18. AP FA18 - UNIT 5 - Chapter 11 Part II Lecture Notes.pdf...

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BIOL 2401Human Anatomy and Physiology IDr. NewsomeChapter 11 Part IIAction PotentialsAs discussed in the muscle tissue section, neurons can initiate action potentials. Review the terms givenbelow using the Chapter 9 course notes on electrical activity in the last unit (thank goodness this isreview and not the initial lecture over this material!).Sodium and potassium influence on electrical activitythese ions create the potential for electricalactivity in muscle cells and neurons.Potassium concentration is higher inside the cell and sodium ishigher outside of the cell. At rest, sodium does not easily enter the cell, but potassium can exitthrough open leak channels.Sodium-potassium pumpactive transport pump on the membrane that pumps out 3 Na+ andbrings in 2 K+ into the cell. This activity maintains concentrations of Na+ and K+ and helps create theresting membrane potential. Requires ATP.Resting membrane potentialdifferent ion permeabilities and different concentrations in andoutside of the cell create a more negative charge on the inside and a more positive charge on theoutside of the neuron.A resting membrane is also said to bepolarized(oppositely charged on theinside and outside of the membrane).Depolarizationshift in membrane potential to a more positive charge on the interior of themembrane due to sodium gates opening and allowing sodium entry into the cell.Action potentiala depolarization that spreads down the entire cell (neuron); requires a thresholdstimulus.Threshold stimulusdepending on the type of neuron, usually about 100 millivolts.All or none responsea depolarization either causes an action potential or doesn’t cause a changein the neuron that can spread (propagate) along the entire membrane.Repolarizationreturn to resting membrane potential by establishing the sodium and potassiumlevels inside and outside of the cell (sodium is moved out of the cell).Refractory periodperiod of time when the membrane cannot respond to an action potentialHyperpolarizedmembrane potential is shifted towards a more negative value (e.g. -70mV shifts tothe more negative -90mV).Direct result of chloride gates opening on the membrane allowing moreCl- to enter the cell or the opening of all K+ gates to allow K+ to exit the cell.Effects of Anesthetics, Sedatives, and Alcohol on the Action PotentialRemember the last time you had a filling, or a tooth extracted at the dentist?(maybe you don't want to remember!). The dentist "numbs" or anesthetizes yourmouth before she begins to drill or work on your teeth. You know that funnyfeeling of numbness. Dental anesthetics such as lidocaine and novocaineinactivatethe sodium gates so action potentials cannot occur. Drilling or pulling of teethproduces many action potentials interpreted as PAIN by the brain.Without novocaine, the drilling onyour teeth would cause a barrage of action potentials carrying pain information to the brain and create

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Term
Fall
Professor
Smith,S
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