Nerves and Action Potentials

The term central nervous system refers to the:

• autonomic and peripheral nervous systems

• brain, spinal cord, and cranial nerves

• brain and cranial nerves

• spinal cord and spinal nerves

• brain and spinal cord

The Schwann cell forms a myelin sheath around the:

• dendrites

• cell body

• nucleus

• axon

• nodes of Ranvier

The neuron processes that normally receive incoming stimuli are called:

• axons

• dendrites

• neurolemmas

• Schwann cells

• satellite cells

Impulse conduction is fastest in neurons that are:

• myelinated

• unmyelinated

• sensory

• motor

• cerebral

An action potential is caused by an influx of these ions into the cell:

• potassium

• sodium

• calcium

• magnesium

• both potassium and sodium

Which one of the following is the correct sequence of events:

1. the membrane becomes depolarized
2. sodium channels open and sodium ions diffuse in
3. the membrane become repolarized
4. potassium channels open and potassium ions diffuse inward while sodium is actively transported out of the cell

• 3,2,4,1

• 2,1,4,3

• 2,1,3,4

• 1,2,4,3

• 4,1,3,2

When a neuron is depolarized, what are the first channels to open?

• Sodium
• Potassium
• Calcium
• ACTH

When a neuron is resting, the inside of the axon has a ____________ charge.

• -55 mV
• -70 mV
• 40 mV
• -75 mV

When a neuron is not engaged in an impulse.

• Resting potential
• Action potential
• Neural potential
• Synaptic potential

Why is -55 mV a significant number?

• This is the largest charge achieved during an action potential
• This is the threshold required to complete an action potential
• This is the resting charge of a neuron
• This is the charge when all the sodium is inside the cell