Question 1

Which of the following best explains why the resting membrane potential ($$V_m) of a $$neuron is negative?

Accepted Answer

Negatively charged macromolecules are trapped inside the cell, the Na$$^+/K$^+$$ pump transports more Na$$^+$$ out than K$$^+ in$$, and the membrane is more permeable to K$$^+$$ than Na$$^+$$

Question 2

Given the ionic concentrations in the squid giant axon (Na$$^+$$ outside: 440 mM, inside: 50 mM; K$$^+$$ outside: 20 mM, inside: 400 mM), which direction will Na$$^+$$ and K$$^+$$ ions move if their respective channels open at rest?

Accepted Answer

Na$$^+$$ will move in, K$$^+$$ will move out

Question 3

Which of the following equations correctly represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation at 37°C?

Accepted Answer

$$E_{ion} = \frac{61.5}{z} \log \left( \frac{[ion]_{outside}}{[ion]_{inside}} \right)$$

Question 4

During the depolarizing phase of the action potential, which event occurs?

Accepted Answer

Voltage-gated Na$$^+$$ channels open, allowing Na$$^+ to $$enter the cell

Question 5

A neuron has a resting potential of $$-60 mV $$and a threshold potential of $$-40 mV. If it $$receives 4 inhibitory postsynaptic potentials (IPSPs) of $$-1 mV $$each, how many excitatory postsynaptic potentials (EPSPs) of $$+2 mV $$each are required to reach threshold?

Accepted Answer

12

Question 6

Which of the following best describes the function of the Na$$^+/K$^+$$ ATPase in neurons?

Accepted Answer

It pumps 3 Na$$^+$$ out and 2 K$$^+ in$$, using ATP hydrolysis

Question 7

Which of the following is TRUE regarding the propagation of an action potential along a myelinated axon?

Accepted Answer

The action potential jumps from one node of Ranvier to the next, a process called saltatory conduction

Question 8

Which of the following statements about chemical synaptic transmission is CORRECT?

Accepted Answer

Voltage-gated calcium channels open in the presynaptic terminal, triggering neurotransmitter release

Question 9

Which of the following toxins would most likely cause continuous muscle contraction by preventing the removal of acetylcholine from the synaptic cleft?

Accepted Answer

Sarin

Question 10

Which of the following best describes the role of GTP in the activation of heterotrimeric G proteins?

Accepted Answer

GTP binding to the G\alpha subunit activates the G protein, causing it to dissociate from G\beta\gamma

Question 11

Which of the following is a direct effect of cAMP as a second messenger in the cell?

Accepted Answer

Activation of protein kinase A (PKA)

Question 12

Which of the following best describes the sequence of events in the GPCR-cAMP signaling pathway?

Accepted Answer

Ligand binds GPCR → G protein activation → Adenylyl cyclase activation → cAMP production → PKA activation

Question 13

Which of the following is a function of the calcium-calmodulin complex in cells?

Accepted Answer

It binds to and activates target proteins such as myosin light-chain kinase (MLCK)

Question 14

Which of the following best describes the mechanism by which IP$$_3$$ increases cytosolic Ca$$^{2+}$$ concentration?

Accepted Answer

IP$$_3$$ binds to a ligand-gated Ca$$^{2+}$$ channel on the ER membrane, releasing Ca$$^{2+}$$ from the ER

Question 15

Which of the following is TRUE regarding receptor tyrosine kinases (RTKs)?

Accepted Answer

RTKs are activated by ligand-induced dimerization and autophosphorylation

Question 16

Which of the following best describes the role of Ras in RTK signaling?

Accepted Answer

Ras is a small G protein activated by GEFs recruited to the RTK, which then activates the MAP kinase cascade

Question 17

Which of the following is a common feature of both GPCR and RTK signaling pathways?

Accepted Answer

Both can activate intracellular signaling cascades that amplify the original signal

Question 18

Which of the following best describes the effect of an antagonist drug on a receptor?

Accepted Answer

It binds the receptor but does not activate downstream signaling

Question 19

Which of the following is a direct result of phosphorylation of substrate proteins by kinases in signal transduction pathways?

Accepted Answer

Altered activity (activation or inhibition) of the substrate protein

Cell Signaling Pathways: Electrical and Chemical Signaling in Neurons

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