Wk 2 - LE 3: neuromuscular (motor unit)

Question 1

What is the equation for force?

Answer 1

f = mxa

Question 2

Concentric muscle action is…

Answer 2

shortening of the muscle (real contraction)

Question 3

Eccentric muscle action is…

Answer 3

lengthening of the muscle

Question 4

Isometric muscle action is…

Answer 4

No length change in muscle

Question 5

Is the number of myocytes within a muscle proportional the the muscle size?

Answer 5

Yes

Question 6

The diameter of myocytes varies in in different muscle sizes (T/F)?

Answer 6

False

Question 7

What type of neuron is responsible for initiating and controlling muscle action?

Answer 7

alpha-motor neuron

Question 8

What is a motor unit?

Answer 8

A single alpha neuron AND the muscle fibres it innervates

Question 9

The number of motor units within a muscle ranges from…

Answer 9

100-1000 MUs proportional to muscle size

Question 10

The number of myocites within a muscle ranges from…

Answer 10

1-1,000000 (million)

Question 11

What is force DEVELOPED by in the muscle?

Answer 11

The myocytes (not neuron!)

Question 12

what is force CONTROLLED by in muscle (firing, impulses)?

Answer 12

The alpha- motorneuron

Question 13

What are the 2 ways to vary the force output of a muscle?

Answer 13

1) by varying the number of motor units recruited

2) varying the firing rate of a-motorneurons

Question 14

‘Firing’ refers to _____ of the neuron

Answer 14

Depolarisation

Question 15

Firing at a low rate (1-2 Hz) leads to a muscle _____

Answer 15

Twitch

Question 16

What is a complete tetanus?

Answer 16

when firing rate is so frequent, twitches become a line instead of fluctuating

Question 17

What is an incomplete tetanus?

Answer 17

Twitching rates too frequent to fall back to zero so gradually increases until at complete tetanus

Question 18

What is Hennemans size principle?

Answer 18

That MU are generally recruited from smallest to largest as the force is increased

Question 19

Movement velocities are influenced by what 3 factors?

Answer 19

1) instrinsic shortening velocity of myocytes
2) MU recruitment speed
3) MU firing rate

Question 20

Maximum force is produced by recruiting ___% of the MU pool

Answer 20

100% (extremely difficult to do)

Question 21

The type of MUs and myocytes involved in movement depends on the ____ and/or ____ of the task

Answer 21

Force and/or speed

Question 22

An alpha motorneuron innervates what type of myocyte?

Answer 22

slow to slow, fast to fast