Structure function and types of neurons
The nervous system is an essential part of the human body that helps in the transmission of signals across the various parts of the body, that is, it releases messages back and forth from the brain to the different parts of the body, and also helps in the coordination of voluntary and involuntary actions of the body.
At the cellular level, the nervous system consists of a special type of cell, called the neuron, also known as a “nerve cell”. The neurons connect to each other using a synapse (which is a structure that acts like a pathway connection that transmits the signals to the other cells) to form the nervous system.
Neurons have special structures that allow them to send signals rapidly and precisely to other cells by providing a common pathway for the passage of these electrochemical nerve impulses. Neurons are responsive in nature, by which we imply that Neurons response to feelings and communicate the presence of that feeling to the central nervous system which in-turn is processed and is sent to the other parts of the body for action. The neurons are the basic constituents of the brain, vertebral spinal cord, the ventral nerve cord and the peripheral ganglia( which is a mass of nerve cell bodies).
Neurons can be categorized into three types: sensory neurons, motor neurons and inter neurons.
Sensory neurons allow us to receive information from the outside world through our senses. The sensory neurons evoke the sensation of touch, pain, vision, hearing and taste. These are usually present in the sensory organs, like the eyes, inner ear and so on, which send these signals to the spinal cord and the brain.
Inter neurons communicate and connect with each other, and represent the majority of the neurons in our brain. They allow us to think see and perceive our surroundings. Motor neurons are neurons that receive impulses from the spinal cord or the brain and send them to the muscles causing muscular contraction, and these also affect the gland secretion.
A typical neuron has a “soma” in its centre, which contains the nucleus of the cell. And hence this is where the protein synthesis occurs.
The neural function is based on the synaptic signalling (the pathway that helps in the transmission of signals) process, which is partly electrical and partly chemical. The electrical aspect depends on properties of the neuron’s membrane. Every neuron is surrounded by a plasma membrane, which is a bilayer of lipid molecules that comprise of various protein structures. A lipid bilayer is a powerful electrical insulator, but in neurons, many of the protein structures embedded in the membrane are electrically active.
Cell division cannot take place in neurons as they lack one of the two cylindrical cellular structures that aid in cell division. This is consistent with a simple cell division nature of the cell.
Dendrites are extensions of the cell with many branches, whose structure can be called as a “dendritic tree” . They project from the cell body and are sometimes referred to as fibres. They are also called as afferent processes because they transmit impulses to the neuron cell body .
There is only one axon that projects from each cell body, which is a finer cable-like projector. It is usually elongated and it carries impulses away from the cell body, that is, away from the ‘soma’. It is an efferent process.
many axons are surrounded by a segmented white fatty substance called myelin sheaths.