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level: 15.2 The nerve impulse

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level questions: 15.2 The nerve impulse

QuestionAnswer
Nerve impulse- A self-propagating wave of electrical activity that travels along the axon membrane - A temporary reversal of electrical potential difference - This reversal is between 2 states, resting + action potential
Stimulus meaning- This excites the neuron cell membrane, causing channels to open - Membrane becomes more permeable to S - So S ion diffuse into neuron down S ion electrochemical gradient - This make inside of neuron less -
The refactory period- After an action potential, the neuron cell membrane cant be excited again straight away - Coz ion channels are recovering + cant be made to open
The charge of the axon- Inside of axon - charged relative to outside (-70 mv) - Known as resting potential
How the establishment of this potential difference is caused (1)- At resting potential, in a neurone, the inside is - (-70mv) - Outside is positive - This electromagnetic gradient is set because of the S-P pumps in the axon surface
How the establishment of this potential difference is caused (2)- Some P ion gated channels are open - Causing SOME P ions to diffuse out
How the establishment of this potential difference is caused (4)- For every 2 P ions transported in, 3 S ions are actively transported out - Causing the outside to have more positives
Action potential process (1)- At resting potential some P ion gated channels are open - But the S ion gated channels are closed
Action potential process (2)- A threshold stimulus will open S ion gated channels - S ions rapidly diffuse into the axon causing DEPOLARISATION
Action potential process (3)- S ion gated channels close, P gates open - P ions diffuse out of the axon causing REPOLARISATION
Action potential process (4)- There is an overshoot of P ions, HYPERPOLARISATION - This allows for a refractory period where the neuron cant be re stimulated
Action potential process (5)- The resting potential of -70mv is returned by active transport - The axon is at resting potential again