Membrane Potential Flashcards
Describe the origin of the resting potential
As K+ ions are not accompanied by anions, charge separation occurs with the intracellular electrical potential becoming negative with respects to the extracellular solution
What are the Potassium and Sodium equilibrium potentials?
For potassium is is around -100mV. This is the charge that will balance the potassium concentration gradient . For sodium it is around +60mV that will balance the concentration gradient
What is depolarisation?
The sudden and rapid increasing the the membrane potential (increase from -ve to +ve)
What it repolarisation?
It is the decrease in the membrane potential from positive back to the resting potential (-70mV)
What is hyperpolarisation?
This is a decreasing in the resting membrane potential (it comes more negative that -70mV
What oocurs when you inject an inexcitable cell with positive ions?
The membrane potential increases slightly but then returns to the resting potential
What occurs when you inject an excitable cell with positive ions?
The cell reaches its threshold potential which causes sodium channels to open and an action potential is generated.
Describe the characteristics of the action potential
The initial depolarisation must reach a critical threshold (threshold potential) and once this is obtained the depolarisation upstroke is generated. It peaks at around +30mV and then the membrane repolarises to the resting potential
Describe the permeability changes to sodium and potassium
The permeability changes of sodium follows the graph of the depolarisation and repolarisation. With it increasing as the membrane potential increases and decreasing when the membrane potential decreases.. The permeability for potassium also increases however there is a delayed reaction due to potassium channels taking longer to open up.
Depolarisation and repolarisation are associated with what?
Depolarisation - Rapid increase in sodium permeability
Repolarisation - Delayed increase in potassium permeability.
Describe the sodium channel as it goes through an action potential
At the resting potential, the cell is closed but has the capabilities to be open. The membrane potential increases and this is sensed by a voltage sensor within the channel and the rapid opening is triggered when the membrane reaches its threshold. As the membrane repolarises the channel is closed an incapable of opening, it will only have the capabilities to open once the cell reaching its resting potential.
Describe the potassium channel during an action potential
At the resting potential the channel is closed. Increase in membrane potential is sensed by a voltage sensor in the channel but the conformation change is slower and therefore the channels only open after the cell has reached its peak. Therefore the potassium channels are also responsible for hyperpolarisation as they also take longer to close.
