Synaptic structure and Neurotransmitters Flashcards
1
Q
Synapse
A
When the nerve impulses reaches the end of the neuron, it must cross a gap to get to the next neuron.
2
Q
Neurotransmitter
A
When a nerve impulse crosses the synapse in the from of a chemical transmitter. They diffuse across the synapse and initiate an action potential in the neuron at the other side.
3
Q
Presynaptic neuron
A
It transmits the signal toward a synapse.
4
Q
Synaptic vesicles
A
This is where the neurotransmitters are stored, that can fuse with the surface to release them into the synaptic cleft.
5
Q
Step by step chemical transmission across the synapse
A
- The action potential arrives. Depolarization occurs in the synaptic knob.
- Causing the calcium channels to open and the calcium ions flood into the synaptic knob.
- The influx of calcium ions causes synaptic vesicles to fuse with Presynaptic membrane, this called an exocytosis. This whole process causes it to release neurotransmitters into the cleft.
- The neurotransmitter (acetylcholine) is released into the synaptic cleft. It then binds to the receptor site on the sodium ion channel.
- The sodium channels open. This allows the sodium ions to flood in and cause depolarization. The depolarization inside the post synaptic neuron must be above the threshold value, if it is reached, a new action potential is sent along the axon of the post synaptic neuron.
- Actelylcholinesterase is a hydrolytic enzyme. It breaks up acetylcholine into acetyle and choline.
- The sodium ion channels close. The two bits diffuse back across the cleft into the Presynaptic neuron which allows the neurotransmitter to be recycled. If it is not broken down this could allow it to continuously generate new action potentials.
6
Q
Acetylcholine
A
In the neuron ATP released by mitochondria is used to recombine acetyl and choline thus recycling the acetylcholine. This is stored in synaptic vesicles for future use.
