- Hormone = a chemical messenger produced by the body. released by endoctrine glands directly into the blood to a target organ
- Endoctrine glands do not have ducts like other glands
- cells in the endoctrine glands must not be affected by hormones som are often secreted in inactive forms
- each hormone affects only specific target cells: they either enter the target cells or bind to complementary receptors on the cell membranes bringing about charactistic responses due to the hormones effects on enzymes
- some hormones trigger a second messenger molecule to activate enzymes within the cell
Peptide (charged) Hormones vs Steroid (lipid soluble) Hormones
Peptide Hormones include EPO, insulin and the human growth hormone
- peptides are not able to pass through cell membranes easily because peptides are charged
Steroid hormones are formed from lipids and have complex ring structures
- STEROID HORMONES PASS THROUGH CELL MEMBRANE and bind to receptors in CYTOPLASM
The hormone-receptor complex functions as a transcription factor, switching enzyme synthesis on or off:
transcription factor fits into promoter region, attached to gene to be transcribed, surrouned by RNA polymerase
Hormonal Control vs Nervous Control
Hormones have slower, longer lasting effects brought about by chemicals carried in the blood. Nervous repsonse are quicker, with short lasting effects, an electrical signal carried by nerves.
How do hormones enhance performance?
- a peptide hormone ( a glycoprotein) naturally produced by the kidneys