Resting membrane potential

Where are ions found and what are they

Either side of a cell membrane are electrically charged particles called ions

What are the two most important ions in nerve signalling

Sodium and potassium

Where is sodium found

outside a neuron

Where is potassium found

In a neuron

Why are cell membranes selective with which ions move across

It wants a difference to be maintained

What creates electrical difference

As both ions carry electrical charge there is a difference in amount of positive and negative charge on either side of the membrane

What is the difference in charge called

Resting membrane potential

What does it mean when a membrane is not producing action potential

It’s not sending out an electrical signal

How many millivolts is the neurone when it isn’t producing action potential

-70 millivolts

What does the minus sign tell us

That the inside of the nerve cell is more negative than the outside

What is the neuron doing at rest

Working to maintain an electrical difference to get ready to respond to the right situation

How is resting membrane potential maintained

At rest more sodium outside and more potassium inside

Potassium can leak out easily because of channels meaning inside becomes more negatively charged

Only a tiny amount of potassium can get through as membrane is more permeable to sodium

A sodium potassium pump helps maintain these differences

How is resting membrane potential maintained

At rest more sodium outside and more potassium inside

Potassium can leak out easily because of channels meaning inside becomes more negatively charged

Only a tiny amount of potassium can get through as membrane is more permeable to sodium

A sodium potassium pump helps maintain these differences

What makes a neurone change its electrical potential

A neurone can receive a signal from another neurone and the signals can cause ions channels in membrane to open meaning voltage gated sodium channels allows sodium to move into cell quickly

What happens to membrane for action potential to be triggered

Resting membrane is -70 and when membrane becomes less negative it reaches threshold of -55 where action potential is triggered

what happens during action potential

1. Depolarisation- when threshold has been reached the sodium channels open meaning neurone becomes more positive

2. Repolarisation- at peak sodium channels deactivate. Potassium channels open where potassium moves outside and take positive charge with them

3. Hyperpolarisation- the dip where potassium channels close and membrane settles to resting potential

How does action potential travel along axon

When an action potential occurs in a section of the membrane the movement of positive charge inside axon affects the membrane next to it meaning it becomes less negative

If it reaches threshold volted gated sodium channels open and a new action potential is produced there

How does action potential vary between different axons

Unmyelinated Axon- action potential happens continuously from section to section along membrane

Myelinated axon- the action potential is generated in any gaps in myelin( ranvier nodes). Action potential struggles however can jump from gap to gap so transmission is faster

What is the short period after an action potential called

The refractory period

What is the refractory period

After an action potential has been initiated where the bit of the membrane cannot produce another one. It helps signal move forward and doesn’t allow it to fall back on itself