1.3 Neuromuscular system

Question 1

Identify the role of the nervous system during exercise exercise?

Answer 1

Recruit different muscle fibre types depending on the demands of the activity.

Question 2

Explain what the nervous system allows the muscles to do

Answer 2

Adjusts the strength of contraction and uses sensory organs to allow a muscle to stretch further in PNF

Question 3

What does PNF stand for

Answer 3

Proprioceptive neuromuscular facilitation

Question 4

Identify and describe what other systems the peripheral nervous system consists of

Answer 4

The peripheral nervous system consists of the nerves that branch out from the spinal cord. The Sympathetic and Parasympathetic systems are part of the peripheral nervous system as they transmit impulses from the brain to the parts of the body that need adjusting during exercise.

Question 5

Describe the structure of the peripheral nervous system?

Answer 5

The peripheral nervous system consists of the nerves that branch out from the spinal cord.

Question 6

Explain the difference between the Sympathetic and Parasympathetic nervous systems and give e.g.

Answer 6

Sympathetic: prepares the body for exercise (fight or flight response) e.g. increase HR, BP

Parasympathetic: opposite effect of the sympathetic nervous system, it relaxes the body and slowing down many high energy functions. Rest and relax e.g. slows heart and breathing rate, lowers BP

Question 7

Identify the different types of muscle fibres

Answer 7

1. Slow Oxidative (type 1)
2. Fast Oxidative glycolytic (type 2a)
3. Fast Glycolytic (type 2x)

Question 8

What factor is genetically determined in terms of skeletal muscles?

Answer 8

Skeletal muscles contain a mixture of all three types of fibre BUT not in equal proportions. The quantity of variety is genetically determined

Question 9

Identify the characteristic of the muscle fibre predominantly used by a marathon runner

Answer 9

Slow oxidative type 1 - Suitable for low intensity exercise over a length period of time - such as long distance running, swimming. Produce energy in the presence of oxygen.

• Slow contraction speed
• small motor neurone size
• low force produced
• low fatiguability
• low anaerobic capacity
• high mitochondrial density
• high capillary density
• high myoglobin content

Question 10

Identify the characteristics of the muscle fibre predominately used by a games player, such as rugby

Answer 10

Fast Oxidative glycolytic type 2a - more resistant to fatigue as they are predominantly used in events such as 1500m/games where a longer burst of energy is required. Energy source for type 2a is glycogen.

• fast contraction speed
• large neurone size
• high force produced
• medium fatiguability
• medium aerobic capacity
• medium mitochondrial density
• medium capillary density
• medium myoglobin content
• high anaerobic capacity

Question 11

Identify the characteristics of the muscle fibre predominantly used by a 100m sprinter

Answer 11

Fast Glycolytic fibres type 2x - these fibres fatigue very quickly therefore used for short, intense bursts of effort. Produce energy anaerobically.

• fast contraction speed
• large neurone size
• high force produced
• high anaerobic capacity
• high fatiguability
• low aerobic capacity
• low mitochondrial density
• low capillary density
• low myoglobin content

Question 12

Identify which muscle fibre has the highest Aerobic capacity

Answer 12

Slow Oxidative type 1

Question 13

Explain why there is a high mitochondrial density in Slow Oxidative fibres?

Answer 13

Mitochondria produces energy in the presence of oxygen therefor slow oxidative muscle fibres produce energy aerobically

Question 14

Explain the difference between the structural and functional characteristics when describing a muscle fibre

Answer 14

Structural characteristic = concerns the make up of the fibre e.g. myoglobin, mitochondrial, capillary density, size, colour

Functional characteristic = what the fibre does - its function e.g. does it fatigue easily , force, contractile speed and force, aerobic/anaerobic

Question 15

Briefly explain the difference in the structural characteristics of a Slow Oxidative and Fast Glycolytic muscle fibre

Answer 15

Slow Oxidative: HIGH capillary density, HIGH aerobic capacity, LOW anaerobic capacity, HIGH mitochondrial density

Fast Glycolytic: LOW capillary density, LOW aerobic capacity, HIGH anaerobic capacity, LOW mitochondrial density

Question 16

Identify what a motor unit consists of

Answer 16

A motor unit consists of a motor NEURONE and its group of muscle fibres

Question 17

True of False:

All the different types of muscle fibres can be found in ONE particular motor unit

Answer 17

FALSE

Only ONE type of muscle fibre can be found in one particular motor unit

Question 18

Explain the contraction of a muscle fibre occurs

Answer 18

The motor neurone transmits a nerve impulse to the muscle fibre for a contraction to occur

Question 19

Describe the structure and function of a motor neurone

Answer 19

Each motor neurone consists of branches which end in the neuromuscular junction on the muscle fibre. The motor neurone transmits a nerve impulse to the muscle fibre allowing it to contract.

Question 20

Describe the ‘all or none law’

Answer 20

The motor neurone sends a signal to the muscle fibres and either all of them contract or none. The impulses have to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit to contract. It is NOT possible for a motor unit to partially contract.

Question 21

Describe the process of wave summation and what it achieves

Answer 21

Wave summation occurs when there is a repeated nerve impulse with no time to relax, producing a smooth sustained contraction rather than twitches/bursts (tentanic contraction). Fast and frequent impulses
Important when increasing the strength of muscular contraction.

Question 22

True or False:

Calcium in required in the process of a muscular contraction

Answer 22

True

Calcium is required because each time the nerve impulse reaches the muscle cell, calcium in released.

Question 23

Describe what is meant by a tetanic contraction?

Answer 23

A muscles fullest contractile state e.g. scrum = applying full force on something thats not moving. A sustained muscle contraction caused by a series of frequent and fast repeated impulses during wave summation.

Question 24

Identify what PNF is it used for?

Answer 24

Advanced stretching technique and the most effective form of flexibility training to improve range of movement

Question 25

Describe what is meant by the CRAC technique

Answer 25

C ontract
R elax
A ntagonist (one contracts one relaxes)
C ontract

Question 26

Which proprioceptor detects how far/fast a muscle is being stretched and produces the stretch reflex?

Answer 26

Muscle Spindles

Question 27

Identify the function and location of Muscle Spindles

Answer 27

Muscle spindles detect how far a muscle is being stretched and produce the stretch reflex. They lay in between the skeletal muscle fibres.

Question 28

Explain the importance of a reflex action and identify which proprioceptor produces it

Answer 28

Muscle spindles trigger the stretch reflex action causing the muscles to contract which prevents over stretching and injury

Question 29

Identify which proprioceptor detects levels of tension in a muscle

Answer 29

Golgi tendon organs

Question 30

Explain the function of Golgi tendon organs

Answer 30

Detect tension in the muscle and produce autogenic inhibition

Question 31

During which stage of PNF are the Golgi tendon organs predominant?

Answer 31

When the muscle is contracted isometrically, Golgi muscle tendons detect the increase in muscle tension and signal to the brain allowing the antagonist muscle to relax and lengthen.

Question 32

How do we control the strength of contraction?

Answer 32

Recruit larger motor units (the bigger the stronger). Recruit more motor units. Recruit more fast twitch muscle fibres.

Question 33

Describe the structure of a motor unit

Answer 33

Motor neurone and group of muscle fibres

Question 34

What is action potential and when is it used?

Answer 34

Its a signal that needs to be strong enough to cross the neuromuscular junction in order for a muscle to contract.

Question 35

True of False:

By increasing the rate of stimulation to a muscle we can get a greater force of contraction

Answer 35

True

By increasing the rate of stimulation to a muscle we can get a greater force of contraction

Question 36

Explain the term ‘twitch’

Answer 36

A single contraction

Question 36

Which proprioceptor produces the reflex action/stretch reflex

Answer 36

Muscle spindles as they detect the overstretch and cause the muscles to contract to prevent injury.

Question 37

What is autogenic inhabitation and what receptors are involved in this process?

Answer 37

The sudden relaxation of muscles in response to high tension.

Question 38

Explain why a muscle is able to stretch further after completing PNF?

Answer 38

Once the muscle is stretched after being isometrical contracted, the golgi tendon organs are responsible for the antagonist muscle relaxing

Question 39

What process is delayed/inactive when a muscle is isometrically contracted after being stretched in PNF?

Answer 39

Stretch reflex

Question 40

What is a passive stretch?

Answer 40

When you stay stretched in a position with the assistance of a partner

Question 41

Describe the structure of the nervous system

Answer 41

The nervous system consists of two main parts.
1. The central nervous system is made up of the brain and spinal cord.
2. The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body (includes the sympathetic & parasympathetic systems)

Question 42

Identify the processes that can increase the strength of a muscular contraction

Answer 42

Wave summation
Spatial summation

Question 43

Describe the process of spatial summation and what it achieves

Answer 43

Spatial summation occurs when the strength of contraction changes by altering the number and size of the muscles motor units.

Sharing workload over different motor units by recruiting different motor units at different times to reduce fatigue.

Difference activities require different strength of contraction, this depends on the number and size of motor units recruited.

Question 44

Describe the function of proprioceptors

Answer 44

Proprioceptors are sensory organs in the muscles, tendons and joints that inform the body of the extent of movement that has taken place.

Question 45

Explain the process of PNF and identify the role of the proprioceptors during this advanced stretching technique

Answer 45

1. Start by the individual performing a passive stretch with a partner. The stretch in the muscle is detected by muscle spindles and if stretched too far, a stretch reflex occurs.
2. The individual then isometrically contracts the muscle in a stationary position. The muscular tension is detected by golgi muscle tendons and deactivating the stretch reflex.
3. The individual performs a passive stretch again and the golgi muscle tendons are responsible for relaxing the antagonist muscle (autogenic inhibition) allowing the muscle to be stretched further.