MCAT Biology : Biology

Study concepts, example questions & explanations for MCAT Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #6 : Glia

Which of the following is a location in the human body where oligodendrocytes will not be found?

Possible Answers:

Frontal lobe

Meninges

Pons

Wernicke's area

Spinal cord

Correct answer:

Meninges

Explanation:

Oligodendrocytes are cells that insulate axons in the central nervous system. They are capable of producing the myelin sheathes for several surrounding cells and are the counterparts of the Schwann cells, which are located in the peripheral nervous system. The central nervous system includes the brain and spinal cord. Oligodendrocytes are responsible for producing the white matter of the central nervous system. The frontal lobe is a region of the cerebrum and will contain myelin. The spinal cord contains distinct white matter and grey matter regions. Wernicke's area is located in the temporal lobe of the cerebrum, and will contain oligodendrocytes. The pons is located in the hindbrain, or brainstem, and will and will also contain oligodendrocytes.

The meninges are the layers of connective tissue that surround the central nervous system. They are made primarily of collagen and do not contain nerve fibers. Oligodendrocytes will not be found in the meninges.

Example Question #7 : Glia

Which of the following describes the difference between oligodendrocytes and Schwann cells?

Possible Answers:

Oligodendrocytes myelinate the central nervous system, while Schwann cells myelinate the peripheral nervous system

Oligodendrocytes and Schwann cell myelinate different structures of the neuron

Both cell types insulate the axons of cells, but use different insulating materials

Oligodendrocytes myelinate the peripheral nervous system, while Schwann cells myelinate the central nervous system

Schwann cells can mylinate multiple axons, while oligodendrocytes can only myelinate one axon per cell

Correct answer:

Oligodendrocytes myelinate the central nervous system, while Schwann cells myelinate the peripheral nervous system

Explanation:

Both oligodendrocytes and Schwann cells are responsible for myelinating axons in order to increase the transmission rate of signals between neurons. The primary difference is their location. Oligodendrocytes myelinate the central nervous system, while Schwann cells myelinate the peripheral nervous system. Oligodendrocytes are also capable of myelinating multiple axons, while Schwann cells can only myelinate one axon per cell.

Example Question #8 : Glia

Which of the following structures creates a myelin sheath for axons in the central nervous system?

Possible Answers:

Nodes of Ranvier

Axon hillock

Schwann cells

Oligodendrocytes

Correct answer:

Oligodendrocytes

Explanation:

Oligodendrocytes and Schwann cells both create myelin sheaths for axons, however, oligodendrocytes function in the central nervous system and Schwann cells function in the peripheral nervous system.

Example Question #9 : Glia

Diseases which destroy the myelin sheath of neurons cause __________.

Possible Answers:

cancer

decreased pain perception

an increase in the speed of nerve conduction

no change

a decrease in the speed of nerve conduction

Correct answer:

a decrease in the speed of nerve conduction

Explanation:

Myelin sheathes function in insulating the neuron, and allows for much faster propogation of the action potential due to saltatory conduction. Loss of the myelin sheath would slow conduction of signals down the neural axon.

Pain perception is conducted to free nerve endings known as nociceptors, which are not myelinated.

Example Question #10 : Glia

Excessive stimulation of the ulnar nerve results in the sensation known as the "funny bone," and can cause discomfort in the elbow and forearm. What cells are responsible for the myelination of the ulnar nerve?

Possible Answers:

Oligodendrocytes

Schwann cells

Astrocytes

Dendritic cells

Correct answer:

Schwann cells

Explanation:

There are two types of cells responsible for the myelination of axons throughout the nervous system. Oligodendrocytes myelinate the axons of neurons in the central nervous system. Schwann cells myelinate neurons in the peripheral nervous system. This question is referring to a nerve in the elbow, which would be in the peripheral nervous system.

Astrocytes are a type of glial cell primarily found in the blood-brain barrier. Dendritic cells play a role in the adaptive immune response, and are not considered part of the nervous system.

Example Question #141 : Biology

Which of the following glial cells produces cerebrospinal fluid?

Possible Answers:

Astrocytes

Ependymal cells

Oligodendrocytes

Microglia

Satellite cells

Correct answer:

Ependymal cells

Explanation:

Ependymal cells, which line cerebral cavities and the central canal, produce cerebrospinal fluid (CSF). CSF is a colorless liquid that protects the brain and spinal cord against injury.

Microglia protect the central nervous system from microbes and debris of injured cells. Astrocytes, located in the central nervous system, provide structural support for neurons in addition to many other tasks involving nutrient and ion regulation. Oligodrendrocytes produce the myelin sheath around the axons of the central nervous system. Satellite cells are not found in the central nervous system, and therefore cannot produce CSF.

Example Question #142 : Biology

What is the major difference between Schwann cells and oligodendrocytes?

Possible Answers:

Oligodendrocytes myelinate central nervous system axons, whereas Schwann cells myelinate peripheral nervous system axons

Schwann cells myelinate axons, while oligodendocytes myelinate dendrites

Schwann cells are the most common glial cell type

Action potentials propagate faster down axons myelinated by Schwann cells

Oligodendrocytes myelinate axons and dendrites, whereas Schwann cells only myelinate axons

Correct answer:

Oligodendrocytes myelinate central nervous system axons, whereas Schwann cells myelinate peripheral nervous system axons

Explanation:

Both oligodendrocytes and Schwann cells produce and maintain myelin along axons. Oligodendrocytes are the most common glial cell type, and provide myelination for all neural axons in the central nervous system. Schwann cells provide myelination for neurons in the peripheral nervous system.

Example Question #1 : Understanding Nervous System Structures

An individual presents to his physician with an abnormal breathing rhythm. The physician suspects that the problem may be originating from his brain. What part of his brain is most likely not functioning properly?

Possible Answers:

Cerebellum

Medulla oblongata

Hypothalamus

Midbrain

Hippocampus

Correct answer:

Medulla oblongata

Explanation:

The medulla oblongata is responsible for autonomic functions, such as breathing rate and heart rate regulation. Dysfunction of the medulla oblongata could result in problems with breathing rhythm.

The cerebellum is responsible for coordination and balance. The hypothalamus regulates the fight-or-flight response, sex drive, thirst, and hunger. The midbrain is the center for auditory and visual signal relay to the cortex. The hippocampus functions in the retention of memories.

Example Question #143 : Biology

Which of the following structures connects the right and left hemispheres of the brain?

Possible Answers:

Hypothalamus

Olfactory bulb

Mammillary Body

Stria terminalis

Corpus collosum

Correct answer:

Corpus collosum

Explanation:

The MCAT contains minimal questions regarding brain anatomy, however, you should have an understanding of a select few structures, one of which is the corpus collosum. The corpus collosum is a bundle of neurons connecting the left and right brain, allowing communication between the left and right hemispheres. If these neurons were damaged somehow, the result would be split-brain syndrome, a condition in which the two halves of the brain do not communicate with one another.

Example Question #144 : Biology

Which of the following activities would you expect to be controlled by the cerebral cortex?

Possible Answers:

Memory

Heart rate

Breathing while asleep

Salivation

Correct answer:

Memory

Explanation:

The cerebral cortex is also referred to as the "higher brain." It acts to process thoughts and store memories. More basic, vital activities such as heart beat and breathing are controlled by other, less developed regions of the brain. Note that the hippocampus plays a role in creating memories, but most memories are stored in the cerebrum; this is the link between long term and short term memory storage.

Learning Tools by Varsity Tutors