GTO reflex?

A

release load to prevent muscle tearing and maintains muscle tone during muscle fatigue (ex: dropping a heavy weight so you do not tear muscle)

34
Q

what are examples of the flexor withdrawal reflex?

A

stepping on a tack
grabbing a hot pan

35
Q

what is the sensory input of the flexor withdrawal reflex?

A

noxious stimulus detected

36
Q

what is activated by a noxious stimulus in the flexor withdrawal reflex?

A

Group 3 afferent neurons

37
Q

what occurs with the flexor withdrawal reflex?

A

crossed extensor reflex

38
Q

what is the function of the crossed extensor reflex?

A

ground stance limb to allow ipsilateral limb to withdraw

39
Q

what reflex crossed the spinal cord?

A

crossed extensor reflex

40
Q

how many spinal cord levels does the crossed extensor reflex span?

A

multiple spinal cord levels to activate many muscles (example activating ankle, knee, hip)

41
Q

what is an UMN lesion?

A

damage to the descending tract before the anterior horn of the spinal cord

42
Q

what is a typical response to an UMN injury/damage?

A

hyperreflexia

increased muscle tone (increased resistance to passive movement)

+Babinski/Hoffman

43
Q

what is a 3+ stretch reflex?

A

brisk (increased; possibly abnormal)

44
Q

what is a 4+ stretch reflex?

A

very brisk, hyperactive, with clonus

45
Q

what is a 5+ stretch reflex?

A

sustained clonus

46
Q

are we more likely to see hyperreflexia with UMN or LMN condition?

A

UMN

47
Q

where does the reticulospinal tract originate?

A

reticular formation

48
Q

where does the reticulospinal tract terminate?

A

bilaterally in the spinal cord

49
Q

where does the reticulospinal tract recive input from?

A

both sides (ipsilateral and contralateral) of cortex

50
Q

what is the dorsal/lateral reticulospinal tract responsible for?

A

descending inhibition (like the brakes of a car)

51
Q

what is the medial reticulospinal tract responsible for?

A

descending excitation (like the gas in a car)

52
Q

what is damaged in a SCI?

A

the lateralcorticospinal tract and reticulospinal tracts

53
Q

what is an analogy for a SCI and the stretch reflex?

A

you are on cruise control, going down a hill, all gas no brakes

53
Q

what causes hypertonia in a SCI and the stretch reflex?

A

hypertonia is due to a loss of descending control?

54
Q

what tracts are damaged with stroke and the stretch reflex?

A

right lateral corticospinal and corticoreticular tracts

55
Q

what is the analogy for stroke and the stretch reflex?

A

all gas no brake

56
Q

what does loss of descending control and excessive neural firing contribute to?

A

hypersensitivity of the muscle spindle

excitable alpha motor neurons

57
Q

where would damage to a LMN be located?

A

at or distal to the anterior horn

58
Q

what are the hallmarks of a LMN injury?

A

hypotonia
hyporeflexia

59
Q

what is a 1+ stretch reflex?

A

present but depressed

60
Q

what is a 0 stretch reflex?

A

no response (areflexia)

61
Q
A

Neuroantomy (22 decks)

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