Question 1

In depolarization the membrane potential moves toward zero,whereas in hyperpolarization the membrane potential moves away from zero.

Accepted Answer

Depolarization is a decrease in the membrane potential, meaning the potential becomes less negative or more positive, and moves toward zero. Hyperpolarization is an increase in the membrane potential, meaning the potential becomes more negative, and moves away from zero.

Question 2

In a myelinated fiber,the action potential jumps from one node of Ranvier to the next.

Accepted Answer

This is known as saltatory conduction, which allows for faster conduction of the action potential compared to unmyelinated fibers where the action potential travels along the entire length of the axon.

Question 3

When a neuropeptide is secreted with one or two other neurotransmitters,it is thought to serve as a neuromodulator,regulating the effects of the other neurotransmitters.

Accepted Answer

When a neuropeptide is secreted with one or two other neurotransmitters, it is believed to act as a neuromodulator, controlling the impact of the other neurotransmitters.

Question 4

In a myelinated neuron,the impulse can travel under the myelin between nodes of Ranvier.

Accepted Answer

The myelin sheath insulates the axon, forcing the electrical impulse to jump from one node of Ranvier to the next, which is a faster way of transmitting the signal than continuously traveling along the entire axon.

Question 5

A neurotransmitter can be excitatory or inhibitory,not both.

Accepted Answer

A neurotransmitter can be either excitatory or inhibitory depending on which receptor it binds to. For example, acetylcholine can be excitatory at neuromuscular junctions and inhibitory in the heart.

Question 6

A neurotransmitter can be either excitatory or inhibitory depending on the postsynaptic receptor.

Accepted Answer

This statement is true. Whether a neurotransmitter is excitatory or inhibitory depends on the type of receptor it binds to on the postsynaptic neuron. Excitatory neurotransmitters typically cause depolarization of the postsynaptic membrane, making it more likely that an action potential will occur, while inhibitory neurotransmitters typically cause hyperpolarization, making it less likely that an action potential will occur.

Question 7

Excitatory neurotransmitters are most likely to initiate an action potential.

Accepted Answer

Excitatory neurotransmitters, such as glutamate, bind to receptors on the receiving neuron, causing depolarization and increasing the likelihood of an action potential being generated.

Question 8

Enkephalins and endorphins are subclasses of amines that are pain relievers.

Accepted Answer

Enkephalins and endorphins are peptides, not amines, that function as neurotransmitters and have pain-relieving properties.

Question 9

The speed of a nerve impulse depends on the neuron's resting potential.

Accepted Answer

The speed of a nerve impulse actually depends on the diameter of the axon and the presence or absence of a myelin sheath. The resting potential of a neuron (typically around -70mV) refers to its state of polarization when it is not actively sending signals.

Question 10

Myelinated fibers conduct impulses faster than unmyelinated fibers.

Accepted Answer

Myelin is a fatty substance that covers certain nerve fibers and helps to speed up the transmission of nerve impulses. Therefore, myelinated fibers conduct impulses faster than unmyelinated fibers.

Question 11

Spatial summation is the effect produced by a rapid succession of stimuli on a single postsynaptic neuron.

Accepted Answer

Spatial summation refers to the combination of multiple signals received at different locations on the neuron's dendrites and cell body at the same time, rather than a rapid succession of stimuli on a single location.

Question 12

When epinephrine and norepinephrine are released into the bloodstream,they are called hormones instead of neurotransmitters.

Accepted Answer

Epinephrine and norepinephrine can function as neurotransmitters in the nervous system and as hormones when released into the bloodstream. The distinction between whether they are called neurotransmitters or hormones depends on how they are released and the mode of action in the body. When they are released by neurons to signal within the nervous system, they are neurotransmitters. When they are released by the adrenal glands to affect the body's physiological response to stress, they are hormones.

Question 13

The neurotransmitter acetylcholine always has an excitatory effect.

Accepted Answer

Acetylcholine can have both excitatory and inhibitory effects depending on the receptors it binds to. For example, the nicotinic acetylcholine receptor is excitatory, while the muscarinic acetylcholine receptor can be either excitatory or inhibitory depending on the subtype and location of the receptor.

Question 14

An inhibitory postsynaptic potential is produced through the hyperpolarization of the postsynaptic membrane.

Accepted Answer

An inhibitory postsynaptic potential (IPSP) is a type of postsynaptic potential that makes the postsynaptic neuron less likely to generate an action potential. IPSPs are produced through the opening of ligand-gated ion channels that allow negatively charged ions (such as Cl-) to enter the postsynaptic neuron, causing the membrane potential to become more negative or hyperpolarized. This increase in negativity makes it more difficult for the neuron to fire an action potential, hence the inhibitory effect.

Question 15

The receptors embedded in the plasma membrane of a postsynaptic neuron are protein molecules.

Accepted Answer

The receptors embedded in the plasma membrane of a postsynaptic neuron are usually protein molecules. These proteins receive chemical messages from neurotransmitters that were released by the presynaptic neuron, and then they trigger responses in the postsynaptic neuron.

Question 16

Whether an impulse is continued through the neuron depends on the magnitude of the voltage in the axon hillock.

Accepted Answer

The axon hillock is responsible for integrating incoming signals from the dendrites and determining whether to generate an action potential. This decision is based on the magnitude of the voltage at the axon hillock threshold. If the voltage exceeds this threshold, an action potential is generated and propagated down the axon. Therefore, the continuation of an impulse through the neuron is dependent on the magnitude of the voltage at the axon hillock.

Question 17

The action potential is called an all-or-none response because if the threshold potential is surpassed,the full peak of the action is always reached; if the threshold potential is not surpassed,no action potential will occur.

Accepted Answer

This is because the opening of voltage-gated ion channels in response to depolarization is an all-or-none phenomenon. Once the threshold potential is reached, a full action potential will be generated, regardless of how strong the depolarizing stimulus was. If the threshold potential is not reached, no action potential will occur.

Question 18

Many anesthetics produce their effects by inhibiting the opening of the potassium channels,blocking the repolarization of nerve impulses.

Accepted Answer

Many anesthetics produce their effects by enhancing the activity of GABA receptors, which increases inhibition in the central nervous system, or by inhibiting the activity of NMDA receptors. They do not primarily work by inhibiting the opening of potassium channels to block repolarization of nerve impulses.

Question 19

The difference in electrical charge between the inside and outside of a membrane is called the membrane potential.

Accepted Answer

The statement is true. The membrane potential refers to the difference in electrical potential that exists between the inside and the outside of a cell membrane. This difference in charges is maintained by the selective permeability of the membrane and the active transport of ions by the cells. The membrane potential plays an important role in many cellular processes, including the conduction of nerve impulses, muscle contraction, and the transport of nutrients and waste products across the membrane.

Question 20

The sensory fibers from the skin generally conduct impulses up to about 130 meters per second.

Accepted Answer

The sensory fibers from the skin conduct impulses at a much slower rate, typically up to about 1-2 meters per second for pain fibers and up to 30-70 meters per second for touch and pressure fibers.

Quiz 13: A: Nervous System Cells