Electrical properties of nerve cells, ions and electrochemical equilibria: Resting membrane potentials Flashcards
Definition of intracellular measuring
Electrode is inside cell to measure electrical activity inside the cell
Definition of extracellular measuring
Electrode is outside cell to measure electrical activity outside the cell
Definition of patch clamping
Electrode is sealed to the cell surface to measure of movement of ions in and out of the cell
Definition of voltage
Measure of electrical work down in the separating charges across membrane
Definition of equilibrium potential
Electrical force=osmotic force
No net movement of ions
Uses of measuring electrical events
ECG
EEG
EMG
3 ways of maintaining the resting membrane potential
ATPase Na+K+ pump moves ions against conc gradients
Channels restrict ion movement through channels, down conc grad
Membrane stores ionic charges on its inner and outer surfaces, capacitor
How does the membrane act as a capacitor
When 1 +ve ion leaves the cell via a channel, 1 -ve ion follows
-ve ion cannot leave the cell but attaches to the inner cell membrane opposite the +ve ion
The greater the separation of the oppositely charged ions, the greater the tendency for the ions to attract each other
What is voltage
Measure of electrical work done in separating charges across the membrane
Describe the osmotic work done by the conc grad
Pump derives energy from ATP hydrolysis, uses this to create conc grad
Gradient=[C]out/[C]in
However this creates electrical drawback in opposite direction
How does conc grad and electrical grad function
As the ions move down their conc grads, there is an increasing tendency for the ions to go down their electrical grad
What is equilibrium potential
When electrical force=osmotic force
How is equilibrium potential determined
If conc grad known
Nernst equation
E=58mV x log[C]out/[C]in
Intracellular concs of Na+ and K+
[Na+] = 10mM [K+] = 140mM
