Harmones

Chemical substances produced by endocrine glands are called hormones. They are transported to target organs through blood. It shows catalytic action like enzymes. But differ from enzymes.

They are produced by endocrine glands which do not have a duct.

They are made up of proteins, steroids, polypetides or aminoacid derivatives.

They are used up in the metabolic reaction.

They reach the target organs through blood and perform their function there.

They have low molecular weight and can diffuse through membranes.

The name hormone was first used by the English physiologists W.M.Bayliss and E.H.Starling in 1909.

Hormon means to stir up or set in motion.

Some of the hormones secreted by the endocrine system includes Thyroxine, parathormone, aldosterone, adrenaline, noradrenaline, insulin and glucagons etc.

Their quantity of hormone secretion plays an important role in the good condition of the body.

If they are secreted in higher quantities (hyper secretion) or lower quantities (hypo secretion) it results in diseases.

Nowadays hormonal injections are given to overcome these problems.

Thus hormone can be defined as the signaling molecules secreted from endocrine glands, that is distributed by blood to nonadjacent target cells.

Peptides regulate other functions such as sleep and sugar concentration. They are made from long strings of amino acids, so sometimes they are referred to as "protein" hormones. Growth hormone, for example, helps us burn fat and build up muscles. Another peptide hormone, insulin , starts the process to convert sugar into cellular energy.

Hormones so perfectly and efficiently manage homeostasis due to negative feedback cycles. Our goal is to keep the concentration of a certain chemical, such as testosterone, at a constant level for a certain period of time, the way that a thermostat works. Using negative feedback, a change in conditions causes a response that returns the conditions to their original state. When a room's temperature drops, the thermostat responds by turning the heat on. The room returns to the ideal temperature, and the heater turns off, keeping the conditions relatively constant