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PhysioEx Ex3Actvy 8
Chemical Synaptic Transmission & Neurotransmitter Release
| Question | Answer |
|---|---|
| What is a major function of the nervous system? | Communication. An axon conducts an action potential from one place to another |
| How is the action potential conducted to several places at a time? | From the axon branches |
| What does the axon terminal do? | It is at the end of each axon branch and it is specialised to release packets of neurotransmitters from small (30nm diameter) intracellular membrane-bound vesicles called synaptic vesicles |
| What are neurotransmitters? | They are the brain chemicals that communicate information throughout our brain and body. They relay signals between nerve cells, called “neurons.” |
| How are these chemicals released? | By exocytosis and diffusion across a small extracellular space (called synaptic gap o cleft) to the target (most often receiving end of another neurone, muscle or gland) |
| What is a chemical synapse? | The region where the transmitter is released from one neurone and binds to a receptor on a target cell |
| What is a postsynaptic potential? | The change in membrane of the target |
| How is exocytosis of synaptic vesicles triggered? | By an increase in calcium ions in the axon terminal |
| How does the calcium enter? | From outside the cell through membrane calcium channels that are opened by depolarisation of the action potential |
| How are neurotransmitters detected? | By the postsynaptic potentials it triggers or by collecting and analysing chemicals at the synapse after robust stimulation of the neurone |
| When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of neurotransmitter per vesicle? | The number os synaptic vesicles released increases when the stimulus intensity is increased. |
| What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+ ? | When a small amount of Ca2+ is added back, a small amount of synaptic vesicles are released. |
| How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid? | The neurotransmitter release was less when Mg2+ was added. |
| How does Mg2+ block the effect of extracellular calcium on neurotransmitter release? | When Mg2+ is added to the extracellular fluid it blocks the Ca2+ channels and inhibits the release of neurotransmitter. |
| What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the extracellular fluid with no Ca2+ ? | Without Ca2+, no neurotransmitter was released because the exocytosis of the synaptic vesicles is dependent upon Ca2+. |
| Why does the stimulus intensity affect the amount of neurotransmitter release at the axon terminal? | The stimulus intensity directly affects the amount of calcium entering the axon terminal and proportionally affects the number of synaptic vesicles that discharge their contents into the synaptic cleft |
| How is the neurotransmitter stored in the axon terminal before it is released? | contained in synaptic vessicles |
| Are neurotransmitter molecules released one at a time or in packets? | in packets |
| Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causes | more synaptic vesicles to undergo exocytosis |
Created by:
meunid