Nerve Cells and Nerve Impulses

Question 1

The nervous system is composed of two types of cells: ______ and _____.

Answer 1

neurons and glia

Question 2

Which part of an animal cell is a network of tubes that modifies & transports proteins?

a) Nucleus
b) Ribosomes
c) Endoplasmic reticulum
d) Plasma membrane
e) Mitochondrion

Answer 2

c) Endoplasmic reticulum

A network of thin tubes that transports newly
synthesized proteins to other locations. Ribosomes may be attached.

Question 3

What is the nucleus?

a) structure that contains DNA; genetic material
b) synthesizes new proteins
c) network of tubes that modifies & transports proteins
d) separates the inside of the cell from the outside
e) performs metabolic activities (makes energy)

Answer 3

a) structure that contains DNA; genetic material

The structure that contains the chromosomes

Question 4

What does a neuron do?

Answer 4

Receive information and transmit it to other cells.

Question 5

What is the mitochondrion?

a) structure that contains DNA; genetic material
b) synthesizes new proteins
c) network of tubes that modifies & transports proteins
d) separates the inside of the cell from the outside
e) performs metabolic activities (makes energy)

Answer 5

e) performs metabolic activities (makes energy)

Mitochondrion: The structure that provides the cell with energy. It requires
fuel and oxygen to function

Question 6

Approximately how many neurons are in the human brain?

Answer 6

100 billion neurons

The human brain contains approximately 100 billion neurons (though that
estimate varies from person to person).

Question 7

Which part of an animal cell synthesizes new proteins?

a) Nucleus
b) Ribosomes
c) Endoplasmic reticulum
d) Plasma membrane
e) Mitochondrion

Answer 7

b) Ribosomes

Site of protein synthesis in the cell

Question 8

What are the four major components of larger neurons?

Answer 8

dendrites, cell body, axon, and presynaptic terminal.

Larger neurons contain four major components: dendrites, cell body, axon, and presynaptic terminal.

The tiniest neurons may lack axons and well-defined
dendrites

Question 9

Branching fibers that extend from the cell body and get
narrower at their end are:
a) Dendrites
b) Dendritic spines
c) Cell body (soma)
d) Axon
e) Myelin sheath: 
f) Nodes of Ranvier
g) Presynaptic terminal

Answer 9

a) Dendrites

Dendrites: Branching fibers that extend from the cell body and get
narrower at their end. The dendrite’s surface is lined with specialized
synaptic receptors, at which the dendrite receives information from
other neurons.

Question 10

List five types of glia.

Answer 10

Astrocytes
Microglia
Oligodendrocytes
Schwann cells
Radial glia

Question 11

What kind of neuron Conducts impulses to muscles and glands from the
spinal cord? 
a) Purkinje cell
b) Motor neuron
c) Sensory neuron
d) Pyramidal cell

Answer 11

b) Motor neuron

Question 12

Swelling at the tip of the axon is the:

a) Dendrites
b) Dendritic spines
c) Cell body (soma)
d) Axon
e) Myelin sheath:
f) Nodes of Ranvier
g) Presynaptic terminal

Answer 12

g) Presynaptic terminal

Presynaptic terminal (end bulb): Swelling at the tip of the axon. The
part of the neuron that releases chemicals that cross the junction between
one neuron and the next.

Question 13

Define nodes of Ranvier.

Answer 13

Interruptions along the myelin sheath

Question 14

Glia are _______ and ________ than neurons:

a) larger and less numerous
b) smaller and less numerous
c) larger and more numerous
d) smaller and more numerous

Answer 14

d) smaller and more numerous

Glia are smaller and more numerous than neurons.

Question 15

Which neuron is sensitive to certain kinds of
stimulation (e.g., light, touch, etc.)?
a) Purkinje cell
b) Motor neuron
c) Sensory neuron
d) Pyramidal cell

Answer 15

c) Sensory neuron

Question 16

A long, thin fiber, which is the information-sending part of the neuron, sending an electrical impulse
toward other neurons, glands, or muscles is the: 
a) Dendrites
b) Dendritic spines
c) Cell body (soma)
d) Axon
e) Myelin sheath: 
f) Nodes of Ranvier
g) Presynaptic terminal

Answer 16

d) Axon

Axon: A long, thin fiber (usually longer than dendrites), which is the
information-sending part of the neuron, sending an electrical impulse
toward other neurons, glands, or muscles.

Question 17

What brings information into a structure?

a) Afferent axons
b) Efferent axons
c) Interneurons

Answer 17

a) Afferent axons

Question 18

Which type of glia absorbs chemicals released by axons and later returns those chemicals back to the axon, remove waste products, cause blood vessels to dilate and recycles glutamate?

Answer 18

Astrocytes: A type of glia that absorbs chemicals released by axons and later
returns those chemicals back to the axon to help synchronize the activity of
neurons. Astrocytes remove waste products as well, particularly those created
after neurons die. Astrocytes also cause blood vessels to dilate to bring in more nutrients at times of increased brain activity. They act as a recycling system for glutamate released by neurons (absorbing excess glutamate then converting it
to glutamine and passing it back into the neurons).

Question 19

What is the cell body (soma) of a neuron?

Answer 19

Cell body (soma): Contains the nucleus, ribosomes, mitochondria, and
other structures found in most cells

Question 20

Neurons entirely located within a single structure of the nervous system are said to be:

a) Afferent
b) Efferent
c) Interneurons

Answer 20

c) Interneurons

Question 21

Why do we need a Blood-Brain Barrier? (5 reasons)

Answer 21

1. The blood-brain barrier is needed because the brain lacks the type of immune
   system present in the rest of the body.
2. Because neurons cannot be replicated and replaced, the barrier is in place to
   minimize the risk of irreparable brain damage.
3. A wall is formed that keeps out most viruses, bacteria, and harmful chemicals.
4. When viruses do enter, like the rabies virus, it can infect the brain and lead to
   death.
5. A virus that enters your nervous system probably stays with you for life (e.g.,
   chicken pox and shingles)

Question 22

What is the refractory period?

Answer 22

The refractory period is a period immediately after an action potential occurs
when the neuron will resist the production of another action potential.

Question 23

Which two glia build the myelin sheaths around certain neurons, and where is each located?

a) Astrocytes
b) Microglia
c) Oligodendrocytes
d) Schwann cells
e) Radial glia

Answer 23

CNS Oligodendrocytes: A type of glia that builds the myelin sheaths around certain
neurons in the brain and spinal cord.

PNS Schwann cells: A type of glia that builds the myelin sheaths around certain
neurons in the periphery of the body.

Question 24

What do efferent axons do?

Answer 24

Sends information away from a structure

Question 25

What does the blood brain barrier do?

Answer 25

It keeps out most viruses, bacteria, and harmful chemicals. The only molecules that can cross the blood brain barrier are molecules for which there is a specific transport mechanism, or molecules which are electrically neutral and thus lipid soluble.

Question 26

What is the cell membrane made of?

Answer 26

Lipid bilayer of cell membrane is made of phospholipid molecules

Question 27

What is the typical resting | membrane potential of a neuron?

Answer 27

-70 millivolts (mV) This may vary from one neuron to another.

Question 28

During the resting potential, chloride channels (or gates) are: a) open b) closed c) mostly closed d) mostly open

Answer 28

a) open During the resting potential, chloride channels (or gates) remain open along the membrane, which allows ions to pass through

Question 29

What cells guide the migration of neurons and the growth of axons and dendrites during embryonic development? a) Astrocytes b) Microglia c) Oligodendrocytes d) Tubule filaments e) Radial glia

Answer 29

e) Radial glia Radial glia: Guides the migration of neurons and the growth of axons and dendrites during embryonic development.

Question 30

During the resting potential, potassium channels (or gates) are: a) open b) closed c) mostly closed d) mostly open

Answer 30

c) mostly closed Potassium channels are mostly closed, causing potassium to cross the membrane slowly

Question 31

What cells builds the myelin sheaths around certain neurons in the brain and spinal cord?

Answer 31

Oligodendrocytes (CNS)

Question 32

What blocks most molecules from passing through the Blood Brain Barrier?

Answer 32

Endothelial cells form walls of the capillaries. These cells are tightly joined in the brain, blocking most molecules from passing. In the rest of the body, the endothelial cells are separated by large gaps.

Question 33

Which glia cells remove waste material as well as viruses, fungi, and other microorganisms? a) Astrocytes b) Microglia c) Oligodendrocytes d) Tubule filaments e) Radial glia

Answer 33

b) Microglia Microglia: Very small cells that remove waste material as well as viruses, fungi, and other microorganisms.

Question 34

During the resting potential, sodium channels (or gates) are: a) open b) closed c) mostly closed d) mostly open

Answer 34

b) closed Sodium gates remain closed, restricting the passage of sodium ions

Question 35

What can cross passively (without using energy) through the blood-brain barrier? a) necessary chemicals (e.g. glucose) b) Small uncharged molecules c) Small charged molecules (i.e. ions) d) Most medicines and drugs

Answer 35

b) Small uncharged molecules Small uncharged molecules (e.g., oxygen and carbon dioxide) and molecules that can dissolve in the fats of the capillary wall can cross passively (without using energy) through the blood-brain barrier.

Question 36

The neuron membrane is selectively permeable. State which of the following can cross, and how. a. water b. glucose c. sodium d. carbon dioxide

Answer 36

a. water can pass freely (though is slowed by polar regions) b. glucose is actively transported across (uses GLUT receptors, which are insulin-dependent in some cell types) c. sodium passively passes through sodium gates (which are closed at resting potential) and via active transport through the Sodium-potassium pump which transports three sodium ions outside of the cell while also drawing two potassium ions d. carbon dioxide can pass freely (passive diffusion across membrane re concentration gradient)

Question 37

At rest, describe the forces at work on sodium ions regarding the: a) electrical gradient b) concentration gradient

Answer 37

The electrical gradient: opposite electrical charges attract, so sodium (which is positively charged) is attracted to the negative charge inside the cell. The concentration gradient (difference in distribution of ions between the inside and the outside of the membrane): Sodium is more concentrated outside the membrane than inside and is thus more likely to enter the cell than to leave it. Given that both the electrical and concentration gradients tend to move sodium into the cell, sodium would be expected to quickly enter the cell. However, when the membrane is at rest, sodium channels are closed.

Question 38

What is hyperpolarization?

Answer 38

Hyperpolarization (increased polarization): Occurs when the negative charge inside the axon increases (e.g., -70 mV becomes -80 mV)

Question 39

Potassium ions are: a) Positively charged b) Negatively charged

Answer 39

a) Positively charged

Question 40

``` When the negative charge inside the axon decreases (e.g., -70 mV becomes -55 mV), it is called: a) Action potential b) Hyperpolarization c) Depolarization d) Threshold of excitation ```

Answer 40

c) Depolarization Depolarization (reduce polarization towards zero): Occurs when the negative charge inside the axon decreases (e.g., -70 mV becomes -55 mV).

Question 41

What can crosses through the blood-brain barrier via an active transport system (a protein-mediated process that uses energy)? a) necessary chemicals (e.g. glucose) b) Small uncharged molecules c) Small charged molecules (i.e. ions) d) Most medicines and drugs

Answer 41

a) necessary chemicals (e.g. glucose) An active transport system (a protein-mediated process that uses energy) exists to pump necessary chemicals, such as glucose, through the blood-brain barrier