Endocrine System - Chapter 13 PDF

CHAPTER 13 The Endocrine System What are hormones? Steroid vs. non-steroid hormones Functions of various hormones Puberty Diabetes Hormones Hormones are molecules that are “messages” from one part of the body to other parts of the body. Produced in endocrine glands Released and circul...

CHAPTER 13 The Endocrine System What are hormones? Steroid vs. non-steroid hormones Functions of various hormones Puberty Diabetes Hormones Hormones are molecules that are “messages” from one part of the body to other parts of the body. Produced in endocrine glands Released and circulate in the blood Hormones are in contact with all cells of the body, as all living cells receive hormones (along with nutrients, oxygen, etc.) Hormones only have an effect on target cells in the body, that have protein hormone receptors Steroid hormones Lipid soluble (from cholesterol) so they can cross the cell membrane Can enter target cells, binds with receptors within cells Slower acting than non-steroid hormones (must enter cells, new proteins must be produced): minutes to hours for the body to respond to the hormone. Steroid hormone examples: Estrogen, Progesterone, Testosterone Steroid hormone action on a target cell Non-steroid hormones Fat insoluble, (made from amino acids) so cannot cross cell membrane and cannot enter cell Bind to receptors on cell membranes of target cells Often cause activation of second messengers within the cell, which activate working enzymes within the cell (ATP converted to cAMP  activation of enzymes in response to glucagon, for example) Faster acting than steroid hormones: (simply activates existing proteins): seconds to minutes for the body to respond Non-steroid hormone action on a target cell Hormones released by neurons of the hypothalamus into the posterior pituitary gland Oxytocin Antidiuretic hormone (ADH) (Vasopressin) Oxytocin: Released by neurons of the hypothalamus into the posterior pituitary gland. Function 1: Causes contractions of smooth muscle of uterus during labor / birth Function 2: Release of oxytocin triggers affectionate “cuddle” behavior, and warm, happy feelings, such as after sex.  Oxytocin: Function 3: 1) Infant nursing stimulates sensory neurons in nipple 2) Sensory neurons stimulate spinal cord neurons which stimulate neurons of hypothalamus 3) Hypothalamus (part of the brain) releases oxytocin into the blood stream of posterior pituitary 4) Oxytocin travels to mammary glands (breasts),causing contraction of smooth muscles of the milk –producing lobules, causing milk ejection into the hungry baby’s mouth. This is a good example of the nervous system and the endocrine system interacting.  Antidiuretic hormone (ADH) (vasopressin) Released into the posterior pituitary gland Function 1: Hypothalamus monitors concentration of water in blood Neurons of hypothalamus release antidiuretic hormone (ADH) into blood vessels of posterior pituitary if concentration of water is low ADH causes the kidneys to retain more water Antidiuretic hormone (ADH) (vasopressin) Function 2: Maintains homeostasis of blood pressure. If blood pressure is low, ADH is released. It causes constriction of some arterioles which increases blood pressure (so it’s sometimes called vasopressin)  Anterior Pituitary Gland The neurons of the hypothalamus cause cells of the anterior pituitary gland to produce several hormones These hormones include: Prolactin Growth Hormone Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH)  Prolactin Prolactin produced during late pregnancy, but is inhibited by estrogen and progesterone (produced in high amounts by the placenta) During pregnancy, estrogen and progesterone levels are high (secreted by placenta). After birth, placenta leaves the woman’s body, estrogen and progesterone levels drop, allowing prolactin to have its effect. Prolactin stimulates milk production in breasts. Nursing stimulates nerves in nipple which carries message to hypothalamus, which causes anterior pituitary to release prolactin. Nursing stops for 1 week  milk production stops Another example in which the nervous and endocrine system interact.  Growth hormone Review: Growth hormone has widespread effects on the body, especially long bones and muscles. Promotes protein synthesis and cell division. Growth hormone is especially important for stimulation of chondroblasts in cartilage growth plate of long bones during adolescence for lengthening them.  Growth hormone disorders Gigantism: Hypersecretion (too much) growth hormone Pituitary Dwarfism: Hyposecretion (too little) growth hormone. Children can be given growth hormone in this case. Once cartilage growth plate is gone (after puberty) no more lengthening of bone is possible Slide 13.10  Growth hormone disorders Acromegaly: Excess secretion of GH during adulthood will cause unusual growth of bone / connective tissue in hands, feet, face, jaw and skin. Usually caused by a tumor of the pituitary gland. Slide 13.10  Luteinizing Hormone (LH) / Follicle Stimulating Hormone (FSH) Maturation of neurons in hypothalamus  stimulation of anterior pituitary  release of LH and FSH for the first time  puberty! FSH / LH (females)  estrogen / progesterone secretion by ovaries FSH / LH (males)  testosterone secretion by testes LH and FSH play important roles in a woman’s menstrual cycle. FSH is important for sperm development, and LH plays a role in testosterone production in men.  Testosterone and puberty Testosterone (a steroid hormone secreted by testes): Functioning sperm Increased size of penis and testes Bone lengthening Muscle growth Increased hairiness Enlarged larynx Increased male sex drive and aggression Estrogen, progesterone and puberty Estrogen (a steroid hormone secreted by ovaries): Long bone growth Widening pelvis Redistribution of fat cells: more fat to bottom, hips and breasts (=breast development) Estrogen and Progesterone (also a steroid hormone created by the ovaries): Important in the menstrual cycle (including ovulation), and in creating and maintaining a thickened uterus (if a woman becomes pregnant) Minute amounts of testosterone-like hormone secreted by women’s (and man’s) adrenal glands (above kidneys). No effect on males (they have a lot of testosterone already). Responsible for limited hairiness in women, some growth of long bones during puberty and female sex drive. Pancreas: Endocrine functions maintain homeostasis of blood sugar Alpha cells of pancreas produce glucagon Glucagon: raises blood sugar level when it’s low (between meals): glycogen to glucose conversion in liver, amino acids converted to glucose, and tryglycerides in adipose tissue converted to free fatty acids and released into blood. Beta cells of pancreas produce insulin Insulin: lowers blood sugar when it’s high (after meals). Glucose absorbed into liver, muscles and adipose tissue, and converted to glycogen and fat. Insulin and glucagon: homeostasis of blood sugar  Diabetes mellitus Type I (juvenile-onset): Failure to produce insulin. Caused by an autoimmune disease: immune system attacks and destroys beta cells of pancreas. Type II (later onset: 45ish) Cells fail to respond to insulin properly (less protein receptors for insulin present?). Usually the beta cells of pancreas later break down, so less insulin is produced as well. Obesity increases risk of type II diabetes up to 93%.  Signs of diabetes mellitus High blood glucose levels  excretion of glucose in urine. High urination rate  water loss, dehydration and extreme thirst Lack of absorption into cells  cells starving for energy, despite high amounts of glucose in blood  muscles fatigued. Cells use proteins / fats for energy (since they are not getting enough glucose), and weight loss occurs. Uncontrolled diabetes: health problems Burning a lot of fat to produce energy produces ketones, which are acidic, and this can lead to metabolic acidosis, in which the blood pH is too low. This can negatively affect brain function: Mild cases cause people to be confused and very tired. Severe cases can result in death. Uncontrolled diabetes: health problems High blood glucose levels  damage to blood vessels (arteriosclerosis) so they no longer adequately supply vital tissues. This can lead to: Blindness Strokes Heart attack Kidney failure Reduced circulation to hands and feet  lack of feeling of wounds  gangrene  amputations. Insulin injection problems If too much insulin is injected, or if it is injected when blood sugar is already low, blood sugar levels go way down, the brain does not receive enough blood, and a person can lose consciousness (hypoglycemia). Eating a sugary snack can fix this. Controlling diabetes Type I diabetics require daily insulin injections, some type II diabetics require insulin as well. Avoid sugar: high blood sugar levels leads to blood vessel damage. Monitor blood glucose, to make sure it is not too high or low. Exercise to lower sugar levels when needed: exercising muscles can absorb blood sugar without insulin. Check toes daily for feeling. Thyroid and parathyroid glands secrete calcitonin and parathyroid hormones  Parathyroid hormone Lowered blood calcium levels causes secretion of parathyroid hormone (PTH) by the parathyroid glands. Removes calcium from bone (stimulates osteoclasts) Increases absorption of calcium by the digestive tract (activates Vitamin D for this) Increases kidney retention of calcium Homeostatic Regulation of Blood Calcium Concentration  Calcitonin Increased blood calcium levels causes secretion of calcitonin by the thyroid gland. Adds calcium to bone (stimulates osteoblasts) Decreases absorption of calcium by the digestive tract Decreases kidney retention of calcium so you lose more calcium when you urinate Review of other hormones Erythropoietin: Low oxygen detected by cells in kidneys, which release erythropoietin to stimulate red blood cell production in the red bone marrow. Epinephrine / norepinephrine: Sympathetic nervous system stimulates adrenal medulla glands to release these for sustained “fight or flight” response: increased heart rate, respiratory rate, more blood flow to skeletal muscles.