Resting Membrane Potential
How is the resting membrane potential measured?
- inserting the tip of a recording microelectrode into the cell, and inserting a reference electrode in the extracellular fluid of the cell
Why does the resting membrane potential exist?
- small buildup of negative ions in the cytosol along the inside of the membrane - an equal buildup of positive ions in the extracellular fluid along the outside surface of the membrane
What are the three major factors that resting membrane potential arises from?
- unequal distribution of ions in the ECF and cytosol - inability of most anions to leave the cell - electrogenic nature of the Na+-K+ ATPases
What is a typical value of resting membrane potential in neurons?
-70 mV
What does the negative sign in front of the number indicate?
the inside of the cell is more negative compared to the outside of the cell
The greater the difference in charge across the membrane...
the larger the membrane potential (voltage)
Where does the buildup of charge occur?
very close to the membrane
What is the volmeter, and what does it do?
where the microelectrode and reference electrode are connected to; measures the difference (voltage) across the plasma membrane
The separation of positive and negative electrical charges is a form of what?
a form of potential energy
How is the cytosol and extracellular fluid elsewhere in the cell?
contains equal numbers of positive and negative charges and is electrically neutral
What are electrodes?
devices that conduct electrical charges
In neurons, what is the range for resting membrane potential?
from -40 to -90 mV
How is it measured?
in volts or millivolts
Which type of cells are mostly polarized, and what is the range of their membrane potential?
most body cells; varies from +5 mV to -100 mV in different types of cells
A cell that exhibits a membrane potential is said to be what?
polarized