Nerve impulses Flashcards
what is a nerve impulse
A nerve impulse is an electrochemical change that travels along a nerve fibre.
what is an electrical potential
Is a difference in the concentration of charged particles between one point and another.
what is the membrane potential
Is the movement of positive/negative ions across a membrane
what is the resting membrane potential
Is the change in difference across a plasma membrane.
what value of mili volts is measured at the resting membrane potential
70 mili volts
what is found outside the plasma memebrane
sodium ions
what is found inside the plasma membrane
potassium ions
what charge is the outside of the plasma membrane
positively charged
what charge is the inside of the plasma membrane
negatively charged
what proteins can be found on the plasma membrane
- potassium leakage channel proteins
- sodium leakage channel proteins
- closed voltage potassium channel
- closed voltage sodium channel
- sodium-potassium pump
why is there a greater concentration of potassium inside the cell
As there is a greater number of potassium-associated proteins. Potassium has the largest effect on the resting membrane potential because the plasma membrane is more permeable to them.
why is there a higher concentration of sodium ions outside the cell, but a low concentration inside the cell?
Because there are fewer sodium-associated proteins. The membrane isn’t permeable to sodium but this leak through.
what is the sodium-potassium pump
controls the movement of potassium and sodium into and out of the cell
what does the sodium-potassium pump require
ATP
how does the sodium-potassium pump function
- The protein binds three sodium ions and a molecule of ATP
- The splitting of ATP provides energy to change the shape of the channel which releases the sodium ions.
- Once released the new shape of the pump allows two potassium ions to bind
- Potassium is released into the cell allowing the pump to revert back to its original shape
what is an action potential
The rapid depolarisation and repolarisation of the cell membrane. A neurotransmitter will cause ligand-gated channels to open when they have a stimulus causing sodium to enter the cell.
what causes the opening of the voltage-gated sodium channels
if the potential difference increases to negative 55mV.
what does the opening of the voltage-gated sodium channels cause
an all or nothing response
what happens if the potential difference increases to negative 55mV (depolarisation)
This causes the membrane to become more permeable to sodium and they are released into the cell. The rapid influx of sodium ions causes the depolarization of the membrane.
what happens when the membrane potential reaches 30mV (repolarisation)
The sodium gates will close and the potassium voltage gates open causing potassium ions to rush out of the cell. This causes the repolarisation of the membrane as the movement of potassium ions causes to cell to become negatively charged.
What is the refectory period
A short period following a stimulus during which a nerve cell or muscle fibre cannot be stimulated again.
Define depolarised/depolarization
The membrane of a nerve cell when there is no difference in electrical charge between the inside and outside of the membrane.
Define repolarised/repolarization
A membrane that has been returned to a polarised state.
Define polarised
The inside of a nerve cell has a negative electrical charge compared with to the outside
What is hyperpolarisation?
This occurs when too many potassium ions go out of the cell causing the membrane potential to drop lower than the resting membrane potential.
What happens if the cell becomes hyperpolarised?
For the cell to reach a steady state period the sodium-potassium pump will function leading to the refractory period.
