Neurons are the cells that transmit electrical impulses around the brain and the other parts of the central nervous system.
- Neurons are the electrically excitable cells that are the fundamental building blocks of the central nervous system of human beings.
- Neurons interconnect the systems and organs that maintain the body’s essential functions.
- Neurons send and receive signals that allow us to sense the external world, move, think, form memories and much more.
- Neurons are of three principal types: motor neurons, sensory neurons and interneurons.
- Neurons connect together via specialized filaments called synapses.
- In the neocortex (making up about 80% of the human brain), approximately 70-80% of nervous tissue is in the form of neurons whilst the remainder is composed of interneurons.
About the anatomy of neurons
- A typical neuron consists of a cell body (soma), dendrites, and a single axon.
- Dendrites and axons form filament-like extensions of the soma.
- Dendrites typically form into a profusion of branches as they extend from the soma.
- An axon can be as long as a metre in length.
- At the farthest tip of the axon’s branches are axon terminals, where the neuron can transmit a signal across a synapse to another cell.
- Interneurons are also referred to as relay neurons, connector neurons, intermediate neurons and local circuit neurons each of which helps to explain their function.
- Interneurons form nodes within neural circuits, enabling communication between sensory or motor neurons and the central nervous system.
- Interneurons can be further broken down into two groups: local interneurons and relay interneurons.
- Local interneurons have short axons and form circuits with nearby neurons to analyse small pieces of information.
- Relay interneurons have long axons and connect circuits of neurons in one region of the brain with those in other regions.
- The interaction between interneurons allows the brain to perform complex functions such as sense-making.
About neurons and the human retina
- There are two principal types of neurons in the retina of the human eye: the rod and cone photoreceptors and ganglion cells.
- There are four principal types of interneurons in the retina of the human eye: horizontal cells, Müller cells, bipolar cells and amacrine cells.
- Rod and cone photoreceptors are sensitive to light and encode it into electrical signals that are transmitted via a complex network of interneurons to the ganglion cells, which then forward visual information via the optic nerve towards the brain.