1.3 The Neuromuscular System Flashcards
What is the autonomic nervous system, briefly outline the role of the neuromuscular system
Sympathetic nervous system - prepares the body for ex
Parasympathetic nervous system - relaxes the body and slows down many high energy functions
Types of muscle fibres - what are the main 3
- Slow oxidative (type 1) - slow twitch
- Fast oxidative glycolytic (type IIa)
- Fast glycolytic (type IIx) - fast twitch
Slow twitch fibres (type 1)
- slower contraction speed than fast twitch
- better adapted to lower intensity ex e.g. long distance running
- produce most of their energy aerobically
Fast twtich fibres (type II)
- faster contraction speed + generate greater force of contraction
- fatigue very quickly and are used for short, intense bursts of effort
- produce most of energy anaerobically
Two types of fast twitch fibres (type II):
Type IIa fast oxidative glycolytic - more resistant to fatigue, used in endurance events
Type IIx fast glycolytic- fatigue much quicker than IIa, used in explosive events e.g. 100m sprint
The effect of training on fibre type
- fibre type appears to be genetically determined
- possible to increase the size of muscle fibres through training
- the increase size is called hypertrophy = greater strength in the muscle
The motor unit - what makes up a motor unit, how does it work…
- muscle fibres are grouped into motor units
- a motor unit consists of a motor neuron and its muscle fibres
- only one type of muscle fibre works with the nervous system so that a contraction can occur
- the motor neurone transmits the nerve impulse to the muscle fibre
- each motor neurone has branches that end in the neuromuscular junction on the muscle fibre
Number of motor units in different type of muscle
small muscle used for controlled movements -
Motor units that only have a few fibres per neurone
Large muscle used for gross motor control -
Motor units with a motor neurone feeding hundreds of fibres per
All or none law
Once the motor n stimulates the muscle fibres, either all of them contract or none of them contract.
Not possible for a motor unit to partially contract
- a minimum amount of stimulation called the ‘threshold’ is required to start a contraction
- if the sequence of impulses is equal to or more than 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
Slow twitch and fast twitch motor units - how the brain recruits different fibres…
- motor units contain the same type of muscle fibre so they are either slow twitch or fast twitch motor units
- brain will recruit slow twitch motor units for low intensity ex
- if greater force of contraction is needed, the brain will recruit fast twitch motor units
What are the 2 ways to increase the strength of contraction
- Wave summation
- Spatial summation
Wave summation
- the greater the frequency of stimuli, the greater the tension developed by the muscle
- wave summation = repeated activation of motor neurone stimulating given muscle fibre results in greater force of contraction.
- each time the nerve impulse reaches the muscle cell, calcium is released (needed for muscle to contact)
- if there are repeated nerve impulses with no time to relax, calcium builds up in msucle cell
- produces a forceful, sustained, smooth contraction = tetanic contraction
Spatial summation
- impulses are received at the same time at different places on the neurone which add up to fire the neurone
- it is the recruitment of additional and bigger motor units within a muscle to develop more force
E.g. basket ball uses large fast twitch to gain height
