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

___ is involved with error correction

the cerebellum

2

Local circuit neurons = ___ = propriospinals

interneurons

3

alpha motor neurons are also called

LMNS or spinal MN

4

LMNS or alpha MNs have large

axons, dendritic trees, cell bodies

5

where are LMNs in the spinal cord?

in the ventral horn

6

Medial ventral horn = ____ muscles

proximal

7

Lateral ventral horn = ___ muscles

distal

8

Motor Neuron Pool = 

 all LMNs innervating one given muscle

9

 in humans, a pool usu. spans __vertebral levels

2-3 

10

Motor Unit = (3)

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

11

all muscle fibers in a motor unit have (2)

identical properties & contract together

12

 a __is the minimum unit that can be contracted

motor unit 

13

in NMJ

there is __ nerve(s) per muscle fiber

1

14

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

NMJ

15

there is no ___ with NMJ

summation

16

3 motor unit ty[es

S, FR, FF

17

how fast is s?

60-120ms

18

how fast is FR

30-80 ms

19

how fast is FF

20-40

20

fatigue of S?

slow

21

fatigue of S?

resistant to fatigue

22

fatigue of FF?

fatigues within seconds

23

order of force with the motor unit types

highest to lowest

FF

FR

S

24

Motor unit type determined by(4)

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

25

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

more slow twitch

26

Twitch = one ___ to a motor unit axon

stimulus

27

Tetanus = repeated stimuli before axon 

recovers

28

Can increase force by

1) Recruitment of a previously silent motor unit


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

29

size principle

recruit ___ units first 

smaller units for smaller force generation

 

30

why do you recruit smaller motor units first

Larger motor units have decreased excitability, more difficult to recruit