Control of muscle Flashcards
What are the two functional subdivisions of the nervous system?
- Somatic nervous system (voluntary)
- Visceral nervous system (involuntary)
What are the two directional subdivisions of the nervous system?
- Afferent nervous system (towards the brain and spinal cord)
- Efferent nervous system (away from the brain and spinal cord)
What type of nerve cell is a motor neurone?
An efferent nerve cell transmitting information from the CNS to muscles
Complete the sentence… “each skeletal muscle fiber is innervated by…”
By one motor neurone
What is a motor unit?
A motor neurone and all of the fibres it innervates.
What is the difference between muscles that have a large motor unit and ones that have a small motor unit?
Muscles that have a small motor unit require low force and fine control.
Muscles that have a large motor unit require large force and low control.
What is a neuromuscular junction?
A specialized chemical synapse between a motor neurone and a muscle
What neurotransmitter is present in neuromuscular junctions?
ACh = acetylcholine
Why is the sarcolemma folded at the neuromuscular junction?
To increase surface area
What happens when an action potential arrives at a neuromuscular junction?
Explain (long answer Qs)
1) Action potential arrives at the axon terminal
2) Voltage gated Ca2+ channels in the pre-synaptic membrane open (this results in an influx of Ca2+ ions into the cell)
3) Ca2+ entry causes pre-synaptic vesicles to release neurotransmitter (ACh) into synaptic cleft.
4) ACh diffuses across the synaptic cleft and binds to ACh receptors in the sarcolemma
5) Ion channels in the sarcolemma open, causing an influx of Na+ ions to enter and an efflux of K+ ions to leave (this causes depolarisation in the post-synaptic membrane)
6) Current of positive charge travels through the cytosol, activating voltage gated Na+ channels in the adjacent sarcolemma. This propagates an action potential along the membrane.
Why do we ensure that there is only one action potential per nerve?
Acetylcholinesterase rapidly degrades ACh left in the cleft.
How can you detect muscle action potentials?
Electromyograhy can be used to detect electrical activity in muscles.
What is the function of T-tubules?
T-tubules conduct an action potential deep into the muscle fibre -> T-tubules are surrounded by the sarcoplasmic reticulum.
What is the function of the sarcoplasmic reticulum?
Store of Ca2+ ions.
What are coupled receptors?
They are voltage-sensitive proteins in the T-tubules which are linked to Ca2+ channels in the sarcoplasmic reticulum.
