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Block 5 Week 3 Dani > Motor Neurons I - Kenyon > Flashcards

Motor Neurons I - Kenyon Flashcards

1
Q

Where do the axons of the lower motor neurons end?

A

At nueromuscular junctions

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2
Q

Are lower motor neurons excitatoryor inhibitory?

A

Excitatory

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3
Q

What type of receptor do the nueromuscular junctions use?

A

Nicotinic receptor

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4
Q

what is the neurotransmitter used at the neuromuscular junction?

A

ACh

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5
Q

Where are the cell bodies located for lower motor neurons?

A

Brainstem or spinal cord

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6
Q

Where are the cell bodies located for upper motor neurons?

A

Brainstem and cerebral cortex

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7
Q

Are upper motor neurons excitatory, inhibitory, or both?

A

Both!!

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8
Q

Is the major pathway from upper motor neurons a direct link to local circuit neurons or to lower motor neurons?

A

Local circuit neurons

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9
Q

Can sensory inputs link directly to both local circuit neurons and motor neuron pools?

A

Yes!

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10
Q

Besides connecting directly to local circuit neurons and to motor neuron pools, what brain macrostructure does sensory info pass through on the way to upper motor neurons

A

Cerebellum

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11
Q

the connections from the sensory input to the local circuit neurons are (excitatory/inhibitory/both)

A

both

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12
Q

the connections from lower motor neurons to skeletal muscle are (excitatory/inhibitory/both)

A

excitatory

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13
Q

Ventral horn controls the (blank) muscles of the body

A

skeletal

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14
Q

the somatic motor nuclei in the brainstem include which nuclei?

A

Oculomotor, trochlear, abducens, hypoglossal ( 3, 4, 6, 12)

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15
Q

The branchial nuclei in the brainstem include which nuclei?

A

Trigeminal, facial, ambiguus, spinal accessory (5, 7, 9 and 10, 11)

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16
Q

the premotor cortex has what general function?

A

Planning, initiating, and directing series of movements in limbs and eyes

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17
Q

The cingulate gyrus has what general function with regards to behavior?

A

Expression of emotions, especially involving facial muscles

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18
Q

Upper motor neurons in the brainstem are in what three nuclei?

A
  1. Vestibular nuclei
  2. Reticular formation
  3. Superior colliculus
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19
Q

Upper motor neurons project (medially/laterally) to the cervical spinal cord

A

medially

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20
Q

Cerebellar neurons influence the activity of (upper/lower) motor neurons

A

upper motor neurons

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21
Q

What is the general function of the cerebellum?

A

Compares actual movement with intended movemetn and makes corrections

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22
Q

Basal ganglia are located in what area of the brain?

A

Forebrain

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23
Q

What nuclei are included in the basal ganglia? (5)

A
  1. caudate and putamen
  2. globus pallidus
  3. substantia nigra
  4. subthalamic nucleus
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24
Q

What will happen to your movements if you have basal ganglia dysfunction?

A

You will have unwanted movements or inability to suppress movements

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25
Q

What kinds of diseases are involved with cerebellar dysfunction?

A

Huntington’s and parkinson’s

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26
Q

What two cell types do local circuit neurons receive input from?

A

Upper motor neurons and sensory neurons

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27
Q

What is the effect of local circuit neurons on lower motor neurons?

A

They excite or inhibit them

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28
Q

Lower motor neurons driving axial (postural) muscles are located (medially/laterally) while those driving distal structures (hands) are located (medially/laterally)

A

postural=medial

distal=lateral

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29
Q

Local circuit neurons controlling posture send projections to (same/opposite/both) sides of the cord? What are these axons called?

A

Both! Commissural axons

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30
Q

Local circuit neurons control posture by (contracting/relaxing) muscles over a large part of the body

A

relaxing

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31
Q

Local circuit neurons controlling limbs have (long/short) projections

A

short projections (wiggling a finger does not involve muscles of the torso)

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32
Q

so is there innervation at multiple levels/crossing over for wiggling your finger?

A

No!

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33
Q

the lateral corticospinal tract crosses over where?

What does it provide?

A

At the pyramids

innervation to distal limbs and fine movements

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34
Q

Does the ventromedial white matter (reticulospinal and vestibulospinal and a tiny bit of corticospinal) cross over at the pyramids?

A

They do not cross over

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35
Q

What are the three columns within the ventromedial white matter that contain fibers that go to axial muscles of posture?

A
  1. Reticulospinal
  2. Vestibulospinal
  3. tiny bits of corticospinal
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36
Q

the Brainstem innervates muscles of the (same/opposite) side

A

same

37
Q

The cortex innervates muscles on the (same/opposite) side

A

opposite

38
Q

A motor neuron and its muscle fiber are known as a (blank)

A

motor unit

39
Q

The lower motor neurons for a given muscle are clustered in what horn of the spinal cord?

A

ventral horn

40
Q

Are the nerve fibers of a lower motor neuron concentrated in one spot in a muscle?

A

No, they are spread out rather randomly throughout the muscle

41
Q

(blank) motor units are red muscle, fatigable, and are continuously active (posture)

A

Slow

42
Q

(blank) motor units are paler and create large forces for short bursts

A

Fast fatigable

43
Q

What motor unit shows a higher intensity force that gradually decreases over several minutes?

A

Fast fatigue-resistant

44
Q

The properties of the alpha motor neurons correlate with the number of skeletal muscle fibers, i.e. the (blank) of the motor unit

A

size

45
Q

Small motor units that are easy to depolarize to threshold, needing fewer EPSPs, are good for what types of muscles?

A

postural

46
Q

larger motor units that are harder to depolarize to threshold, requiring more EPSPs are good for what types of muscles?

A

Fast fatigable muscles

47
Q

In what order are the classes of muscle fibers innervated?

A

Slow, fast-fatigue resistant, then fast fatigable

48
Q

What are the three feedback systems in the spinal cord that help control muscle length and tension?

A
  1. muscle spindles
  2. Golgi tendon organs
  3. Flexion reflex
49
Q

Muscle spindles help control muscle (blank)

A

length

50
Q

Golgi tendon organs help control muscle (blank)

A

tension

51
Q

What reflex helps you move away from an unpleasant stimulus?

A

Flexion tendon

52
Q

(alpha/gamma) fibers cause contraction of the intrafusal spindle fibers

A

gamma

53
Q

Group Ia and group II fibers are (efferent/afferent) fibers going to the (normal muscle/muscle spindle)

A
  1. afferent

2. muscle spindle

54
Q

Group Ia fibers detects rapid changes in (length/tension) of muscle and respond (phasically/gradually)

A
  1. length

2. phasically

55
Q

Group II fibers detects rapid changes in tonic (contraction/stretch)

A

stretch

56
Q

What three fiber types make up the afferents leaving the spindle fibers?

A

gamma, Ia, II

57
Q

Ia fibers relay what part of TVP?

A

The P!

58
Q

T/F: Ia afferents synapse on interneurons before synapsing with lower motor neurons

A

F: they synapse directly onto lower motor neurons

59
Q

Stretching the muscle will increase what afferent fiber activity?

A

Ia

60
Q

stretching a muscle will (inc/dec) lower motor neuron activity to that muscle

A

increase

61
Q

stretching a muscle will (inc/dec) lower motor neuron activity to the opposing muscle

A

decrease

62
Q

muscle spindle fibers follow pathway A (synapse in spinal cord) or pathway B

A

Pathway B–synapse in dorsal horn and exit the cord

63
Q

In what Rexed layer of the dorsal horn do Ia fibers synapse?

A

Rexed 3 (combining info from somatosensory and this lecture)

64
Q

How are local circuit neurons used in the muscle spindle reflex?

A

They receive afferent info from the muscle spindle and relay that to motor efferents to the antagonist muscle to inhibit it

65
Q

Activity in what motor fiber type alters the sensitivity of muscle spindles?

A

gamma

66
Q

what would be the effect if a muscle lacked gamma fiber innervation?

A

Muscle spindle cells (aka intrafusal fibers) wouldn’t contract with the rest of the regular muscle (aka extrafusal), the cerebellum wouldn’t get any afferent input of muscle proprioception and you wouldn’t be able to coordinate your movements

67
Q

Do upper or lower motor neurons set the activity of the gamma fibers?

A

Upper

68
Q

Determine if the following activities are high or low gamma activity:

  1. sitting
  2. stretching
  3. standing on a moving bus
  4. skiing
A
  1. low
  2. low
  3. high
  4. high
69
Q

Encapsulated afferent nerve endings between the muscle and tendon are known as (blank)

A

golgi tendon organs

70
Q

What fiber types are carried by GTO’s?

A

Ib

71
Q

are GTO’s acitvated by tension or length?

A

tension

72
Q

What happens to GTO firing when a muscle is stretched?

A

It increasely only ever so slightly

73
Q

What happens to GTO firing when a muscle contracts under load?

A

It greatly increases in firing

74
Q

What happens to spindle fiber firing when a muscle contracts?

A

Firing is reduced

75
Q

Is the GTO capable of discerning the difference between increased tension from contraction and passive stretch?

A

Yes

76
Q

Are muscle spindle fibers or GTO’s involved in controlling muscle force?

A

GTO

77
Q

Do GTO’s directly synapse onto lower motor neurons?

A

No, they synapse onto local circuit neurons

78
Q

What will the GTO do if it senses that the force is too great on a muscle?

A

it will synapse onto local circuit neurons which will 1) inhibit the homonymous muscle (where the GTO came from) and 2) activate the opposing muscle to drop the weight

79
Q

What kind of loop is the GTO system? Open, closed, negative, positive?

A

Closed negative feedback loop

80
Q

Is the GTO system isolated?

A

No, the gains and set points are subject to control via the descending pathways

81
Q

How do PANs for pain and temp link to lower motor neurons?

A

Both directly and via interneurons

82
Q

In the flexion reflex pathway, explain what happens to your legs when you step on a pin?

A

The ipsilateral leg (stepped on pin) flexes (raises leg up), while the contralateral leg extends

83
Q

Is the flexion reflex pathhway adjustable?

A

yes, via the descending activity

84
Q

Is the spinal cord capable of generating sequences of movements without cortical input?

A

Yes, think about the cat on the treadmill

85
Q

What are the somatic motor nuclei of the midbrain?

A 
OATH
Oculomotor (3)
Abducens (6)
Trochlear (4)
Hypoglossal (12)
86
Q

What are the branchiomotor nuclei of the midbrain?

A 
FATS
Facial (7)
Ambiguus (10)
Trigeminal (5)
Spinal Accessory (11)
87
Q

Where do lesions occur that cause lower motor neuron syndrome?

A

Spinal cord or periphery

88
Q

What are some of the symptoms of lower motor neuron syndrome?

A

Paralysis or paresis (weakness), AREFLEXIA, loss of tone, atrophy, fibrillations, fasciculations

Block 5 Week 3 Dani (12 decks)

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