Question 1

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

Accepted Answer

Graded potentials are conducted electrotonically and can vary in amplitude, while action potentials are all-or-none impulses that propagate without decrement.

Question 2

During the propagation of an action potential, what is the primary effect of the influx of $$\mathrm{Na^+}$$ ions?

Accepted Answer

It spreads positive charge away from the $$\mathrm{Na^+}$$ channels, triggering more voltage-gated $$\mathrm{Na^+}$$ channels to open.

Question 3

Which property of the axonal membrane most directly determines how far a graded potential can travel before decaying?

Accepted Answer

Transmembrane resistance

Question 4

If the length constant $$\lambda of an $$axon is defined as the distance at which the potential falls to $$63\% of $$its original value, which equation correctly represents this relationship?

Accepted Answer

$$V(x) = V_0$ e$$^{-x/\lambda}$$

Question 5

Which of the following changes would most likely increase the conduction velocity of an action potential along an axon?

Accepted Answer

Increasing temperature by $$10^\circ \mathrm{C}$$

Question 6

Saltatory conduction in myelinated axons is primarily due to:

Accepted Answer

Action potentials jumping from one node of Ranvier to the next

Question 7

Which of the following best explains why myelination increases the length constant $$\lambda of an $$axon?

Accepted Answer

Myelination increases transmembrane resistance and decreases capacitance, reducing current leakage and allowing charge to travel farther.

Question 8

A patient is exposed to tetrodotoxin (TTX), a potent neurotoxin. What is the most likely effect on neuronal signaling?

Accepted Answer

TTX blocks voltage-gated $$\mathrm{Na^+}$$ channels, preventing action potential initiation and propagation.

Question 9

Which of the following statements about postsynaptic potentials is TRUE?

Accepted Answer

EPSPs increase the probability of an action potential, while IPSPs decrease it.

Question 10

Which neurotransmitter is found in less than $$10\% of $$neurons but is commonly studied and can be either excitatory or inhibitory depending on the receptor type?

Accepted Answer

Acetylcholine

Question 11

What is the primary role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) at $$the presynaptic terminal during synaptic transmission?

Accepted Answer

To trigger exocytosis of neurotransmitter-containing vesicles

Question 12

Which of the following would most likely result from a mutation that increases the number of voltage-gated $$\mathrm{Na^+}$$ channels at the nodes of Ranvier?

Accepted Answer

Increased conduction velocity along the axon

Question 13

Which equation best describes the relationship between conduction velocity ($$v) $$and axon diameter ($$d) in $$myelinated axons?

Accepted Answer

$$v \propto d$$

Question 14

A neuron receives simultaneous EPSPs and IPSPs at its dendrites. What determines whether an action potential will be generated?

Accepted Answer

The summation of EPSPs and IPSPs at the axon hillock

Question 15

Which of the following is a property that a substance must have to be classified as a neurotransmitter?

Accepted Answer

Its effect must be blocked by the same agents that block natural transmission at the synapse.

Question 16

Which of the following best explains why increasing axon diameter increases conduction velocity?

Accepted Answer

It decreases axoplasmic resistance, allowing local currents to travel farther.

Question 17

Which type of glial cell provides myelination for axons in the central nervous system (CNS)?

Accepted Answer

Oligodendrocytes

Question 18

Which of the following would most likely occur if the membrane capacitance of an axon is decreased?

Accepted Answer

The membrane would charge and discharge more rapidly, increasing conduction velocity.

Question 19

Which of the following is TRUE regarding the effect of temperature on axonal conduction velocity?

Accepted Answer

Increasing temperature by $$10^\circ \mathrm{C}$$ doubles the conduction velocity.

Question 20

Which of the following is a direct effect of an inhibitory postsynaptic potential (IPSP) on the postsynaptic neuron?

Accepted Answer

It decreases the probability of an action potential by hyperpolarizing the membrane, often via $$\mathrm{Cl^-}$$ influx.

Neuronal Signal Transmission: Mechanisms and Properties

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