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Lecture 21

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Life Sciences
Gautam Ullal

Lecture 21March05121030 AMSummaryNoteTaking AreaResting Membrane Resting membrane potentialPotentialThe resting potential is at 70 mVIs at 70mV and is observed Every cell has a membrane potentialin a giant axon of a squidGiant nerve cells of squidLarge diameters axons are very important for quick propulsion to escape 4 things that keep the dangerresting membrane potential The axons of a squid are 400 times the diameter of mammalian axonsareIn squids the axoplasm can be easily squeezed out and replaced by fluid of The capacitor charge of the 1interestmembrane negative inside What keeps the resting membrane potential in a resting statepositive outsideCell membrane capacitanceThe cell membrane itself is chargedThe cell 1Passive Osmotic gradient 2membrane is negatively charged on the inside and positively charged on the things want to go from a outside The resting membrane potential lies at 70mVhigh to a lowPassive Osmotic Forcesmolecules like to move from a high concentration to 2Passive electrical forces as 3a low concentrationThe extracellular compartment of the cell contains Nathe k leaves the inside itions and the inside contains Kions Due to osmotic pressure Naions want becomes more negative in to go inside the cell and Kions want to go outsideturn attracting back the Passive Electrostatic forces and Polyanions As the ions enter and exit the 3positive k ions and cell membrane they change the charge of the outside and inside of the cell polyanions negatively Polyanions are large negatively charged ions located inside the cell they charged proteins inside the attract the Kions inside the cell which in turn creates a negative field at the cell which attract the k ions bottom of the membraneand form a negative field at Active Forces ion channels hydroxylation of sodium and potassium ions 4the bottom of the when sodium is hydrolyzed its diameter becomes larger smaller when membranepotassium is hydrolyzed This allows the sodium to stay outside the cell and Active forces ion channels 4potassium to enter the celland protein pumpsIon channels and Transporters cause unequal distribution of ions There are passive and active across neuronal membranesion channelsThere are two types of Ion ChannelsPassive Ion Channels The sodiumpotassium Allows ions to diffuse down the concentration gradientpump uses 4050 of energy Causes selective permeability to certain ionsand pushes out 3 Na ions Doesnt use any energy ATPand pulls in 2 K ionsActive Ion ChannelsActively move ions against concentration gradientOuabain is a plant toxin that Create ion concentration gradientinhibits the nak pump Uses ATPallowing more sodiumThe Na Kpumpmore calcium in the body The SodiumPotassium pumpis an protein that requires ATP to function It which helps heart throws out 3 sodium ions and throws in 2 Kions Since both are positively contractioncharged it throws out more positive charges then it throws in making the inside negativeAction potentialsIt is usually active after a burst of action potentialwhich causes lots of Action potential is initiated sodium to go inside the cellwhen the sodium ion This pump alone consumes 4050of energychannels are opened and Is slower than Ion channelsallow sodium to enter the It is important to restore the resting membrane potential after an action cellpotentialOuabain inactivates the NaK pump Ouabain is a plant toxinThere are two types of gated Ouabain can be used in case of heart failure it forces the heart to ion channelspump more forcefully This is due to the inactivation of the NaK Voltagegated the channel pump which causes a high accumulation of sodium inside the cell opens when a specific which in turn increases the amount of calcium in the body which voltage of electrical stimulus helps with heart contractions LIFE SCI 2C03 Page 1
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