Endocrine System of animals
The Endocrine system of animals consists of many ductless glands which secrete hormones directly into the blood stream. These hormones affect processes like metabolism, sex drive etc.
A wide variety of physiological processes are carried out by the endocrine system through chemical messengers called “hormones”.
Nervous system is wired control system of the body whereas endocrine system is the wireless control system
A hormone is a specific messenger molecule synthesized and secreted by an endocrine gland or a group of specialized cells. These glands are ductless, which means that their secretions (hormones) are released directly into the blood stream and travel to elsewhere in the body to target organs, upon which they act. This is in contrast to other types of glands in the body such as salivary and sweat glands, which have ducts for carrying the secretions to the points/locations of action.
Note
Hormones are chemicals secreted at variable rates in response to external or internal stimuli by an endocrine gland or a group of cells in very low concentrations (nanomolar to picomolar – 10 -9 to 10 -12 M) directly into the blood for transport to some distant target organs/cells where they alter already existing reactions but cannot initiate new reactions.
Need of Endocrine System
Organs and systems in the body need to communicate with each other so that homeostasis is maintained by endocrine system.
Cells use either chemical and/ or electrical signals to communicate with each other. if chemicals are used, these are hormones usually.
Cell-to-cell communication
Cells can communicate by direct transfer of electrical or chemical signals through gap junctions (proteins side-by-side with a hole down the middle) that connect cells to each other.
Chemical signals are three types-
- Autocrines are chemicals that are produced by a cell and act on the same cell
- Paracrines are chemicals that are produced by one cell and act on nearby cells by diffusing locally through the ECF
- Endocrine substances are chemicals that travel long distances through blood
A science dealing with ductless (endocrine) glands is called endocrinology. endocrinology is made by Greek word “endo” (within) + “krinein” (separate)
Modern (broad) definition of endocrinology-
the study of the adjustments of homeostatic and other activities accomplished by chemical messengers is called endocrinology.
