Chat with AIExam 3: Signaling Across Synapses
Synaptic transmission can be potentiated by release of serotonin on the presynaptic terminal. In the experiments shown in Figure Q3-49, investigators used intracellular recording of the neuron and whole-cell patch recording of the potassium channels to understand how serotonin influences the action potential. 
Figure Q3-49
A. In experiment 1, what happened to the action potential when cAMP and serotonin (5-HT) were added to the extracellular space of the neuron (top trace) and cAMP was injected intracellularly into the neuron (bottom trace)?
B. In experiment 2, what happened to the potassium channel activity when serotonin was added to the outside of the cell and cAMP was added to the inside of the cell?
C. Summarize all the figures. How does serotonin increase the duration of the action potential (include the second messengers in your answer)?
Figure Q3-49
A. In experiment 1, what happened to the action potential when cAMP and serotonin (5-HT) were added to the extracellular space of the neuron (top trace) and cAMP was injected intracellularly into the neuron (bottom trace)?
B. In experiment 2, what happened to the potassium channel activity when serotonin was added to the outside of the cell and cAMP was added to the inside of the cell?
C. Summarize all the figures. How does serotonin increase the duration of the action potential (include the second messengers in your answer)?
(41) 
VerifiedA.The action potential duration increased in the presence of both 5-HT and cAMP.
B. The number of open channels decreased in the presence of both cAMP and 5-HT. This is shown in the figure: the number of open channels in control conditions for 5-HT is about but only channels are open in the presence of extracellular 5-HT. This shows that 5-HT and cAMP close potassium channels.
C. Serotonin is released from the presynaptic neuron. It binds to its receptor (the 5-HT receptor), which activates a G protein and causes an increase in cAMP concentrations. The cAMP activates PKA, which phosphorylates a potassium channel and increases the probability it will be closed (decreases the probability of being opened). Closing a potassium channel increases the duration of the action potential since opening of potassium channels rapidly repolarize an action potential. In the absence of the activation of potassium channels the voltage across the membrane will slowly come back to rest through leak channels.
What is a miniature end-plate potential (mEPP)? Select all that apply.
(37) VerifiedA,C
Figure Q3-34 shows an I-V plot for the NMDA receptor in the presence of external Mg2+. What would the curve look like if Mg2+ were removed from the extracellular media and why? 
Figure Q3-34
Figure Q3-34 (35) VerifiedMg2+ has a voltage dependent block of NMDA receptors. The curve would be the same above (more depolarized) 0 mV when Mg2+ does not block the channel. Below 0 mV there would no longer be the Mg2+ block, so more current could pass through the channel and there would be an increasing inward current at more hyperpolarized voltages. This is depicted in Figure of the book.
Fill in the missing words in the following sentence.
Synaptic transmission at the vertebrate neuromuscular junction usually begins with an action potential that triggers the release of the neurotransmitter ____ from the axon terminal. This molecule diffuses across the ________ _____ and binds to the postsynaptic ______. Once this molecule binds, ____ and ____ ions move across the membrane and produce a ____.
(31) GABA and glycine activate ionotropic channels that conduct chloride. How does the chloride conductance inhibit excitation? Select all that apply.
(39) You identified a new receptor for glutamate. Based on the sequence of the protein you predict that it has seven transmembrane spanning regions. What kind of glutamate receptor do you think this will be most like? Select all that apply.
(36) List properties that differ between ionotropic and metabotropic receptors.
(31) Why do you think there are so many types of presynaptic proteins involved in neurotransmitter release?
(36) Single neurons can only release one type of neurotransmitters. Explain your answer.
(38) Describe, in general terms, experiments that show that Ca2+ is both necessary and sufficient for neurotransmitter release. Start with the assumption that you are recording from the squid giant synapse in which you can stimulate the presynaptic neuron and record the response in the postsynaptic neuron. State which experiment shows necessity and which shows sufficiency.
(38) What mechanisms are used to move neurotransmitter back into vesicles? Select all that apply.
(37) The receptor for which of the following is NOT included in the GPCR superfamily?
(40) What mechanisms are used to clear neurotransmitters from the synaptic cleft? Select all that apply.
(36) What is the current known role of complexin in synaptic transmission?
(32) 
Filters
- Essay(0)
- Multiple Choice(0)
- Short Answer(0)
- True False(0)
- Matching(0)