BIOL 112 1st Edition Lecture24 Outline of Last Lecture I. Feedback LoopsII. InsulinIII. GlucagonIV. PathologyOutline of Current LectureV. Intro to Nervous SystemsVI. NeuronsVII. Action PotentialVIII. Initial ResponseCurrent LectureI. Intro to Nervous Systems•One of the major systems for integration and control of cells in the body•Depends upon cell-cell physical contact•Specific communication•FAST - hormones take seconds to hours to get a response, nerve cellsrespond in milliseconds•complex information handled, not just simple homeostatic feedback loops•Structures:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.•Neuron - nerve cell, den-drites, cell body, axon•Supporting cells - glialcells, astrocytes, myelinsheath•Nerve - a bundle of ax-ons, surrounded by denseconnective tissue•Ganglion - cluster of cellbodies, may include den-drites and axons, sur-rounded by a capsule of connective tissue•Nucleus - ganglion located in brain or spineII. Neurons•Place electrode into a cell - measure electric potential (voltage) across plasma membrane, between inside and outside of cell•Inside of cell is negatively charged, outside is positively charged•Resting Potential•Found in all living cells tested•A characteristic of being alive•a net movement of the positive charge out of the cell, generating -50 to -90 mV across the membrane•generated by all cells, as long as they have intact membranes andare generating ATP•Ion Pump•Active transport system: hydrolysis of ATP•For every ATP consumed, 3 Na+ ions are moved out of the cell, and 2 K+ ions are moved into the cellIII. Action Potential•In addition to resting potential, neurons can show another kind of membrane response•Action Potential: unit of “lan-guage” of nervous system cod-ing of information•How to detect action potential…•impale a cell on recordingelectrode, then add a sec-ond electrode that can “in-ject” current into cell•Can alter voltage acrossplasma membrane - hyperpolarize (inside of cell becomes more negative), depolarize (inside of cell becomes more positive)•Hyperpolarization - causes no major cellular response, cell moves back to normal resting potential voltage•Depolarization - “Rising Phase of Action Potential”•[below a critical threshold] value causes no major cellular re-sponse, cell moves back to resting potential•[above a critical threshold] value causes an intense membrane re-sponse involving movements of ions across the membrane beyondthe usual permeabilityIV. Initial Response•Before stimulation, both ion gates are closed and membrane main-tains resting potential•Stimulation (depolarization) initially causes some Na+ gates to open•Any stimulation of membrane above the threshold value causes mostNa+ gates in vicinity of stimulus to open•Open Na+ gates allow a positive charge to rush into the cell, depolar-izing the cell beyond stimulation level•Effect is to stop depolarization (no more Na+ moving in), and start repolarization (K+ gates open allow rush of + charge out of cell)•Repolarization, or “Falling Phase of Action Potential”•K+ gates remain open as cell repolarizes until voltage across mem-brane reaches (and goes beyond) the resting potential value •K+ gates close and cell recovers to resting