The Structure of a Neuron

• The different types of neuron have different appearances however, they all share the same structure.
• Cell Body (Soma)

  This contains everything the nerve needs to survive. It also contains the nucleus.

  
• Dendrites


  These are branch-like structures that stick out of the cell body. They pick up nerve impulses from other neurons and carry them towards the cell body.
• Axon


  This carries impulses away from the cell body, down the length of the neuron; this electrical impulse is the action potential. The axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up the electrical transmission of the impulse. There are gaps in the sheath (called nodes of Ranvier), which speed up transmission of the action potential by forcing it to 'jump' across the gaps.
• Terminal Buttons/Synaptic Endings/Pre-synaptic Terminal

  This is the end of the axon; it has a variety of names. Here, the action potential has to travel to the dendrites of another neuron through synaptic transmission.
• The Firing of a Neuron

  When a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second, causing an action potential to occur. This creates an electrical impulse that travels down the axon towards the end of the neuron.
• Reflex Arc


  Most environmental information is transmitted from the PNS to the CNS via sensory and relay neurons; the brain then sends behavioural information towards the PNS via relay and motor neurons. However, in some situations (such as touching a hot plate), the impulse is not transmitted to the brain; instead, it moves from a sensory neuron to a relay neuron (within the spinal cord) and directly to a motor neuron (e.g. to drop the plate). Bypassing the brain creates a quicker response; this is called a reflex arc.

  
• Synaptic Transmission

  Neurons communicate with each other within groups known as neural networks. Each neuron is separated from the next by a tiny gap called the synapse. Signals within neurons are transmitted electrically; however, signals between neurons are transmitted chemically across the synapse. When the electrical impulse (action potential) reaches the end of a neuron (the presynaptic terminal) it triggers the release of neurotransmitters from tiny sacs called synaptic vesicles.