| 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 |
