Neuron Structure and the Action Potential

Question 1

Which part of a neuron contains the nucleus and most major organelles?

Accepted Answer

Soma (or cell body)

Question 2

What is the specific region of a neuron where the axon emerges from the cell body?

Accepted Answer

Axon hillock

Question 3

Neuron — What is the functional purpose of the "trigger zone"?

Accepted Answer

Site where action potentials are generated

Question 4

What are the gaps in the myelin sheath along an axon called?

Accepted Answer

Nodes of Ranvier

Question 5

Which neuron type has one axon and two or more dendrites?

Accepted Answer

Multipolar neuron

Question 6

In humans, where are the cell bodies of unipolar (pseudo-unipolar) sensory neurons located?

Accepted Answer

Ganglia

Question 7

Which CNS glial cell type is responsible for maintaining the blood-brain barrier (BBB)?

Accepted Answer

Astrocytes

Question 8

Contrast the location of oligodendrocytes versus Schwann cells.

Accepted Answer

Oligodendrocytes are in the CNS; Schwann cells are in the PNS

Question 9

What is the primary function of microglia in the central nervous system?

Accepted Answer

Immune surveillance and phagocytosis

Question 10

What are the three major functions of the nervous system?

Accepted Answer

Sensation, integration, and response

Question 11

Which brain structure acts as the primary relay station for sensory information?

Accepted Answer

Thalamus

Question 12

How does a graded potential differ from an action potential in terms of stimulus strength?

Accepted Answer

Graded potential size depends on stimulus strength; action potentials are all-or-none

Question 13

Where does an upper motor neuron typically send its signal?

Accepted Answer

To a lower motor neuron in the spinal cord

Question 14

What is the standard value for the resting membrane potential of a neuron?

Accepted Answer

$-70\text{ mV}$

Question 15

Which ion is found in much higher concentrations outside the cell than inside?

Accepted Answer

Sodium ($Na^+$)

Question 16

How many ions does the $Na^+/K^+$ pump move, and in which direction?

Accepted Answer

3 $Na^+$ out, 2 $K^+$ in

Question 17

What type of ion channel opens in response to a chemical messenger binding to it?

Accepted Answer

Ligand-gated channel (or ionotropic receptor)

Question 18

What determines "electrochemical exclusion" in an ion channel?

Accepted Answer

The charge of the amino acids lining the pore

Question 19

Which channel type is responsible for the random "leakage" that helps maintain resting potential?

Accepted Answer

Leakage channel

Question 20

During an action potential, what causes the rapid depolarization phase?

Accepted Answer

Influx of sodium ($Na^+$) through voltage-gated channels

Question 21

What happens to the membrane during repolarization?

Accepted Answer

Potassium ($K^+$) exits the cell

Question 22

What is the typical threshold voltage required to initiate an action potential?

Accepted Answer

$-55\text{ mV}$

Question 23

What is the difference between an EPSP and an IPSP?

Accepted Answer

EPSP depolarizes (toward threshold); IPSP hyperpolarizes (away from threshold)

Question 24

Which type of summation occurs when multiple signals arrive at the same location at different times?

Accepted Answer

Temporal summation

Question 25

What is the role of Calcium ($Ca^{2+}$) at the axon terminal?

Accepted Answer

Triggers the release of neurotransmitter vesicles via exocytosis