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Neurosciences L > L5 Locomotion > Flashcards

L5 Locomotion Flashcards

1
Q

What are the three types of motor units?

A

small
intermediate
large

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2
Q

What is a motor unit?

A

one motor neuron and the muscle fibers it innervates

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3
Q

What is the motor neuron pool?

A

all motor neurons innervating a given muscle

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4
Q

Which motor units have high myoglobin content?

A

small and intermediate

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5
Q

Which motor units are recruited first?

A

small

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6
Q

Which motor units are recruited last?

A

large

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7
Q

What is a muscle spindle?

A

CT sheath that contains muscle fibers

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8
Q

How are muscle spindles arranged?

A

In parallel

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9
Q

What innervates intrafusal muscle fibers?

A

sensory nerve endings

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10
Q

How do sensory nerves enter the spinal cord?

A

Via dorsal roots

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11
Q

What do Ia fibers measure?

A

muscle length and rate of length change

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12
Q

What do group II fibers measure?

A

length

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13
Q

Which fiber group has a faster conduction speed?

A

Ia

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14
Q

What is reciprocal inhibition?

A

an inhibitory interneuron between Ia afferent and motor neurons

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15
Q

What do interneurons innervate?

A

Unstretched muscle

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16
Q

What is a stretch reflex?

A

a muscle is stretched, spindle afferents excite alpha motor neurons

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17
Q

What does the stretch reflex regulate?

A

muscle length via negative feedback

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18
Q

What is proprioception?

A

sense of relative position

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19
Q

What type of afferents provide proprioceptive information?

A

Ia afferents

20
Q

What causes contraction of the two end of muscle fibers?

A

gamma motor neurons

21
Q

What is the effect of gamma motoneuron activation?

A

contraction at the end of the muscle
stretches the middle
promotes Ia activity

22
Q

What are the two classes of descending alpha motoneuron activation?

A

direct activation
indirect activation

23
Q

What facilitates indirect activation of alpha motoneurons?

A

gamma loop

24
Q

Describe the gamma loop?

A

gamma excited –> intrafusal fiber contract –> Ia stretches –> activates alpha motoneuron

25
Q

what does alpha-gamma co-activation produce?

A

movement

26
Q

What is the effect of alpha-gamma co-activation?

A

Ia spindles afferents remain active for load increase

27
Q

Where are Ib nerve ending found?

A

small tendon fascicles

28
Q

How are Ib fibers activated?

A

by tension produced by muscle contraction

29
Q

What is the inverse myotatic reflex (tendon organ reflex)?

A

di-synaptic reflex arc
- synergistic muscles are inhibited
- antagonistic muscles are excited

30
Q

What does the tendon organ reflex regulate?

A

muscle force via negative feedback

31
Q

Why do we have the tendon organ reflex?

A

to reduce muscle force

32
Q

T/F the stretch rflx and tendon organ rflx can work together

A

TRUE

33
Q

What is muscle stiffness?

A

change in force / change in length

34
Q

What the relationship b/n stretch rflx and muscle stiffness?

A

it increases muscle stiffness

35
Q

What the relationship b/n tendon organ rflx and muscle stiffness?

A

it decrease muscle stiffness

36
Q

What is the main effect of reflexes?

A

balancing support and shock absorption in anti gravity muscles

37
Q

What the the flexor rflx a response to?

A

noxious stimulation of muscle or skin

38
Q

What influence spinal cord motor units?

A

descending ptwys from the brain

39
Q

What are upper motor neurons?

A

neurons in the brain

40
Q

What changes occur in motor tone when upper motor neurons are damaged?

A

spinal shock (hypotonia)
spasticity (hypertonia)

41
Q

What contributes to spasticity after spinal cord injury?

A

down-regulation of K-NA cotransporter KCC2

42
Q

T/F BDNF can up regulate the transporter after spinal cord injury

A

True

43
Q

What are the phases of step cycling?

A

extensor phase
flexor phase

44
Q

What does reflex feedback influence?

A

phase duration and pattern

but is not necessary for rhythm generation

45
Q

What can Dysfunctions in brainstem circuits cause?

A

REM sleep disorder (sleep walking)

46
Q

What are the two classes of mechanism for Central pattern generator?

A
  1. cell have intrinsic burts of APs
  2. Emergent network property
47
Q

What is the emergent network property?

A

reciprocal inhibition and adaption account for alternating activity in flexors and extensors

Neurosciences L (5 decks)

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