motor unit

Question 1

What is a motor neuron

Answer 1

a nerve cell which conducts a nerve impulse to a group of muscle fibres

Question 1

What is a motor unit

Answer 1

a motor neuron and the muscle fibres stimulated by its axon

Question 2

Functions of motor unit

Answer 2

carry nerve impulses from the brain and spinal cord to the muscle fibres, initiating muscular contraction

Question 3

What is the action potential

Answer 3

positive electrical charge inside the nerve and muscle cells

which

conducts the nerve impulse down the neuron and into the muscle fibre

Question 4

What is the neurotransmitter

Answer 4

a chemical (acetylcholine) produced and secreted by a neuron
which transmits the nerve impulse across the synaptic cleft
to the muscle fibre

Question 5

What is the all or none law

Answer 5

depending on whether the stimulus is above a threshold, all muscle fibres will give a complete contraction or no contraction at all

Question 6

What is the flow chart of how motor units cause muscular contraction

Answer 6

Question 7

Fill in the blank

A motor unit is made up of the motor …….. and the muscle fibres it stimulates

Answer 7

neuron

Question 8

Fill in the blank

A nerve impulse is conducted down the axon to the synaptic cleft by an ………… ……….

Answer 8

electrical charge

Question 9

Fill in the blank

A ………….. called acetylcholine assist the nerve impulse across the gap into the ……… fibre

Answer 9

neurotransmitter

muscle

Question 10

Fill in the gap

If the electrical charge reaches a ……… value, the muscle fibre will contract in an … or …… fashion

Answer 10

threshold

all or none

Question 11

Extend your knowledge

What is the electrical charge inside of the axon and its outside surroundings?

and when there’s a sudden change in voltage what diffuses into the axon?

Answer 11

There is an electrical difference between the inside of the axon (negative)
and its outside surroundings (positive) termed resting potential.

When the nerve is activated, there is a sudden change in voltage as sodium ions (Na+) diffuse into the axon

This triggers a wave of action potential that travels from the cell body down the axon to the synapse

Question 12

State the parts of a motor unit

Answer 12

Dendrites
Axon
Muscle fibre
Neuromuscular junction

Question 13

How can skeletal muscle contract

Answer 13

It can only contract if it is stimulated by an electrical impulse sent from the cenrtal nervous system

Question 14

How can we vary strength of muscle contraction

Answer 14

Recruit the correct number of motor units for the action being completed

recruit the correct size of the motor units for the action being completed

Question 15

What are slow oxidative muscle fibres

Answer 15

Structurally designed to store oxygen in myoglobin and process oxyegn in the mitochondria which allows athletes to work aerobically

produce a small force, but resist fatigue for a long period of time

predominately used by endurance athletes such as marathoners

red in colour

Question 16

Describe the fast oxidative glycolytic muscle fibres

Answer 16

Structurally designed to produce a large amount of force quickly

can resist fatigue, but not for as long as type 1 muscle fibres

moderate levels of myoglobin and capillaries

red/pink in colour

predominantly used by high-intensity athletes, such as 800m runners

Question 17

Describe the fast glycolytic muscle fibres

Answer 17

structurally designed to work anaerobically and have a large store of phosphocreatine

fatigue very quickly

white in colour

low levels of myoglobin and capilaries

produce very high concentrations

predominantly used by short duration and high intensity athletes such as 100m runners

Question 18

What are the muscle fibre recovery rates?

Answer 18

type 1- 1:1 or 1:0.5 (slow oxidative)
type 2 and 2b - 1:3+ (fast glycolytic)

Question 19

Why is there a difference in recovery rates from type 1 to type 2a/b fibres

Answer 19

type 1 muscle fibres are not damaged,
whereas type 2a and 2b muscle fibres are damaged and worked to exhaustion so they need more time to fully recover (min 48 hours)

Question 20

Which type of contraction is likely to cause most damage

Answer 20

eccentic

Question 21

Relate the exercise intensity to the muscle fibres

Answer 21

low intensity- slow oxidative
higher intensity- fast oxidative glycolytic
high intensity- fast glycolytic recruited alongside all other fibre types