In: Anatomy and Physiology
What is a neuromuscular junction? List and describe the junction. List and describe the roles of the chemicals involved at that site
Neuromuscular junction is a Junction Between nerve fibre and the muscle fibre which is innervated by the nerve.So a neuromuscular junction Consist of-
1.Pre synaptic Membrane -Membrane of Neuronal Axon which supply the muscle
2.Synaptic cleft-The gap between pre synaptic and post synaptic membrane ,through which neurotransmitter is moved to Post synaptic membrane.
3.Post synaptic membrane-Plama membrane of The muscle that contain Acetyl choline receptors,to which Neurotransmitter released from pre synaptic membrane(Acetyl choline) binds.
The Chemicals involved are-
1.Voltage Gated Ca2+ channels ,which release Ca2+-
When the wave of Depolarisation reaches the pre synaptic Axon terminal Voltage Gated Ca2+ channels are Activated.This Activation of Voltage gated ca2+ Channels causes influx of Ca2+ in the Axon Terminal.
2.Synaptic vesicles which release neurotransmitter Acetyl choline -
Synaptic Vesicles that Contain the neurotransmitters should fuses with pre synapptic membrane(Exocytosis) for the release of Neurotransmitter into the Synaptic cleft.This Fusion of Synaptic vesicle occur Only when the Ca2+ released into the axon terminal Binds with the Specific Proteins (Synaptophysin & Synaptobrevin) in the synaptic vesicles.
This binding of Ca2+ to these proteins causes movement and fusion of Synaptic vesicle into pre synaptic membrane-----Release of Neurotransmitters into synaptic Cleft.
3.Acetyl choline receptors-
Neurotansmitter(Acetyl CHoline) which is released into Synaptic Cleft Binds to Acetyl Choline receptors in the Post Synaptic Membrane--which allow entry of some positive ions which makes membrane potential less negative which makes Voltage gated Na+ channels to open
4.Voltage gated Na + Channels which allow entry of Na+ -
The opening of Voltage gated Na+ channels---leads to entry of Na+---this results in the Depolarisation in the Post Synaptic Membrane or Sarcolemma