AP Biology : Understanding Neurons

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Neurons

Action potentials move down myelinated axons via saltatory conduction. This is because __________.

Possible Answers:

they jump from the middle of the gaps to the middle of the myelin sheaths

additional impulses boost their speed periodically

they speed up dramatically in areas with more myelin wrapping, depending on the thickness of the sheath

they jump from gap to gap in between the myelin sheaths

Correct answer:

they jump from gap to gap in between the myelin sheaths

Explanation:

The tiny gaps in between myelin sheaths are referred to as nodes of Ranvier. The action potential will jump from node to node as it moves down the axon.

If an axon existed without these gaps (the entire length was covered in myelin), it would be unable to conduct an action potential.

Example Question #2 : Nervous System

Which portion of a neuron receives neurotransmitters from a previous neuron, signaling the need for propagation of action potential?

Possible Answers:

Synaptic terminal

Axon

Dendrites

Soma

Correct answer:

Dendrites

Explanation:

Neurotransmitters from presynaptic cells are received by the dendrites of postsynaptic cells. There are myriad dendrites on each neuron that then propagate this signal to the soma (or cell body), allowing the signal to be passed down the axon to another neuron.

Example Question #2 : Understanding Neurons

Which of the following statements about axons is true?

Possible Answers:

There are often numerous axons for each neuron

The axon carries action potentials away from the cell body of a neuron

The axon contains the cell nucleus

The axon is the site of neurotransmitter production

Correct answer:

The axon carries action potentials away from the cell body of a neuron

Explanation:

The axon carries action potentials away from the cell body of a neuron via a sequence of continuous depolarization. The cell body, or soma, however, is the site of neurotransmitter production and the location of the nucleus and other organelles. Every single neuron contains only one axon.

Example Question #4 : Nervous System

Which of the following is responsible for creating myelin, for the myelin sheaths of axons?

Possible Answers:

Schwann cells and oligodendrocytes

Schwann cells only

Oligodendrocytes only

None of the other answers are correct

Correct answer:

Schwann cells and oligodendrocytes

Explanation:

Schwann cells produce myelin for neurons of the peripheral nervous system, while oligodendrocytes produce myelin for neurons of the central nervous system.

Example Question #2 : Nervous System

Which of the following best describes the order of information processing in a neuron?

Possible Answers:

Dendrite, cell body, axon, synaptic terminal

Dendrite, axon, synaptic terminal, cell body

Dendrite, synaptic terminal, cell body, axon

Dendrite, axon, cell body, synaptic terminal

Synaptic terminal, dendrite, cell body, axon

Correct answer:

Dendrite, cell body, axon, synaptic terminal

Explanation:

A neuron receives input from other neurons at the dendrites. Neurotransmitters released by other neurons bind to receptors on the dendrites, which carry the signal to the cell body. The signal is then amplified in the cell body before being transferred to the axon. Once the signal transitions to the axon, it is considered an action potential. The signal eventually reaches the end of the axon, where the synaptic vesicles are located, and stimulates release of neurotransmitters to the next neuron's dendrites.

Example Question #3 : Understanding Neurons

Which of the following is true regarding a neuron?

Possible Answers:

If an electrical disturbance is large enough in the cell body, the signal generates an action potential at the dendrite

The propagation of signal through a neuron initiates at the dendrite, enters the cell body, and is transmitted from the axon

Neurons transmit electrical signals from one cell to the other at the cell body

Neurons contain multiple dendrites and cell bodies

Correct answer:

The propagation of signal through a neuron initiates at the dendrite, enters the cell body, and is transmitted from the axon

Explanation:

Neurons have many dendrites, one cell body, and a single axon with several terminal branches. A dendrite receives an external stimulus and causes an electrical disturbance in the cell body. This electrical disturbance is transmitted to the axon, where an action potential is generated if the stimulus is large enough. The action potential is propagated through the axon and is transmitted to a neighboring neuron at the synapse.

A large enough electrical disturbance will generate an action potential in the axon, but no magnitude of stimulus can create an action potential in the dendrites. Neurons do contain multiple dendrites, but they only contain one cell body and one axon. Finally, neurons transmit electrical signals to other neurons at the synapse, not at the cell body.

Example Question #7 : Nervous System

An electrical synapse uses __________ to transmit electrical signals between neurons.

Possible Answers:

desmosomes

gap junctions

anchoring junctions

tight junctions

Correct answer:

gap junctions

Explanation:

There are two types of synapses: chemical and electrical. Chemical synapses use chemical signals called neurotransmitters to transmit nerve signals between neurons, whereas electrical synapses use electrical signals. These electrical signals are transmitted through a gap junction that connects adjacent neurons. Intercalated discs in cardiac muscle contain gap junctions for the purpose of propagating electrical signals to cause systole.

Example Question #4 : Nervous System

Which of the following cells is found in the peripheral nervous system?

Possible Answers:

Oligodendrocytes

Astrocytes

Ependymal cells

Schwann cells

Microglia

Correct answer:

Schwann cells

Explanation:

While both oligodendrocytes and Schwann cells produce myelin sheaths that insulate nervous system signals, only the Schwann cells are found in the peripheral nervous system.

All other cells listed are found only in the central nervous system. Microglia act as immune cells within the cerebrospinal fluid, since lymphocytes are barred entry by the blood-brain barrier. Astrocytes support the neural cells and provide nutrients. Ependymal cells are responsible for secreting cerebrospinal fluid.

Example Question #4 : Understanding Neurons

Which of the following cells are responsible for speeding up the action potentials along the axon of a neuron?

Possible Answers:

Astrocytes

Schwann cells

Ependymal cells

Glial cells

Myocytes

Correct answer:

Schwann cells

Explanation:

The correct answer is Schwann cells. Schwann cells are cells that produce the myelination present on the outer covering of the axon of the neuron. This lipid-rich material helps facilitate the movement of the action potential along the axon from the axon hillock to the axon terminal branches.

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