Skeletal Muscle 1 Flashcards
What is the name of the neuron which will branch and attach to muscle fibres?
Alpha motor neuron
What is a motor unit?
The muscle fibres an alpha motor neuron innervates
What is the size principle?
Small oxidative units are recruited first, then large glycolytic units.
What are the pre synaptic events?
- AP reaches terminal boutons in nerve cell
- depolarisation triggers opening of Ca2+ channels, calcium influx
- increased calcium causes vesicles to fuse with membrane, exocytosis of Ach
- Ach diffuses across synaptic cleft and binds to Ach receptors (2Ach)
- acetylcholinesterase anchored to pre synaptic cell breaks down Ach
What does acetylcholinesterase do, and what targets it?
acetylcholine + water –> choline + acetate, and is targeted by insecticides
Describe vesicle cycling
1) neurotransmitter uptake
2) Vesicles cluster
3) Dock at active zone
4) Vesicles are primed
5) Ca2+ triggered fusion pore opening
6) local refuse
7) fast recycling
8) clathrin mediated endocytosis
9) recycling via endosomes
What is the EPC?
Current measured on the motor end plate, due to tje transient opening of Ach receptor channels. It is restricted to the short time that they are open. It is the sum of all the currents generated.
What is the EPP?
The potential difference generated on the motor end plate, that is suprathreshold. It travels along the muscle cell for a short distance, so is longer than the EPC (the passive charging/discharging of the membrane)
What follow the EPP?
Na+ channels open and depolarisation of the rest of the membrane occurs, propagating the action potential.
What is myasthenia gravis?
An autoimmune disorder which acts on the Ach receptors. As a result, less functional receptors, inhibiting action potential initiation. (Affects facial muscles mainly)
What is the treatment of MG?
anti-Acetylcholinesterases or immunosuppresive drugs.
