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
The absolute refractory period allows for…?
No further action potential to take place, allowing unidirectional propagation
The relative refractory period allows for…?
Only larger stimuli to elicit an action potential
Nodes of ranvier occur on what type of axon?
Myelinated
What is in high concentration at the node of ranvier?
Voltage gated ion channels
Myelinated axons transmit action potentials via what method?
Saltatory conduction; enhancing transmission
