Fill in the Blanks 10.1 Action PotentialOnline version Describe how action potential is propagated along an axon by Helmina Kmrzmn 1 depolarisation Na concentration gradient 3 slow negative influx falling inside restored rising undershoot 35mV 55mV hyperpolarisation 70mV opening polarised 2 negatively positively During resting potential , voltage - gated Na + and K + channels are closed . The inside of the axon is more charged than the outside . Sodium - potassium pump maintains resting membrane potential value by pumping molecules of K + ions out of the cell , and molecules of Na + ions into the cell . In this condition , the axon membrane is said to be . When a stimulus is present , some voltage - gated + channels open , allowing Na + ions to diffuse into the cell , down its . Voltage - gated K + channels remain closed . As a result , the inside of the cell becomes more charged than the outside . This situation is called the of the membrane . If this depolarisation managed to bring the membrane potential value from - 70mV to - , which is the threshold level , a positive feedback mechanism will be triggered . This positive feedback will result in the of more voltage - gated Na + channels . This will result in sodium ions , therefore further depolarising the membrane of the axon . This phase is known as the phase of action potential . The membrane potential becomes positively charged due to the sodium influx , which is measured at around . At the peak of action potential , a feedback will be triggered against the voltage - gated Na + channels . Voltage - gated K + channels start to open , causing more K + ions to diffuse out of the axon cell . As a result , the of the axon becomes more negatively charged . This situation is called the repolarisation of the axon membrane , which is also known as the phase of action potential . When the membrane potential starts to return to the resting potential value , which is - , voltage - gated K + channels start to close . However , due to the and lagging closing of the voltage - gated K + channels , some K + ions managed to exit the cell , even after the resting potential value is achieved . An is observed , where the membrane potential value becomes more negative than the resting potential value . This incident is called the of the membrane . Gradually , all voltage - gated K + and Na + channels manage to close . Resting membrane potential value is .
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