Endocrine Gland Hormone Review

Endocrine System - 1. Endocrine Gland Hormone Review: Endocrine system: a system of organs known as glands which secrete hormones which circulate throughout the body via the bloodstream Major Endocrine Glands: Hypothalamus: works as a bridge between the nervous system and endocrine system, it’s often thought of as the control center for the endocrine system (in addition to stimulating the pituitary gland it makes ADH and oxytocin) Antidiuretic Hormone (ADH): main regulator of fluid volume within the body by stimulating collecting ducts in the kidneys to retain water Oxytocin: stimulates the uterus to contract for females during pregnancy Pituitary Gland: located right below and is stimulated by the hypothalamus (“master gland”) and most other gland’s functions is dependent on this gland Thyroid Gland: wraps around your trachea (windpipe) and regulates your body’s metabolism through T3 and T4 Parathyroid: located right behind the thyroid and is four separate spots, main function is to regulate blood calcium levels through parathyroid hormone (PTH) Adrenal Glands: located right above the kidneys Cortex: outer portion of the adrenal gland and is important for production of steroids (cortisol and aldosterone) Cortisol: stress hormone important for increasing blood sugar in times of stress so we have energy and has anti-inflammatory function Aldosterone: one of the major regulating hormones of our body’s blood volume and how much fluid is in our arteries Medulla: inner portion of the adrenal gland makes catecholamines (epi and NE) important in fight or flight response (sympathetic) Gonads: sexual reproduction organs and release sex hormones (important for secondary sex characteristics) Ovaries: produces estrogen & progesterone Testicles: produces testosterone Pancreas: located in the upper part of the abdomen and controls blood sugar levels through the hormones insulin and glucagon (both peptide hormones) Autocrine Hormones: these are hormones that function at the same organ that secreted it Paracrine Hormones: hormones that function regionally (such as hormones coming from hypothalamus to the pituitary gland) Endocrine Hormones: hormones that function at a distance Intracrine Hormones: involves a cell secreting a hormone that acts within that same cell The Hypothalamus & Pituitary Gland: 2 Parts of the Pituitary Gland: Anterior Pituitary: interacts with hypothalamus through the hypophyseal portal system (capillary system → through the blood) a. Hormones are: FSH/LH (stimulated by hypothalamus release of GnRH), ACTH (stimulated by CRH), TSH (stimulated by TRH), Prolactin (stimulated by stopping of PIF release), and GH (stimulated by GHRH) → endorphin but also other glands i. 2. a. make them too “FLAT PEG”, FLAT is the tropic hormones (hormones that stimulate other endocrine glands) and PEG is the direct hormones (hormones that act directly on the body) Posterior Pituitary: interacts with hypothalamus through a series of nerves in the pituitary stalk ADH and oxytocin (made in the hypothalamus but stored in the posterior pituitary) Hormone Concentration Metabolism & Negative Feedback: Hormone concentration within the body is tightly regulated throughout the body in areas such as the liver (place them into bile and excreted by the digestive system), kidney (filtering waste products from the blood and putting it into the urine), even sometimes sweat Negative Feedback Loop: if hormones are high, they will inhibit its further production Types of Hormones: Proteins/Polypeptide Hormones: most of the body’s hormones (range from small to large), since they are too big to enter the cell, typically bind to receptors on the surface in order to create a cascade effect (Secondary Messengers) Steroids: come from lipids (typically cholesterol) and have a fused 4 ring backbone (3 cyclohexane rings and 1 cyclopentane rings). Since these hormones are made from lipids, their receptors are located inside the cell (primary messengers) Tyrosine Derivatives: come from the amino acid tyrosine and can act sometimes as hormones and sometimes as amino acids (such as those that come from the thyroid gland (act like steroids but aren’t) and the catecholamines (epi/nor that act like proteins/polypeptides)) Cellular Mechanism of Hormone Action: Secondary Messengers: hormone binds to a receptor on a cell and enhances secondary messenger release within the cell (such as GPCR) Primary Messenger: certain hormones, such as steroids and thyroid hormones can cross the cell membrane and directly bind to receptors within the cell (few less moving parts than the secondary messenger pathway) Terpenes, Squalene, Cholesterol, & Steroids: Terpene: a class of lipid molecules that are made out of a repeating set of carbon atoms known as isoprene Squalene: is a 30 carbon repeat of terpene that can be closed through cyclization reactions in order to make cholesterol (in the liver) The first step to cholesterol/steroid formation is the attachment of a pyrophosphate to a terpene molecule