How do neurons transfer information? How does a neuron responding to ‘red’ signals ‘there is/isn’t red’?

How do neurons transfer information? How does a neuron responding to ‘red’ signals ‘there is/isn’t red’?

The neuron is the cell responsible for the transfer of information and electrical impulses around the body. Neurons work by transferring electrical charges from neuron to neuron to get from one point to another.In essence, all information comes into a neuron through the dendrite, flows through the neuron and then leaves to go to the next neuron through the axon. The arms on each side are necessary for the neuron to work properly.Neurons work by passing electrical signals. Starting with the axon, the neuron sends an electrical impulse of data through the arms. No two neurons actually touch; they just are very close to each other. The space between a neuron's axon and another neuron's dendrite is known as the synapse. When the neurons are passing information, the synapse is the portion that is "flinging" the data from one neuron to the other. This process is known as synaptic transmission.

Once the synaptic transmission occurs, the data enters through the dendrites. The electrical signal has now successfully transferred from the first neuron to the second one. The signal then moves to the axon and passes through the synapse to the next neuron's dendrite. In other words, a neuron works by being stations for the electrical signal.

When you stare at a red stimulus, the cells signaling the presence of red will start to fatigue. Thus, when looking at the empty screen these cells will now fire very little. However, because they normally encode through their activity the presence of red or the absence of green, reduction in their activity is interpreted by the brain as the presence of green.Thus, you see a green afterimage.

Neurons are the basic processing structures of the central nervous system. The function of a neuron is to recieve input information from other neurons, process the information and subsequently produce an output information. The structure of a neuron allows it to perform this function. It consists of:

- Dendrites - branching fibers that become more narrow at the end and have a surface lined with specialized synaptic receptors, at which the dendrite receives information from other neurons.
- Dendritic spines - the short outgrowths that increase the surface area available for synapses
- Cell body/soma - that contains the nucleus, ribosomes and mitochondria, which allow the metabolic work to occur
- Axon - thin fiber of constant diameter, in most cases longer than the dendrites, which is the neuron's information sender, conveying an impulse toward other neurons, organ or muscle
- Myelin sheath: an insulating material covering many of the vertebrate axons
- Nodes of Ranvier: interruptions along the myelin sheath
- Presynaptic terminal: the point from which the axon releases chemicals that cross through the junction between one neuron and the next

If the message sent by the output neuron - the action potential, is beyond the excitatory threshold of the input neuron, depolarisation of the membrane occurs. When the potential reaches the threshold, the membrane opens its sodium channels and permits sodium ions to flow into the cell. This causes the electrical impulse to move through the axon and reach its terminal - the terminal buttons causing the release of neurotransimitters a "chemical medium through which signals flow from one neuron to the next at chemical synapses".

Colour vision is possible beacuse of the existance of cones on the retina. There are three types of cones - long, short, medium. The sensitivity of specific cones to certain wavelengths of light allows one to create a spectrum of colours in accordance with the intensity with which each type of cone is stimulated. When percieving red the long cones are highly stimulated, the medium are slightly stimulated wheras the short ones are almost not. After a long stimulation the cone becomes overstimulated and loses its sensitivity. This is usually dealt with through microsaccades however colour is usually on the larger part of the receptive field and so it is
impossible to let the cones rest. When cones get tired they stop responding, as the light sensitive pigments contained within them are bleached. This creates an afterimage, which in the case of red and green was explained above.