BIOLOGY 3201

1. BIOLOGY 3201 Endocrine System

3. OVERVIEW OF ENDOCRINE SYSTEM • https://www.youtube.com/watch?v=YcPicFL5Jnw

4. OPERATION OF THE ENDOCRINE SYSTEM • What is the endocrine system? • The endocrine system is comprised of the hormone – producing glands and tissues of the body.

5. OPERATION OF THE ENDOCRINE SYSTEM • Hypothalamus • Controls the endocrine hormone system (as well as the autonomic nervous system). Maintains the body’s internal environment.

6. Functioning of the Endocrine System: • The endocrine system functions along with the nervous system to help maintain homeostasis. • Endocrine system functions slower than nervous system but gives a more sustained effect. • The endocrine system carries out its functions based upon messages received from the Hypothalamus. • The hypothalamus monitors the blood and sends hormones from glands into the blood when needed.

7. Functioning of the Endocrine System: • It is important to note that hormones do not ‘seek’ out particular organs, but rather organs await the arrival of the hormone. Cells that react to a particular hormone have specific receptors for that particular hormone. • Specific hormones attach to specific receptors in cells. This happens in a “lock and- key” fashion. • Organs that contain receptors for specific hormones are called target organs.

9. The endocrine system also controls: • blood sugar • metabolism • growth • reproductive development and function • other physiological activities

10. Comparison of the Nervous System vs. Endocrine System

11. Components of the Endocrine System • Composed of glands and tissues.

12. Two Types of Glands • A. Endocrine- glands that do not have ducts. Hormones are released directly into the bloodstream for transport to target cells. • B.Exocrine - glands produce chemicals which travel to target organ through channels or ducts (i.e. sweat glands, tear glands, salivary glands, and secrete substances such a sweat, saliva, tears, or digestive enzymes)

14. Hormones • Chemicals that circulate throughout the blood and exert some measure of control over most every organ and tissue in the body • Referred to as ‘chemical messengers’these chemicals travel throughout the body via the blood stream and regulate overall metabolism, maintenance of homeostasis, reproduction and vital body functions.

15. Target Organ • Organ that contains receptors for a particular hormone

16. TYPES OF HORMONES • Hormones are either Steroidal or Nonsteroidal. • 1.Steroid Hormones: Hormones manufactured from a fatty substance called Cholesterol. These substances are “fat soluble” meaning they are able to pass through cell membrane of cells. • Ex: Cortisol, Progesterone, Testosterone

17. How Steroid Hormones Work: • These hormones enter a cell and binds to a protein receptor in the cell. This creates a hormone-receptor complex. • The hormone-receptor complex enters the nucleus where it activates a specific gene in the DNA. • Activated gene produces an enzyme (protein) that initiates a chemical reaction within the cell. https://www.youtube.com/watch?v=m9jOXiYdMeY

19. TYPES OF HORMNES • 2.Non-Steroid Hormones– Hormones composed of proteins, peptides or amino acids. • These hormones are NOT fat soluble. They are unable to enter cells because they are not soluble in the cell membrane. Ex: Adrenaline, ACTH, LH, FSH, ADH

20. How Non-steroid Hormones Work: • A Hormone (called a ‘first messenger’) binds to receptors on surfaces of targetcell. • The binding causes ATP to be changed into Cyclic AMP (cAMP). • Cyclic AMP (Second messenger) causes chemical reactions to occur within the cell. https://www.youtube.com/watch?v=Nt2r5R0ZO5U

22. Antagonistic Hormones • These are hormones that work against each other or they have opposite effects on the body. • Ex: Insulin and glucagon • Ex: Parathyroid Hormone and Calcitonin

23. Tropic Hormones • These are hormones that regulate the hormone production of many other glands. • Ex: Thyroid Stimulating hormone, ACTH

24. Endocrine/Hormone Disorders • Problems with most endocrine glands are either caused by Hyposecretion or Hypersecretion of a hormone. • Hyposecretion: An under secretion of a hormone within the body. • Hypersecretion: An over secretion of a hormone within the body.

25. Feedback Mechanisms and Operation of Hormones: • Hormones regulate endocrine function on the basis of feedback mechanisms. • There are two types of feedback mechanisms: • Negative Feedback Mechanism/Loop • Positive Feedback Mechanism/Loop

26. 1. Negative Feedback Mechanism/Loop • - A mechanism that works to “reverse” or “decrease” changes in the body. • Ex: Hypothalamus – Pituitary Feedback Mechanism

27. Operation of the Hypothalamus-Pituitary Feedback mechanism

29. 2. Positive Feedback Mechanism: • - A mechanism that serves to “increase” the effect of an action. • Ex: Oxytocin Feedback loop.

30. Operation of the Oxytocin Feedback Mechanism/Loop

31. GLANDS OF THE ENDOCRINE SYSTEM

32. 1. Pituitary Gland • Located at the base of the brain. Called the “Master Gland” • Connected to the Hypothalamus • Nervous system sends signals via the hypothalamus to exert control over the pituitary. • Comprised of two glands: Posterior Pituitary Anterior Pituitary

33. Anterior Pituitary • Located toward front of head • Makes up largest portion of pituitary gland • Produces 6 different hormones

34. Hormones of the Anterior Pituitary

35. Somatotropin or Human Growth Hormone -- HGH • TARGET: Bones, Tissues • Regulates growth and development of body tissues • Increases intestinal absorption of calcium increasing cell division and growth in bones and cartilage • Stimulate protein synthesis and lipid metabolism

36. Adrenocorticotropic Hormone (ACTH) • TARGET: Adrenal Cortex • Causes the adrenal cortex to produce cortisol and aldosterone

37. Prolactin (PRL) • TARGET: Mammary Glands • Stimulates milk production (lactogenesis) • Stimulates development of mammary tissue • Increased prolactin levels during pregnancy suppress the production of LH which stops ovulation

38. Thyroid Stimulating Hormone (TSH) • TARGET: Thyroid Gland • Stimulates the release of Thyroxine

39. Follicle Stimulating Hormone (FSH) • TARGET: Ovaries, Testes • Causes the maturation of a follicle within an ovary (where the eggs are released) • Starts development of sperm in males

40. Lutenizing Hormone (LH) • TARGET: Ovaries, Testes • Causes follicle to release an egg • Stimulates production of testosterone in males

41. Posterior Pituitary • Located behind the anterior pituitary • Smaller portion of the pituitary • Does not produce it’s own hormones, but stores two from the hypothalamus

42. Hormones of the Posterior Pituitary

43. Oxytocin • TARGET: Uterine Muscles, Mammary Glands • Causes muscles to contract to help expel baby • Causes mammary glands to contract to release milk

44. Antidiuretic Hormone (ADH) or Vasopressin • TARGET: Blood, Arteries & Collecting ducts ofkidneys • Regulates sodium levels in blood • Causes damaged blood vessels to constrict to reduce blood loss • Causes kidneys to retain water.

45. Note: ADH and Oxytocin are created by the HYPOTHALAMUS and STORED in the posterior pituitary.

46. More on Oxytocin • Stimulates contraction of the smooth muscles in the uterus during childbirth. • Towards the end of the pregnancy, the baby’s head pushes against the opening of the uterus. • Pressure receptors in the uterus send impulses to the hypothalamus. This triggers the release of oxytocin from the posterior pituitary.

47. More on Oxytocin • The presence of oxytocin stimulates the uterine muscles to contract. Each contraction causes additional impulses from the pressure receptors and the release of even more oxytocin. • This process ends with the birth of the baby (positive feedback loop).

49. Problems associated with Pituitary Gland

50. Dwarfism • Cause: Insufficient production of HGH during childhood. • Effect: Causes an abnormally short stature. • Treatment: Injections of HGH https://www.youtube.com/watch?v=S7umVBz3ZsI