motor unit Flashcards
whats a motor unit
a motor neurone and its muscle fibres
whats are motor neurones
nerve cells which transmit the brains instructions as electrical impulses to the muscles
what is a neuromuscular junction
where the motor neurone and muscle fibre meet
difference between muscles controlling fine and gross skills
muscles controlling gross motor control will have motor units with a motor neurone feeding hundreds of fibres
what do muscle fibres do
work with nervous system so that a contraction can occur
whats the all or none law
- where a sequance of impulses has to be of sufficant intensity to stimulate all of the muscle fibres in a motor unit in order for them to contract. if not, none of them contract
- a minimum amount of stimulation is called the ‘threshold’ is required to start a contraction
difference between slow twitch and fast twitch motor units
- 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 activites such as sprinting or power lifting.
whats wave summation
- the greater the frequancy of the stimuli, the greater the tension developed by the muscle.
- where repeated activation of a motor neurone stimulating a given muscle fibre results in a greater force of contraction.
- each time a nerve impulse reaches the muscle cell, calcium is released, as calcium needs to be present for muscle to contract.
- if there are repeated nerve impluses with no time to relax calcium will build up in the muscle cell. producing a tetanic contraction
whats a tetanic contration
a sustained muscle contraction caused by a series of fast repeating stimuli
whats spatial summation
- this occurs when impulses are recieved 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
- means a basketball player will use lots if large, fast twitch motor units in her quads to try and achieve as much height as possible as she jumps.