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Phys Lect 4
| Question | Answer |
|---|---|
| When does the membrane potential equal the nernst potential of a particular ion? | When the membrane is selectively permeable to that ion |
| What makes a membrane selectively permeable to an ion? | OPEN channels. **channels are often gated, meaning that there must be some trigger event that causes channel opening. |
| What ion is MOST responsible for the resting membrane potential? (Remember no ion alone determines the Resting Membrane Potential). | Potassium K+ **Since the Ek and Em are so close together, the membrane at rest is most permeable to K+, The graphical deviation of Em from Ek is due to slight permeability of Na. (resting mem pot is less negative) |
| Which ion is the membrane most permeable to at rest? | K+ which is supported by the fact that the Ek and Em are very similar |
| The membrane potential at a given time is most affected by the ion that is ____ permeable | MOST |
| two factors determine the membrane potential | 1.Nernst potentials. 2.Ion permeability |
| What is the resting membrane potential mV range? What all ions contribute? | -60 to -85mV. (Nernst Potentials) 1.Eca: +125mV. 2.Ena: +70mV. 3.Ecl: -50mV. 4.Ek: -90mV. |
| Does extracellular ion concentration imfluence the resting membrane potential (Em) if the membrane is immpermeable to that ion? | NOOOOPPPEEE |
| Goldman-Hodgkin-Katz Eq | How much a given ion's nernst potential influences the overall membrane potential depends on its relative permeability. The P values (permeability) of K, Cl, and Na range b/w 0-1 and add up to equal 1. |
| The Resting Membrane permeability of Na is ___ the permeability of K | 1/100 |
| Hows is Na+ slightly permeable? | 2 theories: 1.Na channels that allow Na+ to leak back into the cell. 2.1 Na+ for every 100 K+ enters the cell through a K+ channel. |
| What is the relative permeability of Ca2+? | 0. this is why it is not represented in the GHK equation. |
| Influence of Cl- in nerve cells Em? | Impermeant |
| Influence of Cl- in Skeletal muscle/ most other cells? | is permeant, and is therefore represented in GHK equation. Pcl is much smaller than Pk. |
| What is actively responsible for maintaining intracellular [Na+] and [K+] concentrations and preventing the membrane potential from simply dissipating once the ion concentrations balanced? | Na+/K+ ATPase **Therefore it indirectly maintains the resting membrane potential (Em) |
| Increase in Extracellular [K+] | will cause depolarization b/c Ek becomes more positive (the K+ ions are less likely to move out of the cell). |
| Decrease in Extracellular [K+] | will cause hyperpolarization b/c Ek becomes more negative. (the K+ ions will move out of the cell at a more rapid rate). |
| A cell has membrane permeabilities of: Na>K>Ca. In what range is the cell's membrane potential likely to lie? | 0 to +70mV |
| HyperKalemia | Depolarization/ Less negative Em (Less K+ efflux) |
| HypoKalemia | Hyperpolarization/ More negative Em (More K+ efflux) |
Created by:
WeeG
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