The Neruromuscular System

Question 1

Type 1 muscle fibres are also known as?

Answer 1

Type 1 muscle fibres are also known as slow oxidative muscle fibres.

Question 2

Characteristics of slow oxidative (type 1) muscle fibres

Answer 2

• Small motor neuron size
• Large myoglobin content
• High oxidative capacity
• Slow contraction time
• Suited for aerobic exercise
• High resistance to fatigue
• Low force production
• Low glycolytic capacity
• High capillary density

Question 3

What are slow oxidative (type 1) muscle fibres useful for?

Answer 3

Endurance events such as marathon running.

Question 4

Type 2a muscle fibres are also known as?

Answer 4

Type 2a muscle fibres are also know as fast oxidative glycolytic muscle fibres

Question 5

Characteristics of fast oxidative glycolytic (type 2a) muscle fibres

Answer 5

• Large motor neuron size
• Intermediate myoglobin content
• High oxidative capacity
• Fast contraction time
• Suited for lengthy anaerobic exercise
• Medium resistance to fatigue
• High force production
• High glycolytic capacity
• Medium capillary density

Question 6

Type 2b muscle fibres are also know as?

Answer 6

Type 2b muscle fibres are also known as fast glycolytic muscle fibres.

Question 7

Characteristics of fast glycolytic (type 2b) muscle fibres

Answer 7

• Large motor neuron size
• Small myoglobin content
• Low oxidative capacity
• Fastest contraction time
• Suited for short anaerobic exercise
• Low resistance to fatigue
• Highest force production
• High glycolytic capacity
• Low capillary density

Question 8

What sports are suitable for type 2a muscle fibres?

Answer 8

Swimming

Question 9

What sports are suitable for type 2b muscle fibres?

Answer 9

100m sprint

Question 10

Muscle fibres and their motor neuron size

Answer 10

Type 1 - Small motor neuron size

Type 2a - Large motor neuron size

Type 2b - Large motor neuron size

Question 11

Muscle fibres and their myoglobin content

Answer 11

Type 1 - Large myoglobin content

Type 2a - Intermediate myoglobin content

Type 2b - Small myoglobin content

Question 12

Muscle fibres and their oxidative capacity

Answer 12

Type 1 - High oxidative capacity

Type 2a - High oxidative capacity

Type 2b - Low oxidative capacity

Question 13

Muscle fibres and their contraction times

Answer 13

Type 1 - Slow contraction time

Type 2a - Fast contraction time

Type 2b - Fastest contraction time

Question 14

Muscle fibres and what exercise types they are suited to

Answer 14

Type 1 - aerobic exercise

Type 2a - lengthy anaerobic exercise

Type 2b - short anaerobic exercise

Question 15

Muscle fibres and their resistance to fatigue

Answer 15

Type 1 - High resistance to fatigue

Type 2a - Medium resistance to fatigue

Type 2b - Low resistance to fatigue

Question 16

Muscle fibres and their force production

Answer 16

Type 1 - Low force production

Type 2a - High force production

Type 2b - Highest force production

Question 17

Muscle fibres and their glycolytic capacity

Answer 17

Type 1 - Low glycolytic capacity

Type 2a - High glycolytic capacity

Type 2b - High glycolytic capacity

Question 18

Muscle fibres and their capillary density

Answer 18

Type 1 - High capillary density

Type 2a - Medium capillary density

Type 2b - Low capillary density

Question 19

Muscle fibre recruitment explained

Answer 19

Muscle fibre recruitment is dependent on the intensity of the exercise, higher intensity requires more force, lower intensity requiring less force.

Question 20

What is the size principle (Henneman)

Answer 20

Smaller motor units are recruited first as they have a smaller firing threshold than larger motor units.

Question 21

What is the autonomic nervous system responsible for?

Answer 21

The autonomic nervous system is responsible for subconsciously controlling muscular contractions.

Question 22

What two systems make up the autonomic nervous system?

Answer 22

• Parasympathetic nervous system
• Sympathetic nervous system

Both nervous systems innervate the muscle tissues by sending a nervous impulse to them.

Question 23

What is the parasympathetic nervous system responsible for?

Answer 23

The parasympathetic nervous system is responsible for actions that occur when resting

Question 24

What is the sympathetic nervous system responsible for?

Answer 24

The sympathetic nervous system is responsible for actions when active

Question 25

What is the proprioceptive neuromuscular facilitation?

Answer 25

A form of stretching which aims to overcome the stretch reflex, an isometric contraction is performed when the muscle is stretched to its limit.

Question 26

What is the role of muscle spindles?

Answer 26

• Sensory receptors
• Found in the centre of the muscle
• Provide information regarding the length of the muscle to the brain
• This information is used to initiate the stretch reflex when the muscle is stretched to its limit.

Question 27

What is the role of the Golgi tendon organ?

Answer 27

• Sensory receptor
• Found at the connection of the muscle with the bone
• Detects changes in tension of the muscle
• Initiates the Golgi-tendon reflex which reduces muscle tension when it is high.

Question 28

What is the ‘All or None’ law?

Answer 28

Each muscle fibre controlled by a motor unit is either fully contracted or not contracted at all

They can contract in different ways depending on how they are innervated

Therefore, a muscle fibre cannot partially contract

Question 29

What are the three types of motor neuron recruitment?

Answer 29

Spatial summation

Wave summation

Tetanic summation

Question 30

What is spatial summation?

Answer 30

Many motor units firing

Question 31

What is wave summation?

Answer 31

One motor unit firing continuously

Question 32

What is tetanic summation?

Answer 32

A continuous muscle contraction

Question 33

Key structures of motor units?

Answer 33

• Myelin sheath
• Axons
• Myofibrils
• Sacrolemma
• Snyaptic vesicle
• Synaptic cleft
• Motor end plate

Question 34

What is the myelin sheath?

Answer 34

Acts as an electrical insulator around the axons

Question 35

What are axons?

Answer 35

Axons are extensions of a nerve cell that carry an impulse

Question 36

What are myofibrils?

Answer 36

Myofibrils are contractile structures of the muscle consisting of actin and myosin.

Question 37

What is the sacrolemma?

Answer 37

Sacrolemma is the cell membrane

Question 38

What is the synaptic vesicle?

Answer 38

The synaptic vesicles is where acetylcholine is stored

Question 39

What is the synaptic cleft?

Answer 39

The synaptic cleft is the gap between neurons

Question 40

What is the motor end plate?

Answer 40

The motor end plate is where the action potential from an action travels to stimulate a muscle.

Question 41

A motor unit consists of…?

Answer 41

A motor unit consists of a motor neuron and the muscle fibres that it stimulates.

Question 42

Nervous stimulation of a motor unit stages

Answer 42

A motor unit needs to be stimulated to enable a muscular contraction

1) A neuron becomes depolarised, firing an action potential.

2) The action potential reaches the neuromuscular junction.

3) This causes the neurotransmitter acetylcholine to move to the motor end plate.

4) The motor end plate becomes depolarised, resulting in muscular contraction.

Question 43

What is an action potential?

Answer 43

An action potential is an electrical impulse that acts as a signal.

Question 44

Motor units key facts

Answer 44

• Motor units vary in the number of muscle fibres that they stimulate

• The fibres are made up of only one type.

• The brain recruits smaller motor units before larger motor units.

• Smaller motor units consist of slow-twitch muscle fibres

• Larger motor units consist of fast-twitch muscle fibres.