Nucleus

Axon

Schwann cells

Axon terminal buttons

Cell body (soma)Dendrite

Here is a diagram of a nerve cell: a neurone

It has: A cell body, containing the apparatus for maintaining and running the cell It has: A nucleus, containing the genetic material of the cellIt has: Dendrites, which carry electrical/chemical information to the cell bodyIt has: An axon, which passes electrical information down the cellIt has: Schwann cells, for axon development and maintenanceIt has: Axon terminal buttons which pass electrical/chemical information on

Node of Ranvier

Myelin Sheath

Some nerve cells also have: a myelin sheath, allowing faster passage of information along the axonSome nerve cells also have: Nodes of Ranvier, gaps between each cell of myelin

Information is passed to a nerve cell, either by a receptor (a cell that detects things), or by another nerve cell.

The nerve cell then passes the information on to another nerve cell, in a relay.

Where one nerve cell passes information to another, it is called a synapse.

The information carried by a nerve cell is simple, as it is either activated, or not.

There is no complex information, such as in a conversation, instead it is more like the computer language of binary.

The nerve cell is activated when receptors (cells that detect things) on the dendrites are activated.

This causes an electrical impulse to travel down the axon.

Where it causes chemicals to be released from the axon terminal buttons, passing on the information.

The electricity that travels down the axon is caused by chemicals of different charges leaving and entering the axon

Depolarisation

Na+

K+ K+ K+ K+ K+

Na+ Na+ Na+ Na+

Polarised

- charge - charge - charge

+ charge + charge + charge

+ charge + charge + charge- charge - charge - charge

Here is an illustration of nerve activation

Nerve activation involves electricity being passed along the axon

These lines represent the walls of the axonThese lines represent the area outside the axon

Before activation the nerve is polarised – negative charge inside and positive outside. Note that more ions affect this than just K+ and Na+.A disturbance (eg activation) causes Na channels to open in an area of the axon, allowing Na to enter the axon = + charge. Depolarisation

This triggers depolarisation of the next area of the axon, causing a cascade down the axon to the terminal buttons (called an action potential), which release neurotransmitters to pass on the message.

At a certain threshold the Na channels close and K channels open, K leaves, reducing the charge within the axon back to resting levels.Ion pumps then return K and Na to their starting places, resetting the axon for its next activation

Other negatively charged things

Some axons have a myelin sheath, while others don’t

The benefit of this is that electricity can jump through areas of myelin

This is faster than just relying on the diffusion of charged particles (ions)

Un-myelinated fibres can conduct at 2 metres each second

Myelinated fibres can conduct at 30 metres each second