SIGNAL RECEPTION

Definition

A neuron is an electrically excitable cell that processes and transmits informations through electrical and chemical signals. Neurons connect to each other to form neural networks. Neurons are the core component of the nervous system, which includes the brain, spinal cord, and peripheral ganglia. A number of specialized types of neurons exist : sensory neurons respond to touch, sound, light, and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain.

Structure

A typical neuron

possesses a cell body, often called the soma, dendrites and an axon. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres and branching multiple times, giving rise to a complex "dendritic tree". An axon is a special cellular extension that arises from the cell body and travels for a distance, as far as one meter in humans or even more in other species. The axon terminal contains synapses, specialized structures where neurotransmitter chemicals are released to communicate with target neurons or target tissues. The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon (see figure 1). 

Reception and transmission

Dendrites receive the information (= signals) and send it to the soma and then to the axon. In the majority of cases, the signal arrives at the dentrite in the form of a neurotransmitter. They are transduced (converted into and transmitted) in the form of an electric signal, an action potential, that traverses the neuron until the endings of the axon. This is what we mean with neurons being excitable cells, they can generate action potentials. At the endings of the axon, the signal is converted into the release of a neurotransmitter which, in turn, will pass on the message to the next neurons or to a target tissue.