Spinal Cord and Movement 2: Reflexes Lec19 Flashcards Preview

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Flashcards in Spinal Cord and Movement 2: Reflexes Lec19 Deck (42):
1

Extrafuscal (normal) muscle fibers are innervated by 

α motor neurons

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2

Intrafuscal (muscle spindle / stretch receptors) fibers are innervated by

 γ motor neurons
and by Type Ia and Type II sensory neurons

3

Spindles are arranged in ___ with extrafuscal muscle fibers

parallel

4

what do γ motor neurons affect? 

only spindle stiffness, not contraction

5

Muscle spindles send stretch signals via 

type Ia and type II neurons:

6

 Type ___ central (bag) region

Ia:

7

type ___ fire intensely at onset of stretch,

! then slows down.

1a

8

type II firing is at what rate

static, increases linearly with increasing strethc

9

Stretch reflex?

 muscle spindle senses stretch --> spinal cord --> original (homonymous)
and synergist (heteronymous) muscles excited and anatagonist inhibited to counter perturbation

10

during stretch reflex, the Antagonist

muscle is___

inhbhited by interneruons

11

Contraction response:

when extrafuscal muscle contracts,____fire to
shorten intrafuscal fibers

 the γ motor neurons 

12

why do the  the γ motor neurons fire during contraction response? 

to shorten the intrafusal fibers and to keep them sensitive

13

Golgi Tendon Organs (GTO) only fire when muscle ___

actively contracts

14

muscle spindle cares about ___

length

15

golgi tendon cares about ___

tension

16

holgi tendon organs are receptors are ___ fibers

Type Ib

17

golgi tendon organ receptors arranged in ____ with extrafuscal muscle fibers

series

18

muscle spindle is the only afferent that ___

receives a nerve supply

19

difference between gamma motor neurons and alpha MN?

gamma has a smaller soma and a lower conduction velocity

20

____ motor.. innervate intrafusal not at center point
but lower down

gamma

21

____ contraction makes the muscle spindle more sensitive to stim.

intrafusal

22

sensory receptors on intrafusal fibers

type 1a and II

23

___ receptor fires with stretch from distal muscle spindle 

type II

24

biceps  and brachialis are examples of

agonists

25

triceps and biceps are

anatagonists

26

increased load about the elbow causes rotation

--> spindle in biceps are stretched -->

afferents sent to spinal cord activating the

biceps motor neurons

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27

when an anatagonist muscle is inhibited it is by a

 

1a inhibitory interneuron

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28

correction is ____ perturbation

resisting

29

if you ___ of a spindle it becomes silent

reduce

30

when alpha motor neuron is activated without ___ you get silent

gamma MN

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31

golgi tendon reflex involves the ___ interneuron

1b

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32

in golgi tendon reflex action

1b interneuron does what

excites the anatgonist muscle

inhibits the agonist muscle

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33

Flexion-crossed-extension reflex:

 if one limb reflexively withdraws, the limb across the midline ____ to keep you balanced.

extends

34

Central pattern generators are defined as neurons that 

produce coordinated movements in the absence of higher inputs

35

 in cats & humans central pattern generators are  for ___ movements

stepping

36

central pattern generators are activated by (2)

2. stim of Mesencephalic Locomotor Region

2. noradrenergic inputs

37

 if one limb reflexively withdraws, theipsilateral limb ____ to keep you balanced.

flexes

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38

central pattern input can be modified by

training

39

with emg demonstration Low amplitude action potentials...could mean

lost neurons

40

its difficult to activate a nerve AP with direct electrical stimulation but easy to

monitor or record

41

emg -- Can only recruit a few motor units...suggests a

partial problem

42

emg -- Spontaneous, non-rhythmic activity...suggests

dennervated muscle