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14 Cards in this Set
- Front
- Back
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osmolytes
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solutes involved in osmotic pressure regulation
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dominant inorganic osmolyte in ICF (intracellular fluid)
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K+
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Major osmolytes in ECF
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Na+ and Cl-
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regulate permeability of ions (especially Na+ and K+)
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excitable cells
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a separation of charges across the membrane; a difference in the relative number of cations and anions in the ICF and ECF
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membrane potential (measured in mV)
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constant membrane potential present in nonexcitable tissues and in excitable tissues when they are at rest
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resting membrane potential
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Concentration differences of K+ and Na+ inside and outside membrane are maintained by what two methods?
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1. Na+/K+ pump at the expense of energy (ATP)
2. Different solubilities in cell water and affinity for cell proteins (K+ more soluble in internal water) |
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Negative charges of proteins attract K+ more strongly than Na+. Why?
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K+ has a smaller hydrogen shell (sphere of water molecules attracted by the ion's positive charge).
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hypothetical value of the membrane potential where the chemical and electrical gradients are equal and opposite (no net electrochemical gradient to drive a net ion movement across a membrane)
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equilibrium potential
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No further net movement of K+ occurs when the inward electrical gradient counterbalances the outward concentration gradient
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Equilibrium potential for K+ (-90mV)
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Na+ equilibrium potential magnitude
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+61 mV
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Equilibrium potential at rest is more permeable to Na+ or K+?
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25 to 30 more times permeable to K+ than Na+
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resting potential of a typical nerve cell
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-70 mV
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takes into account the relative permeabilities and concentration gradients of all permeable ions
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GHK equation
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