Samples of pure carbon weighing 3.62, 5.91, and 7.07 g were burned in an excess of air. The masses of carbon dioxide obtained (the sole product in each case) were 13.26, 21.66, and 25.91 g, respectively. (a) Do these data establish that carbon dioxide has a fixed composition? (b) What is the composition of carbon dioxide, expressed in % C and % O, by mass?
Clemson University Spring 2016 Human Anatomy and Physiology II Hormone-‐Producing Structures PowerPoint 1/14/16 Notes Slide 1: Hormone-‐Producing Structures Slide 2: Thyroid Gland • Two lobes connected by isthmus across the front • Located around the trachea beneath the larynx • Largest pure endocrine gland à Meaning that it only produces hormones Slide 3: Histological Composition of the Thyroid Gland • The thyroid gland is composed of follicles that are made up of epithelial cells (cuboidalepithelium) that produce thyroglobulin protein which is stored in the follicles as colloid substance • Thyroid hormone is derived from colloid • TSH (Thyroid Stimulating Hormone) stimulates the follicles to produce thyroglobulin, which is a component of thyroid hormone (TH) • Thyroglobuilin will combine with iodine to make TH = thyroxin • The thyroid gland is unique because it is the only endocrine gland that can store its secretions à All other endocrine gland secrete hormones that are immediately released into the blood stream • The thyroid gland also contains other cells located between the follicles called parafollicular cells that produce calcitonin (A different hormone) • Calictonin shuts off osteoplasts (Cells in bones) Slide 4: Thyroid Hormone • TH is actually 2 separate hormones: a) T :3 Thryoglobulin + 3 iodine b) T :4 Thyroglobulin + 4 iodine • Almost every cell in the body has a receptor for Thyroxin (TH) except the brain, spleen, testes, uterus, and the thyroid gland itself • TH is a major hormone that regulates metabolic activity—Oxidation of glucose • Bringing it together: Hypothalamus releases TRH that stimulates that anterior pituitary gland to release TSH that stimulates the thyroid to release T 3 and 4T into the blood stream to bind to specific receptors (Negative feedback mechanism) Slide 5: Functions of Thyroid Hormone • TH stimulates the oxidation of glucose so that it is broken down by the cell to produce energy (Increases basal metabolic rate) and liberates heat -‐ Calorigenic effect: Heat produced when glucose is broken down by the cell for energy • TH helps maintain blood pressure à It causes can increase of adrenergic receptors -‐ TH binds to norepinephrine that then binds to the adrenergic receptors on the blood vessels that causes vasoconstriction so that blood pressure is increased • Regulates tissue growth and development, especially with skeletal and nervous systems -‐ Ex: Permissiveness à Gonadotropins (LH and FSH) cause the development of sex organs and if TH is circulating at the same time as these, great sex organ development is stimulated Slide 6: Synthesis • The anterior pituitary gland secretes TSH which travels to the thyroid gland via blood vessels • TSH triggers the production of thyroglobulin by cuboidal cells that accumulates in the follicles as colloid • TSH also stimulates active transport of iodine into the follicles • Thyroglobulin is then iodized in 2 different circumstances: (Occurring in the colloid) a) Thyroglobulin + 1 iodine = 1 Leads to form3 T b) Thyroglobulin + 2 iodine = 2 Leads to form4 T • T 3 and4 T are still in the colloid at this point and the thyroid will secrete both from the colloid so that they move back into the follicular cells to be packaged into lysosomes • The lysosomes transport T 3 and T4 where they are released into the bloodstream via lysosomal enzymes • Most TH is produced at night Slide 7: Diurnal Cycle • The thyroid is unique in that it can store hormones (2-‐3 months supply worth) • TSH normally is secreted around the time one gets tired (Peaks before sleep and remains high at night) • Produced TH is stored in the extracellular colloid • When energy is needed during the day, the thyroid secretes TH • Effect of sleep deprivation: Not producing as much TH and therefore energy is lost Slide 8: Transport • T and T are released into the blood stream and must bind to transport 3 4 proteins in order to reach specific cell receptors where they are going to have an effect • TBG (Thyroxin Binding Globulin) is the major transport protein where it delivers TH to target cells • TH is an AA based hormone that binds to intracellular receptors (An exception of AA based hormones normally binding to receptors on the surface of cells) à TH functions like a steroid then which is why TBG is so important so that it helps with getting TH inside the cell to its receptors • Transcription by TH is then promoted like a steroid Slide 9: Feedback • Increasing levels of4 T (Thyroxine) inhibit TSH production while falling levels reversibly stimulate TSH production that produces the 4T (Negative feedback) • An increase in body energy needs stimulate the release of TRH that stimulates TSH that stimulates TH release Slide 10: Calcitonin • Hormone produced by the parafollicular cells = C cells (C is for calcitonin) • Its effects are to lower blood calcium levels à It takes calcium out of circulation and stores it in bone and muscle • Calcitonin is most important during rapid skeletal growth and reformation à Plays the biggest role in childhood (And does not have as big of a role once one hits puberty) Slide 11: Action of Calcitonin • Inhibits osteoclast activity à Shuts off osteoclasts so that the breaking down of bone to release calcium is inhibited • Stimulates the uptake of calcium into the bone and muscle Slide 12: Feedback • High calcium levels are humoral stimuli for C cell (parafollicular cell) activity • Low calcium levels inhibit C cell activity à As take out calcium out of circulation, levels get lower so the C cells shut off and calcitonin production stops Slide 13: Parathyroid Gland • Embedded in the posterior portion of the thyroid gland • Has 2 types of cells: Oxyphil and Chief Slide 14: Histological Composition of the Parathyroid Gland • 2 Types of Glandular Cells: a) Oxyphil: It is not clear what these cells do b) Chief: Secrete parathyroid hormone (PTH) • Able to tell the difference between the thyroid and parathyroid because each have different follicles and tissues Slide 15: Parathyroid Hormone (PTH) • PTH is the most important hormone in controlling blood calcium balance of blood • Calcitonin causes a reduction in blood calcium • PTH is an antagonist so that is causes an increase in blood calcium • Therefore, triggers for PTH to be produced by the chief cells is low blood calcium Slide 16: Action of PTH • PTH stimulates the osteoplasts to release calcium and some phosphates into the blood stream (Breaking down bown) • PTH also enhances reabsorption of calcium in the kidneys so that it is kept in the body and not excreted out via urination • PTH increases absorption of calcium in the intestines • Promotes the kidneys to convert Vitamin D to its active form, ca3citriol (D )— Necessary to be present in the intestines in order for calcium to be absorbed by the body Slide 17: Adrenal Glands • Paired glands located atop each kidney • Each is comprised of a cortex and medulla • Cortex: Glandular epithelium = secretory epithelial cells • Medulla: Part of the sympathetic nervous system • Norepinephrine is a neurotransmitter that is released by post-‐ganglionic sympathetic fibers (Secreted by the medulla) • The cortex secretes steroid hormones • All adrenal secretions help fight off stress Slide 18: Adrenal Cortex Hormones • 3 classes of steroids (Corticosteroids) are produced by the cortex: Mineralocorticoids, glucocorticoids, gonadocorticoids • This means that there are 3 different regions and different types of cells that correspond with each steroid as a result • ATCH (Adrenocorticotropic Hormone) is secreted from the anterior pituitary gland and affects the cortex which causes the production of many of the steroids Slide 19: Histological Composition of the Adrenal Glands • 3 zones where each zone produces a different class of corticosteroids: a) Zona glomerulosa (Mineralocorticoids) b) Zona fasiculata (Glucocorticoids) c) Zona reticularis (Gonadocorticoids) Slide 20: Mineralocorticoids • Major hormone from mineralocorticoids is aldosterone (95%) • Aldosterone helps regulate electrolyte concentrations of extracellular fluids in our body—Particularly the sodium-‐potassium combination that are involved in membrane potentials • As aldosterone regulate concentration of electrolytes, water will follow concentration gradients so aldosterone is very important with regulating blood pressure 1/19/16 Notes Slide 21: Action of Aldosterone • Aldosterone stimulates reabsorption of sodium in the kidneys à As blood is filtered, substances are in the filtrate that will go out as urine unless they are reabsorbed into the circulatory system • An osmotic gradient is created with the reabsorption of sodium back into the blood stream by the kidneys so that there is more sodium in the blood stream than in the filtrate that is to be urinated out of the body à Water follows the sodium and this regulates blood volume and therefore blood pressure • Other ions are also linked to sodium and play a role in blood pressure and blood volume control • Essentially, with the reabsorption of sodium by the kidneys, the blood volume changes and this affects the blood pressure • Reabsorption of sodium in the kidneys is aldosterone’s primary action but the corticosteroid is able to affect other glands as well: Sweat, saliva, gastric juice glands for example Slide 22: Feedback • The anterior pituitary gland secretes ATCH that stimulates the adrenal cortex to produce hormones (This is one method of aldosterone production that is not the major method) • Aldosterone secretion by the adrenal cortex is stimulated by: a) Humoral effects: High potassium levels and low sodium levels in the bloodstream b) Low blood volume c) Low blood pressure • ** ATCH functions predominantly on glucocorticoids and not mineralocorticoids (Review) Slide 23: Mechanisms of Secretion – Renin-‐Angiotensin Mechanism • This is main method in which aldosterone is stimulated by • The liver is continuously producing a protein called angiotensinogen that is an inactive form of a protein • The kidneys, when stimulated properly, will produce renin that converts the inactive angiotensinogen into the active form called angiotensin • Angiotensin stimulates the adrenal cortex to produce aldosterone that has effects on the kidneys to reabsorb sodium • Low blood pressure also stimulates the kidneys to start producing renin • Because the liver is producing the inactive angiotensinogen all the time, the production of renin is key for aldosterone production • Overall, there are many other ways that stimulate aldosterone production: Combined effects of the nervous and endocrine activity that maintain homeostasis in the body so there’s a lot of interaction to fine tune all of the complexities that go into relations with aldosterone Slide 24: Mechanisms of Secretion – Plasma Concentration Mechanism • High potassium and low sodium in the blood have a direct effect on the zona glomerulosa (Where the mineralocorticoids are produced à stimulate aldosterone production) • Low potassium and high sodium in the blood inhibit the zona glomerulosa Slide 25: Mechanisms of Secretion – ACTH Mechanism • Stress stimulates CRH production in the hypothalamus à Stimulates corticotrope cells in the anterior pituitary gland to release ACTH à Stimulates aldosterone production in the zona glomerulosa of the adrenal cortex (Not much though with this mechanism) Slide 26: Mechanism of Secretion – Atrial Natriuretic Peptide (ANP) • ANP is a hormone produced by the heart and is secreted due to high blood pressure • High blood pressure puts a lot of stress on the heart so ANP is secreted to inhibit renin which in turn inhibits aldosterone production Slide 27: Glucocorticoids • The major hormone is cortisol • Cortisol regulates energy metabolism of most cells in the body and helps resist stress • Examples of stimulants of stress for cortisol: Cold weather, emotional stresses, etc. Slide 28: Action of Cortisol • Cortisol affects energy metabolism by maintaining blood glucose levels by promoting gluconeogenesis (This is not the main way to regulate blood glucose levels though) • Gluconeogenesis: The production of new carbohydrate from non-‐ carbohydrate sources – FA and proteins are broken down to be used for making glucose and therefore for energy • Cortisol also is related to blood volume and maintaining it à It prevents water from leaving the blood and going into body cells (Inhibits water uptake by body cells) Slide 29: Feedback of Cortisol • The hypothalamus secretes CRH which stimulates the anterior pituitary gland to secrete ACTH which stimulates the adrenal cortex to produce cortisol (Zona fasiculata) • ** ACTH results are predominantly in the production of glucocorticoids • As cortisol is produced and levels rise, it inhibits CRH and therefore ACTH release that shuts cortisol production off Slide 30: Effects of Stress • Stress increases cortisol production which in turn increases gluconeogenesis • FA and protein (to AA) have to be liberated out of storage and be broken down to be reconverted into glucose for energy production • Cortisol causes vasoconstriction which increases blood pressure as a result Slide 31: Gonadocortiocoids • Gonadocorticoids are produced by zona reticularis of the adrenal cortex • The major hormones of the gonadocorticoids are weak androgens à DHEA • DHEA is a precursor for testosterone or estrogen • Glucocorticoids (DHEA included) contribute to the onset of puberty; Prior to puberty there is little produced by the adrenal cortex • DHEA also provides sex drive for women Slide 32: Feedback • CRH from the hypothalamus stimulates ACTH from the anterior pituitary gland to stimulate the production of gonadotropins • There does not seen to be an inhibitor for the production of gonadotropins à Therefore, one the gonadotropins being producing, they continue to do so throughout life Slide 33: Adrenal Medulla Hormones • The adrenal medulla is sympathetic nervous tissue à It uses norepinephrine as a neaurotransmitter that also works as a hormone too • Essentially the adrenal medulla produces modified sympathetic neurons that are released into the circulatory system to the liver and throughout the body (They are not sent to a synapse) • Epinephrine and norepinephrine together makeup adrenaline Slide 34: Histological Composition • Chromaffin cells are modified ganglionic sympathetic neurons that secrete epinephrine and norepinephrine (catecholamines) Slide 35: Action • Stress promotes sympathetic nervous activity (Fight or flight response) which leads to the release of epinephrine and norepinephrine because the nervous tissue has been activated which has also led to an increase in blood sugar as a result • Fight or flight: Means the body is getting ready to fight stress or flee from it and to do this, there has to be energy available which is accomplished by stimulating the release of glucose into the bloodstream • Norepinephrine especially causes the constriction of blood vessels à increase in blood pressure • The fight or flight response causes blood to be sent from the extremities to the brain, heart, and skeletal muscles and circulation is also geared primarily more towards preganglionic sympathetic nerve endings • The release of epinephrine and norepinephrine is also a much shorter response for stress and demonstrates the link between the nervous and endocrine systems Slide 36: Pancreas • The pancreas is located in the abdominal cavity behind the stomach • Has both endocrine and exocrine functions à Therefore, more than one type of cell is present • Exocrine part: Secretes enzymes into a duct that dumps into the small intestine where there is digestion involvement • Endocrine part: Secretes hormones that go to the surface and get into the blood stream (Insulin and glucagon) Slide 37: Histological Composition of the Pancreas • Most of the pancreas is composed of the acinar pancreas that is made up of acinar cells = exocrine portion that produces enzymes for digestion • The Islets of Langerhans (Pancreatic islets) are located throughout acinar portion • 2 types of cell sin the Islets of Langerhans: Alpha (Produce glucagon) and beta (produce insulin) à Both of these hormones are antagonists Slide 38: Glucagon • Functions on the liver to release glucose into the blood stream as free glucose via taking the glucose out of storage (Most glucose is stored in the liver as glycogen) Slide 39: Actions of Glucagon • First, glycogen is broken down into glucose that is released into the bloods stream • Glucagon also stimulates glucose to be synthesized from lactic acid: -‐ When muscles are being used a lot, lactic acid is produced and then circulates throughout the body until it reaches the liver -‐ Liver uses lactic acid as an energy source which can then be converted back into glucose and be used by muscle (or other cells) again for energy -‐ Overall: The waste product of lactic acid from muscle contraction = food source for liver = food source for muscle again • Glucagon essentially function sin increasing blood glucose levels by releasing it into the blood Slide 40: Feedback of Glucagon • Humoral control: Low blood glucose (sugar) levels and high AA levels stimulate the pancreas to produce glucagon from the acinar cells of the Islets of Langerhans • High blood glucose and low AA levels shuts off the production of glucagon • Sympathetic stimulation of the adrenal medulla promotes the release of: Epinephrine and norepinephrine à Help increase blood glucose levels as well and will stimulate glucagon production by the pancreas • Somatostatin (GHIH) production also shuts off glucagon – In terms of not needing as much energy when one is done growing Slide 41: Insulin • Insulin decreases blood glucose levels by signaling cells to take up glucose out of the blood stream • Influences protein and fat metabolism (Anabolic hormone so signals for the build up of these) Slide 42: Actions of Insulin • Signals for glucose to be taken out of the blood stream via enhancing membrane transport of glucose into cells • Inhibits the breakdown of glycogen into glucose (Left as storage) • Inhibits the conversion of AA or FA (Fats) to glucose • Promotes glycogen production predominantly in the liver when there is excess glucose • Rest of excess glucose goes to fatty acid synthesis and further triglyceride storage in adipose tissue • It is important to note that there is some oxidation of glucose when cells take up glucose by the cell for the needed amount of energy by the cell at that time • Glucocorticoids play a similar role with blood sugar level s Slide 43: Feedback of Insulin • High blood sugar levels stimulate the beta cells of the Islets of Langerhans in the pancreas to produce • High levels of AA and FA also stimulate insulin production • Parasympathetic release of acetylcholine stimulates the release of insulin as well • Hormonal influences also exist • ** Sympathetic nervous activity relates to glucagon and parasympathetic nervous activity relates to insulin Slide 44: Gonads • Testes • Ovaries • Both produce the same sex hormones that the adrenal cortex produces (Acts as precursors at this point in the adrenal cortex) à Testosterone and estrogen Slide 45: Sex Hormones • Male: Testosterone • Female: Estrogen, progesterone • Both genders produce all but in different amounts Slide 46: Actions of Gonads • Testosterone: -‐ Stimulates the maturation and maintenance of male reproductive organs -‐ Secondary sex characteristics à Enlarged muscle mass, increased body hair, oil production, deeper voice, etc. -‐ Promotes sex drive -‐ Stimulates male gamete (sperm) production • Estrogen: -‐ Stimulates the maturation and maintenance of the female reproductive organs -‐ Female secondary characteristics à Accumulation of fat in hips/breasts, smoother skin, less oil, higher voice, less hair, etc. • Progesterone: -‐ Functions with estrogen to promote breast development -‐ Functions with estrogen to cause cyclic changes in the uterine lining (menstrual cycle) Slide 47: Feedback of the Gonads -‐ Production of the sex hormones (gonadic hormones) are stimulated by gonadotropins -‐ As high levels of gonadotropins are present, they shut themselves off Slide 48: Pineal Gland • Pea size gland that extends from the third ventricle of diencephalon and is made up of pinealocytes Slide 49: Histological Composition of the Pineal Gland • Pinealocytes are the hormone producing cells in the pineal gland • Responsible for the production of melatonin Slide 50: Melatonin • Promotes drowsiness • Inhibits sexual maturation à Prior to puberty almost no gonadotropin is produced because melatonin shuts it off • Therefore, melatonin helps time puberty (Reduces in levels when puberty is about to occur) • Melatonin is continued to be produced in adulthood and is instead used to make us feel drowsy à Sunlight (UV radiation) inhibits the pineal gland so when the sun sets, inhibition is lost and melatonin levels increase so we sleep (Sleep-‐wake cycle) Slide 51: Thymus • Located beneath the sternum an don top of the heart (Deep to sternum in thorax) • Size diminishes with age à It’s very active in an embryo and child Slide 52: Thymus Hormones • 3 classes of hormones are produced that all influence the development of T lymphocytes (Specialized white blood cells that function to give us immunity): a) Thymoproteins b) Thymic Factor c) Thymosins • When there is an embryo/small child, the thymus produces these hormones that cause the T lymphocytes to be produced to get the body ready to have an immune system before they come in contact with pathogens • With age, immunity declines so it is important to have a strong immunity as a child because it will have to be carried with us until death Slide 53: Other Hormone Producers-‐ Heart • Releases ANP (Atrial Natriuretic Peptide) that shuts off aldosterone production by inhibiting renin production so that there is an increase in urinary output à Sodium is not reabsorbed • ANP production is promoted by high blood pressure, which is reduced by getting the fluids out of the blood via increasing urine production Slide 54: Other Hormone Producers-‐ Gastrointestinal Tract • Many places along the GI tract secrete hormones that affect the digestive activity • Ex: Hormone produce by the small intestine will affect stomach activity; hormone produced by the stomach affects small intestine activity, etc. Slide 55: Other Hormone Producers-‐ Placenta • Both the female and embryo produce the placenta organ • Hormone producing structure of estrogen, progesterone, and hCG (Human Chorionic Gonadotropin) • hCG = what pregnancy tests detect • All of these hormones produced by the placenta will influence the development of the fetus and ovary maintenance Slide 56: Other Hormone Producers-‐ Kidneys • Produce erythropoietin that stimulates the production of red blood cells Slide 57: Other Hormone Producers-‐ Skin • Produces cholecalciferol that is an inactive form of Vitamin D3 • It is converted to the active form of Vitamin D3 = calciferol under the influence of sunlight • Vitamin D3 is also important for the absorption of calcium in the digestive tract Slide 58: Adipose Tissue • Produces leptin • As one takes in excess calories, it is put into storage in adipose tissue, and as adipose tissue increases in amount, the production of leptin increases which reduces appetite and encourages an increase in energy expenditure to try to reduce the amount of energy stored • Also produces resistin that is an antagonist of insulin Slide 59: Endocrine Gland Development • Endocrine glands can arrive from all 3 embryonic germ layers • Mesoderm: Gives rise to the steroid producing endocrine glands • Ectoderm and endoderm: Give rise to the AA derived hormones • Endocrine gland activity changes with age (Excellent ex: Thymus, reproductive hormone activity, etc.) • Endocrine gland activity can be influenced by environmental cuesà Ex: If one is cold, the thyroid gland can release more thyroid hormone to increase metabolic activity to increase heat production