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UCONN - PNB 2264 - Class Notes - Week 4

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UCONN - PNB 2264 - Class Notes - Week 4

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background image Week 4- Excitable Cells Membranes -membranes are semipermeable -ion channels and carriers permit movement of ions across the membrane (change 
concentration gradient)
-the uneven distribution of electrical charge(ions) across the membrane creates 
membrane potential 
- the potential energy stored in the membrane is used to send/ receive signals 
inside the cell 
Membrane Potential (V m ) -membrane potential or voltage is the electric potential inside the cell relative to 
the electric potential outside the cell
-net charge inside and outside is zero =no membrane potential  Key Contributions to Vm + set resting potential(close to 
equilibrium potential)
-cells create Vm through ion concentration gradients, concentration gradients are 
created and maintained by a selective membrane and active transport 
-membranes are unequally permeable to various ions (e.g. more permeable to K+ 
than Na+ at rest)
Examples: - with nonselective channel- everything moves down concentration gradient with no
membrane potential
-with selective(+) channel- positive ions move down concentration gradient, 
electrical potential pushes positive ions back bc like repeals like (ions want away 
from increasingly positive membrane and back to the increasingly negative 
membrane) creating a difference in charge 
Vm Balancing Act: -Two opposing forces – concentration gradient and electrical potential  -electrical potential – like repeals like and opposites attract 
background image Equilibrium potential (Ex) - what if situation for a specific ion  -is the membrane potential at which concentration gradient and electrical potential 
forces are equal and opposite
-If ion doesn’t have a concentration gradient the equilibrium potential is zero Misconception -Despite Movement of Ions, Relative Concentrations of Ions DO NOT CHANGE  -Movement only effect space near membrane not whole cell (adding blue food 
coloring to the ocean)
-Small Movements Produce Big Changes in Vm The Nernst Equation  -used to calculate membrane potential if the cell is permeable to a single ion  -equilibrium potential for an ion is determined by charge and concentration 
K+            EP -75mV Na+         EP +58mV Cl-           EP -59mV E(Na)                          

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School: University of Connecticut
Department: Physiology
Course: Human Physiology and Anatomy
Professor: Kristen Kimball
Term: Fall 2018
Name: PNB 2264
Description: Notes cover all power-point information as well as what was covered in class.
Uploaded: 09/25/2018
3 Pages 51 Views 40 Unlocks
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