Module 2.9: Membrane Potential Flashcards
What does membrane potential mean
It means that membranes are polarized electrically, which is true for all living cells.
What does membrane potential allow for in cells
It allows for cellular communication in excitable cells, is there is a difference in the electrical potential between the inside and the outside of the cell
What is ohms law and how is it measured
The idea that voltage (membrane potential) equals current (ions moving across) x resistance: V = IR. Measured in millivolts mV
What is resting membrane potential
A constant membrane potential in non-excitable tissues and those of excitable tissues at rest
What ions are primarily responsible for generation of the resting membrane potential
Sodium, potassium, and and ions which are negatively charged intracellular proteins found inside a cell only as they can’t permeate.
How do anions get inside of a cell
They’re synthesized from amino acids that have been transported into a cell, and then trapped
How does membrane permeability of potassium and sodium compare when at resting potential
The membrane is about 50 to 75x as permeable to potassium than as to sodium
What are the concentration gradients for potassium and sodium, and the electrical gradients for both
The concentration gradient for potassium is always outward and for sodium is always inward, and the electrical gradient for both is always toward the negatively charged side of the membrane
What would the hypothetical affect on membrane potential be if there was movement of potassium through the membrane, and what would the equilibrium potential of potassium be
Potassium would leave the cell down its gradient, causing the inside of the cell to become more negative in the outside more positive, establishing a negative membrane potential. Since the membrane potential is negative, movement back in and of the potassium is favoured so now two opposing forces are acting. Equilibrium would be reached when net outward concentration gradient and net inward electrical gradient become balanced, called equilibrium potential. The equilibrium potential would be -90 mV
What would be the hypothetical effect of sodium movement on membrane potential
The concentration gradient would move the ion in, a positive charge would build up inside and negative outside, primarily from in form of Cl-. Net inward movement would occur until equilibrium was established by development of opposing electrical gradient that counterbalances. Sodium‘s equilibrium potential is 60 mV
When you have the effects of concurrent potassium and sodium within a cell, why does the potassium influence the resting membrane potential much more than sodium, and what is this result in
Because the more the permeability for a given ion, the more tendency for that ion to drive membrane potential towards its own equilibrium potential. Potassium has a much higher permeability of 50 to 75 mM/L compared to sodium which has only one mM/L permeability. This results in the resting potential being closer to potassiums than sodiums, coming in at -70 mV.
What levels are sodium and potassium found in extra cellular fluid and intracellular fluid of a cell
Potassium is found with 5 ions in the extracellular fluid and 150 ions in the intracellular fluid, and sodium is found with 150 ions in the extracellular fluid and 15 ions in the intracellular fluid
What is the principal extra cellular fluid anion and what is its equilibrium potential
Chloride Cl- , -70mV
Does a chloride ion influence the resting membrane potential in most cells
No because it’s passive and highly permeable so it distributes to achieve an individual state of equilibrium. Rather than it influencing resting membrane potential in most cells, membrane potential passivley influences the chloride distribution
How are membrane potential’s used in a specialized Way in nerve and muscle cells
The cells can rapidly alter their membrane permeability’s to specific ions in response to appropriate stimulation, creating fluctuations in membrane potential which serve as electrical signals
