History Role of hormones first studied by removing an organ and observing the effect on the animal 1889 – scientists removed pancreases from dogs and noticed the ants were gathering in the cages of these dogs but not in the cages of the normal dogs Scientists analyzed the urine of the dogs and found that the urine of the experimental dogs contained a lot of sugar (which attracted the ants!)

They concluded that a hormone produced by the pancreas was responsible for regulating blood sugar (now known to be insulin) PROBLEMS WITH EARLY METHODS: no hormonal responses work independently, some glands produce many different hormones, hormonal concentrations vary throughout the day.

Today... Today hormones are studied using radioactive tracers and advanced microscopes. Trillions of cells in the body must interact with each other  this is the role of the endocrine system! Leptin Progesterone Testosterone

Hormones Means “to excite or set in motion” Chemicals released by cells that affect cells in other parts of the body, classified according to their activation site (i.e. Parathyroid hormone) Some hormones are called non-target hormones because they affect many cells throughout the body (i.e. Growth hormone, insulin, epinephrine)

Endocrine glands Secrete chemicals (endocrine hormones) into the blood

Exocrine glands Secrete substances through ducts or tubes onto a body surface or into a cavity (i.e. Digestive glands) Salivary glands Prostate gland Milk glands

Types of Hormones Hormones are classified into two types: 1. Steroid Hormones 2. Protein Hormones

1. Steroid Hormones Group of hormones made from cholesterol, complex rings of carbon, hydrogen and oxygen Include the male and female sex hormones and cortisol (stimulates liver to convert amino acids into glucose) Fat soluble – can dissolve across cell membranes

Mode of Action – Steroid Hormone 1. Hormone diffuses into its target cell 2. In the cytoplasm, the hormone combines with a receptor molecule to make a hormone-receptor complex 3. The complex then moves to the nucleus and attaches to a specific segment of DNA 4. This binding activates the gene that sends a message to a ribosome in the cytoplasm to begin making a specific protein

Mode of Action – Steroid Hormone

2. Protein Hormones Contain chains of amino acids of varying length, soluble in water, include insulin and growth hormone Insulin

Mode of Action – Protein Hormone 1. Hormone combines with a specific receptor site on the cell membrane 2. Hormone-receptor complex is formed which activates the production of the enzyme adenylyl cyclase 3. This enzyme converts ATP into cyclic AMP 4. Cyclic AMP (cAMP) acts as a messenger  activating enzymes in the cytoplasm to carry out various functions (e.g. Activate enzymes to convert glycogen to glucose)

Mode of Action – Protein Hormone

THE PITUITARY: THE MASTER GLAND Two lobes: Anterior and Posterior Anterior – produces and stores hormones Posterior – stores hormones produced by hypothalamus Exercises control over other endocrine glands

Homework: Copy chart on pg. 377!