Spinal Cord and Movement 1: The Motor Unit Lec18 Flashcards Preview

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Flashcards in Spinal Cord and Movement 1: The Motor Unit Lec18 Deck (41)
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1
Q

___ is involved with error correction

A

the cerebellum

2
Q

Local circuit neurons = ___ = propriospinals

A

interneurons

3
Q

alpha motor neurons are also called

A

LMNS or spinal MN

4
Q

LMNS or alpha MNs have large

A

axons, dendritic trees, cell bodies

5
Q

where are LMNs in the spinal cord?

A

in the ventral horn

6
Q

Medial ventral horn = ____ muscles

A

proximal

7
Q

Lateral ventral horn = ___ muscles

A

distal

8
Q

Motor Neuron Pool = 

A

 all LMNs innervating one given muscle

9
Q

 in humans, a pool usu. spans __vertebral levels

A

2-3 

10
Q

Motor Unit = (3)

A

one cell body + its axon + all the muscle fibers that axon innervates

11
Q

all muscle fibers in a motor unit have (2)

A

identical properties & contract together

12
Q

 a __is the minimum unit that can be contracted

A

motor unit 

13
Q

in NMJ

there is __ nerve(s) per muscle fiber

A

1

14
Q

with __ there is high reliability: muscle contracts every time the axon fires

A

NMJ

15
Q

there is no ___ with NMJ

A

summation

16
Q

3 motor unit ty[es

A

S, FR, FF

17
Q

how fast is s?

A

60-120ms

18
Q

how fast is FR

A

30-80 ms

19
Q

how fast is FF

A

20-40

20
Q

fatigue of S?

A

slow

21
Q

fatigue of S?

A

resistant to fatigue

22
Q

fatigue of FF?

A

fatigues within seconds

23
Q

order of force with the motor unit types

A

highest to lowest

FF

FR

S

24
Q

Motor unit type determined by(4)

A

 activity, pruning/tropic factors, injury/recovery, genetics

25
Q

- Plasticity: 2 months of low-freq stimulation = ___ fibers in cat

A

more slow twitch

26
Q

Twitch = one ___ to a motor unit axon

A

stimulus

27
Q

Tetanus = repeated stimuli before axon 

A

recovers

28
Q

Can increase force by

A

1) Recruitment of a previously silent motor unit


2) Rate-coding of an already firing unit - increase firing rate (temporal summation)

29
Q

size principle

recruit ___ units first 

A

smaller units for smaller force generation

 

30
Q

why do you recruit smaller motor units first

A

Larger motor units have decreased excitability, more difficult to recruit

31
Q

cauda equina includes all nerves to and from the

A

lega and pelvic floor

32
Q

are LMNS myelinated?

A

yes, with schwann cells. so they have rapid conduction velocity

33
Q

size of a ___ varies tremendously

A

muscle unit

34
Q

___ is needed for cross bridge release

A

ATP

35
Q

for ___ total force varies a lot

A

twitch and partially fused 

36
Q

influence of rate on motor unit twitch force

 

highre forces come from more rapid ___

A

erates of stimulation

37
Q

rate coding of an already firing motor unit involves increasting the ___ of an already recruited motor unit

A

firing/discharge rate

38
Q

rate coding invovles ___ fore output

A

partially fused

39
Q

with increased motor size, an alpha m. neuron exhibits

DECREASED?

A
40
Q

with increased motor size, an alpha m. neuron exhibits

INCREASED?

A
41
Q

what would happen if MU recruitment during mvoements was random 

A

if you didnt have precise control over amount of force you woulndt have precision