UNIT 1 (neuromuscular system and muscle fibre types) Flashcards
what is a motor neurone
nerve cells which transmit the brains instructions as electrical impulses to the muscles
what is a motor unit
a motor neuron and all the muscle fibres its innovates
what is the neuromuscular junction
where the motor neuron meets the muscle fibre
what are the 3 muscle fibres
type 1/ slow twitch
type2a(fast)
type2b/x(fast)
what does the CNS consist of
central nervous system:brain and spinal cord
What is PNS (peripheral nervous system)
what connects the muscles to the CNS
what are the 4 main components of a motor neuron and their functions
-dendrites receive electrical signals from other neurons
-cell body process the information received
-axon transmits the electrical impulse to the neuromuscular junction
-axon terminals release neurotransmitters to stimulate muscle action
what does the muscle need to contract
enough action potential (ie nerve impulses) or reaching beyond action potential thresholds
what is the main neurotransmitter in the body
acetylcholine
what is a neurotransmitter
a chemical messenger
how is acetylcholine used during muscle contraction
brain sends a signal through nerves to muscle, acetylcholine is released at the end of the nerve and crosses the synapse between the nerve and the muscle. when it reaches the muscle it binds to receptors causing the muscle to contract
key differences between neurotransmitter and hormones
-hormones are chemical messengers in endocrine system whereas neurotransmitters are chemical messengers in the nervous system
-duration- neurotransmitter very short, hormones very long
-transport- hormones in blood, neurotransmitters over synapse
-production site- hormone secreted by endocrine glands, neurotransmitters released by neurone in brain and spinal cord
what is motor unit size
refers to number of muscle fibres controlled by a single motor neuron
describe the all or none law
states that when a motor unit is activated, all the muscle fibres within that unit will contract, but only if the stimulus is strong enough to reach the threshold
how many motor units for strong contraction
impulses sent down all motor units for forceful movement
how many motor units for weak contraction
impulses sent down few motor units for precise movement
short term reponses of neuromuscular system
-increase in nerve transmissions: immediate increase in neural impulses to muscles
-immediate muscle activation: increase in nerve impulses = rapid recruitment of motor units
-muscle fibre type recruitment:slow twitch fibres are recruited for low intensity, fast twitch fibres are recruited for high intensity explosive movements
-motor unit recruitment: smaller motor units are recruited first for low intensity, larger motor units are recruited as exercise intensity increases
-reflex response:reflex arcs response rapidly to change in muscle length (muscle spindle) and muscle tension (Golgi tendon organ)
what happens during neuromuscular fatigue?
reduced levels of acetylcholine which causes nerve impulses to be slower and inhibits muscle contraction.
if motor unit size is larger will it have more muscle fibres per motor neuron or less
more muscle fibres per motor neuron
long term adaptations of neuromuscular system
-increased motor unit recruitment: allows for more efficient and coordinated muscle contractions during exercise
-enhanced muscle activation:both strength and endurance training lead to increased muscle activation levels
-muscle fibre type adaptations: strength training can lead to hypertrophy and increased strength primarily in fast twitch fibres. endurance will enhance slow twitch fibres
-muscle hypertrophy: strength training leads to increase in muscle size, this is due to an increase in number of myofibrils within muscle fibres
how does low levels of acetylcholine increase anaerobic fatigue
-low acetylcholine weakens the ability of the motor neurons to stimulate muscle fibres, resulting in decreased muscle force and contributing to fatigue
-nerver impulses become weaker and less effectively transmitted to muscles, so contractions become weaker and less coordinated leading to early muscle fatigue during anaerobic activities.
