In a neuron, what causes the rapid depolarising phase of an action potential?
Answer and explanation
Correct answer: C. Sodium ions entering through voltage-gated channels that open at threshold
- Step 1: Reaching threshold opens voltage-gated sodium channels. Step 2. Sodium rushes in down its gradient and makes the inside positive. Answer: sodium influx. Why not the others: potassium leaves the cell during repolarisation, chloride gives inhibition, and calcium entry (not exit) triggers transmitter release.
Practise more Biological and Physical Science Reasoning.
Free questions with an explanation for every one, and full timed GAMSAT (Graduate Medical School Admissions Test) mock tests.
More Biological and Physical Science Reasoning questions
- Which structure in a eukaryotic cell is the main site of ATP production by oxidative phosphorylation?
- A competitive inhibitor is added to an enzyme-catalysed reaction. Compared with the uninhibited reaction, which change is seen in the kineti…
- In a population in Hardy-Weinberg equilibrium, an autosomal recessive condition affects 1 person in 2500. Approximately what proportion of p…
- What is the pH at 25 degrees C of a 0.0010 M solution of barium hydroxide, Ba(OH)2, assuming complete dissociation? (log 2 = 0.30)
- A fixed mass of ideal gas in a rigid container is heated from 300 K to 600 K. What happens to its pressure?
- 2.0 mol of an ideal gas occupies 4.1 L at 300 K. What is its pressure? (R = 0.0821 L atm per mol per K)