A neuron, is a specialised cell which communicates with other neurons, muscles or organs in the body using electrical and chemical signals or impulses.
A resting neuron, is when there is NO electrical impulse, running through the neuron.
This means that there is, a negative charge inside the neuron and a positive charge outside the neuron.
A firing neuron is when an electrical impuse moving along the axon of the neuron, reversing the electrical charge.
E.G. a positive charge inside the cell and a negative charge outside of the cell.
Types of Neurons
There are 3 types of neuron:>>
- Motor Neuron
A sensory neuron, exists in the sensory organs and responds to messages from external stimuli.
These messages are directed to the central nervous system (CNS).
Motor neurons, carry impulses or signals from the central nervous system to a muscle causing it to contract, in addition to this they also affect glands.
An inter neuron, is only found in the Central Nervous System, and they connect neurons to other neurons within the same region of the spinal cord.
Cell body or Soma
The cell body or soma, can be known as the "factory" of the neuron this is because it produces the proteins and has important organelles, such as mitochondria which are a supplier of energy.
It also contains the nucleus and has several outgrowths (dendrites) which allow many connections to be made with other neurons.
The nucleus is an oval shaped structure found in the cell body or soma of the neuron.
It contains the chromosomes, neccessary for the coded production of proteins within the cell, and genetic information (DNA) from which the chromosomes are made for the neuron.
Dendrites are a part of a neuron, it recieves signals ONLY from other nerve cells.
They have a number of receptors in the dendrite membrane to recognize the neurotransmitters (chemicals) released from the axon of another neuron.
The myelin sheath is a material made of fats and proteins (made by the neurons nucleus) which is found all around the axon of a neuron, and acts as a protective layer.
It is made up of "white matter" of the brain.
Its function is to protect the neuron from external influences which might disrupt the transmission of a nerve impulse down the axon of the neuron.
Its other function is to insulate the nerve fibre to increase the speed of nerve transmission.
Nodes of Ravier
A node of ranvier are gaps of nerve fibres that appear at regular intervals in the mylein sheath.
They allow nutrients and waste products to enter & leave the neurone and they also enable nerve impulses to flow through the neurone through a process of polarisation and de - polarisation of the cell membrane.
(related to chemical signals inside and outside the neuron)
Schwann Cells are the cells that produce and are responsible for laying down the protective myelin sheath around the axon.
An axon is a part of a neuron, it is a single nerve fibre that extend from the cell body of a neuron and carries nerve impulses away from the soma.
It is essential for the entire functioning of a neuron as it allows for travel of the impulse.