muscular system

• A skeletal muscle can only contract when stimulated by an electrical impulse sent from the central nervous system
• Motor Neurones: specialised cells that transmit nerve impulses rapidly to a group of muscle fibres. They have a cell body in the brain or spinal cord with an extending axon which branches to connect motor end plates to a group of muscle fibres
• Motor Unit: the muscle fibres and their motor neurone
• Action Potential: positive electrical charge inside the nerve and muscle cells which conducts the nerve impulse down the neurone and into the muscle fibre
• Neuromuscular junction: the point where the axons motor end plates and muscle fibre meet
• Synaptic Cleft: The gap between the motor end plates and muscle fibre
• Acetylcholine: a neurotransmitter closing the gap for the action potential to cross
• All or none law: when a motor unit receives a stimulus and creates an action potential reaches a threshold charge, all the muscle fibres within a motor unit will contract at the same time and with maximum force. If the action potential does not reach the threshold charge, none of the muscle fibres will contract.
• Slow twitch fibres: Slow oxidative
• Slow oxidative: contain large amounts of mitochondria, myoglobin and capillaries, small amount of force, resist fatigue for long periods of time, endurance activities - marathon runners
• Fast twitch fibres: Fast oxidative glycolytic, fast glycolytic
• Fast oxidative glycolytic: contain larger amount of mitochondria than type 11b fibres, large amount of force, resist fatigue well, high intensity activities - 800m
• Fast glycolytic: contain low numbers of mitochondria, large amount of force, fatigue quickly, strength activities - 100m, long jump
• Slow oxidative: Type 1
• Fast oxidative glycolytic: Type 11a
• Fast glycolytic: Type 11b