A Simple Introduction To Chemical Coordination. Our cellular functions need to be regulated constantly and the nerve fibers do not perform this function.

Thus, a special kind of coordination system is required.

The hormonal system is concerned with the control of different metabolic functions of the body, such as the rate of chemical reactions, growth, secretions, etc.

This coordination is called chemical coordination.

Hormones- The Chemical Messengers

Glands are the tissues that release or produce some secretions called secretions.

There are two types of glands in the body, endocrine and exocrine glands.

An endocrine gland is a ductless gland that releases secretions known as hormones.

These hormones affect the cells in other parts of the body.

A hormone is a small soluble organic molecule that is effective in low concentration.

It is essentially a chemical messenger as it transports a signal from one cell to another.

And affects the site where its receptors are present.

Chemical Nature Of Hormones

All the hormones are organic but vary structurally.

They can be classified into:

1. Steroid hormones- These hormones are composed of steroids. Such as hormones secreted by the adrenal cortex, testes, ovaries, and placenta.
2. Proteinous hormones- These hormones are composed of proteins. Such as hormones secreted by the anterior lobe of the pituitary gland.
3. Catecholamine- Hormones secreted by the adrenal medulla.
4. Amino acid derivatives- Hormones secreted by the thyroid gland.
5. Peptide hormones- These include melanocyte-stimulating hormone, oxytocin, vasopressin, etc.

Mode Of Hormone Action

Protein And Peptide Hormones 

Protein and peptide hormones can not pass through cells’ plasma membrane because they are water soluble and the membrane is made of a fatty layer.

These hormones bind with their receptors on the plasma membrane of the target cell, and the second messenger is generated inside the cell.

This second messenger triggers various changes in the cell like activation of enzymes, gene activation, etc.

Basically performs whatever role it has to perform.

Steroid And Thyroid Hormones

A Simple Introduction To Chemical Coordination. These hormones can pass through the membrane because they are lipid soluble.

Receptors of these hormones are present inside the target cells, whether in the nucleus or in the cytoplasm.

Hormones bind with their receptors and form hormone-receptor complex.

This complex then binds to the target cell and activates the reaction.