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0.2.1 Explain how a resting potential is maintained across the axon membrane in a neurone - AQA - A-Level Biology - Question 2 - 2021 - Paper 2
Question 2
0.2.1 Explain how a resting potential is maintained across the axon membrane in a neurone. 0.2.2 Explain why the speed of transmission of impulses is faster along a... show full transcript
Worked Solution & Example Answer:0.2.1 Explain how a resting potential is maintained across the axon membrane in a neurone - AQA - A-Level Biology - Question 2 - 2021 - Paper 2
Step 1
Explain how a resting potential is maintained across the axon membrane in a neurone.
Answer
The resting potential is maintained due to a higher concentration of potassium ions inside the neurone and a higher concentration of sodium ions outside. Potassium ions diffuse out of the neurone, while sodium ions are less permeable to enter. The neurone membrane actively transports sodium ions out and potassium ions in using the sodium-potassium pump, maintaining the resting potential around -70 mV.
Step 2
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon.
Answer
Myelination provides electrical insulation, allowing for the phenomenon of saltatory conduction. In myelinated axons, depolarisation occurs only at the Nodes of Ranvier, allowing the action potential to jump between these nodes. This results in much faster transmission speeds compared to the continuous depolarisation along a non-myelinated axon.
Step 3
Explain why.
Answer
The change in resting potential from -70 mV to 0 mV indicates that no or less ATP is produced due to the respiratory inhibitor, leading to a decrease in the activity of the sodium-potassium pump. This failure to maintain the electrochemical gradient causes sodium ions to flow into the neurone passively, equalizing the potential difference.