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Exercise 3: Neurophysiology of Nerve Impulses: Activity 8: Chemical Synaptic Transmission and Neurotransmitter Release
Lab Report
Pre-lab Quiz Results
You scored 100% by answering 5 out of 5 questions correctly.
- The end of the axon where it contacts a target is called the
You correctly answered: c. axon terminal. - Neurotransmitter is released into the synaptic gap by
You correctly answered: a. exocytosis. - Exocytosis of neurotransmitter from the axon terminal is triggered by an increase in the intracellular concentration of
You correctly answered: c. Ca2+ . - Neurotransmitter released into the synaptic gap reaches the target cell by
You correctly answered: b. diffusion. - At the target, neurotransmitter
You correctly answered: d. does all of the above.
Experiment Results
Predict Question:
Predict Question 1: You have just observed that each action potential in a burst can trigger additional neurotransmitter
release. If calcium ions are removed from the extracellular solution, what will happen to neurotransmitter release at the axon
terminal?
Your answer : c. There will be less neurotransmitter release.
Predict Question 2: What will happen to neurotransmitter release when low amounts of calcium are added back to the
extracellular solution?
Your answer : b. Neurotransmitter release will increase a small amount.
Predict Question 3: What will happen to neurotransmitter release when magnesium is added to the extracellular solution?
Your answer : a. There will be no neurotransmitter release.
Stop & Think Questions:
Why does the stimulus intensity affect the amount of neurotransmitter release at the axon terminal?
You correctly answered: d. Both a and b are correct.
Why is there no neurotransmitter release from the axon terminal when there are no calcium ions in the extracellular
solution?
You correctly answered: c. Exocytosis of the synaptic vesicles is calcium dependent.
Why did the high intensity stimulation fail to trigger the same amount of neurotransmitter release in the presence of
extracellular Mg2+ as in the control extracellular solution?
You correctly answered: a. Mg2+ blocks the calcium channels in the axon terminal.
Experiment Data:
Post-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
- How is the neurotransmitter stored in the axon terminal before it is released?
You correctly answered: c. contained in synaptic vessicles - Are neurotransmitter molecules released one at a time or in packets?
You correctly answered: b. in packets - With the normal extracellular calcium concentration, [Ca2+ ], when the action potential reaches the axon terminal it
triggers
You correctly answered: b. release of neurotransmitter by exocytosis. - Comparing the low intensity stimulus to the high intensity stimulus, the high intensity stimulus causes
You correctly answered: b. more synaptic vesicles to undergo exocytosis
Review Sheet Results
- When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of
neurotransmitter per vesicle?
Your answer:
Increasing stimulus intensity makes more number of synaptic vesicles be released. - What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the
extracellular fluid with no Ca2+ ? How well did the results compare with your prediction?
Your answer:
decresed, as predicted - 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+ ? How well did the results compare with your prediction?
Your answer:
increase a small amount, as predicted. - How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid? How
well did the result compare with your prediction?
Your answer:
neurotransmitter relesade, contradicting with my prediction - How does Mg2+ block the effect of extracellular calcium on neurotransmitter release?
Your answer:
it blocks the calcium channels and inhibits the release of neurotransmitter.