Question 1

Because so many Na ions move into a cell during an action potential and so many K ions move out,no further action potentials can be generated in a given membrane until the Na,K-ATPase pumps can restore the concentration gradient.

Accepted Answer

During an action potential, the number of Na⁺ and K⁺ ions that move across the membrane is relatively small compared to the total number of ions inside and outside the cell, so the concentration gradients of Na⁺ and K⁺ are not significantly disrupted. The cell can generate multiple action potentials before the Na⁺,K⁺-ATPase pumps need to significantly restore the ion gradients.

Question 2

Postganglionic neuron cell bodies of the autonomic nervous system have which category of neurotransmitter receptor?
A)Adrenergic receptor
B)Serotonin receptors
C)M-AchR receptors
D)N-AchR receptors
E)Dopamine receptors

Accepted Answer

Postganglionic neuron cell bodies of the autonomic nervous system have nicotinic acetylcholine receptors (N-AchR).

Question 3

The lipid portion of a cell's plasma membrane constitutes a barrier to current.

Accepted Answer

The lipid portion of a cell's plasma membrane is hydrophobic and therefore creates a barrier to the flow of ions and other charged particles. This helps maintain the electrochemical gradient across the membrane, which is important for many cellular processes.

Question 4

Neuron cell division and nervous system growth continue throughout life.

Accepted Answer

Neuron cell division does not occur in adult nervous systems. However, neurogenesis (the formation of new neurons) can occur in certain parts of the brain, such as the hippocampus, throughout life.

Question 5

The most numerous cells in the CNS are interneurons.

Accepted Answer

The most numerous cells in the CNS are glial cells, not interneurons.

Question 6

The refractory period of an excitable membrane refers to the period of time during which no stimulus,however strong,will elicit a second action potential in the membrane.

Accepted Answer

The refractory period includes both the absolute refractory period, where no stimulus can elicit another action potential, and the relative refractory period, where a stronger-than-normal stimulus can elicit a second action potential.

Question 7

Two neurons joined by an electric synapse function as a single neuron.

Accepted Answer

When two neurons are joined by an electric synapse, they function as a single neuron because the electrical current can flow freely between them, allowing them to synchronize their activity and act as one unit.

Question 8

A myelinated axon is shielded from direct contact with the extracellular fluid all along its length.

Accepted Answer

Myelinated axons have gaps known as nodes of Ranvier where the axon is exposed to the extracellular fluid, allowing for ion exchange necessary for the propagation of action potentials.

Question 9

Which of the following characteristics is not attributed to the sympathetic division of the ANS?
A)Preganglionic neurons tend to be long, with the ganglion located in or near the effector target tissue(s)
B)Preganglionic neurons are short and synapse in ganglia located near the spinal cord
C)Preganglionic neurons release acetylcholine at synapses with postganglionic neurons
D)Postganglionic neurons release norepinephrine at their neuroeffector junctions
E)Postganglionic neuron cell bodies are located in the collateral chain ganglia or vertebral ganglia

Accepted Answer

The answer of Which of the following characteristics is not...

Question 10

Cerebrospinal fluid
A)Has the same composition as blood plasma
B)Acts as a cushion for the brain and spinal cord
C)Is secreted by cells lining the ventricles
D)Both acts as a cushion for the brain and spinal cord and is secreted by cells lining the ventricles are correct
E)All of the choices are correct

Accepted Answer

Cerebrospinal fluid acts as a cushion for the brain and spinal cord, and is secreted by cells lining the ventricles. It does not have the same composition as blood plasma, so option A is incorrect. Option E is incorrect because option A is wrong.

Question 11

Ions other than Na⁺,K⁺ and Cl^- play no role in generating the resting membrane potential of a cell.

Accepted Answer

Other ions, such as Ca2+, Mg2+, and organic anions, can also contribute to the resting membrane potential of a cell.

Question 12

During a hyperpolarizing graded potential,positively charged ions flow away from the site of the initial hyperpolarization on the outside of membrane and toward this site on the inside.

Accepted Answer

The answer of During a hyperpolarizing graded potential,positively charged ions...

Question 13

The Na⁺ and K⁺ channels that open during an action potential are voltage regulated,both responding to hyperpolarization of the membrane.

Accepted Answer

The answer of The Na⁺ and K⁺ channels that open...

Question 14

The action potential elicited by a supra-threshold stimulus is larger than one elicited by a threshold stimulus.

Accepted Answer

The magnitude of an action potential is not affected by the size of the stimulus; as long as the stimulus reaches the threshold, the action potential will always have the same magnitude due to the all-or-none principle.

Question 15

The maintenance of a resting potential in a neuron depends upon the functioning of the Na,K-ATPase pumps in the membrane.

Accepted Answer

The Na,K-ATPase pumps play a critical role in maintaining the resting potential of a neuron by actively moving sodium ions out of the cell and potassium ions into the cell, against their concentration gradients. This helps to establish and maintain the negative charge inside the cell that is necessary for the proper functioning of the neuron. Without the Na,K-ATPase pumps, the resting potential would rapidly decay and the neuron would be unable to generate action potentials or transmit information effectively.

Question 16

A graded potential in a membrane results in an electric current along an adjacent area of membrane and this current diminishes with distance from the site of the initial potential change.

Accepted Answer

This is because graded potentials are local changes in membrane potential that do not spread far from their site of origin. As the current flows along the adjacent membrane, it dissipates or diminishes with distance from the site of the initial potential change.

Question 17

The absolute refractory period of an excitable membrane roughly corresponds to the period when sodium channels are opening and closing.

Accepted Answer

During the absolute refractory period, the voltage-gated sodium channels are either inactivated or closed, preventing the opening of more sodium channels and action potential generation. Therefore, the period when sodium channels are opening and closing roughly corresponds to the relative refractory period.

Question 18

The blood-brain barrier
A)Is formed by cells lining tiny blood vessels in the brain
B)Is present in all parts of the brain
C)Prevents entry of all lipid-insoluble molecules into the brain
D)Both is formed by cells lining tiny blood vessels in the brain and prevents entry of all lipid-insoluble molecules into the brain are correct
E)All of the choices are correct

Accepted Answer

The blood-brain barrier is formed by endothelial cells lining the blood vessels in the brain. It selectively restricts the passage of substances, but not all lipid-insoluble molecules are completely prevented from entering.

Question 19

SNARE receptor protein complexes in presynaptic neurons function as inhibitors of calcium transport to dampen or reduce the amount of neurotransmitter vesicles which participate in exocytosis.

Accepted Answer

SNARE receptor protein complexes in presynaptic neurons facilitate calcium transport to promote the exocytosis of neurotransmitter vesicles, rather than inhibit it.

Question 20

The resting membrane potential of a neuron is constant because the components of the extracellular and intracellular fluid are in equilibrium.

Accepted Answer

The resting membrane potential is not constant due to various factors such as ion gradients, ion channels, and ion pumps that maintain the potential difference across the cell membrane. While equilibrium conditions play a role in establishing the resting membrane potential, it is not the sole determinant of its constancy.

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