Resting and Action Potentials Flashcards
The lipid bilayer of cells performs what function
A barrier preventing ion movement, creating different concentrations
The internal negative charge of a cell is mainly due to…?
The presence of negatively charged proteins
At rest, a neurone permits what?
The diffusion of K+
In a resting neurone, the Na+ channels are…?
Closed
Two forces act upon K+ to allow it’s movement. What are they and what’s their direction?
Diffusion force - K+ diffuse out and electrical force - K+ move in
The resting membrane potential is around what value?
-60mV
Ion pumps provide what function?
Move ions against their concentration gradient
An ion pump is involved in maintaining the resting potential. What is it’s function?
It pumps 3 Na+ out of the cell for every 2 K+ it pumps in, maintaining the internal cell negativity
The equation for membrane K current is…?
Ik = gk (Vm - Ek)
Vm must not = Ek
The equilibrium potential is defined as what?
The electrical potential difference that exactly balances an ionic concentration gradient
The voltage produced by a difference in concentration on a single ion across a membrane can be calculated by…?
The Nernst equation
At body temperature, the Nernst equation is…?
61.54mV log(X+)o/(X+)i
Goldman-Hodgkin-Katz equation is better than Nernst equation, why?
Because it considers the concentration gradients and permeabilities of all ions involved
The electrical activity created by a depolarising current is defined as what?
An action potential
Where are action potentials generated?
The axon hillock
How is a depolarisation wave created?
Positive ions flow towards negative areas and vice versa, creating local currents that depolarise adjacent membranes areas
The overshoot phase of depolarisation is characterised by what?
A membrane potential of above 0mV
The membrane potential decreasing is known as what, and how is it caused?
Repolarisation, due to closure of Na+ channels and opening of K+ channels
What affect does tetrodotoxin have on the body?
Blocks voltage gated Na+ channels, so action potentials cannot form
Voltage gated ion channels are in what state, for which ions?
Na+ and K+ both closed
The arrival of a stimulus has what affect at a membrane?
Causes voltage gated Na+ channels to open and depolarisation
Repolatisation it brought about by what changes?
Closure of Na+ VGIC and the opening of K+ VGIC
What is the value if Ena?
61.54mV
How are different sized stimuli represented in action potentials?
Action potentials are more frequent, with the same amplitude as the stimulus increases
