10) When norepinephrine binds to a metabotropic receptor, how does the associate

Question

10) When norepinephrine binds to a metabotropic receptor, how does the associated G protein activate adenylyl cyclase? a. The G protein trimer attaches to adenylyl cyclase to activate it. b. The GTP-bound a subunit of the G protein binds to adenylyl cyclase to activate it. c. The G protein mediates the release of cAMP-dependent protein kinase (PKA), which activates adenylyl cyclase. d, The G protein dimer binds to and activates adenylyl cyclase Questions 11-12. Refer to the figure below, which shows the Aplysia gill withdrawal circuit Head Skin Stimulate Sensory neuron Record Panel 1 Motor- Depression Sensitization 50 ms Panel 2 Habituation 10 s 11) What mechanism explains the synaptic depression observed in the motor neuron responses caused by repeat stimulation of the presynaptic sensory neuron shown in Panel 1? a. Action potentials arriving at the sensory neuron presynaptic terminals are reduced in amplitude b. At the synapse, calcium influx is increased with each action potential c. The amount of neurotransmitter released per presynaptic action potentai decreases with repeated presynaptic stimulations d. Receptor density on the postsynaptic membrane is reduced. 12) Which of the following statements best describes the cellular mechanism of sensitization occurring in the sensory neuron terminals? a. Protein kinase A dephosphorylates Ca2 channels and decreases the Ca2 current that normally terminates the action potential, which leads to a decrease in Ca2 influx. b. Protein kinase A phosphorylates K channels and decreases the K* current that normally terminates the action potential leading to an increase in Ca2 influx. c. Protein kinase A dephosphorylates K channels and increases the K' current that normally terminates the action potential, which leads to an increase in Ca2* influx. d. Protein kinase A phosphorylates Na channels and decreases the Na* current that normally activates the action potential, which leads to a decrease in Ca2+ influx.

Explanation / Answer

10. b. The GTP bound alpha subunit of the G protein binds to adenylyl cyclise to activate it.

11. d. Receptor density on the postsynaptic membrane is reduced.

12. b. Protein kinase A phosphorylates K+ channels and decreases the k+ current that normally terminates the action potential leading to an increase in ca+ influx.

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