hormonal communication

• The endocrine system is made up of endocrine glands which are responsible for hormonal communication. These hormones are transported via blood and bind to their target cells causing a response.
• Hormones are the chemical messengers transported in the blood. They have long lasting effects and are widespread (eg steroids, proteins, glycoproteins, amines, polypeptides and tyrosine derivatives).
• Steroid hormones are lipid soluble and can diffuse across the cell surface membrane and into their target cells to bind to a receptor often located within the cytoplasm. Oestrogen is an example of SH
• Non-steroid hormones are insoluble in lipids and therefore can not diffuse across the cell surface membrane. Instead, they bind to a complementary shaped receptor on the cell surface membrane of the target cell. This binding causes a cascade of reactions within the cell, and that is how a response is initiated.
• Adrenal glands are endocrine glands located at the top of each kidney. They are made up of the adrenal cortex, medulla and surrounded by a capsule. The cortex and medulla sections secrete hormones.
• three types of hormones secreted by the adrenal cortex:

  1. Glucocorticoids
  2. Mineralocorticoids
  3. Androgens
• glucocorticoids - regulate metabolism and immune responses. Cortisol is an example of this type of hormone.
• mineralocorticoids - control salt and water balance. Aldosterone is an example of this type of hormone.
• androgens - male sex hormones. Testosterone is an example of this type of hormone.