Question 1

Adaptations such as myelinated axons and axons with large diameters would be most useful for which type of organisms?
A) Sedentary animals
B) Slow-moving burrowers
C) Animals with toxic stings
D) Animals with protective shells
E) Fast-moving predator or prey animals

Accepted Answer

Myelinated axons and axons with large diameters allow for faster conduction of nerve impulses, which would be most useful for organisms that need to quickly react to their environment or escape from predators, such as fast-moving predator or prey animals. Sedentary animals, slow-moving burrowers, animals with toxic stings, and animals with protective shells would not benefit as much from these adaptations.

Question 2

Which conditions would most likely have led to the evolution of electrical synapses rather than chemical synapses in a species?
A) Conditions that require thinking
B) Conditions that require rapid escape
C) Conditions that require repetitive motion
D) Any conditions;electrical synapses are faster,so they are always more adaptive.
E) Any conditions;electrical synapses are stronger,so they are always more adaptive.

Accepted Answer

Electrical synapses allow for faster transmission of signals than chemical synapses. This would be advantageous in situations where rapid escape is necessary, such as in predators and prey.

Question 3

After a neurotransmitter diffuses across the synaptic cleft,what is the next action that occurs in transmission of an action potential?
A) Neurotransmitter molecules immediately depolarize the postsynaptic membrane.
B) Neurotransmitter molecules bind to receptor proteins in the postsynaptic membrane.
C) A delay occurs while receptor proteins are synthesized in the postsynaptic membrane.
D) A delay occurs while neurotransmitter molecules are transformed into ions that carry the action potential.
E) A single neurotransmitter molecule immediately triggers an action potential in the postsynaptic membrane.

Accepted Answer

After neurotransmitter molecules diffuse across the synaptic cleft, they bind to specific receptor proteins on the postsynaptic membrane. This binding opens ion channels in the membrane, allowing ions to flow in or out and causing a change in the membrane potential. This change can either depolarize or hyperpolarize the membrane, and if enough depolarization occurs, an action potential may be triggered. Therefore, choice B is the correct answer.

Question 4

The most common type of interconnection between two neurons in the nervous system is a(n)
A) motor end-plate.
B) chemical synapse.
C) electrical synapse.
D) neuromuscular junction.
E) direct connection between cells.

Accepted Answer

Chemical synapses are the most common type of synapse in the nervous system. They involve the release of neurotransmitters from the presynaptic neuron, which bind to receptors on the postsynaptic neuron, causing a change in its electrical activity. This allows for greater flexibility and specificity in the transmission of signals between neurons.

Question 5

What determines the function carried out by a neurotransmitter at a neuron-to-neuron synapse?
A) The type of neurotransmitter released
B) The strength of the action potential generated
C) The type of receptor binding the neurotransmitter
D) The number of neurotransmitter molecules released
E) The rate at which neurotransmitter molecules are released

Accepted Answer

The type of receptor binding the neurotransmitter determines the function carried out by a neurotransmitter at a neuron-to-neuron synapse. Different types of receptors have different effects on the postsynaptic neuron, ranging from excitatory to inhibitory. Therefore, the neurotransmitter will carry out different functions depending on which receptor it binds to.

Question 6

Which type of neurotransmitter is released at the neuromuscular junction of vertebrates?
A) Dopamine
B) Serotonin
C) Glutamate
D) Acetylcholine
E) Norepinephrine

Accepted Answer

Acetylcholine is the neurotransmitter that is released at the neuromuscular junction of vertebrates. It binds to receptors on muscle cells, leading to muscle contraction.

Question 7

The vertebrate neuromuscular junction has often been used as a model for understanding the functioning of a synapse because it
A) involves only one neuron and one muscle cell.
B) operates in the same way as synapses in the brain do.
C) uses acetylcholine,the only well-understood neurotransmitter.
D) can be used to understand both chemical and electrical synapses.
E) has a measurable action potential,unlike neuron-to-neuron synapses.

Accepted Answer

The answer of The vertebrate neuromuscular junction has often been...

Question 8

For summation of membrane potentials and subsequent generation of an action potential to occur,all incoming synaptic potentials must
A) be excitatory (EPSPs).
B) be inhibitory (IPSPs).
C) originate at the same time and place.
D) originate from the same place,although they may occur at separate times.
E) originate at the same time,although they may come from separate places.

Accepted Answer

Incoming synaptic potentials do not have to be exclusively excitatory or inhibitory, and they can originate from different locations. However, for summation to result in the generation of an action potential, the potentials must arrive at the same time. Therefore, option E ("originate at the same time, although they may come from separate places") is the best choice.

Question 9

After neurotransmitter molecules travel across the synaptic cleft and bind to receptors on the postsynaptic cell,remaining molecules in the synaptic cleft are removed rapidly.If the molecules were not removed,transmission of information would most likely
A) continue at the same rate.
B) continue and become faster and faster.
C) continue and become stronger and stronger.
D) stop,because no information is arriving at the nerve terminal.
E) stop,because the membrane would lose its responsiveness.

Accepted Answer

If neurotransmitter molecules are not removed from the synaptic cleft, they will continue to bind to receptors, causing the postsynaptic cell to remain activated. This can lead to desensitization or downregulation of receptors, causing the membrane to lose its responsiveness and stop transmitting information effectively.

Question 10

A series of steps occurs between the arrival of an action potential at a presynaptic axon terminal and the initiation of an action potential in the postsynaptic neuron.What is the last step in this process? A) Opening of Ca²⁺ channels in the presynaptic membrane B) Fusing of synaptic vesicles with the presynaptic membrane C) Spreading of depolarization to neighboring regions of the postsynaptic membrane D) Influx of Na⁺,causing a graded depolarization of the postsynaptic membrane E) Binding of acetylcholine to gated receptor proteins,allowing diffusion of Na⁺ and K⁺

Accepted Answer

The last step in the process between the arrival of an action potential at a presynaptic axon terminal and the initiation of an action potential in the postsynaptic neuron is the spreading of depolarization to neighboring regions of the postsynaptic membrane. This depolarization can then trigger an action potential in the postsynaptic neuron.

Question 11

Suppose an action potential arrives at the axon terminal but the voltage-gated calcium channels at the terminal fail to open.What will most likely happen to the action potential? A) It will stop,because Ca²⁺ will not enter the presynaptic cell and the neurotransmitter will not be released. B) It will stop,because Ca²⁺ will not be available to act as a neurotransmitter in place of acetylcholine. C) It will continue,because Ca²⁺ will be released by an electrical method and the neurotransmitter will be released. D) It will continue,because although the neurotransmitter will not be released,Na⁺ and K⁺ will be released in the postsynaptic membrane. E) It will continue,because although Ca²⁺ will not be released,synaptic vesicles will use another method to fuse with the presynaptic membrane.

Accepted Answer

If the voltage-gated calcium channels fail to open, calcium ions will not enter the presynaptic cell, which means that the neurotransmitter will not be released into the synaptic cleft. Without the release of the neurotransmitter, the action potential cannot continue to the postsynaptic membrane.

Question 12

Which characteristic would best indicate that a particular synapse is a neuron-to-neuron synapse and not a neuromuscular junction?
A) All impulses reaching the postsynaptic cell are inhibitory.
B) All impulses reaching the postsynaptic cell are excitatory.
C) A single nerve impulse from the presynaptic cell generates an action potential.
D) An action potential results from many small signals received over a long time period.
E) An action potential results from the summation of many small signals received in a short amount of time.

Accepted Answer

Neuron-to-neuron synapses often require the summation of multiple small signals to reach the threshold for an action potential, unlike neuromuscular junctions where a single impulse can trigger an action potential.

Question 13

Which statement about a metabotropic neurotransmitter receptor is true?
A) It is a ligand-gated ion channel.
B) It is a voltage-gated ion channel.
C) It has a single,very specific effect on a cell.
D) It often controls production of second messengers.
E) It causes a very rapid,short-lived change in the membrane.

Accepted Answer

Metabotropic neurotransmitter receptors are G protein-coupled receptors (GPCRs) that activate intracellular signaling pathways to ultimately produce a second messenger. This second messenger, in turn, modulates cellular processes such as ion channels, gene expression, and protein kinases. Therefore, option D is the correct choice as it describes the function of the receptor accurately.

Question 14

When an action potential arrives at an axon terminal,it causes the opening of _______ channels,which triggers fusion of neurotransmitter vesicles with the cell membrane.
A) sodium
B) chloride
C) calcium
D) potassium
E) acetylcholine

Accepted Answer

Calcium channels open upon arrival of an action potential, allowing calcium ions to flow into the axon terminal. This influx of calcium triggers the fusion of neurotransmitter-containing vesicles with the cell membrane, releasing the neurotransmitters into the synaptic cleft.

Question 15

At an electrical synapse,how is the action potential able to move from one neuron to the next?
A) The neuron cell membranes are connected by gap junctions.
B) A neurotransmitter carries the action potential across the synaptic cleft.
C) The electrical charge of the action potential jumps across the synaptic cleft.
D) A neurotransmitter binds to the postsynaptic neuron and generates a new action potential.
E) The electrical charge of the action potential bypasses presynaptic boutons and directly enters the synaptic cleft.

Accepted Answer

At an electrical synapse, the neuron cell membranes are connected by gap junctions which allow the action potential to move directly from one neuron to the next through ion movement.

Question 16

A neurotransmitter receptor is a ligand-gated ion channel,and neurotransmitter binding to this receptor results in a rapid but short-lived change in the postsynaptic membrane potential.This type of receptor is most likely
A) synaptic.
B) excitatory.
C) inhibitory.
D) ionotropic.
E) metabotropic.

Accepted Answer

A ligand-gated ion channel is also known as an ionotropic receptor, which means that it directly allows ions to pass through the membrane when activated by a ligand, such as a neurotransmitter. This type of receptor results in a rapid change in the postsynaptic membrane potential because ions are allowed to flow across the membrane almost immediately upon activation. Therefore, the best choice would be D) ionotropic.

Question 17

In transmission of information in the nervous system,what is one way in which the process differs if a neuron,rather than a muscle fiber,serves as the postsynaptic cell?
A) All responses are excitatory.
B) All responses are fast and short-lived.
C) There may be hundreds or thousands of presynaptic cells.
D) The presynaptic cell always releases serotonin rather than acetylcholine.
E) The same receptors are used,regardless of the neurotransmitter released.

Accepted Answer

If a neuron serves as the postsynaptic cell, there may be hundreds or thousands of presynaptic cells making connections with it. In contrast, if a muscle fiber serves as the postsynaptic cell, there is typically only one presynaptic cell (i.e. motor neuron) that connects with it. This is because a muscle fiber receives input from only one motor neuron, whereas a neuron can receive input from many other neurons.

Question 18

After a neurotransmitter such as acetylcholine or glutamate enters a synaptic cleft,several things can happen to it.Which of these does not happen to a neurotransmitter during normal nervous system activity?
A) It remains in the synaptic cleft.
B) It is taken up by a nearby neuron.
C) It is taken up by a nearby glial cell.
D) It is taken up again by the presynaptic neuron.
E) It is broken down in the synaptic cleft by enzymes.

Accepted Answer

Neurotransmitters do not remain in the synaptic cleft; they are either taken up by neurons or glial cells, reabsorbed by the presynaptic neuron, or broken down by enzymes.

Question 19

In a situation that requires the most rapid possible response as an action potential crosses the synaptic cleft,_______ provide fast,invariant signal transmission.
A) motor end-plates
B) nodes of Ranvier
C) chemical synapses
D) electrical synapses
E) neuromuscular junctions

Accepted Answer

Electrical synapses provide fast and efficient signal transmission since they allow direct transfer of ions between neurons, without the need for chemical messengers. This is particularly important in situations where a rapid response is required, such as in reflexes or muscle contractions. The other options listed (motor end-plates, nodes of Ranvier, chemical synapses, and neuromuscular junctions) all involve some form of chemical communication and are not as fast or direct as electrical synapses.

Question 20

Which step is not part of the sequence of events that triggers synaptic transmission from a neuron to a muscle fiber? A) Entry of Ca²⁺ into the presynaptic terminal B) Release of norepinephrine into the synaptic cleft C) Opening of Ca²⁺ channels in the presynaptic terminal D) Arrival of an action potential at the presynaptic terminal E) Fusion of synaptic vesicles with the presynaptic membrane

Accepted Answer

Norepinephrine is not typically involved in the transmission from a neuron to a muscle fiber. Instead, acetylcholine is the neurotransmitter released into the synaptic cleft at the neuromuscular junction. Therefore, the release of norepinephrine is not part of the sequence of events that triggers synaptic transmission in this context.

Quiz 34: Neurons, Sense Organs, and Nervous Systems

Adaptations such as myelinated axons and axons with large diameters would be most useful for which type of organisms?

Which conditions would most likely have led to the evolution of electrical synapses rather than chemical synapses in a species?

After a neurotransmitter diffuses across the synaptic cleft,what is the next action that occurs in transmission of an action potential?

The most common type of interconnection between two neurons in the nervous system is a(n)

What determines the function carried out by a neurotransmitter at a neuron-to-neuron synapse?

Which type of neurotransmitter is released at the neuromuscular junction of vertebrates?

The vertebrate neuromuscular junction has often been used as a model for understanding the functioning of a synapse because it

For summation of membrane potentials and subsequent generation of an action potential to occur,all incoming synaptic potentials must

After neurotransmitter molecules travel across the synaptic cleft and bind to receptors on the postsynaptic cell,remaining molecules in the synaptic cleft are removed rapidly.If the molecules were not removed,transmission of information would most likely

A series of steps occurs between the arrival of an action potential at a presynaptic axon terminal and the initiation of an action potential in the postsynaptic neuron.What is the last step in this process?

Suppose an action potential arrives at the axon terminal but the voltage-gated calcium channels at the terminal fail to open.What will most likely happen to the action potential?

Which characteristic would best indicate that a particular synapse is a neuron-to-neuron synapse and not a neuromuscular junction?

Which statement about a metabotropic neurotransmitter receptor is true?

When an action potential arrives at an axon terminal,it causes the opening of _______ channels,which triggers fusion of neurotransmitter vesicles with the cell membrane.

At an electrical synapse,how is the action potential able to move from one neuron to the next?

A neurotransmitter receptor is a ligand-gated ion channel,and neurotransmitter binding to this receptor results in a rapid but short-lived change in the postsynaptic membrane potential.This type of receptor is most likely

In transmission of information in the nervous system,what is one way in which the process differs if a neuron,rather than a muscle fiber,serves as the postsynaptic cell?

After a neurotransmitter such as acetylcholine or glutamate enters a synaptic cleft,several things can happen to it.Which of these does not happen to a neurotransmitter during normal nervous system activity?

In a situation that requires the most rapid possible response as an action potential crosses the synaptic cleft,_______ provide fast,invariant signal transmission.

Which step is not part of the sequence of events that triggers synaptic transmission from a neuron to a muscle fiber?