Neuronal communication Typeit

An example of a receptor is a , which responds to changes in mechanical pressure. Sensory receptors are known as because they convert one type of energy to another, usually electrical energy. Sensory neurones connect these receptors to the central nervous system using a long dendron and a short , while neurones connect the central nervous system to effectors, which carry out a response. The intermediate neurones which connect these two other types are called neurones.

Some neurones are myelinated because they are insulated from electrical activity along most of their length due to the presence of tightly wrapped cells. Signals are forced to jump between gaps in the myelin sheath known as nodes of Ranvier, which makes transmission along myelinated neurones much than along non-myelinated neurones.

The membrane of an unstimulated neurone is polarised, with a negative resting potential inside. When its plasma membrane is deformed, an action potential is generated as ions enter the neurone and the membrane becomes depolarised, with a positive potential difference inside the axon. In order for repolarisation to occur, ions diffuse out through ion channels that open. This results in as the inside of the axon becomes more negative than usual for a short time, which makes it much harder for a new action potential to be generated. This is known as the period.

Gaps between neurones are called . In order for a signal to cross the gap, such as acetylcholine are required. This allows communication to be carefully controlled at nerve junctions - if impulses from several neurones converge on one postsynaptic membrane, or impulses arrive with high frequency at one neurone, a large concentration of acetylcholine will diffuse across the synaptic cleft, causing of the various signals. Other neurones may reduce the effect of signals combining in order to prevent an action potential, and these are known as synapses.