HORMONES - chemical messangers produced by cells in one part of the body that affect cells in another part of the body - Serve as regulators - speeding up or slowing down certain bodily processes to maintain homeostasis. - transported by the circulatory system (blood) - ENDOCRINE HORMONES - chemicals secreted by endocrine glands into blood - Hormones do not affect all cells. Cells may have receptors for one hormone but not another. The number of receptors found on individual cells vary. (Insulin) - 2 types: 1) nontarget - affect many cells or tissues throughout body (EG - insulin, hGH, epinephrine) 2) target - affect specific cells or tissues (EG - gastrin, parathyroid hormone)

Chemical Classification of Hormones 1) Water Soluble  - majority of hormones  - proteins, peptides, amino acid derivatives  - act from outside the cell by binding to receptor sites on the cell membrane, which activates enzymes in the cytoplasm to carry out specific functions.   2) Fat Soluble/ Steroid hormones  - include male/female sex hormones, cortisol.  - Act from inside the cell, by diffusing into a specific cell and binding with receptor molecules in the cytoplasm, which signals the cell to produce a specific protein.

Anti-Diuretic Hormone (ADH) Regulates water reabsorption in the nephron, which reduces urine output. Osmoreceptors (sensory receptors) detect changes in osmotic pressure in the bodies fluids. Decrease in water = high osmotic pressure (blood is concentrated) Conserving water prevents the osmotic pressure from increasing further Thirst

ADH and the Nephron Approximately 85% of water filtered into the nephron is reabsorbed in the proximal tubule. ADH makes the upper part of the distal tubule and collecting duct permeable to water. This is what makes urine concentrated.

Diabetes Insipidus A common disease associated with ADH Production of excessive amounts of urine (as much as 16 litres a day Caused by the failure of ADH to be secreted or by the failure of the kidney to respond to ADH.

Oxytocin Causes strong uterine contractions during the birthing process After birth it causes weak contractions of the smooth muscle, allowing the uterus to return to its pre-pregnancy size and shape Also used during lactation The suckling action of a newborn stimulates nerve endings which cause oxytocin to be released This causes weak contractions of the smooth muscles forcing milk into the ducts

Anterior Lobe Synthesizes its own hormones

Human Growth Hormone (hGH) Also known as somatotropin Stimulates the elongation of the of the skeleton Its effect is most pronounced on cartilage cells and bone cells Under its influence soft tissues and bones begin to grow Hyperplasia- increasing the number of cells Hypertrophy- increasing the size of cells

Promotes protein synthesis while inhibiting protein degredation. Amino acid uptake increases which in turn provides the raw materials for this protein synthesis.

hGH and Homeostasis It increases fatty acid levels in the blood by promoting the breakdown of fats. Muscles use fatty acids instead of glucose as a source of metabolic fuel This is important for glucose dependent tissues such as the brain hGH increases the use of fat stores, which decreases the amount of fat stored in the body

Aging As a person ages hGH production declines Cellular repair and protein replacement are compromised Protein is often replaced with fat, causing changes in the bodies shape

Thyroid Stimulating Hormone (TSH) Is carried by the blood to the thyroid gland which then releases a number of thyroid hormones. These thyroid hormones help with metabolism. (more on this later)

Adrenocorticotropic Hormone (ACTH) Also known as corticotropin Blood carries ACTH to target cells in the adrenal cortex. This leads to a release of adrenal hormones which will deal with long-term stress (more on this later)

Prolactin (PRL) Responsible for stimulating the glands within the breast to begin producing fluids (milk) It initially causes the production of colostrum which is a very important source of antibodies, milk sugar and milk proteins. Works with oxytocin.

Luteinizing Hormone (LH) Regulates the production of testosterone which is the primary male sex hormone High testosterone levels reduce LH production through feedback inhibition. Also promotes ovulation by controlling the hormones produced by the ovaries The rise of estrogen stimulates LH secretion and ovulation occurs

Follicle Stimulating Hormone (FSH) Stimulates the production of sperm cells Stimulates the development of follicle cells in the ovary Follicle cells secrete estrogen

Thyroid Gland Approximately 60% of the glucose oxidized in the body is released as heat The remaining 40% is transferred to ATP Often consumed during activity Individuals who secrete higher levels (hyperthyroidism) of thyroid hormones will oxidize sugars and other nutrients faster. Don’t gain weight and tend to feel warm

Individuals who do not secrete as much (hypothyroidism), tend to not break down sugars as quickly. Excess sugar is converted into liver and muscle glycogen, but when glycogen stores are filled it is converted into fat. Leads to muscle weakness, cold intolerance, dry skin and hair

Iodine Iodine is an important component of both thyroid hormones When there is inadequate amounts of iodine, the thyroid enlarges, thyroid production stops and secretion of thyroxine drops. This causes more TSH to be produced and consequently the thyroid is stimulated more and more.

PTH also helps enhance absorption of calcium from undigested food A rise in PTH leads to an increase in calcium in the blood and a decrease of phosphate Causes the kidneys and intestines to reabsorb more calcium and the bones to release calcium. 98% of calcium is stored in bones PTH also helps enhance absorption of calcium from undigested food PTH also helps activate vitamin D.

Rickets When there is too little vitamin D rickets occurs. With this disease, too little calcium and phosphorus are absorbed and the bones develop improperly.

Anterior Pituitary Gland hGH deals also with metabolism. See notes from previous class on hGH’s role in metabolism