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Physiology > Reflexes > Flashcards

Reflexes Flashcards

1
Q

Motor output can be…

A

voluntary or involuntary

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2
Q

Motor system conveys information to…

A

muscles

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3
Q

Voluntary muscle responses:

A
  • conscious

- initiated at motor cortex

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4
Q

Signal flow for voluntary motor responses:

A

motor cortex -> brain stem -> spinal cord -> skeletal muscle

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5
Q

Involuntary motor response are also known as…

A

reflexes

- unconscious and subconscious mechanisms

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6
Q

Involuntary motor response is initiated at…

A
  • spinal cord level
  • brain stem
  • cerebellum
  • cortex
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7
Q

Reflex arc is the basic unit of…

A

involuntary neural activity

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8
Q

Reflex arc is an…

A

unlearned, built-in response

- can be modified by learning

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9
Q

Components of reflex arc:

A
  • sense organ/receptor
  • afferent neuron
  • central connection: one or more synapses occurring in the CNS
  • efferent neuron
  • effector tissue (skeletal, cardiac, or smooth muscle, glands)
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10
Q

Reflexes can be…

A

basic (monosynaptic) or complex (polysynaptic)

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11
Q

Autonomic reflexes:

A
  • viscera reflexes
  • polysynaptic
  • has tonic activity
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12
Q

Somatic reflexes can be…

A

monosynaptic or polysynaptic

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13
Q

Monosynaptic reflexes:

A
  • has a single synapse between the afferent and efferent neurons
  • simplest reflex
  • don’t need interneurons
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14
Q

Polysynaptic reflexes:

A
  • more than one synapse between the afferent and efferent neurons
  • need interneurons
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15
Q

Spinal reflexes:

A

reflex mediated by the spinal cord

  • ex: knee jerk
  • has reflex arc
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16
Q

Cranial reflexes:

A

controlled by small section of the brain

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17
Q

Bulk of muscle fibers are…

A

contractile fibers (extrafusal fibers)

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18
Q

What makes up the muscle spindle?

A

intrafusal fibers: thinner fibers found in belly of most muscles

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19
Q

Intrafusal fibers:

A
  • tension sensing fibers
  • set up reflexes to set muscle tension
  • monitor stretch of muscle
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20
Q

Muscle spindle flow of information:

A
  1. registers excess stretch
  2. goes to afferent fiber
  3. synapse in spinal cord
  4. efferent fiber
  5. muscle contracts
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21
Q

Afferent innervation of muscle spindle:

A

intrafusal fibers innervated by two types of fibers w/ modified dendritic receptors

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22
Q

Two types of fibers w/ modified dendritic receptors:

A
  • type 1a afferent fiber

- type 2 afferent fiber

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23
Q

Type 1a afferent fiber has what kind of dendritic ends?

A

annulospiral rings on dendritic ends

nuclear bag fibers

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24
Q

Type 1a afferent fiber transmits info about..

A

muscle length and velocity of contraction

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25
Q

Type 2 afferent fiber has what kind of dendritic ends?

A

flower spray dendritic ends

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26
Q

Type 2 afferent fiber transmits info about…

A

muscle length

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27
Q

Efferent motor output is associated with ____ activation

A

muscle spindle

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28
Q

Components of lower efferent output:

A
  • A alpha motor neurons in ventral horn

- A gamma efferent neurons

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29
Q

A alpha motor neurons:

A
  • large myelinated neurons
  • travels to NMJ of skeletal muscle
  • produces contraction of muscle
30
Q

Somatic motor unit of A alpha motor neurons:

A

alpha motor neuron and all the skeletal muscle fibers that its axon supplies

31
Q

Renshaw cells:

A
  • supplied by A alpha motor neurons
  • transmits inhibitory signals to surrounding motor neurons, which sharpens motor signals
  • is an interneuron
  • in gray matter of spinal cord
32
Q

A gamma efferent fibers:

A
  • myelinated, but smaller than A alpha motor neurons

- determines sensitivity of spindle to stretch

33
Q

A gamma efferent fibers supply…

A

intrafusal fibers of spindle itself

34
Q

Increased output from A gamma fibers leads to…

A

increased contraction of spindle, which increases the sensitivity to stretch

35
Q

T/F: A gamma fibers doesn’t allow the muscle to retain sensitivity of the reflex regardless of muscle length

A

F, it does allow it

36
Q

T/F: A alpha motor neurons and gamma fibers activate at different times

A

F, they coactivate

37
Q

What is the key reflex in maintenance of posture?

A

stretch/myotatic reflex

38
Q

Stretch/myotatic reflex is mediated by…

A

muscle spindle when the muscle is stretched

39
Q

Example of stretch/myotatic reflex:

A

knee-jerk: determines how much background info is coming from the brain

40
Q

How to activate the knee-jerk reflex:

A

tap the patellar tendon below knee and it should stretch the quadriceps muscle

41
Q

Components of stretch/myotatic reflex:

A
  • type 1a fiber
  • collateral synapses
  • type 2 (alpha beta)
42
Q

Type 1a fiber branch of stretch reflex directly synapses w/…

A

A alpha efferent fibers in ventral horn

43
Q

T/F: type 1a fiber branch of stretch reflex is polysynaptic

A

F, it’s monosynaptic

44
Q

Upon stimulation, type 1a fiber branch of stretch reflex produces…

A

contraction of stretched muscle

45
Q

Type 1a fiber branch of stretch reflex has a _____ response to _____

A

dynamic, rapid rate of length change

46
Q

Collateral synapses synapse on…

A

interneurons (polysynaptic)

47
Q

Collateral synapses in the stretch reflex only inhibits…

A

alpha motor neurons to antagonist muscles

- produces IPSPs at level of cord

48
Q

Collateral synapses participate in..

A

reciprocal innervation b/c accompanies stimulation of type 1a fiber branches

49
Q

Some of the type 2 fibers branch to…

A

alpha and gamma efferents

50
Q

Majority of type 2 fibers…

A

ascend to join DCML pathway

51
Q

There is a ______ response to slow prolonged spindle stretch

A

static

52
Q

Inverse myotatic reflex is also known as…

A

negative stretch reflex

53
Q

Inverse myotatic reflex is mediated by…

A

golgi tendon organs

54
Q

Golgi tendon organs in the inverse myotatic reflex responds to…

A

muscle tension relayed to tendon produced by excess muscle contraction

55
Q

Golgi tendon organs in the inverse myotatic reflex have…

A

modified dendritic ends w/ sensory somatic afferent type 1b fibers

56
Q

Type 1b fibers in the inverse myotatic reflex travel in…

A

DCML to cortex

57
Q

Collateral branches in the inverse myotatic reflex has two branches that do different things:

A
  • one sends IPSP to inhibit alpha motor neuron of the muscle initiating the response
  • other stimulates the alpha motor neurons of antagonistic muscles
58
Q

What happens when collateral branches send IPSP?

A

muscle relaxation

59
Q

What happens when collateral branches stimulates the alpha motor neurons of antagonistic muscles?

A
  • contraction of antagonist

- helps equalize the muscle load and can stabilize muscles across a joint

60
Q

Flexor withdrawal reflex is also known as…

A
  • pain reflex
  • withdrawal reflex
  • nociceptive reflex
61
Q

Flexor withdrawal reflex has a _____ response

A

prepotent: preempts spinal pathways from any other reflex activity taking place at that moment

62
Q

Flexor withdrawal reflex stimulates…

A

a variety of sensory receptors

- most strongly stimulated by pain

63
Q

Flexor withdrawal reflex is a ______ reflex

A

polysynaptic

64
Q

Flexor withdrawal reflex has what type of fiber?

A

A delta fiber from nociceptor synapses in dorsal horn of gray matter

65
Q

A delta fiber in the flexor withdrawal reflex synapse w/…

A

2nd order neuron carrying pain via LST to thalamus

66
Q

Collaterals in the flexor withdrawal reflex synapse w/ _____ and causes…

A

series of interneurons, flexion of the ipsilateral limb and extension of contralateral limb
- has double reciprocal innervations to help equalize balance loads and stabilizes muscles across joint

67
Q

Flexion of ipsilateral limb has reciprocal innervations that…

A

inhibits extensors of ipsilateral limb (flexion reflex)

68
Q

Extension of contralateral limb has reciprocal innervations that…

A

inhibits activity of contralateral flexors (crossed-extensor reflex)

69
Q

Damage to the spinal cord will interfere with…

A

spinal reflexes

70
Q

If one suffers damage to spinal cord, he/she will first get…

A

spinal shock that lasts 3-4 weeks

71
Q

Spinal shock is characterized by…

A
  • flaccid paralysis
  • loss of autonomic function
  • loss of all sensation below injury site
  • joint has no resistance to being passively moved
72
Q

What happens when the spinal shock eventually wears off?

A
  • reflexes return gradually and become hyperactive
  • provides greater resistance at joints
  • voluntary movement and sensation might not ever return

Physiology (33 decks)

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