Neurons

• Biopsychologists assume that behaviour and experiences are caused by activity in the nervous system. The nervous system transmits signals for communication via the billions of nerve cells (neurons) it houses. These nerve cells communicate with each other, through electrical and chemical messages, within the body and the brain. Cells that conduct nerve impulses are called neurons. The things that people feel and do are caused by events between neurons that make up the nervous system.
• Structure of a Neuron

  Nucleus 

  Located in the cell body. The control centre of a cell, which contains the 23 pairs of chromosomes. 

  Dendrite 

  Receives the nerve impulse from adjacent neurons via receptor sites on the membrane. They receive the neurotransmitters that have been released across the synapse from the previous cell. 

  Axon 

  Where the electrical signals pass along. 
• Structure of a Neuron

  Myelin sheath

  Insulates /protects the axon from external influences that might effect the transmission of the nerve impulse down the axon.

  Nodes of Ranvier

  These speed up the transmission of the impulse by forcing it to ‘jump’.

  Axon Terminal

  The point where the cell terminates. The buttons contain synaptic vesicles which release neurotransmitters at the membrane into the synapse when triggered via an action potential. 
• Sensory neuron - Function: carries messages of sensation from the PNS to the CNS. Structure: long dendrites and short axons / myelinated / unipolar.

  Relay neuron - Function: transfers messages from the sensory neurons to other relay neurons which decide how to respond and pass messages to motor neurons. Structure: short dendrites and short or long axons / not myelinated / multipolar.

  Motor neuron - Function: carries messages from the CNS to effectors like muscles that respond with movements. Structure: short dendrites and long axons / myelinated / multipolar.
• Neuron structure

  
• Electric Transmission

  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 and towards the synapse.