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Hormones are molecules of different nature that are produced in the secretory or endocrine glands . Working together with the nervous system, they are responsible for us to act, feel and think as we do.
The different types of hormones are released in the blood vessels or in the interstitial space where they circulate alone (bioavailable), or they are associated to certain proteins until they reach the organs or tissues white (or target) where they act. Hormones are part of the group of chemical messengers, which also includes neurotransmitters such as dopamine , serotonin or GABA .
The most important functions of hormones
The functions of the hormones are varied, but whether a hormone comes from a plant, an invertebrate animal or vertebrate, is responsible for regulating several important functions. Now … why are hormones so important?
One of the functions they perform is that they ensure the correct growth. In humans, the pituitary gland is responsible for secreting growth hormones during childhood and adolescence. In invertebrate animals, such as insects, growth hormone is involved in the shedding or renewal of teguments (body coatings), that is, the detachment of the outer layer. In the case of plants, there are several hormones that are responsible for the proper growth of roots, leaves and flowers.
In addition to this very important function, the functions of the hormones include :
- Dynamic action on various bodies
- Activate or inhibit enzymes
- The proper development
- The sexual characteristics
- The use and storage of energy
- Levels in the blood of liquids, salt and sugar
Coordinating with the brain
Another fact that we have to take into account is that some biological processes are less expensive if, instead of creating a constant electrical discharge from the neurons to activate certain regions of the organism, we simply emit hormones and let them be dragged by the blood until you reach your destination. In this way we get an effect that lasts several minutes at a time that our nervous system can be taking care of other things.
In that sense, the hormones work coordinating with the brain to activate and deactivate parts of the body and thus ensure that we adapt to the circumstances in real time. Of course, the effects of the release of these hormones take a little longer to notice that those that cause neurons.
Classification of hormones: what types of hormones are there
Now, there are different classifications of hormones .
What are these classifications and according to what criteria are established? Next we explain it to you.
1. By proximity of your synthesis site to your site of action
Depending on whether they make their effect on the same cells that synthesized it or on contiguous cells, the hormones can be:
- Autocrine Hormones : Autocrine hormones act on the same cells that synthesized them.
- Paracrine Hormones : Those hormones that act near where they were synthesized, that is, that the effect of the hormone produces a cell next to the emitting cell.
2. According to its chemical composition
According to its chemical composition, there are four types of hormones
- Peptide Hormones : These hormones are composed of chains of amino acids, polypeptides or oligopeptides. The vast majority of this type of hormones fail to penetrate the plasma membrane of the target cells, this causes that the receptors of this class of hormones are located on the cell surface. Among the peptide hormones, we find: insulin, growth hormones or vasopressin.
- Derivatives of Amino Acids : These hormones emanate from different amino acids, such as tryptophan or tyrosine. For example, adrenaline.
- Lipid Hormones : These types of hormones are eicosanoids or steroids. Unlike the previous ones if they manage to cross the plasma membranes. Prostaglandins, cortisol and testosterone are some examples.
3. According to its nature
Depending on this class of substances produced by the body through its nature, there are the following types of hormones:
- Steroid Hormones : These hormones come from cholesterol and are produced mainly in the ovaries and testes, as well as in the placenta and adrenal cortex. Some examples are: androgens and testosterone, produced in the testes; and progesterone and estrogen, which are produced in the ovaries.
- Protein Hormones : They are hormones formed by chains of amino acids and peptides.
- Phenolic Derivatives : Despite being of protein nature have a low molecular weight. An example is adrenaline, which intervenes in situations in which much of the energy reserves of the body must be invested in moving the muscles quickly.
4. According to its solubility in the aqueous medium
There are two types of hormones according to their solubility in the aqueous medium:
- Hydrophilic hormones (water soluble) : These hormones are soluble in the aqueous medium. Since target tissue has a membrane with lipid characteristics, hydrophilic hormones can not pass through the membrane. Thus, this type of hormones bind to receptors that are on the outside of the tissue. For example: insulin, adrenaline or glucagon.
- Lipophilic (lipophilic) hormones: These hormones are not soluble in water, but they are soluble in lipids. Unlike the previous ones, they can pass through the membrane. Therefore, the receptors of this type of hormones can bind to intracellular receptors to carry out their action. Examples: thyroid hormone or steroid hormones.
Types of endocrine glands
Hormones are produced in the endocrine glands spread throughout the body. In many ways, our nervous system needs the collaboration of other parts of the body to make the processes that take place within the body are coordinated and a certain balance is maintained.
To achieve this level of coordination, our brain regulates the release of various types of hormones responsible for performing different functions. In addition, this class of substances vary according to the type of gland that secretes them, and their location.
The main endocrine glands are:
- The pituitary or pituitary gland : It is considered the most important gland of the endocrine system, because it produces hormones that regulate the functioning of other endocrine glands. It can be influenced by factors such as emotions and seasonal changes.
- The hypothalamus : This endocrine gland controls the functioning of the pituitary gland, secreting chemicals that can stimulate or inhibit the pituitary’s hormonal secretions.
- The thymus : secretes a hormone called thymosin, responsible for stimulating the growth of immune cells
- The pineal gland : produces melatonin, a hormone that plays an important role in adjusting the cycles of sleep and waking function.
- The testes : These produce hormones called estrogen, the most important is testosterone, which indicates to men that it is time to initiate the corporal changes associated with puberty, for example, the change of voice and the growth of the beard and pubic hair.
- The ovaries : Secrete estrogen and progesterone. Estrogen indicates to the girls the moment they have to initiate the corporal changes associated with puberty.
- The thyroid : In this endocrine gland triiodothyronine and thyroxine, hormones that control the rate at which cells burn fuel to produce energy food occurs.
- The adrenal glands : These glands have two parts. One produces hormones called corticosteroids, which are related to the balance between mineral salts and water, the stress response, metabolism, the immune system and sexual development and function. The other part produces catecholamines, for example, adrenaline
- The parathyroid : From here parathyroid is released, a hormone related to the concentration of calcium in the blood.
- The pancreas : Secrete insulin and glucagon, which allows to maintain a stable concentration of blood glucose and to supply the body with enough fuel to produce the energy it needs.
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