BIOL 112 1st Edition Lecture 24 Outline of Last Lecture I Feedback Loops II Insulin III Glucagon IV Pathology Outline of Current Lecture V Intro to Nervous Systems VI Neurons VII Action Potential VIII Initial Response Current Lecture I 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 cells respond 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 dendrites cell body axon Supporting cells glial cells astrocytes myelin sheath Nerve a bundle of axons surrounded by dense connective tissue Ganglion cluster of cell bodies may include dendrites and axons surrounded by a capsule of connective tissue Nucleus ganglion located in brain or spine II 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 and are 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 cell III Action Potential In addition to resting potential neurons can show another kind of membrane response Action Potential unit of language of nervous system coding of information How to detect action potential impale a cell on recording electrode then add a second electrode that can inject current into cell Can alter voltage across plasma 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 response cell moves back to resting potential above a critical threshold value causes an intense membrane response involving movements of ions across the membrane beyond the usual permeability IV Initial Response Before stimulation both ion gates are closed and membrane maintains resting potential Stimulation depolarization initially causes some Na gates to open Any stimulation of membrane above the threshold value causes most Na gates in vicinity of stimulus to open Open Na gates allow a positive charge to rush into the cell depolarizing 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 membrane reaches and goes beyond the resting potential value K gates close and cell recovers to resting state
View Full Document
Unlocking...