LEC 2

Question 1

3 ways to classify motor neuron type

Answer 1

1. How long to peak - larger mot = faster
2. size of peak - larger = bigger
3. how long to half of peak - larger = faster recovery

Question 2

Name of electrode that is put into body via needle to measure specific deeper muscles

Answer 2

indwelling

Question 3

Describe Heneman’s size principle

Answer 3

the orderly recruitment of smaller neurons before larger ones, same but in reverse for de-recruitment.

• muscle fibre type also correlate to size of neuron e.g. SO fibres usually with smaller neurons etc.

Question 4

contrast:

• motor neuron pool
• Motor unit
• muscle unit

Answer 4

Motor neuron pool - all the motor neurons innervating a particular muscle

Motor unit - cell body and dendrites of a motor neuron, branches of its axon, and the muscle fibres it innervates

Muscle unit - all muscle fibres belonging to a motor unit

Question 5

how do muscle units look within the muscle

Answer 5

muscle fibres are spread out, not grouped together

Question 6

What is the innervation ratio, which muscles have high and low innervation ratio

what happens with aging

Answer 6

of muscle fibres innervated by a single motor neuron

eye have low

quad have high

with aging, ratio change (lose motor units, get higher ratios

Question 7

in spinal cord, where are motor neurons for proximal and distal limbs located

Answer 7

proximal are more proximalo to the spinal cord, distal are more distal in the cord

Question 8

what are the types of motor units that correspond to different muscle fibre types

Answer 8

Slow oxidative - connect to type I

Fatigue resistant - connect to fast oxidative-glycolytic fibres

Fast fatiguable - connect to fast glycolytic fibres

Question 9

describe input resistance for small and large neurons

Answer 9

V=IR

High input resistance for smaller neurons means lower voltage needed to excite

Low input resistance for larger neurons make harder to excite

Question 10

What is rheobase

Answer 10

measure of current that must be put into neuron to get it to fire.

Low rheobase in small motor neurons

Question 11

which size neuron has a faster conduction velocity

Answer 11

Larger have faster conduction velocity

Question 12

Which size neuron has a longer afterhyperpolarization phase

Answer 12

smaller have longer

Question 13

What happens if you attach a slow motor neuron to a fast muscle fibre

Answer 13

it changes behaviour slightly to match motor neuron