1 / 59

Chapter 15

Chapter 15. Endocrine System. Points to Ponder. What is the endocrine system? Compare and contrast exocrine and endocrine glands. What are steroid and peptide hormones? Name the major glands and their functions in the endocrine system.

juan
Download Presentation

Chapter 15

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 15 Endocrine System

  2. Points to Ponder • What is the endocrine system? • Compare and contrast exocrine and endocrine glands. • What are steroid and peptide hormones? • Name the major glands and their functions in the endocrine system. • What is diabetes (Type 1 and 2) and how might you prevent Type 1? • How do the endocrine nervous systems work with the rest of the systems in the body to maintain homeostasis?

  3. Endocrine system • Mostly comprised of glands • Secretes hormones that move through the bloodstream to target cells • target cells respond to certain hormones • Results in a slow but a prolonged response • Takes time to deliver hormones and to take time for cells to respond, but the effect is longer lasting • Makes use of negative feedback mechanism • Rise in blood glucose level causes the pancreas to release insulin, which promotes glucose until blood glucose levels fall

  4. What is a target cell?

  5. 15.1 Endocrine glands Exocrine vs. endocrine glands • Exocrine glands • secrete their products into ducts that carry these products to other organs or outside the body • Endocrine glands • secrete their products directly into the bloodstream

  6. Hormones are Chemical Signals • Hormones • Means of communication between cells, between body parts, and even between individuals • Act at a distance between body parts • Travel in the bloodstream from the gland that produces it to their target cells • Secretions produced by neurosecretory cells in the hypothalamus • Travel in the capillary network that turns between the hypothalamus and the pituitary gland • Secretions stimulate/inhibit the pituitary to secrete its hormones

  7. 15.1 Endocrine glands What are hormones? • Hormones: • Prostaglandins: local hormones • local hormones affect neighboring cells and thus are not carried in the bloodstream • Sometimes promote pain and inflammation • Pheromones: • chemical signals that influence the behavior of other individuals • Pheromone released by men • reduces premenstrual nervousness and tension in women • Peptide hormones: • Bring about an alteration of the target cell’s structure in some way • Consist of peptides, proteins, glycoproteins, and modified amino acids • Steroid hormones: • Are all derived from cholesterol • lipids that enter a cell and affect gene activity and thus protein synthesis

  8. Action of Peptide Hormones • Most hormonal glands secrete peptide hormones • In muscle cells • Stimulation by epinephrine leads to the breakdown of glycogen to glucose • Steps of Hormone Action called Enzyme-cascade: • Bind to a receptor in the plasma membrane - Hormone does not enter the cell  it’s called the first messenger • Formation of cAMP (cyclic adenosine monophosphate) - cAMP acts as a second messenger • Activation of Protein Kinase • Which activates a cascade of enzymes

  9. Action of peptide hormones

  10. Action of Steroid Hormones • Steroid hormones • produced at the adrenal cortex, the ovaries, and the testes • Steps of Hormone Action 1. Enter the cell because they are lipids 2. Binds to a receptor, in the nucleus or cytoplasm 3. Inside the nucleus, • Hormone-receptor complex binds with DNA and activates certain genes 4. Messenger RNA moves to the ribosome in the cytoplasm and protein synthesis follows • This process • Act more slowly than peptides because it takes more time to synthesize new proteins than to activate enzymes already present in cells • But action lasts longer

  11. Action of steroid hormones

  12. 15.2 Hypothalamus and pituitary gland Major glands of the endocrine system • Hypothalamus • Posterior pituitary gland • Anterior pituitary gland • Thyroid gland • Parathyroid glands • Adrenal glands • Pancreas • Testes • Ovaries • Thymus gland • Pineal gland

  13. 15.2 Hypothalamus and pituitary gland 1. Hypothalamus • Regulates internal environment through the autonomic nervous system • Helps control heartbeat • Helps control body temperature • Helps control water balance • Controls glandular secretions of the pituitary gland

  14. 2. Posterior pituitary gland • Stores antidiuretic hormone (ADH) and oxytocin that are produced by the neurosecretory cells in the hypothalamus • ADH: • regulates water balance by reabsorbing water into bloodstream • Action of ADH • Hypothalamus is sensitive to water-salt balance of the blood • When blood is too concentrated, ADH is released from the posterior pituitary • Water is absorbed into the bloodstream to regulate water-salt balance • Negative feedback maintains homeostasis • Oxytocin: • Causes uterine contractions during childbirth • Allows milk to be released during nursing • Controlled by positive feedback which is not a way to maintain homeostasis

  15. 15.2 Hypothalamus and pituitary gland 3. Anterior pituitary gland • Portal system • Consisting of two capillary systems connected by a vein • lines between the hypothalamus and anterior pituitary • Anterior pituitary gland is controlled by hypothalamic-releasing and hypothalalmic-inhibiting hormones • Hormones pass from the hypothalamus to the anterior pituitary via the portal system

  16. Hormones Produced by Anterior Pituitary Hormones that have an effect on other glands: • Thyroid-stimulating hormone (TSH): - stimulates the thyroid to produce thyroid hormones • Adrenocorticotropic hormone (ACTH): - stimulates the adrenal cortex to produce cortisol • Gonadotropic hormones: - stimulate gonads to produce sex cells and hormones ** Blood level of the last hormone in the sequence exerts negative feedback control over the secretion of the first hormone

  17. Hormones Produced by Anterior Pituitary Hormones that do not affect other endocrine glands: • Prolactin (PRL): - stimulates mammary glands to develop and produce milk only after childbirth - Involved in carbohydrate and fat metabolism • Melanocyte-stimulating hormone (MSH): - causes skin cells to produce melanin • Growth hormone (GH): - promotes skeletal and muscular growth by stimulating protein synthesis - Promotes fat metabolism as opposed to glucose metabolism

  18. 15.2 Hypothalamus and pituitary gland What happens when the body produces too much or too little GH? • Pituitary dwarfism • too little GH is produced during childhood that results in small stature • Giantism • too much GH is produced during childhood that results in poor health • Acromegaly • overproduction of GH as an adult that results in larger than normal feet, hands, and face

  19. 15.2 Hypothalamus and pituitary gland What happens when GH is produced in improper results during childhood?

  20. 15.2 Hypothalamus and pituitary gland What happens when GH is produced in high amounts during adulthood?

  21. 4. Thyroid gland • A large gland located below the larynx • Iodine is needed in the diet to allow the thyroid gland to produce its hormones • Triiodothyronine (T3) and thyroxine (T4) • It produces: • Thyroid hormone (TH): Regulates metabolism • Calcitonin: Regulate blood Calcium levels • Calcium plays role in nervous conduction and muscle contraction • Calcitonin helps lower blood Ca2+ levels by stimulating the deposition of calcium in the bones • Hormones do not have a target organ instead they stimulate cells of the body to metabolize at a faster rate

  22. 15.3 Thyroid and parathyroid glands Thyroid abnormalities • Simple goiter • thyroid enlarges due to lack of iodine in the diet • Hypothyroidism – low blood levels of thyroid hormones • Congenital hypothyroidism: - thyroid does not develop properly and is characterized in a short, stocky person that may be mentally retarded • Myxedema: - hypothyroidism in adults characterized by lethargy, weight gain, loss of hair, cold intolerant and thick, puffy skin • Hyperthyroidism – excess thyroid hormones in blood • Exophthalimic goiter: - characterized by enlargement of the thyroid gland, protrusion of the eyes, hyperactive and suffers from insomnia • Thyroid tumor: can also cause hyperthyroidism

  23. 15.3 Thyroid and parathyroid glands Thyroid abnormalities

  24. 15.3 Thyroid and parathyroid glands 5. Parathyroid glands • Small glands embedded in the surface of the thyroid gland • Produces parathyroid hormone (PTH): • causes blood Ca2+ level to increase by promoting osteoclast activity • Promotes reabsorption of Ca2+ by the kidneys • Activates vitamin D at the kidneys to stimulate the absorption of calcium from the intestines

  25. Regulation of blood calcium

  26. 15.4 Adrenal glands 6. Adrenal glands • Glands that sit on top of the kidneys • 2 parts of each gland • Adrenal medulla: • controlled by the nervous system • Adrenal cortex: • portions are controlled by ACTH from the anterior pituitary • Stress prompts the hypothalamus to stimulate a portion of the adrenal gland

  27. 15.4 Adrenal glands Adrenal medulla • Inner portion of the adrenal glands • Hypothalamus initiates stimulation of hormone secretion via the preganglionic sympathetic nerve fibers that travel to the adrenal medulla • Produces • hormones that allow a short-term response to stress (“fight or flight” response) • Epinephrine (adrenaline) • Norepinephrine

  28. 15.4 Adrenal glands Adrenal cortex • Outer portion of the adrenal glands • Produces hormones that provide a long-term response to stress • 2 major types of hormones: Mineralocorticoids and Glucocorticoids • Glucocorticoids: • Secretion is controlled by ACTH released by the anterior pituitary • regulate carbohydrate, protein (in liver) and fat metabolism leading to an increase in blood glucose level • Suppress the body’s inflammatory response but suppresses pain and immunity making a person susceptible to injury/infection • e.g. cortisol and cortisone • Secrete a small about of female and male sex hormones in both sexes

  29. Adrenal cortex • Mineralocorticoids : • regulate salt and water balance leading to an increase in blood volume and pressure • e.g. aldosterone (targets the kidney) • Promotes renal absorption of Na+ and renal excretion of K+ • Secretion is not controlled by anterior pituitary • Renin-angiotensin-aldosterone system: • Na+ and blood volume is low • Kidneys secrete renin • Renin converts plasma protein angiotensinogen to angiotensin I • Angiostensin I changes to Angiostensin II via enzyme in the lung capillaries • Angiotensin II stimulates the adrenal cortex to release Aldosterone • Blood pressure raises b/c: • Angiotensin II constricts the arterioles • Aldosterone causes the kidneys to reabsorb Na+ • If blood volume is high, atria of the heart will stretch • Cardiac cells release atrial natriuretic hormone (ANH) • Inhibits the secretion of aldosterone form the adrenal cortex • This causes excretion of Na+ and thus water to decrease blood volume

  30. Summary of the adrenal glands

  31. Adrenal glands can malfunction • Addison’s disease • Hyposecretion (low) of glucocorticoids by the adrenal cortex • Presence of excessive/ineffective ACTH causes bronzing of skin • Physiological Side Effects: • Glucose can not be replenished during stress • low levels of aldosterone secretion leads to NA+ and water loss resulting in low blood pressure

  32. 15.4 Adrenal glands Adrenal glands can malfunction • Cushing syndrome • hypersecretion of glucocorticoids by the adrenal cortex • characterized by weight gain in the trunk of the body but not arms and legs

  33. 15.5 Pancreas 7. Pancreas • Not under pituitary control • Composed of 2 tissues: • Exocrine: produces and secretes digestive juices • Endocrine (islets of Langerhans): • produce/secrete hormones • Insulin – Secreted After Eating to lower blood glucose level • secreted when blood glucose is high and stimulates uptake of glucose by cells (muscle, liver, and adipose cells) • Glucagon – Secreted Before Eating to raise blood glucose level - secreted when blood glucose is low and stimulates the breakdown of glycogen in the liver and adipose • Stimulates liver break down of glycogen to glucose • Use of fat (glycerol and fatty acids) and protein (amino acids) in preference to glucose as energy source

  34. Regulation of Blood Glucose

  35. Health focus: What is diabetes? • Inability to control blood glucose levels • There are two types: Type 1 and Type 2 • 18 million people in the US have diabetes • General symptoms: • Frequent urination • Unusual hunger and/or thirst • Unexplained change in weight • Blurred vision • Sores that heal slowly or not at all • Excessive fatigue • Long-term effects are blindness, loss of limbs, nerve deterioration, kidney and cardiovascular disease

  36. Type 1: Usually early-onset Autoimmune disorder that tends to run in families Cause and Effect: After/during infection cytotoxic T cells attack/destroy pancreatic cells preventing them from producing insulin Body turns to metabolism of fat leads to buildup of ketones in the blood  acidosis Need insulin injections Diabetes: Understanding the 2 types

  37. Diabetes: Understanding the 2 types • Type 2: • Usually adult-onset and most common type • Tends to occur in obese, sedentary people • Cause and Effect: • Cells do not respond to insulin therefore, the number of protein carriers for glucose remains them same  Insulin resistance • Decrease level of glucose absorption • Usually diet and exercise are important for controlling this and may even prevent this!

  38. Diabetes • Long term complications • Blindness • Kidney disease • Cardiovascular disorders • Atherosclerosis • Heart disease • Stroke • Reduced circulation

  39. Testes and Ovaries • Sex Hormones (estrogen, progesterone, and testosterone) are produced and excreted by the gonads • Hormones feedback to control the hypothalamus secretion of GnRH (gonadotropic releasing hormone) • Which in turn controls the pituitary gland secretion of FSH and LH, gonadotropic hormones

  40. 15.6 Other endocrine glands 8. Testes • Gonads found in males • Produce androgens (e.g. testosterone) • At time of puberty, gonadotropic hormones stimulate the release of increased amounts of testosterone • Stimulates growth of the penis and testes • Responsible for 2 male sex characteristics such as facial, underarm and pubic hair • Prompts the larynx and vocal cords to enlarge resulting in a lower voice • Promotes muscular strength

  41. 15.6 Other endocrine glands 9. Ovaries • Gonads found in females • Produce estrogen and progesterone • Stimulates growth of the vagina and uterus • Responsible for secondary sex characteristics such as female body hair, fat distribution and breast development • Responsible for egg maturation • Regulates the uterine cycle

  42. Hypothalamic-Pituitary-Ovarian Axis Hoyer 2005

  43. Ovarian Histology • Follicular Composition of the Ovary Primordial Follicle Primary Follicle Secondary Follicle Early Antral Follicles

  44. Control Corpora lutea E19 – PND 7 500 µm 1 mg/kg E2 100 mg/kg MXC 20 µg/kg MXC 500 µm 500 µm Antral Follicles 500 µm Antral follicles

  45. Steroidogenic Pathway Granulosa Cells Theca Cells Estrogen in Granulosa Cells LH FSH FSH-R LH-R Plasma membrane Testosterone in theca cells HDL (+) pPKA cAMP Androstenedione in theca cells Cholesterol (C27) Progesterone StAR protein Pregnenolone Inner Mitochrondrial Membrane C27 P450scc Mitochondria Pregnenolone Zachow

  46. Incubation • Egg enveloped by abdominal fold, “brood pouch” • Numerous blood vessels • Body Heat  Egg • Prolactin  Stimulate Development http://www.emperor-penguin.com/emperor-rookery.html

  47. Prolactin in Males and Females • Prolactin Levels: Male=Female Courtship • Source:Lactotrophic Cells Anterior Lobe-Pituitary • Induce Parental Behavior • Care for egg and young (Vleck, C.M, et al 1999) http://www.coolantarctica.com/gallery/penguins/emperor_penguin_37.htm

  48. Prolactin: Male Gentoo Penguins • Before and during Incubation • Brood Pouch develops under the influence of an increase in prolactin and sex steroids • Chick Phase • Nest Failure • Decrease Plasma Prolactin (ug/liter -1) (Williams, T.D. et al 1993)

More Related