Membrane Potentials Flashcards
Are plasma membranes polarised?
yes
What is membrane potential?
separation of opposite charges across the membrane
What are the units for membrane potential?
mV
Is the membrane itself charged?
No
Which cells have the ability to produce rapid, transient changes in their membrane potential when excited (e.g. action potentials)?
excitable cells e.g. nerve and muscle cells
When is resting membrane potential constant?
in non-excitable cells, and in excitable cells at rest
What are the intracellular and extracellular values for chlorine?
extracellular - 110
intracellular - 7
What are the intracellular and extracellular values for sodium?
extracellular - 150
intracellular - 15
What are the intracellular and extracellular values for potassium?
extracellular - 5
intracellular - 150
Is the resting membrane potential more permeable to potassium or sodium?
potassium (100x more)
Which gradient, concentration or electrical, moves K+ into the cell?
electrical
When both the electrical and concentration gradients acting on K+ are equal, what is this?
equilibrium potential for K+ (EK)
No further net movement of K+ would occur
The equilibrium potential for any given ion can be calculated using what?
Nernst equation
What is the equilibrium potential for sodium?
+60mV
What is the equilibrium potential for potassium?
-90mV
What is the value of the resting membrane potential?
-70mV
What can be used to calculate the value of the resting membrane potential?
Goldman-Hodgkin-Katz equation
What is a specialised use of membrane potential in nerve and muscle cells
Rapidly and transiently alter their membrane permeabilities in response to appropriate stimulation, resulting in fluctuations in Em.
Nerve impulses in nerve cells and triggering contraction in muscle cells.
Changes in Em linked to secretion of insulin from pancreatic beta-cells.
What is the single most important factor in setting the cell membrane potential?
K+ equilibrium potential
