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Human Physiology H3b
Test 2 Material begins here: Handout 3-last page
| Question | Answer |
|---|---|
| Concentration gradients | Ins resp. for RMP: Na, K and A (amine); conc diffs in Na and K are PRODUCED AND MAINTAINED by the Na/K pump [Na] ECF = 150mM, ICF = 15mM [K] ECF 5mM, ICF = 150mM |
| Concentration gradients cont. | B/c each turn of the Na/K pup removes a net +1 charge from ICF, it directly contribs to the RMP; 2 K IN and 3 Na OUT so a net +1 charge w? each turn of the pump |
| Your concentration dollars at work... | The cell membrane IS permeable to NA and K (though not equally) and MVMT of only a TINY fraction of wither ions results in large electrical differences-therefore, ion concentrations do NOT change |
| What is the affect on membrane potential of K moving down its concentration gradient? | K leaks out; diffusion pushes from H to L until equilibrium; inside the cell is more negative |
| What is teh affect on membrane potential of Na moving down its concentration gradient? | Na rushes INTO cell, cell becomes more POSITIVE on the inside than the outside |
| RMP | electrical differences, cells keep and maintain to do diff types of work. Based on 2 things: 1. Different conc. of charged particles/ions 2. Selective permeability of the membrane |
| Membranes more permeable to... | Na and K; Na more so |
| Na/K pump is minor but imoportant | But not a contributing factor of electrical difference but keeps CONCENTRATION DIFFERNECE the SAME. |
| A simplified story... | For a call that is only perm to K, the equilibrium potential is the balance between: the CHEMICAL force Driving K ut of the cell and the ELECTRICAL force pulling K in to the cell and Equilibrium Potentials are calc'ed by Nerst equation |
| Equilibrium potential for Na and K | K = -90mV, Na = 60mV |
| Equilibrium potential for Na | for a cell that is only permeable to NA, the equiilibrium potential os the balance point between: the chemical force driving Na INTO the cell and the electrical force pulling NA OUT of the cell; |
| Equilibrium Potntial for Na tells us that... | if the cell is only permeable to NA, the RMP = equilibrim potential so RMP = +60 in ICF inside of hte cell. |
| RMP of cells | cells = -70 mV, K = -90, Na = +60 |
| The real world RMP | cells are permeable to both K and NA at rest, Goldman-Hodgkin-Katz equation, and results in a STEADY STATE |
| Cells (-70mV)are more permeable to K( -90mv) at rest... | Because closer to RMP for K |
| RMP is | the result of cells being selectively permeable to both Na and K, moreso to K than Na due to diff number of channel proteins, leak channels always open at rest, 25% more K than Na resulting in RMP = -70, making slightly moe positive |
| Changes in RMP | cells can use as a way to opem other chnls and produce signals involved in initiating some activity |
| Goldman-Hodgkin- Katz equation | a modified Nernst that considers relative perms of the ions that contribute to membrane potential |
| "Results in a steady state" | Generation of a memrane potential by constant, passive mvmnt of NA and K down their conc. gradients and active maintenance of concentrations by Na/K pump |
| Changes in ion permeability change the membrance potential | MP changes when perm to Na, K, Ca or Cl changes, change from RMP is described as depol, hyperpol adn repolarization adn the actual # of ions that move to affect change is very small |
| depolarization | more + than normal (resting state) change; a change inside the cell |
| hyperpolarization | more - than resting state (normal) because 1. more chnls and mor K leave, can't get more than -90 mv w/K or open Cl chnls; a change inside the cell |
| repolarization | returning to normal (resting state)due to a change inside the cell |
| If we change perm to any charged particle Na, K, Ca or Cl by opening or closing chnls from resting state.... | we need to know waht the conc. diff is: if none, then NO EFFECT on MP Ex. Ca is low inside and high outside so if chnl is opened, inside becomes more positive Ex. Cl is low inside and high outside, w/chnl opened, inside becomes more negative |
| Your membrance transport systems at work :insulin secretion | resting: low glucose or secreting insulin due to an increase in glucose levels |
| Low glucose (resting) | low ATP prod; K out = cell less + so negatively charged b/c gated K chnl |
| if increase in glucose | increase in ATP; Ca comes in, K chnls close, RMP depolarizes and becomes more + inside cell so insulin gets secreted/released |
Created by:
Lkellyfly
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