Which three cues gate ion channels?

• Voltage, ligand, and mechanical pull
• Heat, light, and sound waves all around the cell
• Sodium, potassium, and calcium

What decides which ion species a channel passes best?

• The width of the hole alone
• The pore-lining amino acids
• The thickness of the whole membrane

A single ion channel eases part way open like a dimmer switch.

A drug makes each sodium channel spend twice as much time open. What happens to the whole-cell current?

• The whole-cell current grows
• The whole-cell current reverses direction
• Each single opening gets smaller

What causes the rising phase of the action potential?

• Potassium channels open and sodium stays shut
• The membrane leaks until it runs flat
• Sodium channels open and sodium rushes in

A touch receptor fires when pressed, so its cue must be ligand. True or false?

A toxin locks voltage-gated sodium channels shut, yet a normal spike still rises past threshold. True or false?

Leo sees a noisy trace hovering between the open and closed levels and says the channel rests half open. What is wrong?

• The channel is broken and stuck half open
• Two channels are open at once
• Fast flickering between open and shut