BIOL 1080 Study Guide - Final Guide: Hypercalcaemia, Posterior Pituitary, Pineal Gland
Document Summary
Hormones are secreted in very small amounts by endocrine glands (made of secretory cells that are in several diferent organ systems) that difuse into the bloodstream to targeted issues that have appropriate receptors that bind the hormone when present. There are two classes of hormones: lipid soluble (derived from cholesterol and include estrogen and testosterone) and water-soluble hormones (protein or pepide hormones that include epinephrine). Lipid soluble hormones pass through the cell membrane easily and combines with receptor molecules in the cytoplasm that transport it into the nucleus, where it ataches to dna to acivate certain genes. Water-soluble hormones do not pass the cell membrane but bind to a receptor on the membrane surface which acivates a cascade of messengers which acivates many dormant proteins within the cell to carry out a funcion. Posiive vs negaive feedback loops in hormone signaling.