Week 12 Quiz

An axon in a nerve that runs down the leg is wrapped in myelin. Which glial cell made that myelin, and what does the myelin do to the signal?

Select one.

• A Schwann cell; it lets the signal jump node to node, so conduction is faster
• An oligodendrocyte; it lets the signal jump node to node, so conduction is faster
• A Schwann cell; it covers the whole axon, so conduction is slower
• An astrocyte; it forms a barrier, so the signal stops at each node

A neuron is resting and not firing. Which value describes its resting membrane potential?

Select one.

• About +70 mV, with the inside positive
• About −70 mV, with the inside negative
• About −55 mV, with the inside negative
• About +30 mV, with the inside positive

In the course's illustrative ruler-drop set, five catches land at 18, 22, 19, 21, and 20 cm. What is the average catch distance?

Select one.

• 100 cm
• 4 cm
• 20.0 cm
• 22 cm

Which sequence puts the phases of an action potential in the correct order, starting from rest?

Select one.

• Rest → repolarization → depolarization → hyperpolarization → rest
• Rest → hyperpolarization → depolarization → repolarization → rest
• Rest → depolarization → hyperpolarization → repolarization → rest
• Rest → depolarization → repolarization → hyperpolarization → rest

Which ion movement drives the rising phase, depolarization, of an action potential?

Select one.

• Na⁺ rushing into the neuron
• K⁺ flowing out of the neuron
• Na⁺ pumped out of the neuron
• K⁺ pumped into the neuron

A neuron rests at −70 mV and reaches threshold at −55 mV. How large is the rise from rest to threshold?

Select one.

• 125 mV
• −15 mV
• 15 mV
• 55 mV

Once a neuron reaches threshold, a stronger stimulus produces a bigger action potential than a weaker one.

True or false.

• True
• False

Select every statement that describes the sodium-potassium pump in a neuron's membrane.

Select every option that applies.

• It moves 3 Na⁺ out and 2 K⁺ in for each ATP it spends
• It restores the ion gradients after the spike
• It moves ions against their gradients, so it is active transport
• It opens at threshold and lets Na⁺ rush in during depolarization
• It moves 3 K⁺ in and 2 Na⁺ out for each ATP it spends

During depolarization, Na⁺ flows into the neuron through voltage-gated channels, down its gradient, with no ATP spent. What kind of membrane transport is this?

Select one.

• Active transport, because the ions move fast
• Bulk transport, because many ions move at once
• Active transport, because a protein carries the ions
• Passive transport, through a channel protein

An action potential has arrived at an axon terminal. Which event comes next at the synapse?

Select one.

• Neurotransmitter binds receptors on the next cell
• Voltage-gated Ca²⁺ channels open and Ca²⁺ flows in
• An electrical spark jumps across the synaptic cleft
• K⁺ flows into the terminal and releases the vesicles