Question 1

Which of the following best describes the difference between graded potentials and action potentials in neurons?

Accepted Answer

Graded potentials can summate and decrease in strength as they travel, while action potentials are propagated without loss of amplitude.

Question 2

A patient is given a local anesthetic that blocks voltage-gated Na+ channels. What is the most likely effect on neuronal signaling?

Accepted Answer

Graded potentials will be unaffected, but action potentials will fail to propagate.

Question 3

Which physical property of an axon most directly increases the velocity of action potential conduction?

Accepted Answer

Increased membrane resistance due to myelination

Question 4

In a demyelinating disease such as multiple sclerosis, which of the following best explains the resulting decrease in conduction velocity?

Accepted Answer

Loss of myelin increases current leak, causing depolarization to fall below threshold at the next node.

Question 5

Which equation best represents the relationship between conduction velocity ($v$), axon diameter ($d$), and membrane resistance ($R_m$) in a myelinated neuron?

Accepted Answer

$v \propto d 	imes R_m$

Question 6

A neuron is exposed to a toxin that increases extracellular K+ concentration. What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative (depolarized).

Question 7

Which of the following is TRUE regarding synaptic transmission at a chemical synapse?

Accepted Answer

The presynaptic neuron releases a neurocrine that binds to receptors on the postsynaptic cell.

Question 8

Which type of neurocrine receptor is most likely to produce a rapid postsynaptic response?

Accepted Answer

Ionotropic receptor (ligand-gated ion channel)

Question 9

A neurocrine acts as a neurotransmitter at one synapse and as a neuromodulator at another. What determines its function?

Accepted Answer

The type of receptor present on the postsynaptic cell

Question 10

Which of the following best describes the role of the nodes of Ranvier in action potential conduction?

Accepted Answer

They contain a high density of voltage-gated Na+ channels, allowing action potentials to be regenerated.

Question 11

Which of the following is a correct sequence of events during action potential propagation along a myelinated axon?

Accepted Answer

Depolarization at one node causes current to flow to the next node, where voltage-gated Na+ channels open.

Question 12

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin increases membrane resistance, reducing current leak and allowing rapid conduction between nodes.

Question 13

Which of the following is a function of metabotropic neurocrine receptors?

Accepted Answer

Activate G-proteins that can interact with ion channels or membrane-bound enzymes for slower, modulatory responses.

Question 14

Which signal transduction pathway is associated with metabotropic receptors and leads to increased intracellular Ca$^{2+}$?

Accepted Answer

Phospholipase C pathway

Question 15

A neuron receives multiple subthreshold graded potentials at its dendrites. What is the most likely outcome at the axon hillock?

Accepted Answer

No action potential will be generated unless the graded potentials summate to reach threshold.

Question 16

Which of the following best describes the effect of increasing the number of synapses on a postsynaptic neuron?

Accepted Answer

It increases the complexity of integration and the potential for summation of signals.

Question 17

Which of the following equations best represents the Nernst equation for the equilibrium potential ($E_K$) of potassium?

Accepted Answer

$E_K = \frac{RT}{zF} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$

Question 18

Which of the following is TRUE regarding neuromodulators?

Accepted Answer

They act on postsynaptic cells to produce slow, long-lasting responses.

Neuronal Electrical Signaling and Synaptic Communication

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