What Is Endocrine System & It's Function

 Endocrine system interacts with the nervous system inorder to control the activity within all the cells in the body. The endocrine system is comprised primarily of glands, which are organs that secrete a particular compound. This compound acts as a messenger, traveling throughout the bloodstream and delivering that message to cells all over the body.

  These compounds are called hormones, and the messages they carry may tell cells to start dividing, or to start synthesizing a particular protein, whether their target is a particular tissue, or if they simply act as intermediaries that communicate with other endocrine glands.

These compounds interact with receptors in the plasma membrane of a cell, and the chemistry that occurs as a result, which will elicit an appropriate response within the cells.

Organs of the endocrine system and their specific functions.

The organs of the endocrine system are very small, and scattered around the body. These endocrine glands differ from the exocrine glands that produce sweat and saliva in that these ones produce hormones, which are typically released into the bloodstream.
• These glands include the pituitary and pineal glands, and the hypothalamus, all of which are parts of the brain.
Thyroid and parathyroid glands, found in the neck in front of the trachea.
Adrenal glands and the pancreas, which are in the lower torso, as well as
• The gonads, which are called testes for a male and ovaries for a female.

Other organs also contain clusters of endocrine cells, like the small intestine, stomach, kidneys, and heart, as these also secrete hormones at certain times, though it is not their primary function.

Major hormonal axes of the body
- Hypothalamic-pituitary-adrenal  
  axis, which regulates cortisol,
- Renin-angiotensin-
  aldosteroneaxis, which helps to 
  regulate sodium, potassium, and
  water balance.

Hormon produce by Organs of the endocrine system,

Hormonal axes typically belong to one of just two categories. The first kind are amino acid-derived or small proteins, and the second kind are steroids.
Any of these hormones are secreted by glands when they encounter certain stimuli, and these can be of three varieties.   
  Humoral stimuli involve changes in the concentrations of certain components in the bloodstream, like particular ions or nutrients.
  Neural stimuli involve stimulation by nerve fibers. And hormonal stimuli involve interaction with other hormones,

so sometimes a hormone will interact with a gland, and as a result the gland will secrete some other hormone. These hormones can elicit the intended effect in even very low concentration, and they circulate in the blood either free, or bound to a protein carrier, depending on their solubilities.

Organs of endocrine system

1). pituitary gland
  This is a small sac comprised of a posteriorlo be and an anterior lobe, which hangs from the hypothalamus via the infundibulum. This gland secretes at least eight hormones. In the posterior lobe, these are neurohormones that arrive ready-made from the hypothalamus, while the anterior lobe secretes its own hormones.
  The neural connection between the pituitary gland and the hypothalamus is called the hypothalamic-hypophyseal tract, and the two main hormones that travel through here to be secreted by the posterior pituitary are called oxytocin and and antidiuretic hormone, or ADH, also called vasopressin.
Oxytocin is released during childbirth, and is also involved in the release of milk during breastfeeding. In addition, it is involved in sexual and affectionate behavior between mates, promoting couple bonding.
ADH is completely different, inhibiting urine formation formation during times of high blood osmolarity or low blood pressure, thus helping the body avoid dehydration.

The anterior pituitary has a different role,manufacturing and secreting a variety of hormones that in turn regulate other endocrine glands. These hormones are growth hormone, which promotes tissue growth and directs cells to metabolize fat,
Thyroid-stimulating hormone, which stimulates the thyroid gland as one might expect,
Adrenocorticotropic hormone which stimulates the adrenal cortex,
Follicle-stimulating hormone and luteinising hormone, which regulate the gonads, and
• Prolactin, which stimulates milk production in females.
  Any of these can be released when a particular stimulus is received from the hypothalamus.

2) Thyroid gland
This is comprised of two lobes connected by the isthmus, and it produces thyroid hormone, which is actually two hormones, thyroxine and triiodothyronine, also known as T4 and T3 respectively. This is a hormone that affects almost every cell in the body by increasing metabolism, regulating tissue growth, and maintaining blood pressure.

3) Parathyroid glands
parathyroid gland, of
which there are typically four. These secrete parathyroid hormone, which regulate calcium and phosphate levels in the blood.

4). Adrenal glands
Adrenal glands which are each comprised of an inner adrenal medulla and an outer adrenal cortex. The cortex synthesises a wide variety of steroid hormones called corticosteroids.

Mineralocorticoids like aldosterone regulate ion concentrations like sodium and potassium.
Glucocorticoids like cortisol and cortisone influence influence metabolism by keeping blood glucose levels consistent, and they also maintain blood pressure by influencing vasoconstrictors.   
Cortisol also triggers gluconeogenesis, where glucose is made from fats and amino acids.
• Gonadocorticoids are sex hormones like androgens, which are typically converted into testosterone.

The adrenal medulla, on the other hand, synthesise catecholamines like epinephrine and norepinephrine. These are important in emergency situations, so the perception of danger triggers their release, upon which they induce high levels of glucose in the blood and a faster heartbeat, which are good for evading danger.

5). Pineal gland
  Pineal gland is found in the diencephalon of the brain. This produces melatonin, which helps us sleep. That wraps up the glands that are devoted solely to endocrine function.

6). Pancreas
Pancreas is found in the abdomen, and it is responsible for making the hormones glucagon and insulin. These regulate blood glucose levels.
Glucagon is a polypeptide made of 29 amino acid residues which will stimulate an increase of glucose in the blood. Much of its activity occurs in the liver, where it triggers breakdown of glycogen, and glucose synthesis by other means, as well as the release of the resulting glucose.
Insulin is a larger peptide, made of 51 residues of amino acids, qualifying as a small protein. This will stimulate a decrease of glucose inin the blood by inhibiting glycogen breakdown and glucose synthesis.

  So glucagon and insulin have nearly opposite actions in the body, as glucagon release is triggered by fasting, and insulin release is triggered by eating.

7). Gonads
Gonads produce sex hormones just like the adrenal cortical cells. • The ovaries produce estrogens and progesterone, which control the development of reproductive organs and secondary sex characteristics in females.
• The testes produce testosterone, which controls the development of reproductive organs and secondary sex characteristics in males.
• The placenta is a temporary endocrine organ which exists during fetal development in a pregnant woman. It secretes steroid and protein hormones that influence pregnancy, and support the development and growth of the fetus.

There are other organs that also produce hormones.

Adipose cells release leptin, which communicates how much fat is stored in the body, as well as resistin and adiponectin, which are related to response to insulin.

Enteroendocrine cells in the gastrointestinal tract release peptide hormones that regulate digestion.

Cardiac cells that secrete atrial natriuretic peptide, or ANP, which regulates blood volume and blood pressure, as well as B-type natriuretic peptide, or BNP, in response to stretching caused by increased blood volume.

The kidneys secrete erythropoietin, which promotes red blood cell production, as well as renin, which is associated with aldosterone release.

Bones can secrete osteocalcin, which promotes the release of insulin.

The skin produces cholecalciferol when exposed to a type of ultraviolet light, which is an intermediate in vitamin D production.

This remarkable system of communication is critical for human development, and our bodily functions depend on the ability of hormones to travel everywhere they need to go.