The Resting Cell Membrane Flashcards
Define what membrane potential is
-voltage difference across their plasma membrane
How can you measure the membrane potential ?
- using a micro electrode which is a fine glass micropipette.
- this pipette is filled with KCL.
- it is penetrated through the membrane
- it measures membrane potential as an expression of the voltage inside the cell relative to outside.
What is the resting membrane potential of a neurone ?
-70mV
What is the resting membrane potential of skeletal muscle ?
- -90mV
What is the resting membrane potential of a smooth muscle myocyte ?
-50mV
What is the resting membrane potential of a cardiac myocyte ?
-80mV
What ion channel sets up the intracellular and extracellular concentrations of Na+ and K+?
- Na+/K+ ATPase :
- it pumps 3NA+ out of the cell and 2K+ into the cell.
- contributes 5mV to the resting membrane potential
What is the normal extracellular concentration of potassium ?
4.5mM
What is the normal extracellular concentration of Sodium ?
145mM
What is the normal extracellular concentration of chlorine ?
124mM
What is the normal extracellular concentration of Anions ( other than chlorine )
40mM
What ions have a lower concentration inside the cells than outside ?
- sodium
Chlorine
What ions have a higher concentration inside the cells than outside ?
- potassium
- anions other than chlorine
What does the Nernst equation help find out ?
Equilibrium potential
- if the value is negative , ions travel from inside the cell to outside
- if the value is positive , then ions travel from outside to inside
What Channel is membrane resting potential dominated by ?
- K+ channels
- they are always open , an equilibrium is set at around -70mV.
- depending on the type of cell eg cardiac , nerve , skeletal there would be different ion channels opens which help increase or decrease the resting membrane potential.
