muscular contractions Flashcards
motor units, action potential neurotransmitters, muscle fibre types
What are motor units?
Made up of a motor neuron and a group of muscle fibres.
What is a neurone?
A type of nerve cell.
What is an axon?
Carries the action potential from the cell body to the neuromuscular junction.
What is a synapse?
The tiny gap between the terminal end of the axon and the muscle surface where information is transmitted from one neuron to the next
What is the neuromuscular junction?
The point where the motor neuron meets the muscle fibre.
What is acetylcholine?
the neurotransmitter released at the neuromuscular junction and diffuses across the synapse
What is the all or none law?
A motor unit contracts fully or not at all.
What happens when we increase or decrease the rate of stimulation?
We get an increase or decrease in contractile strength.
What is resting potential?
Where there is a lower charge inside the neurone than outside the neurone.
What is action potential?
The electrical impulse carried down the axon.
What is a neurotransmitter?
Chemical transmitters which diffuse across a synapse to initiate muscular contraction.
Steps to answer a motor unit question
- the nerve sends an impulse from the CNS which travel down the axon
- when action potential is reached…
- ACh is secreted at the neuromuscular junction
- the impulse crosses the synapse
- if the action potential is above the threshold…
- the all or none law is applied
What type of activity are type I (SO) fibres used for?
Endurance eg. marathon, road cycling
What type of activity are type IIa (FOG) fibres used for?
Games players eg. hockey, football
What type of activity are type IIb/x (FG) fibres used for?
Power events eg. javelin, 100m sprint
Name five structural features of type I fibres
size: small
colour: red
mitochondria: many
glycogen store: low
capillaries: high
Name five structural features of type IIa fibres
size: intermediate
colour: pink
mitochondria: some
glycogen store: intermediate
capillaries: intermediate
Name five structural features of type IIb/x fibres
Size: large
colour: white
mitochondria: few
glycogen store: high
capillaries: low
Name three functional features of type I fibres
Contractile speed: low
contractile force: low
Fatigue resistance: high
Name three functional features of type IIa fibres
Contractile speed: intermediate
contractile force: intermediate
Fatigue resistance: intermediate
Name three functional features of type IIb/x fibres
Contractile speed: high
contractile force: high
Fatigue resistance: low
What do we mean by the term twitch?
A single contraction
What is the purpose of mitochondria?
Produces energy in the presence of O2
What does a high number of capillaries indicate?
The performer is and aerobic athlete
What is the purpose of a high glycogen store?
It can be broken down very quickly to produce anaerobic energy
Which type of muscle fibre would a long distance rower primarily use and why?
Fast Oxidative Glycolytic and mainly aerobic respiration
therefore they will produce a large force quickly and have the capacity to resist fatigue
Which type of muscle fibre would a triathlete primarily use and why?
Slow Oxidative and aerobic respiration
therefore they will produce a slow force of contraction for long periods
Which type of muscle fibre would a high jumper primarily use and why?
Fast glycolytic and mainly anaerobic respiration
therefore they will produce maximal force
