neuromuscular system Flashcards
aerobic
- ‘with oxygen’
- refers to exercise that is low to medium intensity where the oxygen demand of muscles is met
anaerobic
- ‘without oxygen’
- refers to energy as high intensity where the demand for oxygen by the muscles is so high it cannot be met.
hypertrophy
where the muscle has become bigger and stronger
motor unit
a motor neurone and its muscle fibres
motor neurones
nerve cells which transmit the brains instructions as electrical impulses to the muscles
neuromuscular junction
where the motor neurone and the muscle fibre meet
all or none law
where the sequence of impulses has to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit for them to contract
- if not none of them contract
wave summation
where there is a repeated nerve impulse with no time to relax so a smooth sustained contraction occurs, rather than twitches - a tetanic contraction
tetanic contraction
a sustained muscle contraction cause led by a series of fast repeating stimuli during wave summation
spatial summation
- when the strength of a contraction change by altering the number and size of the muscles motor units
- the activation of these motor units is staggered, enabling a sustained contraction to be maintained as some motor units are contracting while others are relaxing, delaying fatigue
muscle spindles
these detect how far and how fast a muscle is being stretched and produce the stretch reflex
golgi tendon organs
these are activated when there is tension in a muscle
isometric contraction
where there is tension in a muscle but no visible movement
autogenic inhibition
where there is a sudden relaxation of the muscles in response to high tension
- the receptors involved in this process are Golgi tendon organs
role of the sympathetic and parasympathetic nervous systems
transmit information from the brain to the parts of the body that need to adjust what they are doing to prepare for exercise
role of sympathetic system
- prepares the body for exercise
- fight or flight
role of parasympathetic system
- relaxes the body and slows down many high-energy functions
- rest and digest’
slow twitch fibres (type 1)
- slower contraction speed than fast fibres and are better adapted to lower intensity exercise such as long-distance running
- they produce most of their ATP aerobically and have specific characteristics that allow them to use oxygen more effectively
fast twitch fibres (type 2)
- fast contraction speed and can generate a greater force of contraction
- fatigue quickly and are used for short, intense bursts of effort
- produce energy anaerobically
type 2a fibres
- more resistant to fatigue and are used for events such as the 800m in athletics where a longer burst of energy is needed
type 2x fibres
- fatigue very quickly and are used for highly explosive events e.g. 100m in athletics where a quick, short burst of energy is needed
characteristics of slow twitch (type 1) fibres
Contraction speed: slow
Motor neurone size: small
Force produced: low
Fatigability: low
Mitochondrial density: high
Myoglobin content: high
Capillary density: high
Aerobic capacity: very high
Anaerobic capacity: low
characteristics of fast twitch (type 2a) fibres
Contraction speed: fast
Motor neurone size: large
Force produced: high
Fatigability: medium
Mitochondrial density: medium
Myoglobin content: medium
Capillary density: medium
Aerobic capacity: medium
Anaerobic capacity: high
characteristics of fast twitch (type 2x) fibres
Contraction speed: fast
Motor neurone size: large
Force produced: high
Fatigability: high
Mitochondrial density: low
Myoglobin content: low
Capillary density: low
Aerobic capacity: low
Anaerobic capacity: very high
functional characteristics of muscle fibres
- contraction speed
- force produced
- fatigability
- aerobic capacity
- anaerobic capacity
structural characteristics of muscle fibres
- motor neurone size.
- mitochondrial density.
- myoglobin content.
- capillary density.
how to increase the strength of a contraction
- wave summation
- spatial summation
what are muscle spindles and golgi tendon organs types of?
proprioceptors
role of muscle spindles in PNF
- sensitive proprioceptors that lie between skeletal muscle fibres
- they provide excitory signals to the central nervous system about how fast and how far a muscle is being stretched
- the central nervous system then sends an impulse back to the muscle telling it to contract, which triggers the stretch reflex, causing it to contract to prevent overstretching, reducing the risk of injury
role of golgi tendon organs in PNF
- found between the muscle fibre and tendon, they detect levels of tension
- then the muscle is contracted isometrically, they sense an increase in muscle tension and send inhibitory signals to the brain, which allows the antagonist muscle to relax and lengthen, known as autogenic inhibition
3 stages of PNF stretching
Individual performs passive stretch with help of partner and extends leg until tension is felt. Stretch detected by the muscle spindles and excitory signals cause a stretch reflex should occur if stretched too far.
Then isometrically contracts the muscle for 10 seconds by pushing leg against partner who supplies resistance. Golgi tendons activated due to tension and the inhibitory signals they send override the excitory signals from the muscle spindles, delaying the stretch reflex.
When leg is passively stretched again, the golgi tendon organs are responsible for the antagonist muscle relaxing, which means the leg stretches further. Can be repeated until no more gains are possible.
stage 1 of pnf stretching
- individual performs passive stretch with help of partner and extends leg until tension is felt
- stretch detected by the muscle spindles and excitory signals cause a stretch reflex should occur if stretched too far
stage 2 of pnf stretching
- then isometrically contracts the muscle for 10 seconds by pushing leg against partner who supplies resistance
- golgi tendons activated due to tension and the inhibitory signals they send override the excitory signals from the muscle spindles, delaying the stretch reflex
stage 3 of pnf stretching
- when leg is passively stretched again, the golgi tendon organs are responsible for the antagonist muscle relaxing, which means the leg stretches further
- can be repeated until no more gains are possible
The training that elite performers undertake may include proprioceptive neuromuscular facilitation (PNF) stretching. Explain the role of the muscle spindles and golgi tendon organs in PNF stretching. (3)
- golgi tendons detect a stretch in the muscles
- the muscles then relax because of an inhibited stretch reflex
- this is designed to prevent injury
- allows a greater range of movement
Contraction of different types of muscle fibres involves the use of motor units. What do you understand by the term ‘motor unit’? (2)
- made up of a motor neurone and muscle fibres
- all fibres are fast or slow twitch within that motor unit
- the sequence of impulses has to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit for them to contract
- if not none of them contract
How are motor units involved in the process of spatial summation? (2)
- motor units cause an increase in the strength of contraction
- using bigger units and more motor units will increase the strength of the contraction
- fast-twitch units produce more force than slow-twitch units
describe the characteristics of the main muscle fibre type used by marathon runners. (4)
- slow oxidative fibre/type 1
- slow motor neurone conduction capacity
- high numbers of mitochondria
- high myoglobin content
- high capillary density
- less powerful
The training that elite performers undertake may include PNF stretching. Explain the role of the muscle spindle apparatus and golgi tendons during PNF stretching. (5)
- Muscle spindles detect changes in muscle
(fibres) - Cause stretch reflex
- Designed to prevent overstretching/protective
- Aim of PNF to override the stretch reflex
- Golgi tendon organs/GTO activated/detect
overstretching of muscles - Causes the muscles to relax/autogenic
inhibition - Allows greater range of movement than the
initial stretch/greater range of movement
Describe the structural characteristics of the main muscle fibre type used by a triathlete. (4)
- Slow twitch fibres/type I
- Small motor neurone size
- High mitochondrial density
- High myoglobin content
- Large capillary density
