Spinal Cord and Movement 1: The Motor Unit Lec18

Question 1

___ is involved with error correction

Answer 1

the cerebellum

Question 2

Local circuit neurons = ___ = propriospinals

Answer 2

interneurons

Question 3

alpha motor neurons are also called

Answer 3

LMNS or spinal MN

Question 4

LMNS or alpha MNs have large

Answer 4

axons, dendritic trees, cell bodies

Question 5

where are LMNs in the spinal cord?

Answer 5

in the ventral horn

Question 6

Medial ventral horn = ____ muscles

Answer 6

proximal

Question 7

Lateral ventral horn = ___ muscles

Answer 7

distal

Question 8

Motor Neuron Pool =

Answer 8

all LMNs innervating one given muscle

Question 9

in humans, a pool usu. spans __vertebral levels

Answer 9

2-3

Question 10

Motor Unit = (3)

Answer 10

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

Question 11

all muscle fibers in a motor unit have (2)

Answer 11

identical properties & contract together

Question 12

a __is the minimum unit that can be contracted

Answer 12

motor unit

Question 13

in NMJ

there is __ nerve(s) per muscle fiber

Answer 13

1

Question 14

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

Answer 14

NMJ

Question 15

there is no ___ with NMJ

Answer 15

summation

Question 16

3 motor unit ty[es

Answer 16

S, FR, FF

Question 17

how fast is s?

Answer 17

60-120ms

Question 18

how fast is FR

Answer 18

30-80 ms

Question 19

how fast is FF

Answer 19

20-40

Question 20

fatigue of S?

Answer 20

slow

Question 21

fatigue of S?

Answer 21

resistant to fatigue

Question 22

fatigue of FF?

Answer 22

fatigues within seconds

Question 23

order of force with the motor unit types

Answer 23

highest to lowest

FF

FR

S

Question 24

Motor unit type determined by(4)

Answer 24

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

Question 25

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

Answer 25

more slow twitch

Question 26

Twitch = one ___ to a motor unit axon

Answer 26

stimulus

Question 27

Tetanus = repeated stimuli before axon

Answer 27

recovers

Question 28

Can increase force by

Answer 28

1) Recruitment of a previously silent motor unit
2) Rate-coding of an already firing unit - increase firing rate (temporal summation)

Question 29

size principle

recruit ___ units first

Answer 29

smaller units for smaller force generation

Question 30

why do you recruit smaller motor units first

Answer 30

Larger motor units have decreased excitability, more difficult to recruit

Question 31

cauda equina includes all nerves to and from the

Answer 31

lega and pelvic floor

Question 32

are LMNS myelinated?

Answer 32

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

Question 33

size of a ___ varies tremendously

Answer 33

muscle unit

Question 34

___ is needed for cross bridge release

Answer 34

ATP

Question 35

for ___ total force varies a lot

Answer 35

twitch and partially fused

Question 36

influence of rate on motor unit twitch force

highre forces come from more rapid ___

Answer 36

erates of stimulation

Question 37

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

Answer 37

firing/discharge rate

Question 38

rate coding invovles ___ fore output

Answer 38

partially fused

Question 39

with increased motor size, an alpha m. neuron exhibits

DECREASED?

Answer 39

Question 40

with increased motor size, an alpha m. neuron exhibits

INCREASED?

Answer 40

Question 41

what would happen if MU recruitment during mvoements was random

Answer 41

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