Lecture 4

Question 1

What is meant by Membrane potential

Answer 1

The potential difference between the inside and outside of a cell, measured in millivolts

Question 2

Describe the measurement and size of membrane potentials

Answer 2

Membrane potentials are measured using a glass pipette called a microelectrode. It is filled with a conducting solution of KCl.
At rest an animals membrane potential ranges between -20mV to -90mV. Cardiac and skeletal cells are in the vicinity of -80 to -90mV whereas nerve cells range from -50 to -75mV.

Question 3

Explain why membrane potentials occur

Answer 3

As a result of the concentrations of ions inside and outside the cell, set up by pumps and ion channels

Question 4

Describe the composition of ions inside and outside the cell of:
Na
K
Cl
Other anions

Answer 4

Inside Outside
Na+ = 10mM Na+ = 145mM
K+ = 150mM K+ = 5mM
Cl- = 8mM Cl- = 110mM
A- = 167mM A- = 40mM

Question 5

Explain how altering ionic permeability changes the membrane potential

Answer 5

Increasing the permeability to a particular ion moves the membrane potential towards to equilibrium potential for that membrane

Question 6

Describe how neurotransmitters can change the membrane potential

Answer 6

The neurotransmitter binds to the post synaptic membrane and causes a change in the shape of the receptor so that Na+ ions enter. This flow causes a excitatory post-synaptic potential