How does our body know 'what to do'
Feeling, knowing, doing anything depends on special structures called nerves. Neuronal cells in the body act as various messengers according to the need involved. We are born with all the nerve cells we will ever have. There are about 100-billion nerve cells in our brain. If any nerve cell is somehow damaged, it will not be replaced by a new cell. Each nerve cell is known as a neuron. We will learn about the morphology of the nerve cell in the next section. The nervous system, as you may recall reading earlier, consists of 100-billion neurons and the glial cells. The whole brain is a collection of neuronal and glial cells. These cells are also responsible for higher functions of the brain like learning, memory, speech etc. This fascinating study of biological function of nervous system is called as neurobiology.
So how does our body get to know, what to do? The terminal endings of the nerves are equipped with sensitive receptors. They generate the impulse in relation to any change in the environment i.e., temperature, pressure, touch and send them to main part of the nerve cell, to be transmitted to the brain. The brain receives such messages from various axonal tips. Further brain decides what information has to be processed. If actions are necessary, brain signals the muscles to carry out the work required. We will learn about this mechanism in greater details later here in this unit. A neuron releases its messages as chemicals. These are capable of changing polarity of cells. This is because of the ionic nature of the chemicals. Since it is achieved through movement of ions, we call them ionic channels. Their movement is termed as gait. The ions which play a major role are Ca++, Na++, K+. They are able to create energy for nerve cells to function in a better manner. This creates some amount of electricity in the cell, which can be measured in volts. This principle was discovered by an Italian scientist Alessandre Volta during his experiment on frog leg muscle. We will understand the functioning of the nerve cell better by first getting to know the morphology of the nerve cell.