Physiology 3 Membrane potential

Question 1

What is membrane potential?

Answer 1

The membrane potential is the potential difference between the inside and outside of a cell

Question 2

Animal, muscle and nerve cell membrane resting potentials

Answer 2

Animal –20 to – 90 mV.
Cardiac/Skeletal – 80 to – 90 mV.
Nerve -50 to -75 mV.

Question 3

4 types of membrane transport + examples and speed

Answer 3

• Channels -> Nav, Kv -> Electrochemical gradient - fast
• Carriers/Exchangers, GLUT1-4 -> conc. gradient
• Primary active transport -> Na/K ATPase, ATP for energy
• Secondary active transport -> Na/Ca exchanger, ionic gradient for energy

Question 4

Intra and extracellular ionic concentrations of (Typical Mammal cell)
K+
Na+
Cl-
A - (Anions other than Cl-)

Answer 4

K+ ) Intra - 10mM - Extra - 145mM
Na+ ) Intra - 150mM - Extra - 5mM
Cl- ) Intra - 8mM - Extra - 110mM
A - ) Intra - 167mM - Extra - 40mM

Question 5

Meaning of depolarisation and hyperpolarisation

Answer 5

Depolarisation - A decrease in membrane potential
Cell interior becomes less negative
e.g. – 70 mV to – 50 mV
Hyperpolarisation - An increase in membrane potential
Cell interior becomes more negative
e.g. – 70 mV to – 90 mV

Question 6

Increasing membrane permeability to a particular ion moves the membrane potential towards the Equilibrium Potential for that ion -> What are the equilibrium potentials for 4 physiological ions

Answer 6

K+ -> -90mV
Cl- -> -70mV
Na+ -> +70mV
Ca2+ -> +120mV

Question 7

3 Types of gating stimuli

Answer 7

Ligand gating - response to binding of a chemical ligand
Voltage gating - response to changes is membrane potential
Mechanical - response to membrane deformation