Physio Intro

8/8/2019 Physio Intro

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Definition: The property of a livingorganism that regulates its internalenvironment so as to maintain a stable,constant condition.



Loop of HenleIs more permeable

to water

Loop of HenleIs less permeable

to water



Bioelectricity (sometimes equated withbioelectromagnetism) refers to the electrical,magnetic or electromagnetic fields produced

by living cells

, tissues or organisms .Biological cells use bioelectricity to storemetabolic energy, to do work or triggerinternal changes, and to signal one another.

Examples include the cell potential of cellmembranes and the electric currents that flowin nerves and muscles

, as a result of actionpotentials .



mediated process of moving particles acrossbiological membrane against the concentrationgradient from areas of low concentration toareas of high concentration.Specialized trans-membrane proteins recognisethe substance to be transported and allow it tocross the membrane when it otherwisewouldn't, either because one of the bilipid layerof the membrane is impermeable or because itis moved against the concentration gradient.



P rimary Active transportpumps are involved and use the chemical energy ofAT P

Secondary Active Transportthere are no usage of energy but involve the pore-forming proteins which form channels through cellmembrane



sodium is transported out of the cell andpotassium into the cell by thesodium/potassium pump , a form of activetransport.



F unction:helps maintain resting potential , avail transport andregulate cellular volume .



M echanism ± The pump, with bound AT P , binds 3 intracellular Na + ions. ± AT P is hydrolyzed, leading to phosphorylation of the pump at

a highly conserved aspartate residue and subsequent release of

ADP ± A conformational change in the pump exposes the Na + ions to

the outside. The phosphorylated form of the pump has a lowaffinity for Na + ions, so they are released

± The pump binds 2 extracellular K + ions. This causes thedephosphorylation of the pump, reverting it to its previousconformational state, transporting the K + ions into the cell

± The unphosphorylated form of the pump has a higher affinityfor Na + ions than K + ions, so the two bound K + ions arereleased. AT P binds, and the process starts again



-P assive transport is a type of diffusion-There are 3 types of diffusion:

1) Simple Diffusion2) F acilitated Diffusion3) Osmosis



D iffusion

-No energy needed-Down concentration gradient

1) Simple D iffusion-molecules involved: water, carbon dioxide,oxygen, ethanol, urea-process whereby a substance passes through amembrane without the help of a carrier protein

Factors that affect net rate of diffusion:-concentration difference

-membrane electrical potential-pressure



H igher

concentration ofsubstances

L owerconcentratio

n ofsubstances



2 ) Facilitated D iffusion

-molecules involved: hydrophilic organic molecules,ions.E.g.: glucose molecules, sodium ions, chloride ions-requires:i) carrier proteinsii) ion channels



3) O smosis

-a type of diffusion-molecules involved: water molecules-movement of water from an area with higherconcentration of water to an area with lower

concentration of water across a partially permeablemembrane

F actors that affect rate of osmosis:

-osmotic pressure-number of osmotic particles (molar concentration)-the osmole/ ·osmolality·



www.mansfield.ohio-state.edu/.../campbl08.htm

Physio Intro

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