A-Level Biology OCR A
Axon Membrane Sodium Ions Action Potential Influx Potassium
Along unmyelinated axons, action potentials propagate as a wave of depolarization along the entire membrane, with localized circuits causing sequential opening of voltage-gated sodium channels.
Along unmyelinated axons, action potentials propagate as a wave of depolarization along the entire membrane, with localized circuits causing sequential opening of voltage-gated sodium channels.
| Front |
Describe and explain how an action potential is transmitted along an unmyelinated axon. |
| Back |
Transmitting action potential:- At resting potential, axon membrane is polarised
- Stimulus casues sudden influx of sodium ions & reversal of charge on axon membrane - action potential & membrane is depolarised
- Localised electrical circuits established by influx of sodium ions cause opening of sodium voltage-gated channels a litte further along axon
- This resulting influx of sodium ions in this region causes depolarisation
- Behind this new region of depolarisation, sodium voltage-gated channels close and potassium ones open
- Potassium ions begin to leave axon along electrochemical gradient
- This depolarisation is propagated in same way further along axon, outward movement of potassium ions has continued to extent that axon membrane behind action potential has returned to original state - repolarised (-ve inside +ve outside)
- Following repolarisation the axon membrane returns to its resting potential, ready for new stimulus
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A-Level Biology OCR A