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Endocrine System Study Guide Regulation- The process by which living things are able to respond to their environment Nervous System vs. Endocrine System The Nervous System is fast acting, has short lived effects, send electrochemical messages through impulses, in which the message travels along neurons and neurotransmitters, in which messages travel across the synapse The Endocrine system is slow-acting, has longer lasting effects, messages are chemical, in the form of hormones, and travel in the blood The Endocrine System Is made of a series of glands that secrete hormones into the bloodstream How are endocrine glands different from exocrine? o Exocrine secretions are secreted into an organ or cavity o Endocrine secretions go into the bloodstream What are two examples of exocrine glands discussed in the Fall? o Pituitary Gland o Pancreas Hormones Hormones are the chemical messengers of the endocrine system Hormones affect the rate of metabolic activity in a specific (target) body tissue Hormones attach to receptors on/in target cells and either activate or repress protein synthesis and activate enzymes already present in the cytoplasm Hormone secretion works through feedback mechanisms, positive and negative feedback, negative feedback stops producing a certain hormone because it would be harmful to have it in your system for too long, an example is when you are dehydrated, and ADH is produced to cause some water reabsorption if you then decide to drink a quart of water, the ADH production will stop because you have already replenished your water supply and if it is produced more disastrous effects could occur, it will cause, positive feedback is much rarer, and is when the hormone continues to get produced until the desired result is achieved, an example is childbirth, hormones cause the uterus to contract, until the end result, which is the birth of the baby to occur Four Classes of Hormones I. Peptide Hormones- usually short chains of amino acids but can include polypeptides and protein hormones, though their amino acid chains are generally short as well examples are insulin and thyroxin II. Amino Acid Derivatives- Hormones derived from a single amino acid chain, an example is epinephrine, which is formed on another amino acid derivative, tyrosine III. Steroids- complex rings of carbon carbon and hydrogen atoms, steroids are lipid based, as they are synthesized from cholesterol, and have a structure similar to cholesterol, they are secreted from the ovaries, placenta, testes, and adrenal cortex IV. Prostaglandins- Made of two fatty acid carbon chains attached to a five carbon ring, and are considered a special type of hormone because they are made by every cell in the body, instead of specialized glands, act locally, prostaglandins are not really “hormones” as they exert their effects on nearby cells instead of being carried by the bloodstream but are considered because they have effects similar to hormones and act in conjugation with those of the endocrine system, If hormones affect the Rate of Metabolic activities, what must they Effect in the Target Cells? Hormones can cause the activation or inhibit the activity of an enzyme already present in the cell Hormones can cause enzymes to be produced or not produced, in this instance, the hormones must interact with the DNA of the cell Hormones can cause an enzyme to continue performing its task until the end result is achieved (Positive Feedback) and hormones can stop the enzyme while it is performing its task because an overabundance would be produced (Negative Feedback) Two Modes of Enzyme Action One messenger model o Lipid hormones are able to diffuse through the cell membrane and bind to receptors located in the cytoplasm of the cell o Lipid soluble hormones target the cytoplasmic receptors which readily diffuse into the nucleus and act on DNA, inhibiting or stimulating the production of certain proteins Two messenger model o Peptide based hormones are unable to diffuse through the plasma membrane o The first message is the binding of the hormone to the membrane receptor o The second messenger within the cell translates the outer message and carries out its function within the cell o Peptide hormones must bind with cell-surface receptors which activates a chemical pathway that involves a second messenger, which is often the chemical cAMP (cyclic adenosine monophosphate) (AMP, ADP and ATP are nucleotides, made of a phosphate, sugar and nitrogenous base) Steps: 1. The binding of the hormone on the receptor site of the cell membrane activates a second membrane protein (referred to as G-protein/GTP) 2. The activated G-protein in turn, activates the membrane enzyme, adenylate cyclase, suing the energy from a GTP molecule 3. Adenylate cyclase then catalyzes the production of cAMP from ATP o The cAMP then activates specific enzymes within the cell and thus initiates the hormone’s specific action A hormone’s effect depends on the type of receptor and the secondary messenger present o Same receptors but different intracellular proteins The Hypothalamus The hypothalamus is a region of the brain that can receive nerve impulses from the brain and scan the chemical composition of the blood The hypothalamus is the connection between the nervous and endocrine systems The hypothalamus sends chemical signals to the pituitary gland One region of the hypothalamus secretes hormones called releasing hormones called releasing factors that controls the secretions of the anterior pituitary gland One region of the hypothalamus secretes and stores peptide hormones via the secretions of the posterior pituitary gland The Pituitary Gland Called the master gland Controls the other glands of the endocrine system Hormones of the Pituitary Gland 1. Thyroid Stimulating Hormone-TSH, stimulates cells of the thyroid to release thyroxin 2. Growth Hormone-GH, controls growth by causing bones to increase in size, also causes cells to reproduce at a quicker rate 3. Follicle-Stimulating Hormone- FSH - Stimulates the production of eggs in the ovaries of females and sperm in males 4. Luteinizing Hormone- LH - Controls the production of sex hormone in males and females, and controls the release of eggs in females 5. Prolactin- Stimulates milk production and breast development in females 6. Adrenocorticotropic Hormone- ACTH - Stimulates production and release of steroid hormones from adrenal cortex; used in treatments of arthritis, asthma, and allergies 7. Epinorphins- block pain senses by binding to receptors on the brain 8. Oxytocin Hormone- produced by the hypothalamus and secreted by the posterior pituitary, causes attraction, stimulates of smooth muscles of uterus during childbirth, maternal behaviors, and sperm ejaculation in males 9. Antidiuretic hormone- (ADH/vasopressin) produced by hypothalamus secreted by posterior pituitary, causes the nephrons of the kidney to excrete less water in the urine as they are more permeable to water reabsorption Thyroid Gland Located in the pharynx just below the larynx and in front of the trachea o The thyroid gland releases thyroxin Thyroxin controls metabolism in the cells of the body Thyroxin contains iron Thyroxin regulates the rate of fat, protein and carbohydrate metabolism as well as cellular respiration o The thyroid gland also produces calcitonin Calcitonin prevents excessive rise in blood calcium Dynamic Equilibrium Ability of the body to keep the chemical composition of the blood within a limited range o Example: Blood Sugar levels Negative Feedback- process by which blood chemistry remains in equilibrium In negative feedback, a substance causes a response to occur in the body This response then shuts off the original signal Once this signal is shut off, the response decreases, causing the signal to be released again Parathyroid Glands Produce parathormone and are located in the thyroid Parathormone controls the metabolism of calcium which is necessary for growth, health of bones and teeth Blood Clotting- nerve functions + muscle contraction Adrenal Glands Found over the kidneys o 2 glands in one, adrenal medulla and adrenal cortex Adrenal Medulla Center of gland and are controlled by the nervous system Adrenaline (epinephrine)- stimulates the elevation of blood-glucose concentration, and stimulates “fight or flight” reactions Noradrenaline (norepinephrine)- Stimulates reactions similar to those produced by adrenaline, but causes more vasoconstriction and is less effective in the conversion of glycogen to glucose Adrenal Cortex Glucocorticoids (corticosterone, cortisol, cortisone etc.)- Stimulate formation of carbohydrate from protein, thus elevating glycogen stores and helps maintain normal blood sugar levels o Stimulated to be released by ACTH from anterior pituitary gland Mineralocorticoids (aldosterone, deoxycorticosterone, etc- Stimulate kidney tubules to reabsorb more water and less sodium Cortical sex hormones- (testosterone)- stimulates the development of secondary sexual characteristics especially those of the male Other Glands Thymus- secretes thymosin, which stimulates the production of T lymphocytes Located on center of chest Pineal Gland- secretes melatonin “biological clock” Located in the brain Kidney- secretes erythropoietin which increases RBC production Renin- renin leads to the production of angiotensin which raises blood pressure by constricting arterioles Fat cells- Secrete leptin Gonads- Reproductive glands Testes- Male Gonads o Testosterone- male hormone Stimulates the development of secondary sex characteristics in males (deeper voice, body hair, sperm production, muscle development and growth spurts) Also helps to regulate the development of sperm Ovaries- Female gonads o Produces two hormones Estrogen- responsible for the secondary sex characteristics in females (breast development, menstruation, broadening of hips, body hair) Progesterone- helps to regulate the menstrual cycle The Pancreas Endocrine cell clusters are referred to islet cells or islets or langerhans Each islet has a good blood supply and within a cluster of these cells, there are two cell types, alpha and beta cells Alpha cells secrete glucagon; beta cells secrete insulin Both are involved in the regulation of metabolism but have opposing effects Hormones of the pancreas control blood sugar levels o Insulin is released by the pancreas and attaches to the cells of the muscles and liver Insulin causes these cells to take sugar out of the blood o Glucagon- target cells are in the liver Causes the liver to release glucose in the blood ALL CREDS GO TO MS. MAGGIO, I JUST TYPED UP THE NOTES SHE GAVE AND ADDED SOME INFORMATION FROM THE TEXTBOOK ~Tasdid Khandaker