Hormones are traditionally defined as substances produced by endocrine glands that are released into the bloodstream and act on target tissues, binding to specific receptors. They are responsible for the most varied functions, acting from the growth of a person to the regulation of their reproductive capacity, their behavior and their metabolism. Hormones are linked to physiological, morphological and biochemical responses, therefore.
→ What are endocrine glands?
At endocrine glands they produce secretion and release it into the bloodstream. This released secretion is what we call a hormone. As an example of an endocrine gland, we can mention the pituitary, thyroid, ovaries and testes.
→ How do hormones work?
Hormones are released into the bloodstream and act as chemical signalers.. Some hormones work very close to where they were produced; others, however, travel long distances to reach the organ in which it will play its role.
The organ or tissue where the hormones act is called the target tissues or target organs.
These sites have receptors that recognize specific hormones, responding only to these substances. This feature is extremely important to prevent that a hormone affects the action of another organ or tissue.The main regulator of the secretion of different hormones in the human body is the mechanism of feedback, which can be positive or negative, the latter being responsible for the secretion of most hormones.
At the feedback negative, the system response occurs to reverse the direction of a change. To understand this mechanism, just think about the drop in glucose. This stimulus causes the islet of Langerhans cells to produce glucagon release this hormone, stimulating the liver to release glucose and thus increase its concentration in the blood.
→ Some hormones in the human body
Hypothalamus: responsible for producing oxytocin and the antidiuretic hormone (ADH). Oxytocin promotes the contraction of the uterus during childbirth and stimulates the ejection of milk. ADH, on the other hand, guarantees the reabsorption of water by the nephrons.
Hypophysis: it produces several hormones, such as thyrostimulant (TSH), growth hormone (GH) and prolactin. TSH stimulates the thyroid to produce its hormones. GH stimulates bone growth. Prolactin stimulates the mammary glands to produce milk.
Thyroid: produces thyroxine (T4), triiodothyronine (T3) and calcitonin. Hormones T3 and T4 act on metabolism, and calcitonin inhibits calcium loss from bones.
Parathyroid: it produces parathyroid hormone, which is responsible for maintaining adequate blood calcium levels by stimulating the removal of this mineral from the bones.
Pancreas: produces the insulin and glucagon, two hormones related to controlling the amount of sugar in the blood.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-hormonio.htm