The endocrine system

The endocrine system is an integration system influencing the metabolic activities of cells. It functions through hormones – chemical messengers synthesized by endocrine glands namely – hypothalamus, pineal, pituitary, parathyroid, thyroid, gonads, and adrenals.

Hormones – They are the chemical substances produced by the endocrine glands that control the metabolic functions of other cells.

1. Steroid based hormones – cholesterol derivatives.
2. Amino acid-based hormones: single modified amino acids, amino acid derivatives, proteins, peptides, glycoproteins.
3. Eicosanoids — derivatives of arachidonic acid, 20-carbon polyunsaturated fatty acid

Mechanisms of Hormone Action

Synthesized hormones affect on target cells by:

Changing in membrane permeability as a result of the closing and opening of the channels.

Deactivation or activation of regulatory molecules — covalent modification.

Synthesis of regulatory molecules involves changes in gene expression. All these effects result in physiological changes, including :

1. Mitotic stimulation
2. Contraction or relaxation
3. Induction of secretory activity.