The Human Nervous System - Structure and Function - All Explained

The nervous system is a regulatory system that controls a variety of body functions. The nervous system can detect changes occurring in various organs and take corrective action when needed to maintain the constancy of the internal environment. The nervous system also regulates activities that change almost instantly, such as muscle contractions and perception of danger. The body is made up of many receptors that receive incoming information about what is happening within the body and what is happening in the outside environment. Specifically, these receptors represent our eyes, ears, skin, nose, and stomach. We act on that information via the nervous system.

The basic structural and functional unit of the nervous system is the neuron. These are elongated, highly branched cells. The body contains about 100 billion neurons. Neurons respond to electrical and chemical signals, conduct electrical impulses, and release chemical regulators. Overall, neurons allow us to perceive what is occurring in our environment. They help us engage in learning, store vital information in memory, and control the body's voluntary (and involuntary) actions.

The brain and spinal cord make up the central nervous system (CNS). The brain stores information, reacts to incoming information, solves problems, and generates thoughts. In addition, the brain plans a course of action based on the other sensory inputs. Responses to the stimuli are carried out mostly through the peripheral nervous system (PNS) to accommodate one's will.

Simply put, the nervous system receives information through stimulation of various receptors, processes this information, and sends out signals for an action that needs to be taken through its various branches. Actual transmission of the signal uti­lizes a change in the sodium and potassium concentration in the neuron. There is an influx of sodium and a loss of potassium as the message is sent. Ion concentrations are then restored to normal amounts in the neuron and it is ready to conduct another message.

When the signal must bridge a gap (synapse) between the branches of different neurons, the message is generally converted to a chemical signal called a neurotransmitter. The neurotransmitter, itself is then released into the gap, thereby passing the signal from one neuron to another. Another type of cell may also be at the receiving end of the neurotransmitter, such as a muscle cell. If the signal is sent to an­other neuron, this allows it to continue on to its final destination. The neurotransmitters used in this process are often made from common nutrients found in foods, such as amino acids. Examples are the amino acid tryptophan being converted to the neurotransmitter serotonin, and the amino acid tyrosine being converted to the neurotransmitters dopamine, norepinephrine, and epinephrine.

Other nutrients also play a role in the nervous system. Calcium is needed for the release of neurotransmitters from neurons. Vitamin B-12 plays a role in the formation of a myelin sheath, which provides a form of insulation around specific parts of most neurons. Finally, a regular supply of carbohydrate in the form of glucose is important for providing for the energy needs of the brain. The brain can use other fuels, but gen­erally relies on glucose.