Membrane Potentials and Excitability

What is the function of the membrane?

Provides cellular structure 

Physical barrier that prevents free passage of barriers

Name the type of ion channels

Leak channels and Gated channels

What are leak channels?

Leak channels are always open

Each channel is selective for specific ions

Name the types of gated channels

Ligand-gated ion channels

– Ligand receptor embedded in the channel

– Ligand binding to receptor induces conformational change to open

or close the channel

• Voltage-gated ion channels

– Voltage sensor in the ion channel protein

– Changes in membrane potential induce a conformational change

to open or close the channel

What is Resting Membrane Potential (RMP)

RMP is the difference in electrical charge across the plasma membrane in the cell ‘at rest’

How do you calculate Equilibrium potential?

60𝑙𝑜𝑔10

[𝑖𝑜𝑛]𝑜𝑢𝑡

[𝑖𝑜𝑛]𝑖𝑛

How does depolarisation occur?

Influx of positively charged ions

How does hyperpolarisation occur?

Efflux of positively charged ions

Influx of negatively charged ions

When is the action potential generated?

If depolarisation at a certain point reaches a threshold voltage of ~ -55 mV,

an action potential is generated

What is action potential?

Brief, rapid, large (≅100mV)

change in membrane potential

during which potential reverses

What is the refractory period?

Period when a further stimulus will not trigger another action potential.