Question 1

Prolonged changes in neuronal activity are achieved through the activation of which of the following?

Accepted Answer

G-protein coupled channels are involved in prolonged changes in neuronal activity through second messenger systems, which can lead to long-term changes in gene expression and synaptic strength. Voltage gated chloride channels, transmitter gated sodium channels, and voltage gated potassium channels are important for neuronal signaling and maintaining resting membrane potential, but are not directly involved in prolonged changes in neuronal activity.

Question 2

Hypoventilation causes arterial blood carbon dioxide levels to rise. Higher arterial blood carbon dioxide levels increase neuronal activity.

Accepted Answer

The first statement is correct as hypoventilation leads to retention of carbon dioxide and consequent rise in arterial blood carbon dioxide levels. The second statement is not correct, as higher arterial blood carbon dioxide levels actually decrease neuronal activity through the mechanism of cerebral vasodilation and neuronal depression.

Question 3

Hypoventilation is most likely to have which of the following effects on a typical neuron in the central nervous system?

Accepted Answer

Hypoventilation results in decreased levels of oxygen and increased levels of carbon dioxide in the bloodstream. This can lead to respiratory acidosis, which can depress neuronal activity in the central nervous system.

Question 4

Forced rapid breathing results in alkalization of the blood, which would lead to which of the following changes in neuronal activity?

Accepted Answer

An increase in alkalinity of the blood due to forced rapid breathing would lead to an increase in neuronal activity. This is because increased alkalinity leads to a decrease in carbon dioxide levels, which is a potent vasodilator. Vasodilation leads to an increase in blood flow and oxygenation, which enhances neuronal activity.

Question 5

Which of the following neurotransmitters is thought to be involved in the phenomenon of presynaptic inhibition?

Accepted Answer

GABA is the neurotransmitter most commonly associated with presynaptic inhibition. It acts on presynaptic receptors to decrease calcium influx and decrease neurotransmitter release from the presynaptic neuron.

Question 6

Transmission of the electrical signal from the dendrites to the soma of a neuron occurs by which of the following?

Accepted Answer

Electrotonic conduction is the process by which electrical signals are passively transmitted across the dendrites and soma of a neuron. This involves the movement of ions through the neuron's membrane, which changes the membrane potential without generating an action potential.

Question 7

Transmitter activation of ion channels on dendrites can dictate neuronal excitation or inhibition acutely by affecting which aspect of the soma membrane?

Accepted Answer

Transmitter activation of ion channels on dendrites can change the electrical potential at the soma membrane, which can lead to neuronal excitation or inhibition.

Question 8

Which of the following statements best describes the role of calcium in the release of a neurotransmitter substance from the presynaptic nerve terminal?

Accepted Answer

Calcium entry into the presynaptic terminal is necessary for the release of the neurotransmitter. When an action potential reaches the presynaptic terminal, it depolarizes the membrane, causing voltage-gated calcium channels to open. The entry of calcium ions triggers the fusion of neurotransmitter-containing vesicles with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft. Therefore, without calcium entry, neurotransmitter release cannot occur.

Question 9

Posttetanic facilitation is thought to be the result of which of the following?

Accepted Answer

Posttetanic facilitation is believed to result from a buildup of calcium in the presynaptic terminal. This increased calcium concentration can lead to a greater release of neurotransmitter in response to subsequent action potentials.

Question 10

An excitatory postsynaptic potential is most likely to result from which of the following?

Accepted Answer

An excitatory postsynaptic potential (EPSP) results from the opening of ion channels that allow positive ions such as sodium to enter the cell, depolarizing the membrane potential. The most likely ion channel to produce this effect is the opening of sodium channels (choice C). Choices A, B, and D do not involve the influx of enough positive charge to depolarize the membrane potential and lead to an EPSP.

Question 11

In a neuron with a resting membrane potential of -65 mV, the distribution of which ion across the neuronal membrane represents the greatest potential electromotive force?

Accepted Answer

Sodium has the greatest potential electromotive force because it has a higher concentration outside the cell (extracellular fluid) compared to inside the cell (intracellular fluid). This concentration gradient creates a strong driving force for sodium to flow into the cell, depolarizing the membrane potential. Therefore, sodium is the ion most responsible for initiating the action potential.

Question 12

Increased conductance of which of the following ions is most likely to have the least effect on membrane potential?

Accepted Answer

Chloride ions typically have an equilibrium potential close to the resting membrane potential of most cells. Therefore, changes in chloride conductance have a smaller effect on membrane potential compared to ions like potassium and sodium, whose equilibrium potentials are far from the resting membrane potential.

Question 13

In a neuron with a resting membrane potential of -65 mV, the distribution of which ion across the neuronal membrane represents the least potential electromotive force?

Accepted Answer

The resting membrane potential of a neuron is primarily determined by the concentration gradients and membrane permeabilities of potassium and sodium ions. Chloride ions, on the other hand, typically have a concentration gradient that opposes the membrane potential, meaning that they have the least potential electromotive force across the membrane. Calcium ions, although they can contribute to neuronal signaling, are generally found in lower concentrations and are not as heavily involved in establishing the resting membrane potential.

Question 14

The opening of which of the following ion channels would have the least effect on the resting membrane potential of an average neuron?

Accepted Answer

The resting membrane potential of a neuron is primarily determined by the balance of potassium ions inside and outside the cell. Opening chloride channels would have little effect on the resting membrane potential because chloride ions are negatively charged and tend to be at equilibrium with the resting potential. Sodium ions are positively charged and tend to depolarize the cell, while opening potassium channels would hyperpolarize the cell. Therefore, of the three choices, opening chloride channels would have the least effect on the resting membrane potential.

Question 15

An inhibitory postsynaptic potential is most likely to result from opening which of the following?

Accepted Answer

Opening potassium channels allows positively charged potassium ions to leave the cell, leading to hyperpolarization of the membrane potential and therefore an inhibitory postsynaptic potential (IPSP). Opening sodium channels (choices B and C) would lead to depolarization and an excitatory postsynaptic potential (EPSP), while opening calcium channels (choice D) would lead to an influx of calcium ions and could contribute to either EPSPs or other signaling processes.

Quiz 46: Organization of the Nervous System, Basic Functions of Synapses, and Neurotransmitters