Membrane Potentials Flashcards
(29 cards)
What is the sodium concentration inside and outside cells?
Inside 15mM
Outside 150mM
What is the potassium concentration inside and outside cells?
Inside 140mM
Outside 5mM
What is a potassium leak?
Potassium moves out of the cell down its concentration gradient, through the k+ channels in the cell membrane
Leaving behind the negatively charged onions
What is a membrane potential?
Voltage across the plasma membrane
What is a resting potential?
The membrane potential of a cell not sending signals (-70mV)
What is the Nernst equation used for?
Used to calculate the equilibrium potential of a specific ion in a cell
What is an equilibrium potential?
The membrane potential at which the electrical and chemical gradients of a specific ion are balanced
What is the Goldman equation used for?
To calculate the resting potential of a cell, taking into account multiple ion permeabilites
What is the equilibrium potential of sodium?
+60mV
What is the equilibrium potential of potassium?
-90mV
What is the equilibrium potential of membrane?
-70mV
Why is the membrane closer to Ek than ENa?
Membrane is more permeable to k+
What happens in depolarisation?
Membrane potential is more positive than the resting potential
What happens in repolarisation?
Membrane potential returns to resting potential after depolarisation
What happens in hyperpolarisation?
Membrane potential is more negative than the resting potential
Why do changes in membrane potential occur?
Cells contain gated ion channels that open or close in response to stimuli
Give the 5 basic steps of a neuronal action potential
1- stimulation 2- depolarisation (Na+ ions in) 3- Repolarisation (K+ ions out) 4- hyperpolarisation 5- resting state
What happens if the stimulus doesn’t cause sufficient depolarisation?
The membrane doesn’t reach ENa as channels inactivate
How does local anaesthetic work?
By blocking the sodium channels - you don’t get depolarisation and so no action potential will take place
What happens at the synapse of a neuronal nerve?
Action potential causes neurotransmitter release. Calcium floods in allowing the fusion of vesicles to cell membrane and neurotransmitters bind to the receptor which causes an effect on the cell
What is the resting potential of a cardiac action potential?
-90mV
What are the differences between cardiac and neuronal action potentials?
Shape, duration and resting membrane potentials
Give the basic stages in a cardiac action potential
0-depolarisation
1- repolarisation begins
2- plateau
3- repolarisation
What happens when a cardiac action potential depolarises?
Sodium channels open
