AP Psychology : Biology

Study concepts, example questions & explanations for AP Psychology

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Example Questions

Example Question #41 : Neurons And Action Potentials

What is an action potential?

Possible Answers:

A short-term change in the polarization of a nerve cell, which allows for communication between cells.

The predisposition of a system to act in a certain way, in keeping with previous behaviors.

The latent energy within a system, which allows it to perform any action.

A chemical compound which is emitted by neurons in the brain in order to signal inhibitory or excitatory responses in others.

None of these

Correct answer:

A short-term change in the polarization of a nerve cell, which allows for communication between cells.

Explanation:

An action potential occurs when a neuron transmits an electrical charge down its axon, which terminates in the release of chemical signals in the form of neurotransmitters. These neurotransmitters communicate with other neurons, allowing for the flow of information between the cells of the nervous system. The chemical compounds emitted by neurons as a result of action potential are known as neurotransmitters. Though the release and binding of neurotransmitters to receptor sites on dendrites may result in either inhibitory or excitatory responses, they themselves are referred to as action potentialsAlthough an action potential is able to occur by way of a maintained electrical gradient within the neuron, it is not correctly described as 'the latent energy of a system'. Likewise, an action potential is not a behavioral predisposition.

Example Question #42 : Biology

Which of the following best describes the role of a neuron?

Possible Answers:

Neurons are responsible for the production of enzymes during digestion

None of these

Neurons are a form of energy storage for the body

Neurons determine the color of wavelengths of light entering the retina

Neurons allow communication between cells within the brain and body

Correct answer:

Neurons allow communication between cells within the brain and body

Explanation:

Neurons transmit electrical signals between one another, which allows for the communication of incoming stimuli from sensory receptors with the brain, communication of internal states of the body, communication between the brain and muscles to coordinate movement, and communication between the many cells of the brain to allow for the complex array of processes that form the basis for our everyday lives. Although neurons in the visual centers of the brain will indeed play a role in processing color information, at the level of the retina this information is derived from the the cones in photoreceptor cells, and subsequently communicated to the brain via the optic nerves. Neurons will communicate messages between the brain and glands of the body, but they themselves are not responsible for the production of enzymes. Neurons do not serve as energy stores for the body.

Example Question #41 : Neurons And Action Potentials

Action potentials are described as being "all or nothing". Why is this?

Possible Answers:

All of these

This is incorrect because action potentials may occur at various intensities, ranging from weak to strong.

None of these

Action potentials occur either in very large quantities, or are scarce.

They either occur, or they do not (i.e. there are no "half", or "semi" action potentials).

Correct answer:

They either occur, or they do not (i.e. there are no "half", or "semi" action potentials).

Explanation:

Action potentials created by neural impulses are described as being "all or nothing" because the cell either gains sufficient stimulation to release an action potential, or it does not. Once the minimum threshold for excitation is reached, an action potential will be triggered regardless of further stimulation, and no signal will be weaker or stronger than any other. That being said, continued stimulation of a neuron may lead to continued firing of action potentials, which may trigger a stronger or enduring response over time. At the scale of the individual action potential; however, the activity of the neuron may be considered as either a value of 0 (i.e. no action potential), or 1 (i.e. action potential). No decimals are used in this measure.

Example Question #41 : Neurons And Action Potentials

What is a neuron's resting potential?

Possible Answers:

Correct answer:

Explanation:

The membrane potential of a neuron rests at -70mV when not receiving stimulation. After receiving sufficient stimulation to pass the threshold potential of -55mV, the action potential triggers, rapidly increasing the membrane potential to a peak of 40mV, before dropping to -90mV during the refractory period, and finally returning to a resting potential of -70mV after the action potential has completed. This entire process can take place in as little as 4 milliseconds. 

Example Question #41 : Neurons And Action Potentials

What is a neuron's resting potential?

Possible Answers:

The chemical state of a neuron receiving no stimulation, and not firing an action potential.

The average time a neuron spends at rest (not performing action potentials).

The electrical state of a neuron receiving no stimulation, and not firing an action potential.

The probability of an individual neuron firing at a given time.

The stage of hyperpolarization in a neuron following an action potential, which must expire before another action potential may be fired.

Correct answer:

The electrical state of a neuron receiving no stimulation, and not firing an action potential.

Explanation:

All animal cells are polarized, because they maintain a difference in voltage between their interiors and their surroundings. This is measured at the cell membranes and known as a membrane potential. The resting potential of a neuron is the value its membrane potential keeps as long as it is not receiving stimulation or undergoing an action potential. In a typical neuron, this resting potential is -70 millivolts (mV). This value does not reflect the average time a neuron spends at rest. The stage of hyperpolarization of a neuron is known as the refractory period. Although the resting potential of a neuron implicates its chemical state and contributes to its probability of firing an action potential, neither of these statements are correct definitions for the term.

Example Question #41 : Biology

Which of the following correctly identifies the stages of an action potential?

Possible Answers:

Refractory period, depolarization, repolarization

Depolarization, repolarization, refractory period

Depolarization, refractory period, repolarization

Refractory period, repolarization, depolarization

Repolarization, refractory period, depolarization

Correct answer:

Depolarization, repolarization, refractory period

Explanation:

A stimulus begins the propagation of the action potential, and channels open to admit sodium into the cell. This leads to a rapid depolarization, as the positively charged sodium ions rush in to balance out the negative resting potential of the neuron (-70mV). At the peak of depolarization, the interior of the cell becomes more positively charged than the exterior. Repolarization subsequently occurs, as the sodium channels are closed, and potassium channels opened in their stead, allowing positively charged potassium ions to exit the cell, restoring the negative membrane potential of the neuron. The refractory period ensues. After the opening and closing of the sodium channels, they are briefly set in an inactive state, and cannot be opened again until the membrane resting potential is restored. During this time, sodium and potassium pumps return sodium to the exterior and potassium to the interior of the cell. As it is impossible for any region of the cell to depolarize during this stage, action potentials may not occur and the neuron is at rest.

Example Question #41 : Neurons And Action Potentials

Action potential

This graph displays the action potential of a neuron. What are the correct labels for the stages labeled A, B, and C?

Possible Answers:

A: Repolarization

B: Refractory Period

C: Depolarization

A: Depolarization

B: Repolarization

C: Refractory Period

A: Refractory Period

B: Depolarization

C: Repolarization

A: Refractory Period

B: Repolarization

C: Depolarization

A: Repolarization

B: Depolarization

C: Refractory Period

Correct answer:

A: Depolarization

B: Repolarization

C: Refractory Period

Explanation:

A stimulus begins the propagation of the action potential, and channels open to admit sodium into the cell. This leads to a rapid depolarization, as the positively charged sodium ions rush in to balance out the negative resting potential of the neuron (-70mV). At the peak of depolarization, the interior of the cell becomes more positively charged than the exterior. Repolarization subsequently occurs, as the sodium channels are closed, and potassium channels opened in their stead, allowing positively charged potassium ions to exit the cell, restoring the negative membrane potential of the neuron. The refractory period ensues. After the opening and closing of the sodium channels, they are briefly set in an inactive state, and cannot be opened again until the membrane resting potential is restored. During this time, sodium and potassium pumps return sodium to the exterior and potassium to the interior of the cell. As it is impossible for any region of the cell to depolarize during this stage, action potentials may not occur and the neuron is at rest.

Example Question #41 : Neurons And Action Potentials

What is the role of the myelin sheath?

Possible Answers:

The myelin sheath insulates neurons and speeds their transmission of signals.

The myelin sheath nourishes the neurons.

The myelin sheath secures neurons in place.

The myelin sheath protects neurons from radiation damage.

The myelin sheath protects neurons from attack by pathogens.

Correct answer:

The myelin sheath insulates neurons and speeds their transmission of signals.

Explanation:

Myelin is a fatty substance produced by glial cells which encases some neurons and serves to insulate them, allowing electrical signals to transmit more quickly along them. Myelin cannot protect the neurons from radiation damage, or from attack by pathogens. Glial cells in the brain form myelin, and contribute to the nourishment and support of nerve cells; however, myelin itself does not serve this function. When myelin deteriorates, nerve transmission can be impaired, as in the case of multiple sclerosis.

Example Question #41 : Neurons And Action Potentials

Which of the following best describes communication between neurons?

Possible Answers:

Neurons communicate through electrical, chemical, and auditory signals.

Neurons communicate through chemical signals only.

Neurons communicate through electrical signals only.

None of these

Neurons communicate through both electrical and chemical signals.

Correct answer:

Neurons communicate through both electrical and chemical signals.

Explanation:

Neurons communicate both through transmission of electrical signals (i.e. action potential), and chemical signals (i.e. neurotransmitters). Although the action potential is triggered by electrical stimulation and propagates along the cell axon as an electrical depolarization, the information carried by this charge is not passed on to the next neuron via the electrical charge itself. Instead, the action potential signals for the release of neurotransmitters from the terminal buttons at the end of the axon, which bind to receptors on the dendrites of linked neurons in a form of chemical communication. It is important to note that auditory signals are not utilized by neurons to communicate.

Example Question #41 : Neurons And Action Potentials

How are neurons different from other cells in the body?

Possible Answers:

Neurons do not have a cell membrane or a cell wall. 

Neurons have specialized parts called axons and dendrites, which help to send and receive information from other neurons.

Neurons do not have a nucleus.

Neurons are only found in the bloodstream.

Neurons have a smaller percentage of cytoplasm.

Correct answer:

Neurons have specialized parts called axons and dendrites, which help to send and receive information from other neurons.

Explanation:

The correct answer is "neurons have specialized parts called axons and dendrites, which help to send and receive information from other neurons." Specifically, axons take information away from the cell body and dendrites bring information to the cell body. Only neurons have these two specialized parts, which helps them to maintain electrochemical communication with other neurons.

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