motor unit + muscle fibres Flashcards
what are motor neurones?
specialised cells which transmit nerve impulses to a group of muscle fibres
motor unit
a motor neuron + muscle fibres
5 steps for a muscle contraction to occur
1) impulse sent by the cell body in the cerebellum
2) impulse (action potential) sent down the motor neurone through the motor end plates with the synaptic cleft
3) neurotransmitter called ACETYLCHOLINE is secreted into the synaptic cleft to transmit nerve impulses across the gap
4) if the change is above the threshold. the muscle fibres will contract
5) this happens in an all or none fashion
vary the strength of a muscle contraction
- recruit MORE or LESS (NUMBER) of motor units –> e.g. send impulse down less fibres for weaker contraction
- recruit BIGGER or SMALLER (SIZE) of motor units
e. g. when we overthrow or under throw
3 types of muscle fibres
Type 1 = Slow Oxidative (SO)
Type 2a = Fast Oxidative Glycolytic (FG)
Type 2b = Fast Glycolytic (FG)
describe Type 1 muscle fibre
Slow Oxidative (SO)
- structurally designed to store O2 in myoglobin and process this in the mitochondria = allows athlete to work anaerobically
- produce a small force but resist fatigue for long periods of time
- predominantly used by endurance athletes such as long distance runners
describe Type 2a muscle fibre
Fast Oxidative Glycolytic (FOG)
- structurally designed to produce a large amount of force quickly
- also resist fatigue, but not for as long as Type 1 muscle = SO
- moderate levels of myoglobin
- predominantly used by high intensity athletes for several minutes e.g. 800m runner
describe type 2b muscle fibre type
Fast Glycolytic (FG)
- structurally designed to work anaerobically
- large store of phosphocreatine
- fatigue very quickly
- low levels of myoglobin + O2
- produce very fast contractions + predominantly used by short duration athletes e.g. 100m sprint
work to recovery ratio for all 3 muscle fibre types
type 1:
1:1, 1:0.5
type 2a/2b:
1:3 –> worked to exhaustion so need longer time to recover
