Test_13_Answers

Test_13_Answers - Lecture 13. Neurotransmitter Systems...

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Lecture 13. Neurotransmitter Systems Review questions 1 of 3 Lecture 13. Neurotransmitter Systems Question 1: If you could place microelectrodes into both a presynaptic and a postsynaptic neuron, how would you determine whether the synapse between them was chemically or electrically mediated? Q1 Answer: A microelectrode placed in the presynaptic and postsynaptic neuron would show different results for electrical and chemical transmission. For electrical transmission, the two electrodes would show identical or similar changes in electrical activity, i.e. , the action potential in the presynaptic membrane would produce an action potential in the postsynaptic membrane. Chemically mediated synapses operate differently. An action potential in the presynaptic membrane causes neurotransmitter release in the synaptic cleft, and the postsynaptic membrane might respond to the neurotransmitter with changes in conduction, but not an action potential. An action potential is generated in the postsynaptic neuron of a chemically mediated synapse only if the whole neuron is sufficiently depolarized. This action potential would not be evident in a postsynaptic dendrite or cell body (typical synaptic sites); you would have to record for the axon of the postsynaptic neuron. Question 2: List the criteria that are used to determine whether a chemical serves as a neurotransmitter. What are the various experimental strategies you could use to show that ACh fulfills the criteria of a neurotransmitter at the neuromuscular junction? Q2 Answer: Three certain criteria must be met for a molecule to be considered a neurotransmitter. 1) The molecule must be synthesized and stored in the presynaptic neuron. 2) The molecule must be released by the presynaptic axon terminal upon stimulation. 3) The molecule, when experimentally applied, must produce a response in the postsynaptic cell that mimics the response produced by the release of the neurotransmitter from the presynaptic neuron. Immunohistochemistry shows where specific molecules are localized, and in situ hybridization shows where specific mRNA transcripts for specific proteins are located. These methods could be used to demonstrate the presence of ACh in the presynaptic terminal at the neuromuscular junction. It would be useful to show that the synthesizing enzyme is present as well. Question 3:
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Test_13_Answers - Lecture 13. Neurotransmitter Systems...

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