Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MABS Physiology > lecture 9 > Flashcards

lecture 9 Flashcards

mechanisms of neuronal transduction

1
Q

what happens when sensory fibers enter the spinal cord?

A

they are transmitted to higher centers or they synapse locally to elicit motor reflexes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

where are the motor neurons located?

A

they are located in the anterior portion of the cord of the cord aka the ventral horn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how much bigger are the motor neurons located in the anterior portion of the cord compared to other motor neurons?

A

50-100% times bigger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

where are the sensory neurons located?

A

they are located in the dorsal horn and so they receive a stimulus and transmit to the higher centers of the nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

]what the two types of anterior motor neurons?

A

alpha (lower motor neurons) and gamma motor neurons(which work on sensory apparatus called muscle spindles or intrafusal fibers)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the alpha motor neurons?

A

they give rise to large alpha A fiber, upon stimulation they excite extrafusal fibers (collectively called a motor unit) and these neurons go to the muscle cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the gamma motor neurons?

A

give rise to smaller type A gamma fibers and go to small special skeletal muscle fibers called intrafusal fibers; note that more of these neurons makes the muscle more sensitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is important to note about interneurons?

A

they help us create reflex type movements and comprise the neural circuitry for the motor reflexes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

define the Renshaw Cell Inhibitory System

A

immediately after the anterior motor neuron axon leaves the body of the neuron, collateral branches from the axon pass to adjacent Renshaw cells. These are inhibitory cells that transmit inhibitory signals to the surrounding motor neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Renshaw cells are inhibitory cells that transmit inhibitory signals to the surrounding motor neurons, T/F?

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are propiospinal fibers?

A

they travel up and down the cord for 1-2 segments and provide the pathways for multisegmental reflexes, like the registration of pain and temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

when we initiate voluntary muscle movements, what fibers are we innervating?

A

the extrafusal fibers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the two types of sensory receptors of the muscle?

A

muscle spindle and golgi tendon organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the muscle spindle?

A

these sense muscle length and change in length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the golgi tendon organ?

A

these sense tendon tension and change in tension, these consist of sensory nerve endings interwoven among collagen and are type 1b afferent motor neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what type of neuron is the golgi tendon organ?

A

Type 1b afferent motor neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are the signals from the mentioned sensory receptors (muscle spindle and golgi tendon organ) of the muscle for?

A

intrinsic muscle control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

in terms of the the muscle spindle, there are two important endings, what are they?

A

primary ending and secondary ending

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what type of neurons are the primary endings of the muscle spindle? where do these go?

A

these are Type 1a afferent motor neuron and they go to the bag fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how would you describe the shape of the primary ending?

A

annulospiral ending located in the center of the receptor area and encircles the central portion of each intrafusal fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what type of neurons are the secondary endings of the muscle spindle? where do these go?

A

type II afferent fibers and these innervate the chain fibers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how would you describe the actions of the secondary fibers?

A

innervate the receptor region on one or both sides of the primary ending and they spread like branches on a bush, hence the word, chain fibers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the extrafusal fibers?

A

alpha motor neurons that give rise to large type A alpha fibers and are collectively called a motor unit and are outside and around the muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are the intrafusal fibers?

A

these are gamma motor neurons that are small, special skeletal muscle fibers within the muscle spindle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

in terms of physiologic function of the muscle spindle, what do we call the simplest manifestation of muscle spindle function?

A

muscle stretch reflex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what happens when a muscle is stretched suddenly?

A

excitation of the spindles causes a reflex contraction of the large skeletal muscle fibers of the stretched muscle and also of closely allied synergistic muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is the importance of the coactivation of alpha and gamma motor neurons?

A

they keep the length of the receptor portion of the muscle spindle from changing during the course of the muscle contraction and so this phenomenon keeps the muscle spindle from opposing the muscle contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

T/F, coactivation of the alpha and gamma motor neurons maintains the proper damping function of the muscle spindle, regardless of change in muscle length

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

when alpha motor neurons are stimulated by upper centers, what other motor neuron is stimulated?

A

gamma motor neurons are also stimulated (both extrafusal and intrafusal fibers contract at the same time)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

In terms of the role of muscle spindles in voluntary motor activity, what percent of motor nerve fibers to the muscle are small type A gamma efferent fibers?

A

31%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is the name of the efferent fibers that make up 31% of the motor nerve fibers to the muscle, this is in terms of the role of muscle spindles in voluntary motor activity.

A

type A gamma efferent fibers

32
Q

in terms of the role of muscle spindles in voluntary motor activity when alpha motor neurons are stimulated, what other motor neurons are stimulated? what is this called? what is the effect on extrafusal and intrafusal fibers?

A

gamma motor neurons; coactivation of alpha and gamma neurons; it causes them to contract at the same time

33
Q

what is the golgi tendon organ?

A

these sense tension and change in tension

34
Q

what so golgi tendon organs consist of?

A

sensory nerve ending interwoven among collagen

35
Q

what motor neurons are the golgi tendon organ?

A

type 1b afferent motor neuron

36
Q

in terms of coactivation of alpha and gamma motor neurons what happens if gamma motor axons are cut?

A

the spindle loses activity when muscle contracts

37
Q

what is maintained during alpha-gamma coactivation?

A

maintains spindle function when muscle contracts

38
Q

during active contraction of the muscle, what motor neurons cause the contraction of the extrafusal muscle fibers with consequent relation of intrafusal fibers?

A

alpha motor neurons

39
Q

in active contraction are the spindles activated?

A

no

40
Q

what is the tension like in active contraction?

A

tension is slow, no adjustment made to increase resistance

41
Q

during muscle contraction is the golgi tendon organ activated? effect?

A

yes; causes relaxation

42
Q

in active contraction of the muscle, what fibers and motor neurons are involved?

A

type Ib fibers and alpha motor neurons

43
Q

what is active contraction with Gamma Coactivation?

A

Intrafusal and extrafusal fibers contract; spindles activated, reinforcing contraction stimulus via 1a fibers in accord with resistance

44
Q

in active contraction with Gamma Coactivation, is the golgi tendon organ activated? effect?

A

Tendon organ is activated, causing relaxation if load is too big

45
Q

in the damping mechanism in smoothing muscle contraction what happens when the spindle is not working properly?

A

the muscle contraction is jerky

46
Q

in neuronal circuitry of the stretch reflex, what is the monosynaptic pathway?

A

pathway allows a reflex signal to return with the shortest time delay to the muscle after excitation of the spindle

47
Q

in the neuronal circuitry of the stretch reflex, what is the monosynaptic stretch?

A

a single synapse between the afferent and efferent neurons

48
Q

what does the monosynaptic reflex oppose?

A

sudden changes in muscle length

49
Q

what is the purpose in the clinical application of the stretch reflex?

A

To determine how much background excitation or tone the brain is sending to the spinal cord

50
Q

what is being tested in the clinical application of the stretch reflex?

A

the facilitation of gamma efferents

51
Q

what is the effect of cortical lesions in the clinical application of the stretch reflex?

A

increase muscle stretch reflexes

52
Q

what is the name of the reflex tested in the clinical setting?

A

knee jerk reflex

53
Q

what is spinal reflex circuit?

A

when a skeletal muscle is abruptly stretched and a reflexive contraction of the same muscle occurs, increasing muscle tension and opposing the stretch.

54
Q

for what is the spinal reflex circuit strong? what is this reflex also called?

A

in physiological extensor muscles; myotatic reflex

55
Q

what is the knee jerk reflex?

A

A light tap on the patellar tendon deflects the tendon, which then pulls on and stretches the quadriceps femoris muscle

56
Q

what neurons are affected in the knee jerk reflex?

A

type 1a sensory neurons

57
Q

what happens physiologically to the body when we use the knee jerk reflex?

A

Passive stretching a skeletal muscle causes a reflexive contraction of that same muscle and relaxation of the antagonist muscle

58
Q

what is stimulated in the reflexive contraction of the knee jerk response?

A

The reflex stimulates in the spinal cord → the motor neurons to the extensor muscles → inhibits the motor neurons to the flexor muscle

59
Q

what does the stretch reflex depend on?

A

the nervous system and requires sensory feedback from the muscle

60
Q

what abolishes the stretch reflex?

A

Cutting the dorsal (sensory) roots to the lumbar spinal cord

61
Q

what is the effect of the knee jerk reflex?

A

the stretch reflex in the quad

62
Q

so in the knee jerk reflex, we see reciprocal innervation. What is this?

A

As the knee jerk reflex causes contraction of the quadriceps muscle → there is an antagonist relaxation during contraction (semitendinosus muscle antagonist to knee jerk reflex)

63
Q

what neuron are affected in reciprocal innervation?

A

Branches of the group Ia sensory axons excite specific interneurons that inhibit the α motor neurons of the antagonists

64
Q

what is the reflex the inverse myotatic reflex is also called?

A

golgi tendon reflex

65
Q

in the inverse myotatic reflex, what is the effect of the golgi tendon organs?

A

they become aligned in series with the muscle and super sensitive to the tension of a tendon and respond to force generated by muscle

66
Q

what sensory axons are involved in the Golgi tendon reflex?

A

group 1b sensory axons and these excite both the excitatory and inhibitory interneurons within the spinal cord
This circuit inhibits the muscle in which tension has increased and excites the antagonist muscle (opposite of stretch reflex)

67
Q

what does the inverse myotatic reflex inhibit?

A

the motor neurons to the extensor muscle and stimulates the motor neurons to the flexor muscle

68
Q

T/F, the inverse myotatic reflex uses more of the golgi tendon organ then it uses the sensory type 1b neuron?

A

T

69
Q

why does the golgi tendon want to equalize the force among muscle fibers?

A

to prevent too much tension on the muscle

70
Q

what is the inhibitory nature of the tendon reflex?

A

if the tension on the muscle and tendon is too high than inhibitory effect occurs providing relaxation of the entire muscle (lengthening reaction)

71
Q

what is the purpose of the protective mechanism in the golgi tendon reflex?

A

prevents tearing of the muscle or avulsion of the tendon from its attachments to the bones

72
Q

what type of reflex happens when you touch a hot pan?

A

reflexive

73
Q

what are the neurons that stimulate the flexor reflex?

A

from fast pain afferent neurons in the skin

74
Q

how is the flexor reflex different from a simple stretch reflex?

A

Unlike simple stretch reflexes, coordinate movement from entire limb or even pairs of limbs

75
Q

so in a leg that feels pain, what does the reflex inhibit? what about the opposite leg?

A

the motor neurons to the extensor muscle and stimulates the motor neurons to the flexor muscle; In the opposite leg, the reflex stimulates the motor neurons to the extensor muscle and inhibits the motor neurons to the flexor muscle (supports the body weight when the other leg flexes)

76
Q

how do reflexes affect movement?

A

it affects coordination of several muscle groups

Reflexive Movement
- Spinal integration, input to the brain
Postural reflexes
- Cerebral integration, maintains balance, input to cortex

MABS Physiology (57 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions