Endocrine System



Endocrine System

Endocrine System

Introduction

The nervous system sends electrical messages to control and coordinate the body. The endocrine system has a similar job, but uses chemicals to “communicate”. These chemicals are known as hormones. A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs, upon which they act. Note that this is in contrast to our digestive glands, which have ducts for releasing the digestive enzymes.

Pheromones are also communication chemicals, but are used to send signals to other members of the same species. Queen bees, ants, and naked mole rats exert control of their respective colonies via pheromones. One common use for pheromones is as attractants in mating. Pheromones are widely studied in insects and are the basis for some kinds of Japanese beetle and gypsy moth traps. There are three general classes (groups) of hormones. These are classified by chemical structure, not function.

steroid hormones including prostaglandins which function especially in a variety of female functions (aspirin inhibits synthesis of prostaglandins, some of which cause “cramps”) and the sex hormones all of which are lipids made from cholesterol,

amino acid derivatives (like epinephrine) which are derived from amino acids, especially tyrosine, and

peptide hormones (like insulin) which is the most numerous/diverse group of hormones.

The major glands and their cause include:

Hypothalamus And Pituitary Gland

The pituitary gland is called the “master gland” but it is under the control of the hypothalamus. Together, they control many other endocrine functions. They secrete a number of hormones, especially several which are important to the female menstural cycle, pregnancy, birth, and lactation (milk production). These include follicle-stimulating hormone (FSH), which stimulates development and maturation of a follicle in one of a woman's ovaries, and leutinizing hormone (LH), which causes the bursting of that follicle (= ovulation) and the formation of a corpus luteum from the remains of the follicle.There are a number of other hypothalamus and pituitary hormones which affect various target organs.One non-sex hormone secreted by the posterior pituitary is antidiuretic hormone or ADH. This hormone helps prevent excess water excretion by the kidneys. Ethanol inhibits the release of ADH and can, thus, cause excessive water loss.

Thyroid Gland

Thyroid hormones regulate metabolism, therefore body temperature and weight. The thyroid ...