4. The Neuromuscular System Flashcards
Motor neurone definition
Nerve cell that carries signals from the brain & spiral cord to the muscles in the body which tell them to move
Motor unit definition
Made up of one motor neurone & all the muscle fibres it controls - allows muscles to produce different strengths of movement
Neuromuscular junction definition
Place where a motor neurone meets a muscle fibre - ‘connection point’ that allows a signal to reach a muscle causing it to contract
Central nervous system definition
Made up of brain & spinal cord - acts as body’s control centre
Peripheral nervous definition
Includes all nerves outside CNS - connects CNS to rest of body, sensors nerves & includes motor nerves
Neuromuscular system function
- Nervous system - CNS: brain & spinal cord process & send out signals
PNS: nerves carry signals to & from CNS to reach muscles - Brain sends messages down spinal cord & through motor neurones in PNS
- motor neurones connect to muscle fibres at neuromuscular junctions
- chemical message crosses from motor neurone to muscle making it contract
- Motor units - movement strength depends on motor units
-smaller movements = smaller m.u
-larger movements = larger m.u
Motor unit role
For muscle to contract it has to be sent an impulse (action potential) from the cerebrum via the spinal cord
Impulses travel along nerves motor neurone) to the muscle
A motor unit is the whole system which in the impulse travels from the cell to the nerve to the muscle for it to contract
In order for muscles to contract, the action potential (nerve impulses) being towards the muscle (from the brains have to be great enough → reaching beyond the action potential threshold
Neurotransmitters
The most important one in regulating exercise response are acetylcholine & norepinephrine
Acetylcholine role
It is a neurotransmitter that helps nerves communicate with muscles & other nerves → main role is to trigger muscle contractions
- Brain sends signal through nerves to muscle
- Acetylcholine released at end of nerve, crosses synapse
- Binds to receptors at muscle causing fibres to contract
Also helps with memory, attention & alertness
Motor unit size
Refers to number of muscle fibres controlled by a single motor neurone
Small mu size: fewer muscle fibres per neurone →10 - 100 fibres
Large mu size: more muscle fibres per neurone →500 - 1000 fibres
All or none law
Refers to how a muscle will contract or not at all → the impulse has to reach at/ beyond the action potential threshold for the muscle to contract
Strong contraction: impulse sent down lots /all motor units
Weak contraction: impulse sent down less motor units so less muscle fibres contract
Short-term responses of neuromuscular system
- increase in nerve transmission
-Immediate muscle activation - motor unit recruitment
-Muscle fibre type recruitment - reflex responses
- blood flow regulation
Long-term (chronic) adaptations of neuromuscular system
- increased motor unit recruitment
- enhanced muscle activation
- muscle fibre type adaptations
-Increased m.u synchronisation & improved m.n firing rates
-Summation of motor units - muscle hypertrophy
What are the 3 muscle fibre types?
Type 1 - slow twitch
Type 2A - fast twitch oxidative
Type 2B - fast twitch glycolytic
Type 1 muscle fibre - structural characteristics
- Small fibre size
- large number of capillaries
- large number of mitochondria
- high myoglobin store
- low PC stores
-Iow glycogen stores
