At the neuromuscular junction, nerve impulses are carried across synaptic cleft by neurotransmitters.
At the neuromuscular junction, nerve impulses are carried across synaptic cleft by neurotransmitters.
The correct option is A sarcoplasm, sarcoplasmic reticulum, calcium ions
1. At the neuromuscular junction, there are voltage-gated calcium channels. When an action potential reaches the synapse these channels open, causing calcium ions to flow into the cell.
2. These calcium ions cause the synaptic vesicles to fuse with the cell membrane, releasing their contents (the neurotransmitter Acetylcholine) by exocytosis.
3. The neurotransmitters diffuse across the synaptic cleft.
4. The neurotransmitter binds to the neuroreceptors in the post-synaptic membrane, causing the channels to open.
5. This causes a depolarization of the post-synaptic cell membrane, which may initiate an action potential if the threshold is reached.
6. The neurotransmitter is broken down by a specific enzyme in the synaptic cleft; for example, the enzyme acetylcholinesterase breaks down the neurotransmitter acetylcholine. The breakdown products are absorbed by the pre-synaptic neurone by endocytosis and used to re-synthesise more neurotransmitter, using energy from the mitochondria. This stops the synapse being permanently on.
sarcoplasm, sarcoplasmic reticulum, calcium ions
1. At the neuromuscular junction, there are voltage-gated calcium channels. When an action potential reaches the synapse these channels open, causing calcium ions to flow into the cell.
2. These calcium ions cause the synaptic vesicles to fuse with the cell membrane, releasing their contents (the neurotransmitter Acetylcholine) by exocytosis.
3. The neurotransmitters diffuse across the synaptic cleft.
4. The neurotransmitter binds to the neuroreceptors in the post-synaptic membrane, causing the channels to open.
5. This causes a depolarization of the post-synaptic cell membrane, which may initiate an action potential if the threshold is reached.
6. The neurotransmitter is broken down by a specific enzyme in the synaptic cleft; for example, the enzyme acetylcholinesterase breaks down the neurotransmitter acetylcholine. The breakdown products are absorbed by the pre-synaptic neurone by endocytosis and used to re-synthesise more neurotransmitter, using energy from the mitochondria. This stops the synapse being permanently on.
