Question 1

How do researchers measure ion movements through single channels?

Accepted Answer

Patch clamping is a technique that measures the electric current caused by the movement of ions across a small patch of the plasma membrane.The membrane is electrically depolarized or hyperpolarized and maintained (clamped)at that potential by an electronic feedback device.The inward or outward movement of ions across a patch of membrane can be quantified from the amount of electric current needed to maintain the membrane potential at the designated "clamped" value.

Question 2

Why are nongated channels important in the generation of an inside-negative electric potential (voltage)of 50-70 mV across the plasma membrane of cells?

Accepted Answer

If there is no ion movement across the membrane,there is no membrane potential.This is true even if there is a difference in ion concentrations on either side of the membrane.The presence of K⁺ channels that are usually open allows for ion movement from the inside of the cell to the outside and the creation of a negative membrane potential inside the cell.

Question 3

During a knee jerk reflex,which of the following steps occurs first?
A)stretch receptor is activated
B)interneuron sends an inhibitory signal to the hamstring muscle
C)motor neuron stimulates the quadriceps muscle
D)action potential travels along a sensory neuron

Accepted Answer

The knee jerk reflex begins with the activation of stretch receptors in the muscle spindles when the patellar tendon is tapped.

Question 4

The resting potential of a typical neuron is:
A)−60 mV.
B)0 mV.
C)20 mV.
D)50 mV.

Accepted Answer

The resting potential of a typical neuron is around -60 mV, which means the inside of the neuron is negatively charged compared to the outside. This negative charge is due to the presence of more negatively charged ions (such as proteins) inside the neuron compared to outside, as well as the selective permeability of the cell membrane to different ions.

Question 5

Which cells produce myelin?
A)oligodendrocytes
B)Schwann cells
C)astrocytes
D)Schwann cells and oligodendrocytes
E)all of the above

Accepted Answer

Myelin, which insulates nerve fibers to increase the speed at which electrical impulses propagate along the nerve cells, is produced by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.

Question 6

Action potentials are propagated in only one direction,down the axon.Explain how the absolute refractory period of the voltage-gated Na⁺ channels and the brief hyperpolarization resulting from K⁺ efflux produces this outcome.

Accepted Answer

The answer of Action potentials are propagated in only one...

Question 7

During an action potential,which happens first?
A)opening of voltage-gated Na⁺ channels
B)closing of voltage-gated Na⁺ channels
C)opening of voltage-gated K⁺ channels
D)closing of voltage gated K⁺ channels

Accepted Answer

During an action potential, the opening of voltage-gated Na⁺ channels occurs first, leading to an influx of Na+ ions into the cell, causing depolarization.

Question 8

The resting membrane potential in animal cells depends largely on nongated _____ channels.
A)Ca²⁺
B)H⁺
C)K⁺
D)Na⁺

Accepted Answer

The resting membrane potential in animal cells is primarily determined by the concentration gradients of ions such as Na⁺, K⁺, and Cl⁻ across the plasma membrane, as well as the permeability of the membrane to these ions. Among these ions, the K⁺ channels are the most important in determining the resting membrane potential since they are far more permeable than other ions at rest. Therefore, the correct choice is C) K⁺ channels.

Question 9

Action potentials:
A)vary in intensity
B)vary in frequency and timing
C)result in a decrease in resting potential
D)all of the above

Accepted Answer

Action potentials do not vary in intensity; they are all-or-none events. Instead, the frequency and timing of action potentials convey information. Additionally, action potentials result in a temporary increase in membrane potential, not a decrease, as ions rapidly move across the membrane.

Question 10

Action potentials are:
A)pulses of ion flow along axons.
B)brief local voltage changes within a neuron from inside-negative to inside-positive.
C)transmembrane potentials that result from the action of the Na⁺/K⁺ ion pump.
D)electrical signals used by glial cells to transmit information.

Accepted Answer

Action potentials refer to the rapid pulse-like movement of ions along the axon of a neuron. This movement is crucial for transmitting signals within the nervous system.

Question 11

In a human brain,the number of glial cells is:
A)about 1/10 the number of neurons.
B)about the same as the number of neurons.
C)about 10 times the number of neurons.
D)about 100-200 times the number of neurons.

Accepted Answer

Glial cells are about 10 times the number of neurons in the human brain, playing crucial roles in support, insulation, and nutrient supply to neurons.

Question 12

The birth of new neurons in the adult brain occurs in:
A)the dentate gyrus.
B)the brainstem.
C)olfactory bulb.
D)neural tube.

Accepted Answer

The dentate gyrus is a region of the hippocampus where neurogenesis (birth of new neurons) occurs throughout adulthood. The other options do not typically exhibit neurogenesis in adulthood.

Question 13

Where are voltage-gated Na⁺ channels concentrated?
A)spaced uniformly along the axon membrane
B)clustered at the nodes of Ranvier
C)clustered at the axon terminus
D)embedded within the myelin sheath

Accepted Answer

Voltage-gated Na⁺ channels are concentrated at the nodes of Ranvier, which are the gaps in the myelin sheath covering the axon. This clustering helps to speed up the propagation of action potentials down the axon.

Question 14

Fruit flies carrying the shaker mutation have motor neurons with an abnormally long action potential because of:
A)a defect in the Na⁺/K⁺ pump.
B)a defect in voltage-gated Na⁺ channels.
C)a defect in non-voltage-gated K⁺ channels.
D)a defect in voltage-gated K⁺ channels.

Accepted Answer

The shaker mutation affects voltage-gated K⁺ channels in motor neurons, leading to an abnormally long action potential.

Question 15

Repolarization during the refractory period is largely due to the:
A)opening of non-voltage-gated K⁺ channels.
B)opening of voltage-gated K⁺ channels.
C)opening of voltage-gated Na⁺ channels.
D)action of the Na⁺/K⁺ pump.

Accepted Answer

During the refractory period, the membrane potential is hyperpolarized and repolarized. This is largely due to the opening of voltage-gated potassium (K⁺) channels, which allows for the efflux of K⁺ ions from the cell, leading to repolarization. The action of the Na⁺/K⁺ pump is important for maintaining the resting membrane potential but does not play a significant role in repolarization during the refractory period. The opening of voltage-gated sodium (Na⁺) channels is responsible for depolarization, not repolarization. Non-voltage-gated K⁺ channels do not have a significant impact on membrane repolarization during the refractory period.

Question 16

Which of the following is NOT a function of astrocytes?
A)stimulate blood vessels in the brain to maintain tight junctions
B)provide growth factors to neurons
C)produce extracellular matrix
D)excite muscle cells

Accepted Answer

Astrocytes are glial cells in the central nervous system that have several functions, including supporting neurons, regulating the chemical environment in the brain, and regulating blood flow. However, they do not excite muscle cells.

Question 17

Which of the following represents a correct structure-function relationship for neurons?
A)cell body - sends signal to another cell
B)axon - contains the nucleus of the cell
C)dendrite - forms synapses with other neurons
D)axon termini - receive incoming signals

Accepted Answer

Dendrites receive incoming signals from other neurons and form synapses with them. This relationship allows for the transmission of information between neurons.

Question 18

What starts an action potential in a post-synaptic neuron?

Accepted Answer

The answer of What starts an action potential in a...

Question 19

How are most voltage-gated channels inactivated?
A)by ligand binding
B)by changes in membrane potential
C)through interaction with other membrane proteins
D)by closing spontaneously soon after opening

Accepted Answer

Most voltage-gated channels are inactivated by closing spontaneously soon after opening. This occurs through a process called "fast inactivation", where a part of the channel called the inactivation gate swings shut shortly after the activation gate opens. This prevents the channel from staying open for an extended period of time, and helps to regulate ion flow across the membrane.

Question 20

Which cells produce myelin sheaths?
A)Schwann cells and oligodendrocytes
B)astrocytes
C)afferent neurons
D)interneurons

Accepted Answer

Myelin sheaths are produced by both Schwann cells (in the peripheral nervous system) and oligodendrocytes (in the central nervous system). Astrocytes, afferent neurons, and interneurons do not produce myelin.

Quiz 21: Nerve Cells

How do researchers measure ion movements through single channels?

Why are nongated channels important in the generation of an inside-negative electric potential (voltage)of 50-70 mV across the plasma membrane of cells?

During a knee jerk reflex,which of the following steps occurs first?

The resting potential of a typical neuron is:

Which cells produce myelin?

Action potentials are propagated in only one direction,down the axon.Explain how the absolute refractory period of the voltage-gated Na⁺ channels and the brief hyperpolarization resulting from K⁺ efflux produces this outcome.

During an action potential,which happens first?

The resting membrane potential in animal cells depends largely on nongated _____ channels.

Action potentials:

Action potentials are:

In a human brain,the number of glial cells is:

The birth of new neurons in the adult brain occurs in:

Where are voltage-gated Na⁺ channels concentrated?

Fruit flies carrying the shaker mutation have motor neurons with an abnormally long action potential because of:

Repolarization during the refractory period is largely due to the:

Which of the following is NOT a function of astrocytes?

Which of the following represents a correct structure-function relationship for neurons?

What starts an action potential in a post-synaptic neuron?

How are most voltage-gated channels inactivated?

Which cells produce myelin sheaths?