1.3 The Neuromuscular System Flashcards
What are neuromuscular responses to exercise?
- Increased number of muscle fibres recruited.
- Increased rate of fibre recruitment.
Why are more fibres recruited during exercise?
As fibres become fatigued, more fibres will be recruited as the brain attempts to maintain desired force.
Recap - what are the two parts of the autonomic nervous system and what are they responsible for?
Sympathetic and parasympathetic.
Sympathetic speeds up heart rate and parasympathetic brings it back down to resting level.
Recap - which receptor system is located in the muscles and detects muscular movement?
Proprioceptors.
Athletes with more slow twitch muscle fibres tend to do better in what type of events?
Endurance events such as walking or long-distance running.
Athletes with more fast twitch muscle fibres tend to do better in what type of events?
Events involving a short burst of intense exercise such as 100 metres and shot put.
name the three types of muscle fibres.
Slow twitch type 1;
Fast twitch type 2a;
Fast twitch type 2b.
Is it possible to change your fibre types?
No, they cannot be changed, however they can take on characteristics of other fibre types.
If a performer does an excessive amount of long-distance aerobic training, what happens to their muscle fibres.
The type of fibres stay the same, however some may adapt to take on characteristics of slow twitch.
What determines the number of different muscle fibres a person has?
Their genetics.
What is the ‘muscle fibre composition’?
The make-up / percentage of fast and slow twitch fibres.
Is it possible to change a slow twitch muscle fibre into a fast twitch muscle fibre or vise-versa?
No fibres cannot be changed between fast and slow.
Is it possible to change a fast twitch muscle fibre 2a into a fast twitch muscle fibre 2b or vise-versa?
Yes, the two fast twitch muscle fibre types are interchangeable.
Suggest the muscle fibre composition of a cheetah.
Cheetahs have a very high percentage of fast twitch muscle fibres.
What is the name for fast twitch muscle fibres type 2a?
fast oxidative glycolitic, (FOG).
What is the name for fast twitch muscle fibres type 2b?
fast twitch glycolitic, (FTG).
What is the contraction speed for the three muscle types?
Type 1 - Slow
Type 2a - Fast
Type 2b - Fastest
What is the size (of individual muscle fibres) for the three muscle types?
Type 1 - Small
Type 2a - Medium
Type 2b - Large
What is the relative force produced for the three muscle types?
Type 1 - Low
Type 2a - High
Type 2b - Very high
What is the fatiguability for the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - High
What is the number of mitochondria in each muscle for the three muscle types?
Type 1 - Many
Type 2a - Some (low)
Type 2b - Few (very low)
What is the myoglobin concentrations for the three muscle types?
Type 1 - Very high
Type 2a - Some (low)
Type 2b - Few (very low)
What is the glycogen stores for the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - High
What is the capillary density for the three muscle types?
Type 1 - High
Type 2a - Low
Type 2b - Very low
What is the aerobic capacity for the three muscle types?
Type 1 - Very high
Type 2a - Medium
Type 2b - Low
What is the anaerobic capacity for the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - Very high
What is the elasticity for the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - Very high
What is the excitability for each of the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - Very high
What is the phosphocreatine stores for each of the three muscle types?
Type 1 - Low
Type 2a - Medium
Type 2b - Very high
How are each of the muscle types powered?
Type 1 - Aerobically
Type 2a - Anaerobically but with a small percentage of oxygen
Type 2b -Anaerobically
What colour are type 1 muscle fibres and why?
Red because of the large amount of red blood cells that carry oxygen.
What colour are type 2a muscle fibres and why?
They are usually pinkish as they have a sparse number of red blood cells.
What colour are type 2b muscle fibres and why?
White because they have few to no red blood cells.
Which systems does the type 2b muscle fibres use for energy?
ATP / PC system for energy as no red blood cells.
What type of muscle fibre would a discuss thrower have?
- Type 2b / fast twitch glycolytic / FTG.
- Due to the fast speed of contraction required.
- Also due to the high force of contraction, it requires a powerful, strong contraction.
What is a motor unit?
The one motor neurone that comes from the brain and links to the neuromuscular junctions.
T / F - One motor neurone is used to stimulate a single whole muscle.
False, many motor neurones are required to stimulate a number of fibres in the muscle to contract the whole muscle.
What does a motor neurone stimulate?
A number of fibres within a muscle.
T / F - Each motor unit contains only one type of muscle type.
True, a motor unit contains one type of muscle fibre only.
In a motor unit, what happens during contraction to the motor units?
All of the motor units contract or none of them do.
What are the features in the structure of a motor neurone?
- Nucleus.
- Cell body.
- Dendrites.
- Axon.
- Mylien Sheath.
- Nodes of Ranvier.
Function of the mylien sheath?
Protect and insulate the axon so that ion exchange can occur at only the nodes.
The mylien sheath is a layer of what cells?
Shwann cells.
What do the dendrites do?
Project into the grey matter (of the brain) to receive impulses and conduct them to the cell body.
What does the cell body do?
It contains the nucleus of the motor neurone.
Where is the cell body located?
In the grey matter of the spinal cord.
Where is the nucleus located?
It is held within the cell body.
Function of the axon?
Transmits impulses from the nucleus to the muscle fibres.
What are the nodes of Ranvier?
gaps in the mylien sheath on the outside of the axon.
What is the function of the nodes of Ranvier?
They speed up conduction velocity and reduce ‘ion-run down’, it only happens here so it is more efficient.
What is the rough speed of transmission with a mylien sheath and without one?
With = 5m/s or less
Without = 100 m/s or greater
(20x greater)
What is the general figure for resting potential? (with units)
-70mV
What is the resting potential measured in?
millivolts (mV)
What is meant by the term, resting potential?
The charge difference between the outside of a neurone membrane and the inside.
Explain why the neurone membrane is polarised?
Because there is a difference in charge between the outside and inside of the membrane.
Stimulation of the neurone causes Na+ gates to open in the membrane, what does this lead to?
Na+ rushes into the neurone from the outside, resulting in depolarisation of the membrane in the area where stimulation occurred.
When is an action potential produced?
When charge changes and reaches a threshold of -50mV.
How does an action potential travel down a neuromuscular junction?
The opening of one Na+ gate triggers the opening of the next and a wave of depolarisation occurs.
What is meant by all or none?
If the minimum threshold is not reached then no action potential occurs.
How is a membrane repolarised?
It is returned to resting state by the sodium / potassium pump.
Why must the neurone be repolarised?
So that is can be stimulated again.
What is hypertrophy?
Where the muscle becomes bigger and stronger.
What is a neuromuscular junction?
Where the motor neurone and the muscle fibres meet.
What types of training would cause the adaptation of Type IIb fibres to Type IIa fibres?
Long, slow, distance, continuous, endurance training types.
In which type of sporting activities would the adaptation of Type IIb fibres to Type IIa fibres be relevant to the sportsperson?
Activities requiring aerobic endurance rather than speed, such as triathlons or marathons.
What does PNF stretching stand for?
Proprioceptive Neuromuscular Facilitation stretching.
Muscle spindles and Golgi tendons are what type of receptors?
Proprioceptors.
What are the name for the very sensitive proprioceptors that lie between skeletal muscle fibres.
Stretch receptors.
What do stretch receptors provide?
They provide excitory signals to the CNS about how fast and how far a muscle is being stretched.
How does a stretch receptor cause a muscular contraction?
The receptor detects the muscle stretching and sends a signal to the CNS, the CNS then sends a signal back to the muscle telling it to contract, triggering the stretch reflex.
What causes a stretch reflex?
Stretch receptors detect muscle stretching and send excitory signals to the CNS. The signal is sent back to the muscle telling it to contract, this is the stretch reflex.
What is the purpose of a stretch reflex?
The reflex action prevents over-stretching to reduce the risk of injury.
How does the body prevent over-stretching?
The body has a natural stretch reflex which contracts a muscle to prevent it.
Where are Golgi tendons found?
They are found between the muscle fibre and tendon.
What is the function of Golgi tendons?
To detect levels of tension in the muscles.
What is PNF?
An advanced stretching technique which is effective for flexibility training to increase range of motion.
How does PNF stretching work?
Stimulates proprioceptors in the muscle and tendon to cause muscular relaxation in the antagonistic muscle.
When a muscle is contracted isometrically in PNF, what do Golgi tendons do?
Detect increased muscle tension and send inhibitory signals to the brain which allow the antagonistic muscle to relax and lengthen.
What is autogenic inhibition?
Where Golgi tendons send inhibitory signals to the brain which allow the antagonistic muscle to relax and lengthen.
Which muscle is relaxed when PNF stretching?
The antagonistic muscle.
When the antagonistic muscle relaxes in PNF stretching, what does this cause?
A greater range of movement due to increased flexibility and lengthens.
Which receptors detect levels of tension in the muscle?
Proprioceptors -> Golgi Tendon Organs.
Where are Golgi Tendon Organs found?
In the tendons, which join muscle fibre to bone.
When are Golgi Tendon Organs activated?
They are activated when there is tension in a muscle.
Muscle spindles and Golgi Tendon Organs are types of what receptors?
Proprioceptors.
What is an isometric contraction?
Where there is tension in a muscle but no visible movement.
Give an example of a PNF stretch:
Behind head chest stretch. Prone quadriceps stretch. Overhead triceps stretch. Overhead lat stretch. Seated front deltoid stretch.
During PNF stretching, what does CRAC stand for?
Contract,
Relax,
Antagonist,
Contract.
Is partner aided PNF stretching an active or passive stretch?
Passive, an external force is provided by the partner.
How long is a PNF stretch held for at the maximum range off movement?
a few seconds up to 30 seconds, dependant on the performer.
During PNF stretching, the stretch is held at the maximum range of movement. What type of contraction is the muscle undergoing?
Isometric contraction.
What relation does PNF stretching have to the stretch reflex?
PNF aims to over-ride the stretch reflex.
Which muscle fibre ‘type’ is SLOW TWITCH?
type 1.
Which muscle fibre ‘type’ is FAST OXIDATIVE GLYCOLYTIC?
type 2a.
Which muscle fibre ‘type’ is FAST GLYCOLYTIC?
type 2b.
What is hypertrophy?
Where a muscle has become bigger and stronger.
What is a tendon?
A cord or band of dense, tough, inelastic, white, fibrous tissue which connects muscle to bone.
What is wave summation?
Where the nerve impulse is repeated with no time to relax, creating a smooth, sustained contraction.
What is a tetanic contraction?
A forceful, sustained, smooth contraction caused by a series of repeating fast stimuli.
What type of contraction is involved in PNF stretching?
Isometric contraction (not moving).
