Chapter 9 and 12 Test

Question 1

During a hyperpolarization, the inside of the plasma membrane becomes less / more (select one) negative and is less likely / more likely (select one) to generate a nerve impulse.

Answer 1

more…less likely

Explanation: During hyperpolarization, the inside of the plasma membrane becomes more negative. This makes it less likely to generate a nerve impulse because the membrane potential is further from the threshold needed to trigger an action potential.

Question 2

Neurons can be classified by structure and function. Which of the neurons shown below (A, B, or C) is an example of a bipolar neuron?

Answer 2

B

Explanation: Bipolar neurons have one axon and one dendrite extending from the cell body. In the image, neuron B fits this description. Neuron A is a multipolar neuron, and neuron C is a unipolar neuron.

Question 3

Which of the following gated ion channels open and close in response to changes in membrane potential?

• Mechanically-gated
• Chemically (ligand)-gated
• Voltage-gated

Answer 3

Voltage-gated

Explanation: Voltage-gated ion channels open and close in response to changes in the membrane potential. Mechanically-gated channels respond to physical deformation, and chemically (ligand)-gated channels respond to the binding of a chemical messenger.

Question 4

Which of the following statements about graded potentials is false?

• Graded potentials occur when a neurotransmitter is released into the synapse between two neurons and binds a ligand-gated ion channels.
• Graded potentials only initiate action potentials if they are excitatory enough.
• An excitatory postsynaptic potential is associated with hyperpolarization.
• Most neurons receive both excitatory and inhibitory inputs from thousands of other neurons and only if EPSP’s are greater can an action potential occur.
• All are correct statements.

Answer 4

An excitatory postsynaptic potential is associated with hyperpolarization.

Explanation: An excitatory postsynaptic potential (EPSP) is associated with depolarization, not hyperpolarization. Hyperpolarization is typically associated with inhibitory postsynaptic potentials (IPSPs).

Question 5

Which of the structural classes of neurons below is typically associated with motor (efferent) neurons?

• unipolar
• bipolar
• multipolar

Answer 5

multipolar

Explanation: Motor (efferent) neurons are typically multipolar. They have multiple dendrites and a single axon, which allows them to integrate a large amount of information from other neurons.

Question 6

Graded potentials are short-distance signals that travel through neurons, while action potentials are long-distance signals.

• True
• False

Answer 6

True

Explanation: Graded potentials travel over short distances within a neuron and decrease in strength as they spread out from the point of origin. In contrast, action potentials are long-distance signals that propagate along the length of the axon without decreasing in strength.

Question 7

The brain’s main inhibitory neurotransmitter is glutamate.

• True
• False

Answer 7

False

Explanation: The brain’s main inhibitory neurotransmitter is gamma-aminobutyric acid (GABA), not glutamate. Glutamate is the main excitatory neurotransmitter in the brain.

Question 8

An IPSP causes hyperpolarization of the neuron cell membrane making an action potential less likely.

• True
• False

Answer 8

True

Explanation: An inhibitory postsynaptic potential (IPSP) causes hyperpolarization of the neuron cell membrane, making it less likely to reach the threshold for an action potential.

Question 9

Most neurons are highly mitotic (i.e. capable of undergoing cell division).

• True
• False

Answer 9

False

Explanation: Most neurons are not highly mitotic. Neurons in the adult brain typically do not undergo cell division and are considered postmitotic.

Question 10

Although a neuron will receive both EPSPs and IPSPs, only if IPSPs predominate can an action potential occur.

• True
• False

Answer 10

False

Explanation: An action potential will occur if excitatory postsynaptic potentials (EPSPs) predominate and bring the membrane potential to the threshold. IPSPs inhibit the likelihood of an action potential occurring.

Question 11

Immediately after an action potential has peaked, K+ gates open leading to repolarization.

• True
• False

Answer 11

True

Explanation: After an action potential peaks, voltage-gated K+ channels open, allowing K+ to flow out of the neuron, leading to repolarization of the membrane potential.

Question 12

If a neurotransmitter’s effects are excitatory, that means they are _______________ and the likelihood of an action potential occurring.

• hyperpolarizing / increase
• depolarizing / increase
• hyperpolarizing / decrease
• depolarizing / decrease

Answer 12

depolarizing / increase

Explanation: Excitatory neurotransmitters cause depolarization of the postsynaptic membrane, increasing the likelihood of an action potential occurring.

Question 13

Which of the following gated ion channels open and close in response to the binding of a specific neurotransmitter?

• Mechanically-gated
• Voltage-gated
• Chemically (ligand)-gated

Answer 13

Chemically (ligand)-gated

Explanation: Chemically (ligand)-gated ion channels open and close in response to the binding of a specific neurotransmitter. Mechanically-gated channels respond to physical deformation, and voltage-gated channels respond to changes in membrane potential.

Question 14

An action potential will travel fastest along which type of axon?

• A non-myelinated axon
• A myelinated axon

Answer 14

A myelinated axon

Explanation: Myelinated axons allow action potentials to travel faster due to saltatory conduction, where the action potential jumps from one node of Ranvier to the next.

Question 15

If a neuron is stimulated simultaneously by a single axon terminal repeatedly, this would be an example of ______________ summation.

• Spatial
• Temporal

Answer 15

Temporal

Explanation: Temporal summation occurs when a single presynaptic neuron fires action potentials in rapid succession, leading to a buildup of neurotransmitter release and a greater postsynaptic potential.

Question 16

Which letter shows the location of where an action potential would be initiated?

• A
• C
• D
• G
• F

Answer 16

D

Explanation: The action potential is typically initiated at the axon hillock, which is the region labeled D in the diagram. This area has a high density of voltage-gated sodium channels and is the site where the threshold potential is reached to trigger an action potential.

Question 17

What is the name of the synapse structure labelled ‘A’?

• Postsynaptic neuron
• Receptors for Neurotransmitters
• Synaptic vesicles with Neurotransmitters
• Axon terminal
• Synaptic cleft
• Presynaptic neuron

Answer 17

Axon terminal

Explanation: The structure labeled ‘A’ is the axon terminal, which is the end part of the neuron where neurotransmitters are stored in synaptic vesicles before being released into the synaptic cleft.

Question 18

Put the events of the generation of a graded potential in the correct order:

• 1. An A.P. arrives at the pre-synaptic neuron terminal
• 2. Neurotransmitters bind to ligand-gated ion channels on the post-synaptic neuron allowing an influx of Na+ ions
• 3. Neurotransmitters diffuse across the synaptic cleft to the post-synaptic membrane
• 4. Vesicles containing neurotransmitters fuse with the pre-synaptic membrane and release their contents into the synaptic cleft
• 5. Voltage gated Ca++ channels open and Ca++ is released into the axon terminal
• 6. A localized graded potential is generated

Answer 18

1, 5, 4, 3, 2, 6

Explanation:

An action potential (A.P.) arrives at the pre-synaptic neuron terminal.
Voltage-gated Ca++ channels open and Ca++ is released into the axon terminal.
Vesicles containing neurotransmitters fuse with the pre-synaptic membrane and release their contents into the synaptic cleft.
Neurotransmitters diffuse across the synaptic cleft to the post-synaptic membrane.
Neurotransmitters bind to ligand-gated ion channels on the post-synaptic neuron allowing an influx of Na+ ions.
A localized graded potential is generated.

Question 19

Which of the following neurotransmitters is associated with mood, social behavior, appetite, digestion, sleep, memory, and sexual desire and function? Drugs that block its reuptake can help relieve anxiety or depression.

• Serotonin
• Glutamate
• GABA
• Norepinephrine

Answer 19

Serotonin

Explanation: Serotonin is a neurotransmitter that plays a key role in mood regulation, social behavior, appetite, digestion, sleep, memory, and sexual desire. Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs commonly used to treat depression and anxiety by blocking the reuptake of serotonin.

Question 20

What is the name of the synapse structure labelled ‘E’?

• Axon terminal
• Synaptic vesicles with neurotransmitters
• Presynaptic neuron
• Synaptic cleft
• Receptors for neurotransmitters
• Postsynaptic neuron

Answer 20

Synaptic cleft

Explanation: The synaptic cleft is the small gap between the presynaptic neuron (axon terminal) and the postsynaptic neuron where neurotransmitters are released to transmit signals from one neuron to another.

Question 21

Axodendritic and axoaxonal synapses are the most common types of synapses.

• True
• False

Answer 21

False

Explanation: The most common types of synapses are axodendritic synapses, where the axon of one neuron connects to the dendrite of another. Axoaxonal synapses, where the axon of one neuron connects to the axon of another, are less common.

Question 22

Graded potentials can occur in a variety of intensities unlike action potentials which are one size only.

• True
• False

Answer 22

True

Explanation: Graded potentials vary in amplitude and are dependent on the strength of the stimulus. Action potentials, on the other hand, follow an all-or-none principle and are always the same size regardless of stimulus strength once the threshold is reached.

Question 23

The arrival of a neurotransmitter at the post-synaptic neuron cell membrane opens voltage-gated ion channels.

• True
• False

Answer 23

False

Explanation: The arrival of a neurotransmitter at the postsynaptic neuron cell membrane opens chemically (ligand)-gated ion channels, not voltage-gated ion channels. Voltage-gated ion channels are opened by changes in membrane potential.

Question 24

The plasma membrane has two primary types of ion channels: leakage channels which are always open, and gated channels which open and close.

• True
• False

Answer 24

True

Explanation: The plasma membrane contains leakage channels that are always open, allowing ions to move across the membrane freely, and gated channels that open and close in response to specific stimuli.

Question 25

At rest, a neuron has higher K+ concentrations outside the plasma membrane and higher Na+ concentrations inside the plasma membrane.

• True
• False

Answer 25

False

Explanation: At rest, a neuron has higher concentrations of K+ inside the cell and higher concentrations of Na+ outside the cell. The Na+/K+ pump helps maintain this distribution by pumping Na+ out of the cell and K+ into the cell.