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Week Three Notes

by: Marisa Loken

Week Three Notes Bio 385

Marisa Loken
GPA 3.0
Human Physiology
Dr. Jennifer Bray

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About this Document

Here are week three notes! Don't forget that we have a test coming up next week! Monday in the notes is the last day for the exam notes. Wednesday and Friday are the beginning of chapter four!
Human Physiology
Dr. Jennifer Bray
Class Notes
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This 4 page Class Notes was uploaded by Marisa Loken on Friday September 18, 2015. The Class Notes belongs to Bio 385 at University of Wisconsin - Stevens Point taught by Dr. Jennifer Bray in Fall 2015. Since its upload, it has received 119 views. For similar materials see Human Physiology in Biology at University of Wisconsin - Stevens Point.


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Date Created: 09/18/15
Physiology Notes Week Three Reminder TEST NEXT WEEK Tuesday September 15 2015 Membrane Potential The plasma membranes of all cells are polarized electrically Membrane potential O 0000 CO The separation of opposite charges across the plasma membrane When anions and cations are equal on both sides no potential When excess positive ions positive potential Electrically negative charges on both sides separate to make neutral In nonexcitable cells and excitable cells at rest is constant Nonexcitable ranges from 40 to 80 Measured in millivolts mV Typical resting membrane potential RMP Vm is 70 mV neurons 90mV skeletal muscle In uenced by the permeability of a few important ions Sodium potassium large anions negative proteins 0 Potassium is 2530 times more permeable at rest compared to sodium Magnitude of Potential More charge has more membrane potential number of separated ions NaK ATPase Pump The NaK ATPase pump transports 3 Na out of the cell for every 2 K it pumps in Cell loses more positive charge than gains Primary role of the pump is to actively maintain Na K concentration gradients Only makes a small direct contribution to the resting membrane potential Equilibrium Potentials Is the potential that would exist at equilibrium for a given ion 2 opposing factors 0 0 Concentration gradient Electrical gradient K acting alone would establish an equilibrium potential of 90 mV 0 Attracted to inside of cell39s negative charge Na acting alone would establish an equilibrium potential of 60mV 0 When inside reaches 60mV Na gets pushed out Equilibrium potentials are determined using the Nernst Equation o Eion 612 log ionoutionin 0 Z valence of ion 0 Eion equilibrium potential for given ion For NaK z 1 For Cl z1 For 2Ca z 2 Resting Membrane Potential RMP is 25 to 30 more times more permeable to K than Na Therefore RMP is closer to Energy of Potassium RMP 70 mV 0 Comes from GoldmanHodgkinKatz Equation Excitable Tissues Nervemuscle cells have the ability to produce rapid transient changes in their membrane potential when excited Steady State No net movement of ions takes place because all passive leaks are exactly balanced by active pumping Thursday September 17 2015 Beginning of Material for Exam 2 Chapter 4 Principles of Neural Communications Excitable Cells Neurons and muscle cells can rapidly and transiently alter their membrane permeabilities Membrane Electrical States Depolarization o Decrease in potential membrane less than negative Repolarization 0 Return to resting potential after depolarization Hyperpolarization 0 Increase in potential membrane more negative Triggering Event A triggering event triggers a change in the membrane potential by altering membrane permeability 4 types of gated channels 0 Voltage Gated Channel Open in response to changes in membrane potential 0 Chemically Ligand Gated Channels Open by something binding to them 0 Mechanically Gated Channels Activated by stretch o Thermally Gated Channel Respond to temperature Types of Potential Changes Two Kinds o Graded Potential GP Short distance signals Occur in the dendrites and the cell body Small changes 0 Action Potential AP Long distance signals Occur along axons Large changes lnput zone receives incoming signals Trigger zone initiates action potential axon hiliack Conducting zone conducts the action potentials over long distances Output zone transports the signalsto the next cell Graded Potential Flow is between the active area and adjacent inactive area Flow is PASSIVE no energy required The magnitude of a GP varies directly with the magnitude of a stimulus Examples postsynaptic potential endplate potentials receptor potentials Die out over a short distance decremental Summation 0 Charges sum together at the cell body and triggers the action potentials Action Potential An action potential is a brief rapid large change in membrane potential Occur when an excitable cell membrane is depolarized to threshold potential At threshold changes in Na and K permeability are initiated Friday September 18 2015 VoltageGated K Channels Voltagegated K channels have one activation gate Can exist in 2 conformations 0 Closed 0 Open VoltageGated Na Channels Na Channels have 2 gates 0 Activation gate sliding door 0 Inactivation gate ball and chain Can exist in three conformations 0 Closed but capable of opening 0 Open activated 0 Closed and not capable of opening inactivated Action Potential Propagation An AP generates a new AP in the area next to it Action Potentials propagate in one direction Action Potentials do not diminish as they propagate nondecremental Action Potentials Very few K and Na actually cross the membrane during an action potential Only about 1 out of every Refractory Periods The NaK pump gradually restores the ions that moved during the action potential After an AP the membrane enters its refractory period Refractory periods ensure oneway propagation of Action Potentials Action Potential Characteristics All or none Variable strength of stimuli are coded by varying the frequency of action potentials not their size


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