1.3: The Neuromuscular System Flashcards
1
Q
What is the autonomic nervous system?
A
- regulates the function or our internal organs such as the heart and also controls some of our skeletal muscles within the body.
2
Q
What is the neuromuscular system?
A
- where the nervous system and the muscles work together to allow movement.
3
Q
Changes in the neuromuscular system:
A
- take place before, during and after exercise.
- these changed prepare the body for exerciser and allow for the change into demands of different intensities or exercise.
4
Q
Sympathetic nervous system - during exercise:
A
- part of the peripheral nervous system
- prepares the body for exercise and is often referred to as the ‘fight or flight response’
5
Q
Parasympathetic nervous system - during exercise:
A
- has the opposite effect of the sympathetic nervous system
- relaxes the body and slows down many high energy functions.
‘rest and relax’
6
Q
What are the three types of muscle fibre?
A
- slow oxidative (type 1) (also known as slow twitch)
- fast oxidative glycolytic (type 11a)
- fast glycolytic (type 11x)
7
Q
The relative proportion of each fibre type in different people?
A
- varies, e.g, in an elite endurance athlete there will be a greater proportion of slow twitch fibres in the leg muscles, and in the elite springer a greater proportion of fast twitch fibres in the leg muscles.
- postural muscles tend to have a greater proportion of slow twitch fibres as they’re involved in maintaining body position over a long period of time.
8
Q
What are slow twitch fibres?
A
- slower contraction speed than fast twitch fibres
- better adapted to lower intensity exercise such as long-distance running.
- they produce most of their energy aerobically - therefore have certain characteristics that allow them to use oxygen more effectively.
9
Q
What are fast twitch fibres?
A
- must faster contraction speed and can generate a greater force of contraction.
- however they fatigue very quickly and are used for short, intense bursts of effort.
- they produce most of their energy anaerobically.
- two types
10
Q
What are the two types of fast twitch fibres?
A
- type 11a (fast oxidative glycolytic; these fibres are more resistant to fatigue and used in events such as the 150 in athletics where a longer burst of energy is needed.
- type 11x (fast glycolytic; these fibres fatigue much quicker than type 11a and are used for highly explosive events such as the 100m in athletics where a quick, short burst of energy is needed.
11
Q
Characteristics of slow and fast twitch fibres - type 1:
A
- contraction speed (metres per second): slow (110)
- motor neurone size: small
- motor neurone conduction capacity: slow
- force produced: low
- fatiguability: low
- mitochondrial density: high
- myoglobin content: high
- capillary density: high
- aerobic capacity: very high
- anaerobic capacity: low
- myosin ATPase/glycolytic enzyme activity: low
12
Q
Characteristics of slow and fast twitch fibres - type 11a:
A
- contraction speed (metres per second): fast (50)
- motor neurone size: large
- motor neurone conduction capacity: fast
- force produced: high
- fatiguability: medium
- mitochondrial density: medium
- myoglobin content: medium
- capillary density: medium
- aerobic capacity: medium
- anaerobic capacity: high
- myosin ATPase/glycolytic enzyme activity: high
13
Q
Characteristics of slow and fast twitch fibres - type 11x:
A
- contraction speed (metres per second): fast (50)
- motor neurone size: large
- motor neurone conduction capacity: fast
- force produced: high
- fatiguability: high
- mitochondrial density: low
- myoglobin content: low
- capillary density: low
- aerobic capacity: low
- anaerobic capacity: very high
- myosin ATPase/glycolytic enzyme activity: very high
14
Q
Hypertrophy definition:
A
- where the muscle has become bigger and stronger
- it is possible to increase the size of muscles fibres through training.
15
Q
What is a motor unit?
A
- consists of a motor neurone and it’s muscle fibres.
- only one type of muscle fibre can be found in one particular motor unit.
16
Q
What are motor neurones?
A
- nerve cells which transmit the brain’s instructions as electrical impulses to the muscles.
- each motor neurone has branches that end in the neuromuscular junction on the muscle fibre.
17
Q
Neuromuscular junction definition:
A
- where the motor neurone and the muscle fibre meet.
18
Q
Muscle fibre examples:
A
- small muscle that is used for fine motor control, e.g. the muscles controlling eye movements, will have motor units that only have a few fibres per motor neurone.
- a large muscle used for gross motor control, such as the quadriceps when the leg is extended, will have motor nuts with a motor neurone feeding hundreds of fibres.
19
Q
What is the all or none law?
A
- where a sequence of impulses has to be of sufficient intensity to stimulate all the muscle fibres in a motor unit in order for them to contract.
- if the sequence of impulses is equal to or more rm an the threshold, all the muscle fibres in a motor unit will contract. If the sequence of impulses is less than the threshold; then no muscle action will occur.
20
Q
Slow twitch and fast twitch motor units:
A
- motor units contain the same type of muscle fibre so they are either slow twitch or fast twitch motor units.
- the brain will recruit slow twitch motor units for low intensity activity such as jogging or long-distance swimming.
- if a greater force of contraction is needed, the brain will recruit fast twitch motor units for activities such as sprinting or power lifting.
21
Q
How to increase the strength of contraction?
A
A basketball player jumping for a rebound needs to exert as much force to gain the height needed to win the rebound.
- in order to increase the strength of force exerted by her quadriceps muscles to extend her knee as she jumps, the following must happen:
- wave summation
- spatial summation
22
Q
What is wave summation?
A
- where there is a repeated nerve impulse with no time to relax so a smooth, sustained congestion occurs, rather than twitches.
- the greater the frequency of stimuli, the greater the tension developed by the muscle.
- each time the nerve impulse reaches the muscle cell, calcium is released. Calcium needs to be present for a muscle to contract.
- is there are repeated nerve impulses with no time to relax, calcium will build up in the muscle cell - producing a tetanic contraction.
23
Q
What is a tetanic contraction?
A
- a sustained muscle contraction caused by a series of fast repeating stimuli.
24
Q
What is spatial summation?
A
- when the strength of a contraction changes by altering the number and size of the muscle’s motor units.
- occurs when impulses are received at the same time at different places on the neurone which add up to fire the neurone.
- the recruitment of additional and bigger motor units within a muscle to develop more force - the basketballer will use lots of large, fast twitch motor units in quads to try to achieve as much height possible for the rebound.
25
What is the proprioceptive neuromuscular facilitation (PNF)?
- an advanced stretching technique.
| - also considered to be one of the most effective forms of flexibility training for increasing range of motion.
26
Example of PNF techniques:
- most practical is the CRAC technique (contract-relax-antagonist-contract).
27
What are proprioceptors?
- sensory organs in the muscles, tendons and joints that inform the body of the extent of movement that has taken place.
28
What are the types of proprioceptors?
- muscle spindles
| - Golgi tendon organs
29
What are muscle spindles?
- very sensitive proprioceptors that lie between skeletal muscle fibres.
- often referred to as stretch receptors as they provide information (excitory signals) to the CNS about how fast and how far a muscle is being stretched.
- they detect how far and how fast a muscle is being stretched and produce the stretch reflex.
- the reflex action that causes the muscle to contract to prevent over-stretching reduces the risk of injury.
30
What are Golgi tendon organs?
- found between the muscle fibre and tendon.
- they detect levels of tension in a muscle.
- when the muscle is contracted isometrically in PNF, they sense the increase in muscle tension and send inhibitory signals to the brain which allows the antagonist muscle to relax and lengthen - this is known as autogenic inhibition.
31
Autogenic inhibition definition:
- when there is a sudden relaxation of the muscle in response to high tension.
- the receptors involved in this process are Golgi tendon organs.
