Instruction: pick the one best answer. This is also useful on the USMLE step 1.
1. What is a collection of nerve cell bodies outside of the central nervous system called?
a. Schwann cells
b. Basket cells
c. Ganglion
d. Neuroglia
e. Satellite cells
Answer: c
Schwann cells are responsible for the myelination of neurons in the peripheral nervous system. Basket cells are a type of neuron seen in the cerebellum. A ganglion is a collection of nerve cell bodies outside of the CNS. Neuroglia are the supporting cells in the central nervous system Sometimes, neuroglia called glial cells or glia. Satellite cells are found in the ganglia of the peripheral nervous system.
2. What percentage of neurons are interneurons?
a. 0.1%
b. 1%
c. 20%
d. 80%
e. 99.9%
Answer: e
Interneurons are the neurons between the sensory and motor neurons. 99.9% of all neurons are interneurons.
3. What are sensory neurons?
a. Unipolar
b. Pseudounipolar
c. Bipolar
d. Multipolar
e. Both a and b
Answer: e
Sensory neurons are unipolar. Unipolar neurons are sometimes also called pseudounipolar.
Neurons can be classified based on the number of axons and dendrites stemming off of the cell body. A unipolar neuron has one process which branches off of it This process then immediately divides into two. Thus, a unipolar neuron is sometimes also called a pseudounipolar neuron. Sensory neurons are unipolar.
A bipolar neuron has two process that branch from it: an axon and a dendrite. Bipolar neurons are not very common and are found in some of the organs for special senses. Bipolar neurons are found in the retina, inner ear, and the region of the nose involved with smell.
Multipolar neurons have one axon and many (at least two) dendrites that branch off of it. Most neurons are multipolar. Motor neurons and interneurons are multipolar.
4. What is the end of an axon called?
a. Ganglion
b. Perikaryon
c. Astrocyte
d. Nissl
e. Terminal bouton
Answer: e
A ganglion is a collection of neuron cell bodies outside of the central nervous system. The cell body of a neuron is called a perikaryon or soma. An astrocyte is a supporting cell seen in the central nervous system. The basophilic clusters of ribosomes and rough endoplasmic seen in neuron cell bodies is called Nissl, Nissl bodies or Nissl substance. The terminal bouton is the end portion of an axon. It is also called an axon terminal or end bulb. The terminal bouton will be associated with another neuron in a synapse.
5. What is the connective tissue covering around the brain and spinal cord?
a. Meninges
b. Myelinated nerve fibers
c. Cell bodies
d. Nodes of Ranvier
e. Neurofilaments
Answer: a
A ganglion is a collection of nerve cell bodies outside of the central nervous system. White matter is myelinated nerve fibers. Gray matter is essentially neuron cell bodies. Nodes of Ranvier are the gaps that occur in the myelin sheath. Neurofilaments are a type of intermediate filaments seen in neurons.
6. Which meninx is made of a dense irregular connective tissue?
a. Dura mater
b. Arachnoid
c. Pia mater
d. Both a and b
e. All of the above
Answer: a
The meninges cover the brain and spinal cord. There are three: dura mater, arachnoid, and pia mater.
The dura mater is the outer meninx. The dura mater is composed of dense irregular connective tissue.
The arachnoid is made of a delicate spider web like connective tissue.
The pia mater is the innermost meninx. It covers the brain intimately.
Note from Sarah Bellham: Arachnoid is derived from the Greek word for spider. It is used in the words arachnophobia, arachnids and arachnoid.
7. What is a group of fibers traveling together?
a. Tracts
b. Islets
c. Soma
d. Cortex
e. Nuclei
Answer: a
A group of fibers traveling together to a destination is a tract. Islets of Langerhans are seen in the pancreas. Soma is another term for a neuron cell body. The outer part of the brain is gray matter called the cortex. The conglomerations of gray matter deep within the cerebrum and cerebellum are called nuclei.
8. Where is white matter?
a. Outer surface of the cerebrum and cerebellum
b. Outer surface of the spinal cord
c. Inner portion of the brain
d. Both a and b
e. Both b and c
Answer: e
The outer part of the cerebrum and cerebellum is gray matter. It is called the cortex. Underneath the cortex, is white matter. Gray matter is also found in conglomerations within the cerebrum and cerebellum where it is called nuclei.
Gray matter is found in the central portion of the spinal cord in a butterfly shape. White matter is on the outer portion of the spinal cord.
Note from Sarah Bellham: Notice that the distribution of gray matter and white matter for the brain and spinal cord is the reverse of each other. On the cerebrum and cerebellum, gray matter is on the outer portion, white matter is deeper. For the spinal cord, white matter is on the outer portion, and gray matter is deeper.
9. Which of the following forms myelin in the central nervous system?
a. Astrocytes
b. Ependymal cells
c. Oligodendrocytes
d. Microglia
e. Schwann cells
Answer: c
Neuroglia are the supporting cells of the central nervous system. Sometimes, neuroglia called glial cells or glia. Astrocytes, ependymal cells, oligodendrocytes, and microglia are all neuroglia.
Of the neuroglia cells, astrocytes are the most abundant and the largest. These are star shaped cells involved in the blood brain barrier.
Ependymal cells line the ventricles and spinal canal.
Oligodendrocytes form myelin in the central nervous system.
Microglia are the central nervous system macrophages.
Schwann cells are seen in the peripheral nervous system and are not considered neuroglia. Schwann cells are responsible for the myelination of neurons in the peripheral nervous system.
10. What is the primary component of myelin?
a. Amino acids
b. Protein
c. Carbohydrate
d. Lipid
e. Both b and c
Answer: d
The primary component of myelin is lipid. It is formed by the cell wrapping itself around the axon. Thus, it is primarily the plasma membrane of either the Schwann cells or the oligodendrocytes.
source: Histology world
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