The Endocrine System
Signalling by using hormones
- Hormones are molecules released by endocrine glands directly into the blood, acting as messengers, carrying signals from the endocrine gland to a specific target tissue/cell.
- There are two types of hormone:
- Protein and peptide hormones and derivatives of amino acids (adrenaline/insulin/glucagon)
- Steroid hormones (sex hormones)
- Endocrine glands release hormones directly into the blood via blood capillaries, the picture below shows different endocrine glands in the human body.
- Exocrine glands do not release hormones.
The Target Tissue
- The target cells have receptors on their plasma membranes that are complementary to the specific shape of the hormone molecule.
- Homones can therefore travel around the blood without affecting cells around it that…