MCAT Biology : Neuron Structure and Types of Neurons

Study concepts, example questions & explanations for MCAT Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Nervous System And Nervous Tissue

In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon. 

Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.

 

Untitled

In the cell body associated with the axon depicted in Figure 1, integration of incoming electrical signals is necessary in order to determine whether or not an action potential is initiated by the cell. The region where this integration takes place is the __________.

Possible Answers:

Axon hillock

Suprachiasmatic nucleus

Nucleolus

Supraoptic nucleus

Nissl body

Correct answer:

Axon hillock

Explanation:

The axon hillock is located near the boundary of the cell body and the beginning of the axon. This region is where the totality of incoming nervous signals onto a single cell are summed, and only if this sum meets the threshold does the axon fire an action potential itself.

Example Question #64 : Systems Biology And Tissue Types

How does the sodium-potassium pump accomplish its function of maintaining the electrochemical potential across a cell membrane?

Possible Answers:

It passively moves three sodium ions out of the cell and two potassium ions in, both against their concentration gradients

It actively moves three sodium ions out of the cell and two potassium ions in, both against their concentration gradients

It actively moves two sodium ions out of the cell and three potassium ions in, both against their concentration gradients

It passively moves three sodium ions out of the cell and two potassium ions in, both along their concentration gradients

None of these answers are correct

Correct answer:

It actively moves three sodium ions out of the cell and two potassium ions in, both against their concentration gradients

Explanation:

The sodium-potassium pump moves three sodium ions out of the cell for every two potassium ions it moves in. ATP is used to accomplish this because the direction of movement for both ions is against their concentration gradients.

By removing three sodium ions for the entry of every two potassium ions, the pump creates an electrical imbalance: three positive charges exit the cell, but only two enter. There is a net movement of positive charge out of the cell, leading to the electrochemical gradient. The ion imbalance leads to the negative resting potential of the cell.

Example Question #3 : Nervous System And Nervous Tissue

The sodium-potassium pump is an antiporter that moves sodium ions out of the cell and potassium ions into the cell. This pumping action requires ATP. What can you conclude about the electrochemical gradient of sodium?

Possible Answers:

Sodium concentration is higher outside the cell because the pump drives sodium ions along their electrochemical gradient

Sodium concentration is lower outside the cell because the pump drives sodium ions against their electrochemical gradient

Sodium concentration is lower outside the cell because the pump drives sodium ions along their electrochemical gradient

Sodium concentration is higher outside the cell because the pump drives sodium ions against their electrochemical gradient

Correct answer:

Sodium concentration is higher outside the cell because the pump drives sodium ions against their electrochemical gradient

Explanation:

The question states that the sodium-potassium pump requires ATP, indicating that the pumping action uses energy and is classified as active transport. Recall that active transport involves movement of molecules against their electrochemical gradient. This means that the sodium and potassium ions are moved against their gradients. Since they are moving against their gradients, sodium and potassium ions must move from a region of low concentration to a region of high concentration.

The question states that sodium ions are moving from the inside to the outside of the cell; therefore, there must be a higher concentration of sodium ions outside the cell than inside the cell.

Example Question #4 : Nervous System And Nervous Tissue

In humans, nerve impulses are transmitted with the coordinated action of sodium and potassium ion channels. These channels open in a specific sequence, to allow for membrane potential changes to take place in a directional manner along the length of an axon. 

Figure 1 depicts a single phospholipid layer of a cell membrane, and three transmembrane channels important to action potential propagation.

 

Untitled

The cell body associated with the axon depicted in Figure 1 takes in neural impulses from a variety of other neurons. A tract that carries such impulses into the cell body is __________.

Possible Answers:

called a dendrite, and a neuron always has only one dendrite and one axon

called a dendrite, and uses ions different from the sodium and potassium used by axons to conduct signals

called a dendrite, and is always myelinated by oligodendrocytes

called a dendrite, and is always myelinated by Schwann cells

called a dendrite, and is often present in greater numbers on a single cell than the single axon

Correct answer:

called a dendrite, and is often present in greater numbers on a single cell than the single axon

Explanation:

A dendrite carries electrical signals into the cell body of a neuron. This dendrite, however, is typically not myelinated like the axon. There are also frequently many dendrites, while a single axon is the typical rule. Different types of neural cells can carry different arrangements of dendrites depending on their function.

Example Question #5 : Nervous System And Nervous Tissue

Which component of a neuron is responsible for electochemically stimulating nearby cells?

Possible Answers:

Dendrite

Soma

Nucleus

Axon

Correct answer:

Axon

Explanation:

The axon ends in a terminal bud, which transmits signals to target cells by releasing neurotransmitters across the synapse. The soma is the body of the cell and contains the nucleus. This is where the majority of protein synthesis occurs. The dendrites receive electrochemical stimuli from other neurons and cells and transmit the signal to the soma and axon.

Example Question #6 : Nervous System And Nervous Tissue

The primary purpose of the sodium/potassium pump is to __________.

Possible Answers:

export two sodium ions, import three potassium ions, and cause an action potential

export three sodium ions, import two potassium ions, and establish cell membrane resting potential

export two potassium ions, import three sodium ions, and cause an action potential

export two sodium ions, import three potassium ions, and establish cell membrane resting potential

export two potassium ions, import three sodium ions, and establish cell membrane resting potential

Correct answer:

export three sodium ions, import two potassium ions, and establish cell membrane resting potential

Explanation:

Na+/K+ ATPase always exports three sodium ions out of the cell and imports two potassium ions into the cell. The export of three positively charged sodium ions for the import of only two positively charged potassium ions results in a net -70mV charge across the cell membrane, which is known as the cell membrane resting potential.

Example Question #1 : Nervous System And Nervous Tissue

Which of the following is NOT true of the neural soma and axon?

Possible Answers:

Increased ribosomal activity in the axon hillock

Decreased voltage-gated sodium channel density in the soma

Nodes of Ranvier distinct on the axon only

Increased mitochondrial activity in the axon

Lack of myelination in the soma

Correct answer:

Increased ribosomal activity in the axon hillock

Explanation:

All of the following are true characteristics of the neural axon and soma except “increased ribosomal activity in the axon hillock.” The axon hillock is a site of neurotransmitter transport. These molecules are produced and packaged in the soma of the neuron, before being translocated to the axon hillock via microtubule tracks. There is little to no ribosomal activity in the axon of a neuron, since most ribosomes are located near the nucleus of a cell, which is the site of mRNA release.

Example Question #2 : Nervous System And Nervous Tissue

What is the source of neurons and glia that innervate the pancreas?

Possible Answers:

Cranial nerves

Enteric nervous system

Central nervous system

Somatic nervous system

Correct answer:

Enteric nervous system

Explanation:

The enteric nervous system (ENS) is a component of the autonomic nervous system, which is a component of the peripheral nervous system. The ENS is responsible for innervating the digestive organs and, thus, regulating digestion.

The central nervous system is composed of the brain and spinal cord, while the peripheral nervous system prolifertates the body. The somatic nervous system is under voluntary control, while the autonomic is involuntary. The cranial nerves are a set of specialized nerves that branch directly off of the spinal cord.

Example Question #9 : Nervous System And Nervous Tissue

Ependymal cells are a type of glial cells that __________.

Possible Answers:

synthesize and secrete myelin 

phagocytose bacteria or damaged neurons within the central nervous system

release neurotransmitters into the synapse 

help create the blood-brain barrier 

secrete cerebrospinal fluid in the central nervous system

Correct answer:

secrete cerebrospinal fluid in the central nervous system

Explanation:

Along with capillaries, the ependymal cells create the choroid plexus. The choroid plexus is responsible for synthesizing and secreting cerebrospinal fluid around the brain and the spinal cord. 

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: