HORMONES Chemical messengers Produced by endocrine glands Controlled by pituatory gland (controlled by hypothalamus) Released into bloodstream in small amounts Passed to receptor sites Have a specific effect Variety of functions therefore variety of structures

NEGATIVE FEEDBACK MECHANISM EXAMPLE Eating chocolate Increased blood glucose level Production of insulin Makes body take up glucose Stored as glycogen Blood glucose level is lowered

COMPARE CHOLESTEROL TO SEX HORMONES CholesterolTestosterone

OTHER SEX HORMONES ProgesteroneAndrosterone

SEX HORMONES Differences in structure give rise to differences in physiological function E.g. presence of methyl and hydroxyl groups Take notes on HORMONES AND THEIR ROLES on page 344

ORAL CONTRACEPTIVES During pregnancy, progesterone prevents ovulation Estrogen prevents irregular flow during menstrual cylce In oral contraceptive the two hormones act together to stop release of folicle stimulating hormone (fsh) and luteinizing hormone (lh) by the pituatary Ovulation is inhibited Drug mimics progesterone

MODE OF ACTION

ORAL CONTRACEPTIVE MODE OF ACTION Read and take notes using page 345

STEROIDS Abuse by athletes

TESTOSTERONE Male secondary sexual characteristics Muscle growth Used to stimulate muscle growth in e.g. cancer sufferers

HARMFUL SIDE EFFECTS Effects of aging increased Impotence Baldness Growth of facial hair More violent behaviour High blood pressure Increased risk of heart attacks

QUESTIONS Page 360 Questions 27 and 28