Lecture 2 Flashcards
(20 cards)
What is depolarisation?
Any positive increase in membrane potential
What voltage is the extracellular potential?
0V
What is repolarisation?
When the membrane potential is returning to it’s resting potential
Are action potentials all or nothing signals?
Yes
What is a refractory period?
The time during and after and action potential when it is more diffcilt to fire a subsequent action potential
What is the absolute refractory period?
The period of time when another action potential can not be elicited
What is the relative refractory period?
When a bigger stimulus than usual is needed to kickstart an action potential
Where does a lot of the negative charge come from in cells?
Proteins
Why is there a big concentration gradient in calcium?
It allows rapid changes in calcium to occur for signalling purposes
What is an equilibrium potential?
When the Electrical gradient=the concentration gradient
What is the equilibrium potential for K+?
90mV
During an absolute refractory period can the Na+ channels open?
No
During a relative refractory period can the Na+ channels open?
Yes however they are recovering and the K+ channels are open which oppose depolarisation meaning that a bigger force is needed
What type of kinetics do carriers and pumps follow?
Michealis-menton
What is primary active transport?
When a solute is transferred across a membrane against it’s electrochemical gradient this requires the hydrolysis of ATP to produce energy
What is secondary active transport?
When a solute is transferred against it’s concentration gradient by coupling with a solute which has a favourable gradient
What are co-transporters?
A secondary active system carrier which carries both solutes in the same direction normally using the sodium gradient
What is an exchanger?
A secondary active transport mechanism which carries the solutes in opposite directions, again this normally uses the sodium gradient.
What inhibits the Na/K pump?
Ouabain
Give 3 key facts about the sodium potassium pump
Pumps 3Na for 2K
Inhibited by ouabain
k+gradient sets up resting membrane potential, Pump maintains K+ gradient
