1.1a muscle fibre types and contraction Flashcards
fast glycolytic
-large PC stores for ATP-PC system
-largest amount of force
-anaerobic exercise - high intensity (100m sprint)
fast oxidative glycolytic
-produce large amount of force quickly
-resist fatigue
-high intensity work lasting several mins
slow oxidative
-myoglobin transports oxygen to mitochondria
-mitochondria processes oxygen into energy
-works aerobically
-produces small amounts of force over a long period of time
resistant to fatigue - endurance events (10000m)
how long do SO muscle fibres take to recover
each fibre recovers quickly and available for recruitment in 90 seconds
work relief ratios for SO fibres
low aerobic work relief ratios
1:1 work:relief
how often can aerobic activity be performed for SO fibres?
doesn’t cause damage so daily basis
low-intensity use of SO recommended after heavy weight training to increase blood flow and enhance healing
when are FG fibres recruited
in last 2-20 seconds of muscle contraction, near exhaustion or when maximal efforts are required
followed by DOMS 24-48 hours later
how long do FG take to recover
need much longer to recover than SO
take 4-10 days to recover after exhaustion
leave 48 hours before using same muscle group again
when are FG fibres recruited
in last 2-20 seconds of muscle contraction, near exhaustion or when maximal efforts are required
followed by DOMS 24-48 hours later
work:relief ratio FG fibres
high work:relief ratio 1:3+
3-5 mins rest between sets of 2-6 reps
when do muscles contract?
when stimulated by an electrical impulse
where is an electrical impulse sent from?
central nervous system
what is a motor neuron
a specialised cell that transmits nerve impulses rapidly to a group of muscle fibres
they have a cell body in the brain/spinal cord and axon that branches to connect motor end plates to muscle fibres
what is a motor unit
the motor neuron and its muscle fibres
carries nerve impulses from brain and spinal cord to muscle fibres - initiates muscular contraction
what is a neurotransmitter
a chemical (acetylcholine) produced and secreted by a neuron which transmits the nerve impulse across the synaptic cleft to the muscle fibre
when is the neurotransmitter used?
when the action potential needs to cross the synaptic cleft
what is an action potential?
positive electrical charge inside the nerve and muscle cells that conducts the nerve impulse down the neuron and into the muscle fibre
when is an action potential created?
when enough of the neurotransmitter is secreted and the electrical charge is above the threshold
what is the all-or-none-law?
whether the stimulus is above a threshold, all muscle fibres will give a complete contraction or none at all
process of muscle contraction
- nerve impulse initiated by the motor neuron cell body
- nerve impulse conducted down the axon of motor neuron by nerve action potential to synaptic cleft
- acetylcholine (neurotransmitter) secreted into synaptic cleft to conducted nerve impulse across the gap
- if the electrical charge is above a threshold, the muscle fibre will contract
- happens in an all-or-none fashion
small motor units and muscle fibre type for activity
small motor units stimulate relatively small muscle fibres
motor unit produces low and slow amount of force over a long period of time
-resists fatigue
good for sustained muscular contraction eg maintenance of posture
large motor units and muscle fibre type for activity
large motor neurons stimulate many muscle fibres
creates a motor unit which produces a large amount of force rapidly
-fatigues quickly
good for brief exertions of large force
eg jumping, throwing
