motor unit

Question 1

whats a motor unit

Answer 1

a motor neurone and its muscle fibres

Question 2

whats are motor neurones

Answer 2

nerve cells which transmit the brains instructions as electrical impulses to the muscles

Question 3

what is a neuromuscular junction

Answer 3

where the motor neurone and muscle fibre meet

Question 4

difference between muscles controlling fine and gross skills

Answer 4

muscles controlling gross motor control will have motor units with a motor neurone feeding hundreds of fibres

Question 5

what do muscle fibres do

Answer 5

work with nervous system so that a contraction can occur

Question 6

whats the all or none law

Answer 6

• 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

Question 7

difference between slow twitch and fast twitch motor units

Answer 7

• 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.

Question 8

whats wave summation

Answer 8

• 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

Question 9

whats a tetanic contration

Answer 9

a sustained muscle contraction caused by a series of fast repeating stimuli

Question 10

whats spatial summation

Answer 10

• 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.