Flashcards in Pharmacology 5 - Action Potentials Deck (61)
What is depolarisation?
The membrane potential becomes less negative (more positive)
What is hyper polarisation?
Membrane potential becomes more negative
What in general causes changes in membrane potential?
Name for movement of ion into a cell?
Name for movement of ion out of a cell?
What drives the passive movement of an ion through an ion channel?
The electrochemical gradient
What are required to allow movement of ions across membranes?
Ion channels (Transporters)
What aids the movement of Na+?
In what direction does Na+ flow?Why? (3)
InwardlyThe concentration gradient is inwardsThe electrical gradient is inwardsThe membrane potential is negative to the equilibrium potential for Na+
What is the membrane potential?
The difference in electrical potential between the interior and anterior aspects of the cell
What is the approximate membrane potential for many neurones?
What is the equilibrium potential?
membrane potential where the net flow through any open channels is 0.
What is the driving force for Na+ influx equal to?
(Vm - Ena)
Since the driving force for Na+ is negative, in what direction does Na+ move?
What is conductance?
The degree to which an object conducts electricity
Ina = (sodium current)?
Ina = gNa (Vm - Ena)Na+ current = Na+ conductance X driving force
What enables the movement of K+?
In what direction does K+ flow?Why? (2)
Outwardsthe concentration gradient is outwards (has an energy that exceeds that of the electrical gradient (which is inwards))The membrane potential is positive to the equilibrium potential for K+
What is the equilibrium potential of Na+?
What is the equilibrium potential of K+?
What is the driving force of K+ efflux equal to?
(Vm - Ek)
In terms of the driving force, why does K+ move inwards?
The driving force is positive (+20mV)
Does K+ channel opening cause hyper polarisation or depolarisation?
Does Na+ channel opening cause hyper polarisation or depolarisation?
What are some factors that can open gated ion channels?
Membrane voltage (voltage-gated ion channels)Chemical substances (ligand-gated ion channels)Physical stimuli e.g. mechanical, thermal
What are the 2 ion channels responsible for the action of action potential in neurones?
Voltage-activated Na+ channels (Nav) - depolarising Voltage-activated K+ channels (Kv) - hyper polarising
What side of a cell membrane (inside or outside) is positively and negatively charged?
Inside = negativeOutside = positive
How many glycoprotein subunits make up the K+ channels?
How many glycoprotein subunits make up the Na+ channels?
1 (acts as if there is 4 separate parts)