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WEEK 6:
Resting Membrane Potential
| Question | Answer |
|---|---|
| intracellular and extracellular ions | (9) Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, PO4-, glucose, protein |
| Na+ intracellular mmol/l | 10 |
| K+ intracellular mmol/l | 140 |
| Ca2+ intracellular mmol/l | 0.0001 |
| Mg2+ intracellular mmol/l | 30 |
| Cl- intracellular mmol/l | 4 |
| HCO3- intracellular mmol/l | 10 |
| PO4- intracellular mmol/l | 60 |
| glucose intracellular mmol/l | 0.1 |
| protein intracellular | 16g/dl |
| Na+ extracellular mmol/l | 140 |
| K+ extracellular mmol/l | 4 |
| Ca2+ extracellular mmol/l | 2.5 |
| Mg2+ extracellular mmol/l | 1.5 |
| Cl- extracellular mmol/l | 100 |
| HCO3- extracellular mmol/l | 27 |
| PO4- extracellular mmol/l | 2 |
| glucose extracellular mmol/l | 5.5 |
| protein extracellular mmol/l | 2g/dl |
| describe plasma membrane potential (Vm) inside and outside the cell | inside more negative than the outside |
| RBC membrane potential | -30mV |
| smooth muscle membrane potential | -90mV SM |
| skeletal muscle membrane potential | -90mV SKM |
| neuron membrane potential | -70mV |
| RBC cell diameter | 7 um |
| smooth muscle cell diameter | 10um |
| skeletal muscle cell diameter | 10-100um |
| neuron cell diameter | 1um |
| RBC ratio of plasma membrane to cell diameter (7um) | 0.001 RBC |
| smooth muscle ratio of plasma membrane to cell diameter (7um) | 0.001 SM |
| skeletal muscle ratio of plasma membrane to cell diameter (7um) | 0.001-0.0001 |
| neuron ratio of plasma membrane to cell diameter (7um) | 0.01 |
| how do you measure membrane potential | intracellular microelectrodes |
| intracellular microelectrodes | direct, accurate measurement of Vm |
| what can cause ions to move | concentration gradient + voltage gradient |
| how do ions move | negative to positive, positive to negative (opposites attract) |
| neuron with K+ impermeable membrane | no K+ channels + no net diffusion + system is isosmotic (no water gradient |
| neuron with K+ permeable membrane | K+ channels + net diffusion via facilitated diffusion |
| diffusion potential (nernst potenital/Ek) definition | voltage of electrostatic force of an ion is equal + opposite to the chemical force of the concentration gradient |
| diffusion potential for K+ is called | Ek |
| Nernst potential equation | Ek(i-o) = 61 Log10 ([K+]o/ [K+]i) |
| when cell membrane is only K+ permeable, what is it equal to? | Vm= Ek |
| explain the relationship between the external K+ concentration affect membrane potential (Vm) of skeletal muscle | linear relationship where increasing K+ concentration makes skeletal muscle have a higher membrane potential |
| internal K+ concentration of skeletal muscle | 145mM |
| how can cells have Vm> Ek (higher membrane potential than K+ diffusion potential) | if cell has passive permeability to Na+ (more Na+ influx so more positive Vm meaning Vm> Ek so K+ effluxes out of cell to repolarise cell, eventually balancing Vm back to resting potential) |
| when Vm= Ek how many ions move | less than 1/100,000 ions move for equilibrium |
| when Vm> Ek | small amount of both Na+ moves in and K+ out |
| role of Na+/K+ ATPase pump | 3 Na+ out 2 K+ in to maintain resting potential (-70mV) and restore ion balance after AP |
Created by:
kablooey
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