WELCOME TO A&P UNIT 9 SEMINAR! We will begin at the top of the Hour. By Dr. Daudi K. Langat

Learning Objectives Distinguish between endocrine and exocrine glands and define the terms hormone and prostaglandins Identify and locate the primary endocrine glands and list the major hormones produced by each gland Describe the mechanisms of steroid and nonsteroid hormone action Explain how negative and positive feedback mechanisms regulate the secretion of endocrine hormones Identify the principal functions of each major endocrine hormone and describe the conditions that may result from hyposecretion or hypersecretion Define diabetes insipidus, diabetes mellitus, gigantism, goiter, cretinism, and glycosuria

This is today’s Seminar Topic: You will be discussing the pituitary (master) gland, hormones, and their functions to the body and the nervous system. You will emphasize the importance of the endocrine system to homeostasis by looking at some endocrine disorders.

Important information: Exam Revision

“Notes” in PowerPoint

How to get the “Project” Instructions

Project Instructions

Format of the final project

Functions of the Endocrine System Performs the same general functions as the nervous system  Communication  Control Provides slower, longer-lasting control by hormones secreted into and circulated by the blood

MAJOR ENDOCRINE GLANDS No ducts (Opposite of Exocrine glands) Secrete hormones into intercellular spaces and from there, into the blood. Binds to target organs or cells

Answers Major classes of hormones: –Steroid hormones (estrogen, testosterone, progesterone) –Non-steroid hormones Protein/Peptide hormones (FSH, LH, Prolactin) Amino-acid-derived hormones (thyroxine) Prostaglandins These hormones provide communication between endocrine glands and target organs. Steroids hormones are lipid soluble and pass directly through the plasma membrane of the target cell. Protein/Peptide hormones work through a second messenger mechanism, which is a chemical that provides communication within a hormone’s target cell

Mechanism of Non-steroid Hormone Action

Mechanism of Steroid Hormone Action

Regulation of Hormone Secretion Hormone secretion is controlled by homeostatic feedback  Negative feedback: Mechanisms that reverse the direction of a change in a physiologic system  Positive feedback: (Uncommon) mechanisms that amplify physiologic changes

Negative Feedback: Insulin

Prostaglandins (or tissue hormones) are powerful substances found in a wide variety of body tissues A prostaglandin is often produced in a tissue and diffuses only a short distance to act on cells in that tissue Several classes of prostaglandins include prostaglandin A, prostaglandin E, and prostaglandin F Prostaglandins influence many body functions, including respiration, blood pressure, gastrointestinal secretions, and reproduction Prostaglandins

The Glands and Hormones

Pituitary Gland Anterior pituitary gland (adenohypophysis)  Major hormones  Thyroid-stimulating hormone (TSH)  Adrenocorticotropic hormone (ACTH)  Follicle-stimulating hormone (FSH)  Luteinizing hormone (LH)  Growth hormone (GH)  Prolactin hormone (PH)

Pituitary Gland (cont’d.)  Functions of major anterior pituitary gland hormones  TSH o Stimulates growth of the thyroid gland o Stimulates it to secrete thyroid hormone  ACTH o Stimulates growth of the adrenal cortex o Stimulates thyroid to secrete glucocorticoids and mineralocorticoids

FSH – Initiates growth of ovarian follicles each month in the ovary and stimulates one or more follicles to develop to the stage of maturity and ovulation – Stimulates estrogen secretion by developing follicles – Stimulates sperm production in the male LH – Acts with FSH to stimulate estrogen secretion and follicle growth to maturity – Causes ovulation – Causes luteinization of the ruptured follicle and stimulates progesterone secretion by corpus luteum – Causes interstitial cells in the testes to secrete testosterone in the male Pituitary Gland (cont’d.)

 GH o Stimulates growth by accelerating protein anabolism o Accelerates fat catabolism and slows glucose catabolism o By slowing glucose catabolism, tends to increase blood glucose to higher than normal level (hyperglycemia)  Prolactin or lactogenic hormone o Stimulates breast development during pregnancy and secretion of milk after the delivery of the baby

Posterior Pituitary Gland Hormones Antidiuretic hormone (ADH)  Accelerates water absorption from urine in the kidney tubules into the blood, thereby decreasing urine secretion Oxytocin  Stimulates the pregnant uterus to contract  May initiate labor  Causes glandular cells of the breast to release milk into ducts

Hypothalamus Actual production of ADH and oxytocin occurs in the hypothalamus After production in the hypothalamus, hormones pass along axons into the pituitary gland The secretion and release of posterior pituitary hormones are controlled by nervous stimulation

Conditions of pituitary and hypothalamus gland Direct action hormones: Hyperfunction results in –Gigantism and acromegaly Hypofunction of pituitary results in dwarfism.

Thyroid and Parathyroid Glands View from the frontView from the back

Thyroid Gland Hormones Thyroxine (T 4 )  Most abundant  To be produced in adequate amounts, diet must contain sufficient iodine Triiodothyronine (T 3 )  More potent  Considered by physiologists to be the principal thyroid hormone Calcitonin  Decreases the blood calcium concentration by inhibiting breakdown of bone, which would release calcium into the blood

Parathyroid Gland Parathyroid hormone (PTH)  Increases blood calcium concentration by increasing the breakdown of bone with the release of calcium into the blood  Has opposite effect of calcitonin, because PTH acts to increase calcium Disorders of the Thyroid gland -Hyperthyroidism * Graves disease -Hypothyroidism * Goiter * Cretinism * Myxedema

Adrenal Glands Adrenal cortex  Three cell layers (zones) secrete hormones  Outer layer secretes mineralocorticoids  Middle layer secretes glucocorticoids  Inner layer secretes sex hormones (Androgens), small amounts of male hormones secreted by adrenal cortex of both sexes

Mineralocorticoids Increase blood sodium Decrease body potassium concentrations by accelerating kidney tubule reabsorption of sodium and excretion of potassium Glucocorticoids Maintain normal blood glucose concentration by increasing gluconeogenesis, the formation of “new” glucose from amino acids produced by the breakdown of proteins, mainly those in muscle tissue cells

Play an essential part in maintaining normal blood pressure Make it possible for epinephrine and norepinephrine to maintain a normal degree of vasoconstriction, a condition necessary for maintaining normal blood pressure Act with epinephrine and norepinephrine to produce an antiinflammatory effect to bring about normal recovery from inflammation of various kinds Produce antiimmunity, antiallergy effects Glucocorticoids (cont’d.)

Results from hypersecretion of glucocorticoid hormone by a tumor of the middle zone of the adrenal cortex. Cushing Syndrome: Before and After Treatment

Adrenal Glands Adrenal medulla  Hormones  Epinephrine (adrenaline)  Norepinephrine  Help the body resist stress by intensifying and prolonging the effects of sympathetic stimulation  An increased epinephrine secretion is the first endocrine response to stress

Pancreas (Pancreatic Islets) Hormones  Glucagon is secreted by alpha cells  It increases the blood glucose level by accelerating liver glycogenolysis (conversion of glycogen to glucose) Insulin is secreted by beta cells.  It decreases the blood glucose by accelerating the movement of glucose out of the blood into cells, which increases glucose metabolism by cells.

Stress Responses Induced by High Concentrations of Glucocorticoids in Blood Stress Responses Induced by High Concentrations of Glucocorticoids in Blood

Diabetes Mellitus

Female Sex Glands The ovaries contain two structures that secrete hormones  The ovarian follicles  Little pockets in which egg cells, or ova, develop  Secrete estrogen, the “feminizing hormone”  The corpus luteum

Effects of estrogen  Development and maturation of breasts and external genitals  Development of adult female body contours  Initiation of menstrual cycle Female Sex Glands (cont’d)

Male Sex Glands The interstitial cells of the testes secrete the male hormone testosterone Effects of testosterone  Maturation of external genitals  Beard growth  Voice changes at puberty  Development of musculature and body contours typical of the male

Thymus Hormone: Thymosin  This hormone plays an important role in the development and function of the body’s immune system

Placenta Hormones  Chorionic gonadotropins: tropic hormones secreted by cells of the chorion, the outermost membrane that surrounds the baby during development in the uterus  Estrogens  Progesterone

Pineal Gland The pineal gland is a small gland near the roof of the third ventricle of the brain  Glandular tissue predominates in children and young adults  Tissue becomes fibrous and calcified with age  Called third eye because its influence on secretory activity is related to the amount of light entering the eyes

Pineal Gland  Secretes melatonin, which  Inhibits ovarian activity  Regulates the body’s internal clock Pineal Gland (cont’d)

Other Endocrine Structures Other organs (stomach, intestines, and kidneys) produce endocrine hormones  Atrial natriuretic hormone (ANH)  Secreted by atrial wall of the heart  Stimulates sodium loss from the kidneys Leptin  Newly discovered hormone  Secreted by fat-storing cells  Controls how full or hungry we feel

Let’s Review! Chapter 10

Slide 45 Which of these is a local regulator? A.Hormone B.Prostaglandin Cortisol is produced by the A.Pituitary B.Thyroid C.Parathyroid D.Adrenal cortex E.Adrenal medulla

Slide 46 A primary role of melatonin is in A.Regulating reproductive functions B.Regulating the body’s internal clock C.Stimulating development of white blood cells D.Influencing water balance in the body E.Triggering the release of pituitary hormones

Slide 47 Which of these is a steroid hormone? A.Testosterone B.Melatonin C.Insulin D.Oxytocin E.Parathyroid hormone

Slide 48 The second messenger system is a form of A.Hormone manufacturing B.Signal transduction C.Local regulation D.Reusing or recycling old hormones E.Cheating

Slide 49 Diabetes mellitus results from reduced effects of the hormone A.Glucagon B.Adrenalin C.Epinephrine D.Insulin E.Hydrocortisone

Question What’s the difference between an endocrine and exocrine gland?

Answer Endocrine glands are ductless glands, and they secrete hormones into intercellular spaces. Exocrine glands secrete into ducts that empty onto a surface or into a cavity.

Question What is an example of a negative feedback loop for the regulation of hormone secretion?

Answer There are many!! One example: – blood glucose triggers secretion of insulin. Since insulin promotes glucose uptake by cells, the blood glucose level is restored to its lower, normal level.

Question Where is the pituitary gland located?

Answer The pituitary gland lies buried deep in the cranial cavity in the small depression of the sphenoid bone. The pituitary stalk attaches the gland to the hypothalamus.

Questions What are the zones or areas of the adrenal cortex? What are the hormones produced by the zones or areas of the adrenal cortex?

Answers The outer zone secretes hormones called mineralocorticoids; the main mineralocorticoid is the hormone aldosterone. The middle zone secretes glucocorticoids; the main hormone is hydrocortisone. The inner zone secretes small amounts of sex hormones that resemble testosterone.

Critical Thinking Question We have already studied the nervous system and discussed its many important functions. What functions do the endocrine system and nervous system have in common?

Answer The endocrine system and nervous system have the same general functions: communication and control. The nervous system provides rapid, brief control by fast-traveling nerve impulses, whereas the endocrine system provides slower but longer-lasting control.

???????????????? What questions do you have for me? Don’t forget that your final project is due to the dropbox no later than midnight ET on Tuesday night!!