The Psych Diaries

Instructions: Choose the best answer (A–D). Then check the answer key at the bottom.

1) An action potential begins when the neuron reaches its…

• A) refractory period
• B) resting potential
• C) threshold
• D) hyperpolarisation

Answer

Correct Answer:C

Explanation: The neuron reaches ‘threshold’ once its charge reaches -55mV. At this point, the neuron is depolarised enough to trigger the opening of voltage gated sodium channels. This causes rapid depolarising and fires an action potential. Think of it like the neuron’s ‘point of no return’.

2) At resting membrane potential, the inside of the neuron is…

• A) positive compared to the outside
• B) negative compared to the outside
• C) exactly equal to the outside
• D) randomly changing every second

Answer

Correct Answer:B

Explanation: The sodium potassium pump pushes 3 Na+ ions out and 2 K+ ions in. This helps to maintain a more negative charge inside the cell.

3) Depolarisation occurs when ______ ions rush into the neuron.

• A) potassium (K⁺)
• B) calcium (Ca²⁺)
• C) sodium (Na⁺)
• D) chloride (Cl⁻)

Answer

Correct Answer:C

Explanation: Remember how reaching threshold triggers the voltage gated sodium channel to open? What do you think comes in through the voltage gated sodium channel? I always remember it as ‘SO it begins…” SO for sodium signaling the beginning of the action potential.

4) Which channels open first during an action potential?

• A) voltage-gated potassium channels
• B) voltage-gated sodium channels
• C) ligand-gated chloride channels
• D) sodium-potassium pumps

Answer

Correct Answer:B

Explanation: The cell needs to become positive. It happens this way.

5) Repolarisation happens mainly because…

• A) sodium (Na⁺) leaves the neuron
• B) potassium (K⁺) enters the neuron
• C) potassium (K⁺) leaves the neuron
• D) chloride (Cl⁻) leaves the neuron

Answer

Correct Answer:C

Explanation: After the neuron has reached its peak action potential (around 30-40+ mV) it wants to go back to being negatively charged. Voltage gated potassium channels open and there is a big efflux of K+. Less positive ions in the cell –> less positive charge in cell.

6) At the peak of an action potential, voltage-gated sodium (Na⁺) channels…

• A) open wider and wider
• B) inactivate (close temporarily)
• C) turn into potassium channels
• D) pump sodium out of the cell

Answer

Correct Answer:B

Explanation: Key word here being ‘temporary’. They don’t RIP…they just rest until they are needed again. Like my attention span once the lecture is 90% done.

7) Hyperpolarisation means the membrane potential becomes…

• A) more positive than normal resting potential
• B) more negative than normal resting potential
• C) exactly 0 mV
• D) permanently stuck at threshold

Answer

Correct Answer:B

Explanation: After the voltage gated potassium channels open, there’s an overshoot of potassium ions leaving. So the cell is more negative than normal resting potential. Our trusty sodium potassium pump takes care of this and brings everything back to normal.

8) During the absolute refractory period…

• A) the neuron cannot fire another action potential
• B) the neuron can fire an action potential easily
• C) sodium-potassium pumps stop working
• D) the membrane potential becomes permanently positive

Answer

Correct Answer:A

Explanation: No, it doesn’t matter how strong the stimulus is. It’s not happening. Key word being ‘absolute’.

9) During the relative refractory period…

• A) the neuron cannot fire another action potential no matter what
• B) the neuron can fire another action potential but needs a stronger stimulus
• C) the neuron fires continuously without stopping
• D) potassium channels are permanently closed

Answer

Correct Answer:B

Explanation: See the word ‘relative?’ It can happen but it needs to be a pretty strong stimulus.

10) The “all-or-none” principle means…

• A) action potentials vary in size depending on the stimulus
• B) action potentials are either full strength or not at all
• C) action potentials only happen in some neurons
• D) action potentials slowly fade as they move down the axon

Answer

Correct Answer:B

Explanation: Action potentials don’t work like your toaster’s settings. There’s only one strength level and it doesn’t change depending on the strength of the stimulus.

11) The main role of the sodium-potassium pump is to…

• A) maintain sodium and potassium concentration gradients over time
• B) directly cause the rapid depolarisation phase
• C) open voltage-gated channels
• D) stop action potentials from happening

Answer

Correct Answer:A

Explanation: Remember the golden ratio? 3 NA+ out –> 2 K+ in. Balance.

12) Which direction does potassium (K⁺) move during repolarisation?

• A) into the neuron
• B) out of the neuron
• C) it does not move
• D) it swaps places with sodium

Answer

Correct Answer:B

Explanation: We want the cell to go back to being negatively charged so all those positively charged potassium ions gotta go OUT.

13) The membrane potential becomes less negative (moves toward 0) during…

• A) resting potential
• B) depolarisation
• C) hyperpolarisation
• D) relative refractory period

Answer

Correct Answer:B

Explanation: Remember this step? When all the positive sodium ions come in through the sodium gated channels?

14) Action potentials travel in one direction along the axon mainly because…

• A) ions only move forward, never backward
• B) the refractory period prevents the signal from travelling backward
• C) potassium channels block forward movement
• D) the neuron chooses the direction consciously

Answer

Correct Answer:B

Explanation: During the refractory period the axon segment behind temporarily can’t fire again. This stops the signal jumping back and ensures it moves forward. Maybe we should all strive to be like a neuron…

15) Which sequence shows the correct order of the action potential phases?

• A) depolarisation → resting → hyperpolarisation → repolarisation
• B) resting → depolarisation → hyperpolarisation → repolarisation
• C) resting → threshold → depolarisation → repolarisation → hyperpolarisation → resting
• D) threshold → resting → repolarisation → depolarisation → hyperpolarisation

Answer

Correct Answer:C

Explanation: Neuron goes from resting and negative –> stimulus trigger –> threshold reached –> GO!!! –> sodium comes in and cell gets more positive (depolarisation) –> alright peak action potential reached –> time to repolarise –> get out potassium –> oops too negative now –> sodium potassium pump comes in clutch –> back to resting