Question 1

Which is FALSE about the equilibrium potential of a given ion across a membrane?

Accepted Answer

Anions have a negative charge, so if they are in higher concentration inside the cell than outside, their equilibrium potential will be negative. The other choices are all true statements about equilibrium potential.

Question 2

A threshold stimulus applied to an excitable membrane is one that is just sufficient to:

Accepted Answer

A threshold stimulus is the minimum amount of stimulation required to trigger an action potential in an excitable membrane, such as the membrane of a neuron. It is the point at which the depolarization caused by the incoming signal becomes large enough to open voltage-gated ion channels and produce an action potential. Therefore, choice C is the correct answer.

Question 3

Which is TRUE about the resting membrane potential?

Accepted Answer

The resting membrane potential is established with relatively few ions needing to be distributed unevenly across the cell membrane, creating a voltage difference. This is due to the cell membrane's selective permeability to certain ions and the action of ion pumps.

Question 4

Which of these would occur if the concentration of ATP were depleted in a typical nerve cell?

Accepted Answer

ATP is required for the function of the sodium-potassium pump which maintains the concentration gradient of Na+ and K+. Without sufficient ATP, the pump would not function properly, leading to a higher concentration of sodium ions inside the cell and lower concentration of potassium ions. This would lead to a less negative resting membrane potential in the nerve cell.

Question 5

The diffusion potential due to the concentration gradient for Na⁺ across a nerve cell membrane:

Accepted Answer

The answer of The diffusion potential due to the concentration...

Question 6

An action potential in a neuronal membrane differs from a graded potential in that:

Accepted Answer

An action potential is propagated without decrement, whereas a graded potential decrements with distance.

Question 7

Which is FALSE about neurons?

Accepted Answer

Neurons receive information on their dendrites and transmit it to other neurons through their axons, not the other way around.

Question 8

The difference in electrical charge between two points:

Accepted Answer

The difference in electrical charge between two points is referred to as the potential difference between those points.

Question 9

The equilibrium potential of K⁺ ions in nerve cells is about -90 mV. The membrane potential of typical nerve cells at rest is -70 mV. Therefore

Accepted Answer

The equilibrium potential of K⁺ ions is more negative than the resting membrane potential. Therefore, increasing the permeability of the membrane to these ions will lead to an influx of negatively charged ions, making the membrane potential more negative inside with respect to outside. Option B is incorrect because the membrane potential at rest is negative, and there is no net diffusion of positively charged ions into the cell. Option C is incorrect because changing the resting membrane potential to -80 mV will not change the equilibrium potential of potassium ions, so there will be no effect on the diffusion rate of potassium ions out of the cell. Option D is incorrect because there are other ions present in the resting membrane potential, such as sodium and chlorine. Option E is incorrect because the equilibrium potential of potassium ions (-90 mV) is already more negative than the resting membrane potential (-70 mV), which means there is no need for another ion with a more negative equilibrium potential.

Question 10

Which is TRUE about the Na⁺, K⁺ ATPase pump in neurons?

Accepted Answer

The Na⁺, K⁺ ATPase pump generates a small electrical potential by pumping 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell, making the inside of the cell more negative relative to the outside.

Question 11

The membrane potential of most neurons at rest is:

Accepted Answer

The answer of The membrane potential of most neurons at...

Question 12

Which of the following is NOT true about axon transport?

Accepted Answer

Axon transport refers to the movement of materials from the cell body to the axon terminals or vice versa, but it does not involve transport across the axonal membrane. Therefore, choice C is not true.

Question 13

According to the equation expressed as Ohm's law, which of these would cause the greatest increase in current?

Accepted Answer

Ohm's law states that I = V/R, where I is the current, V is the voltage, and R is the resistance. To increase the current, we would want to increase the voltage and/or decrease the resistance. Option C doubles the voltage and reduces the resistance by half, which would have the greatest combined effect on increasing the current.

Question 14

Which of the following is/are functions of the human nervous system?

Accepted Answer

All of the choices are correct. The human nervous system receives, stores, and processes information on the internal and external environments, brings about changes in physiology and/or behavior to ensure optimal functions of homeostatic mechanisms, coordinates movement, and does not secrete hormones (this is a function of the endocrine system).

Question 15

Which of the following statements concerning the permeability of a typical neuron membrane at rest is TRUE?

Accepted Answer

At rest, most of the voltage-gated Na+ channels are in the closed state. This accounts for the low permeability of the membrane to Na+ at rest. The permeability to K+ is relatively high due to the presence of leak channels that are always open. Therefore, option D is the correct statement.

Question 16

Which would result from an increase in the extracellular concentration of K⁺ above normal?

Accepted Answer

An increase in extracellular K+ concentration reduces the gradient for K+ to leave the cell, causing depolarization of resting nerve cells.

Question 17

Which is NOT an example of a graded potential?

Accepted Answer

Graded potentials are changes in membrane potential that can vary in amplitude and can either depolarize (EPSP) or hyperpolarize (IPSP) the membrane. Pacemaker potentials are graded potentials that lead to the generation of an action potential, which is a stereotyped all-or-none event and is not graded. Therefore, choice E is not an example of a graded potential.

Question 18

Which is TRUE about typical, resting neurons?

Accepted Answer

Resting neurons have a higher permeability to potassium ions due to the presence of leak channels that allow for the diffusion of potassium ions out of the cell. The concentration of potassium ions is greater inside the cell than outside, while the concentration of sodium ions is greater outside than inside. This creates an electrochemical gradient that can be used to generate an action potential. Sodium ions can enter the cell during depolarization, but they do not contribute significantly to the resting potential. Therefore, option C is the correct choice.

Question 19

Which of the following is NOT true of glial cells?

Accepted Answer

Glial cells actually outnumber neurons in the nervous system, with an estimated ratio of around 1.5 to 1.

Question 20

Which is NOT true of myelin?

Accepted Answer

Myelin only covers the axon, not the cell body or dendrites.

Quiz 6: Neuronal Signaling and the Structure of the Nervous System