Question 1

The term saltatory conduction refers to the fact that

Accepted Answer

Saltatory conduction refers to the rapid propagation of action potentials along myelinated axons through a process of "jumping" from one Node of Ranvier to the next. This occurs because the insulation provided by the myelin sheath prevents the dissipation of the electrical signal, allowing it to skip over the myelinated regions and travel more quickly down the axon.

Question 2

If you were to insert a microelectrode through the cell membrane of a neuron, you would be able to demonstrate that

Accepted Answer

When a microelectrode is inserted through the cell membrane of a neuron, it will detect a potential difference between the inside and outside of the cell. This potential difference is due to the fact that the inside of the cell is more negatively charged compared to the outside. This difference in charge is maintained by the selective permeability of the cell membrane to different ions, such as potassium and sodium. Therefore, choice B is the correct answer.

Question 3

Within a neuron, the transmission of information is usually ________. Between neurons, the transmission of information is usually ________.

Accepted Answer

Within a neuron, the transmission of information is usually electrical because signals are transmitted as electrical impulses along the axon. Between neurons, the transmission of information is usually chemical because the electrical impulse triggers the release of neurotransmitters into the synaptic cleft, which diffuse across the gap and bind to receptors on the next neuron.

Question 4

In the nervous system, these cells provide structural support and insulation for neurons.

Accepted Answer

Glia, also known as neuroglia, are non-neuronal cells in the nervous system that provide a variety of functions, including structural support and insulation for neurons. They make up about 90% of the cells in the human brain and come in several different types, including astrocytes, oligodendrocytes, and microglia. The other options listed are not directly involved in providing structural support or insulation for neurons.

Question 5

___________ enable(s) the rapid transmission of action potentials down an axon and increase(s) the distance over which transmission can occur.

Accepted Answer

Myelin is a fatty covering that surrounds and insulates axons, allowing for rapid transmission of action potentials down the axon. It also increases the distance over which transmission can occur by preventing loss of the electrical signal. The soma and dendrites are involved in receiving and processing signals, while neurotransmitters are involved in transmitting signals between neurons, but do not directly enable the rapid transmission of action potentials down an axon.

Question 6

The primary reason why neurons are refractory for a short period after firing action potentials, and the reason underlying the absolute refractory period, is that the

Accepted Answer

During an action potential, voltage-gated sodium channels open and allow an influx of sodium ions into the cell, depolarizing the membrane. These channels then become inactivated, preventing another action potential from firing immediately. This is known as the absolute refractory period, during which no amount of stimulation can generate another action potential. The channels eventually transition back to a closed, but not inactivated, state, allowing the neuron to fire again during the relative refractory period. The inactivation of sodium channels is the primary reason for the refractory period. The sodium-potassium pump does play a role in returning the membrane potential to its resting state after an action potential, but it is not the primary reason for the refractory period.

Question 7

Demyelinating diseases such as multiple sclerosis disrupt normal neural communication by

Accepted Answer

Demyelinating diseases such as multiple sclerosis cause the deterioration of the fatty substance called myelin, which normally insulates axons, facilitating the rapid conduction of nerve impulses. The loss of myelin disrupts the normal neural communication, leading to a range of symptoms, including weakness, numbness, and cognitive impairments.

Question 8

The value of the membrane potential to which an axon must be depolarized to initiate an action potential is called the ________ potential for that neuron.

Accepted Answer

The threshold potential is the value of the membrane potential that must be reached in order for an action potential to be generated in a neuron. This is typically around -55mV to -50mV for most neurons.

Question 9

In which of the following diseases is myelin damaged or lost?

Accepted Answer

Multiple sclerosis is a chronic autoimmune disease that damages the myelin sheath surrounding nerve fibers in the central nervous system, leading to symptoms such as vision disturbances, muscle weakness, and cognitive impairment. Alzheimer's, Parkinson's, and schizophrenia do not involve damage or loss of myelin.

Question 10

At the resting state, a higher concentration of ________ is found outside a neuron and a higher concentration of ________ is found inside a neuron.

Accepted Answer

At the resting state, there is a higher concentration of sodium (Na) ions outside of a neuron and a higher concentration of potassium (K) ions inside the neuron. Option B correctly represents this distribution of ions. The other answer choices are unrelated neurotransmitters and are not relevant to the distribution of ions at the resting state.

Question 11

The Hodgkin-Huxley cycle describes how the depolarization of the membrane causes voltage-gated sodium channels to ________, allowing ________ sodium ions to enter the cell. This change in sodium concentration then causes ________ of the cell.

Accepted Answer

The Hodgkin-Huxley cycle describes how the depolarization of the membrane causes voltage-gated sodium channels to open, allowing more sodium ions to enter the cell. This change in sodium concentration then causes further depolarization of the cell.

Question 12

If you inserted a micropipette into a neuron without harming the cell and pumped in a small quantity of calcium ions, each of which carried two positive charges, how would this affect the membrane potential?

Accepted Answer

Calcium ions carry a positive charge, and the influx of positive charges into the neuron would increase the positive charge inside the cell. As a result, the membrane potential would become less negative (or depolarized) relative to the resting potential. This could trigger the opening of voltage-gated ion channels and generate an action potential if the depolarization reaches a certain threshold.

Question 13

The ease with which a cell membrane will permit ions to cross is referred to as

Accepted Answer

Permeability refers to the ease with which molecules or ions can pass through a membrane. The higher the permeability, the easier it is for ions to cross the membrane. The concentration gradient refers to the difference in the concentration of ions between the inside and outside of the cell, which affects the movement of ions across the membrane, but is not a measure of how easy or difficult it is for them to do so. Action potential and conductivity are related to the electrical activity in cells, but are not measures of membrane permeability.

Question 14

The two main classes of cells in the nervous system are

Accepted Answer

The two main classes of cells in the nervous system are neurons and glial cells. Neurons are responsible for transmitting electrical and chemical signals, while glial cells provide support and protection to neurons. Dendrites and axons are both parts of neurons, and axons are a subset of neurons, so choices A and B are incorrect. Choice D is also incorrect, as dendrites are a type of neuron and not a separate class of cells.

Question 15

Ouabain is a toxin that works by permanently inhibiting the activity of sodium-potassium pumps embedded in neuronal membranes. How would ouabain administration affect the resting potential of a neuron?

Accepted Answer

The sodium-potassium pump helps maintain the resting potential of a neuron by pumping out three sodium ions for every two potassium ions it brings in, creating a net negative charge inside the cell. Inhibiting this pump with ouabain would lead to an accumulation of sodium ions inside the neuron and a decrease in the gradient between the inside and outside of the cell, thus reducing the magnitude of the resting potential and shifting it toward zero.

Question 16

The nodes of Ranvier are

Accepted Answer

The nodes of Ranvier are gaps or points along the axon of a neuron that are not covered by myelin. They are important for the conduction of electrical impulses along the axon. Options A and B are incorrect because they refer to structures that are not related to the nodes of Ranvier. Option C is also incorrect because calcium ions are not stored in postsynaptic neurons, but rather play a role in the process of neurotransmitter release at synapses.

Question 17

The term concentration gradient refers to a difference in the

Accepted Answer

Concentration gradient refers to the difference in the number or concentration of a substance on one side of a cell membrane compared to the other side. This can be seen in the difference in the number of ions, molecules, or particles on opposite sides of the membrane. Therefore, option B is the correct choice. The other options, including the number of ion types or permeability of the membrane, may be related to ion movement, but do not directly refer to a concentration gradient.

Question 18

Two main types of projections extend from the cell body of a neuron. ________ receive inputs from other neurons, while ________ send information to other neurons.

Accepted Answer

Dendrites receive inputs from other neurons, while axons send information to other neurons. The other options are incorrect: synapses are the junctions between neurons where communication occurs, glia are non-neuronal cells that support neuron function, and including glia as a second option is redundant with the first option.

Question 19

If electrical currents on multiple dendrites sum together at the axon hillock, and the current flows across the neuronal membrane to the spike-triggering zone, what is likely to happen?

Accepted Answer

If enough electrical currents from multiple dendrites sum together at the axon hillock and create a depolarization large enough to reach the threshold, then an action potential will be initiated and propagated down the axon.

Question 20

The poison tetraethylammonium (TEA) interferes with normal neural communication. The toxin binds to and blocks voltage-gated potassium channels in the neuron cell membrane. Which of the following best describes the effects of TEA on the action potential?

Accepted Answer

TEA blocks voltage-gated potassium channels, which normally open during the repolarization phase of the action potential to restore the resting membrane potential. Therefore, if potassium channels are blocked, the repolarization phase will be inhibited, leading to prolonged depolarization of the membrane and disrupted neural communication.

Quiz 2: Structure and Function of the Nervous System