Muscle and Movement

Question 1

What initiates nerve impulses?

Answer 1

Neurotransmitters

Question 2

What is responsible for relaying signals?

Answer 2

neural transmission

Question 3

What is the role of motor neurons?

Answer 3

activate skeletal muscle

Question 4

What is a neuromuscular junction?

Answer 4

the synapse between a motor neuron and muscle fibre

Question 5

what is a motor unit?

Answer 5

An alpha motor neuron and all the muscle fibres it innervates

Question 6

what are the principles of muscle contraction and force? (4)

Answer 6

1. Alpha motor neuron activates bundle of muscle cells
2. each muscle cell produces equal amount of force
3. no. of alpha motor neurons activated will contribute to force produced by motor units
4. relative force gained by muscle contraction dependant on no. of motor units activated

Question 7

what controls how many muscle cells need to be activated?

Answer 7

the brain

Question 8

in which direction to skeletal muscle cells contract?

Answer 8

horizontally (lengthways)

Question 9

when do skeletal muscle cells contract?

Answer 9

when signal from motor neuron arrives at neuromuscular junction

Question 10

how are skeletal muscle cells bundled?

Answer 10

horizontally

Question 11

what muscle cells contract together?

Answer 11

skeletal muscle cells

Question 12

what causes skeletal muscle cells to contract?

Answer 12

when a group of motor neurons activated

Question 13

what determines the amount of force generated by skeletal muscle cell contraction?

Answer 13

number of motor neurons collaborated (recruitment of multiple motor neurons)

Question 14

how can skeletal muscle contraction be sustained?

Answer 14

multiple stimulation of same motor neuron at short intervals

Question 15

what unit is used to show frequency of stimuli?

Answer 15

~msec range (millisecond)

Question 16

how do you achieve summation?

Answer 16

give 2 stimuli at short enough intervals (<200ms)

Question 17

what happens when the interval of 2 stimuli is as short as 50ms apart?

Answer 17

total contraction force doubled

Question 18

how do you produce tetanus?

Answer 18

give continual stimuli at maximal strength

Question 19

how does a twitch become summation?

Answer 19

more frequent activation (greater tension)

Question 20

what causes force generated by motor unit to fuse?

Answer 20

when second activation occurs before muscle relaxes

Question 21

how are cardiac muscles arranged?

Answer 21

tandemly (sequentially one after another)

Question 22

how do cardiac muscles contract?

Answer 22

one after another in direction signal travels from

Question 23

what causes cardiac muscle cells to contract?

Answer 23

signal from pacemaker cell (autorythmic cardiac muscle cell)

Question 24

what causes contractile cardiac muscle cells to contract?

Answer 24

when signal from neighbouring cell is transported through the insulated wall of intercalated disc

Question 25

what direction does the signal travel in cardiac muscle cells

Answer 25

unidirectionally (activates one cell after another)

Question 26

what is the order of the action potential in cardiac muscle cells? (3)

Answer 26

1. action potentials of autorythmic cells
2. action potential passed to contractile cells
3. heart pumps blood

Question 27

what are intercalated discs?

Answer 27

specialised junctions between cardiac muscle fibres

Question 28

how are intercalated discs specialised to their function? (2)

Answer 28

1. have holes allowing signalling molecules to travel
2. insulated, only permitting signalling molecules to travel

Question 29

what are the 2 differences between skeletal muscle cells and cardiac muscle cells? (2)

Answer 29

1. skeletal muscle cells activated by motor neuron
2. contractile cardiac cells activated by adjacent neighbouring cell