Week 7 - The Motor Unit

Question 1

how many pairs of nerves does the PNS have ?

Answer 1

43 pairs

Question 2

how many pairs of nerves are cranial nerves ?

Answer 2

12

Question 3

how many pairs of nerves are spinal nerves ?

Answer 3

31

Question 4

what are the 5 spinal nerves ?

Answer 4

• cervical nerves
• thoracic
• lumbar
• sacral
• coccygeal

Question 5

how many pairs of cervical nerves are in the PNS ?

Answer 5

8

Question 6

where are cervical nerves located

Answer 6

head and neck

Question 7

how many pairs of thoracic nerves are in the PNS ?

Answer 7

12

Question 8

where are thoracic nerves located ?

Answer 8

upper extremities, chest, upper abdomen

Question 9

how many pairs of lumbar nerves are in the PNS ?

Answer 9

5

Question 10

where are lumbar nerves located ?

Answer 10

lower abdomen, hips, legs

Question 11

how many pairs of sacral nerves are in the PNS ?

Answer 11

5

Question 12

where are sacral nerves located ?

Answer 12

lower extremities, pelvis

Question 13

how many pairs of coccygeal nerves are in the PNS ?

Answer 13

1

Question 14

where are coccygeal nerves located ?

Answer 14

coccyx

Question 15

define nerve

Answer 15

a bundle of fibres within a connective tissue sheath

Question 16

define neruon

Answer 16

a single nerve

Question 17

what are the 3 types of neuron ?

Answer 17

• efferent (motor)
• afferent (sensory)
• interneurons (connector)

Question 18

what type of motor neuron initiates a muscle contraction ?

Answer 18

alpha motor neurons

Question 19

what type of motor neuron innervate muscle spindles ?

Answer 19

gamma motor neurons

Question 20

what are the 6 components of a motor neuron ?

Answer 20

• cell body (soma)
• dendrites
• axon
• terminal branches
• myelin sheath
• Ranvier node

Question 21

define soma

Answer 21

• cell body
• contains nucleus
• within grey matter of spinal cord or ganglia

Question 22

define dentrites

Answer 22

• projections of the cell body

- receive signals from other neurons

Question 23

define axon

Answer 23

• the nerve fibre
• exits spinal cord via ventral root
• large in motor neurons

Question 24

define terminal branches

Answer 24

• unmyelinated branches at end of axon

- form neuromuscular junction with muscle fibres

Question 25

define myelin sheath

Answer 25

• insulates axon to aid with transmission of signals

- schwann cells

Question 26

define Ranvier node

Answer 26

• gap between the schwann cell

- action potential jumps from one node to the next

Question 27

define motor unit

Answer 27

the functional unit of the neuromuscular system

Question 28

what are the 3 types of motor unit ?

Answer 28

• type I
• type IIa
• type IIX

Question 29

what is the full name of type I motor units ?

Answer 29

slow twitch oxidative

Question 30

what is the full name of type IIa motor units ?

Answer 30

fast twitch oxidative

Question 31

what is the full name of type IIx motor units ?

Answer 31

fast twitch glycolytic

Question 32

what activities use type I motor units ?

Answer 32

• endurance

- maintaining posture

Question 33

what type of activities use type IIa motor units ?

Answer 33

• swimming

- cycling

Question 34

what type of activities use type IIx motor units ?

Answer 34

• sprinting

- jumping

Question 35

what determines motor unit type ?

Answer 35

nerve fibres

Question 36

what are the 2 ways pf increasing muscle contraction force?

Answer 36

• number of muscle units that are recruited

- frequency of stimulation

Question 37

define EMG

Answer 37

electromyography

- measure muscle activation

Question 38

what determines the size of an EMG signal ?

Answer 38

• # of MU activated
• MU action potential firing rate
• MU type activated

Question 39

what can you measure with an EMG ?

Answer 39

• when muscle is turned on / off
• whether muscles is active / passive
• magnitude of activation