1.3.6 Physiology Of Muscular Contraction Flashcards
What are the characteristics of type 1a (slow twitch fibres)
High mitochondrial density, slow contractions time, high resistance to fatigue, high oxidative capacity
What are characteristics of type 2a( Fast oxidative glycolytic) fibres?
High oxidative capacity, fast contraction time, medium resistance to fatigue, high force production, medium capillary density
What are characteristics of type 2x ( fast glycolytic) fibres?
Low oxidative capacity, fastest contraction time, low resistance to fatigue, highest force production, low capillary density, high glycolytic capacity.
Give sporting examples for when each fibres type would be used.
Slow twitch (1a)= endurance events ( long distance running)
FOG (2a) = intermittent exercise (football), middle distance ( 400m )
Fast glycolytic (2x) = 100m sprint
What is the all or none law?
If an action potential is reached due to nerve impulse stimulating the motor unit. All the muscle fibres within that motor unit will be activated. If action potential is not reached then none of the muscle fibres in that motor unit will be activated.
What are 3 ways we can vary our contraction strength?
- The number of motor units recruited, more motor units recruited= more force produced.
- Type of muscle fibres recruited, 2x will produce more force than type 1
- Summation
What is spatial summation?
Many motor units firing, and sharing the workload.
What is wave summation?
Impulses stimulate muscle fibres before it has time to fully relax. Results in prolonged contraction with greater force output. (When lifting heavy weights)
What is neuromuscular transfer?
An impulse is generated in the brain, it is then transported down the spinal cord (CNS) via an axon. The impulse then reaches the muscles fibres where it can stimulate muscular contraction.
What is the neuromuscular transfer and sliding filament theory Process?
1) impulse known as action potential is generated within a cell in the cerebellum.
2)travels down an axon
3) nervous impulse arrives at the neuromuscular junction causes the release of neurotransmitter called acetylcholine which travels across the synaptic cleft and depolarises the motor end plates.
4)This causes the release of calcium ions from the sarcoplasmic reticulum.
5) Calcium attaches to the troponin on the actin filament.
6) Tropomyosin alters its shape, exposing the active binding site.
7) The myosin filaments now able to attach to the actin filaments to creat a cross bridge.
8) Breakdown of ATP releases energy which enables the power stroke.
9) Z-lines are now closer to m-line causing shortening of muscle.
10) recharge stage occurs which allows the process to be repeated as long as ATP and Calcium are still present. When one or both run out, the muscle will undergo relaxation.
What happens during the resting phase in the sliding filament theory?
Muscle is relaxed due to lack of calcium in the myofibril resulting in a lack of myosin bound to actin.
What happens during the excitation phase in sliding filament theory?
Cross bridge is formed. Acetylcholine results in the depolarisation of the motor end plates. Releasing calcium ions that then bind to troponin changing its shape. Changed shape causes Tropomyosin to move from the active site of actin.
What happens during the contraction phase of the sliding filament theory?
Breakdown of ATP provides energy required for myosin to pull on the actin, resulting in the muscle being shortened. (Push stroke)
What happens during the recharge phase of the sliding filament theory?
Ratchet mechanism. Contraction phase is repeated until ATP and Calcium run out
What happens during relaxation phase of the sliding filament theory?
Calcium re-enters the sarcoplasmic reticulum meaning the cross bridges formed between actin & myosin no longer exist.
