The Endocrine System

1. The Endocrine System By Dana Mease

2. Learning Target • Students will understand and know the important organs and rolls of the endocrine system. • Warm-up • Name all the glands in the endocrine system.

3. The job of the endocrine system • The nervous system sends electrical messages to control and coordinate the body. The endocrine system has a similar job, but uses chemicals to “communicate”. These chemicals are known as hormones. • A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream.

4. The Endocrine Organs

5. Chemical Types of hormones Amino acid based molecules Including proteins, peptides and amines Ex. Catecholemines Steroids Made from cholesterol. Sex hormones from gonads. Prostoglandins Derive from fatty acids. Unlike most hormones, prostoglandins do not travel through the blood stream, they stay put within the cells. Aid with constriction of respiratory passageways, stimulate contraction of uterus during labor, enhance blood clotting, and promote inflammation and pain. Hormones

6. Activation & Transportation • The endocrine system is regulated by feedback in much the same way that a thermostat regulates the temperature in a room. For the hormones that are regulated by the pituitary gland, a signal is sent from the hypothalamus to the pituitary gland in the form of a "releasing hormone," • Though the hormones travel throughout the body via bloodstream, each one affects only the cells that are genetically programmed to receive it, known as target cells or target organs. • In order for a target cell to respond to an organ, specific protein receptors must be present, which allows the hormone to attach and respond.

7. Hormone Action • There are typically 2 methods in which hormones trigger cell changes; • Direct Gene activation-steroid hormone diffuses through the plasma membrane, and binds to a receptor protein in the nuclei. • Second messenger system- nonsteroid hormones bind to the outer membrane receptor, and sets off several reactions that activate an enzyme. That enzyme then produces a second messenger molecule, then the target cell responds to the hormone.

8. Hypothalamus • The hypothalamusis located in the lower central part of the brain. This part of the brain is important in regulation of satiety, metabolism, and body temperature. In addition, it secretes hormones that stimulate or suppress the release of hormones in the pituitary gland • The Hypothalamus, along with the Pituitary gland, form the chief link between the nervous and endocrine systems.

9. Hormones of the Hypothalamus Corticotrophin Releasing Hormone (CRH): CRH Stimulates the secretion of corticotropin in the pituitary Thyrotropin-releasing hormone(TRH), stimulates the secretion of thyroid-stimulating hormone from the pituitary, and also the hormone prolactin Gonadotropin-releasing hormone It stimulates the synthesis and release of the two pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Luteinizing Releasing Hormone (LRH): LRH also targets the ovaries and the testes, and its receptors are cells which promote ovulation and increase progrestone synthesis and release. Growth Hormone Releasing Hormone (GHRH): GHRH targets the anterior pituitary to release growth hormones to most body tissues, increase protein synthesis, and increase blood glucose.

10. Pituitary Stalk • The pituitary gland is functionally linked to the hypothalamus by the pituitary stalk. • When hormones from the hypothalamus are released they are Delivered to the anterior pituitary via the hypophyseal portal system (the system of blood vessels that links the hypothalamus and the anterior pituitary in the brain.) • Although the pituitary gland is known as the master endocrine gland, both of its lobes are under the control of the hypothalamus

11. Pituitary gland • The Pituitary gland is Approximately the size of a pea and weighs about 0.5 grams. • It is a protrusion off the inferior end of the hypothalamus,at the base of the brain. • There are two parts. • The anterior & the posterior

12. Anterior Pituitary • The anterior pituitary consists of about 80 percent of the entire pituitary gland. • Two of the Six anterior pituitary hormones have major effects on non-endocrine targets. • The other four are Tropic hormones,which stimulate other endocrine organs to secrete their hormones.

13. Hormones of the anterior pituitary • Adrenocorticotropin hormone(ACTH)- Regulates the endocrine activity of the cortex portion of the adrenal gland. • Thyroid-stimulating hormone (TSH) - Stimulates growth and activity of the thyroid gland. • Prolactin-PRL- induces growth of the mammary gland. Stimulates lactogenesis or milk production after giving birth. • Growth Hormone(GH)- Stimulates growth of bone and tissue. Also plays a role in maintaining blood sugar homeostasis. • Both GH and PRL are the only two hormones of the pituitary gland that have major effects on non-endocrine organs.

14. Hormones of the Anterior Pituitary cont. • The male and female reproductive system respond to the same pituitary hormones, although in different ways. The two gonadtropic hormones regulate the hormonal activity of the ovaries and testes. They are known as: • Follicle-stimulating hormone (FSH) • In females FSH stimulates follicle development in the ovaries, triggers the development of egg cells (Ova) • In Males, FSH stimulates the production of sperm. • Luteinizing hormone (LH) • In females it triggers ovulation or an egg from the ovary and produces progesterone and some estrogen. • In Males it stimulates Testosterone production. (Also known as Interstitial cell-stimulation hormone ICSH, for males only)

15. Posterior pituitary • The Posterior pituitary doesn’t actually make its own hormones. • It acts as a storage area for hormones made by the Hypothalamus.

16. Hormones of the Posterior Pituitary • Oxytocin- Stimulates contractions of the uterine during childbirth, and causes milk ejection while nursing. • Doctors use synthetic oxytocic drugs to induce labor. • Antidiuretic hormone(ADH) chemical that prevents urine production. Causes Kidneys to reabsorb more water. • Alcohol inhibits ADH secretion and results in output of large amounts of urine.

17. Thyroid • The thyroid is stimulated by TSH from the anterior pituitary Thyroid hormones also help maintain normal blood pressure, heart rate, digestion, muscle tone, and reproductive functions.

18. Thyroid Hormones • Thyroid Hormone- The body’s major metabolic hormone. Thyroid hormone controls the rate at which glucose is converted into body heat and chemical energy. • Every cell in the body is a target cell of this hormone. • It also plays a role in bone growth and development of the brain and nervous system in children. • Calcitonin- Causes calcium to deposit in bones, therefore deceases blood calcium level.

19. Thyroid • Inside the thyroid, it is composed if hollow structures called follicles, which store sticky colloidal material. • Thyroid hormone is derived from colloid.

20. Parathyroid glands • The parathyroid glands are two pairs of small glands embedded in the posterior surface of the thyroid gland, one pair on each side. • They release parathyroid hormone (PTH) which plays a role in regulating calcium levels in the blood and bone metabolism.

21. Effects of PTH • When the calcium levels in blood drop below a certain level, the parathyroid releases PTH, which stimulates osteoclasts to break down calcium phosphate crystals found in bone and release it into the bloodstream. • Parathyroid hormone stimulates the production of the active form of vitamin D in the kidney. Vitamin D induces synthesis of a calcium-binding protein in intestinal epithelial cells that facilitates efficient absorption of calcium into blood. • In the Kidneys, it triggers reabsorption of calcium from the urine.

22. PTH cont.

23. Adrenals • The Adrenal glands are Situated above the kidneys. • Each one consists of two separate parts: A medulla (Neural tissue) surrounded by a cortex (Glandular)

24. Adrenal cont. • The outer Adrenal cortex produces hormones called corticosteroids, which regulate the long term stressors, such as the body's metabolism, the balance of salt and water in the body, the immune system, and sexual function. • The adrenal medulla produces hormones called catecholamines (for example, adrenaline). These hormones help the body cope with short term physical and emotional stress by increasing the heart rate, blood pressure, and blood glucose levels.

25. Pancreas • The pancreas is an elongated organ located toward the back of the abdomen behind the stomach. • The pancreas has digestive and hormonal functions. • The pancreatic islets are the hormone producing tissue scattered throughout the pancreas.

26. Pancreas cont. • Two important hormones produced by the islets are insulin and Glucagon. • Insulin is released by beta cells. A low level of the hormone is continuously secreted, but if glucose level in the blood increases, more of the hormone is produced, and vice versa. • The Job of insulin is to increase body cells’ ability to transport glucose across the plasma membrane and produce energy. • Glucagon is released by the alpha cells and is stimulated by low glucose blood levels. Its primary target is the liver, which stimulates the break down of stored glycogen to glucose and to release the glucose into the bloodstream. • Somatostatin is produced in the delta cells, and inhibits the production of both hormones.

27. Pancreas

28. Pineal gland • The Pineal Gland is a small, pine cone shaped gland that sits on top of the third ventricle of the brain. • The Gland is often referred to as the “third eye”.

29. Pineal cont. • The pineal gland secretes the hormone, Melatonin, in response to the signals it receives from the retina (assisted by the hypothalamus) • In darkness, the pineal gland secretes melatonin, while in the presence of light it suppresses it. • Melatonin is important in the regulation of the sleep cycle, as increased levels of melatonin lead to fatigue.

30. Thymus • The Thymus is located in the anterior portion of the chest cavity just behind the sternum • The thymus decreases in size as development continues. • The main function of the thymus is to provide an area for T-lymphocyte to mature. • Secretes a hormone known as thymosin which promotes the development of lymphocytes.

31. Ovaries • The ovariesare the gonads or sex organs in females. The two almond-sized ovaries are located on each side of the pelvis, one at the end of each fallopian tube. • The ovaries do not really begin functioning until puberty, when the gonadtopic hormones stimulate them. • As well as producing ova, they produce two types of steroid hormones estrogens and progesterone.

32. Ovaries cont. • Estrogens stimulate secondary sex characteristics: enlargement of the breasts, appearance of hair under the arms and in the genital area, and the accumulation of fat in the hips and thighs. • Progesterone works with estrogens to prepare the uterus to receive a fertilized egg. This results in periodic changes in the uterine lining, also known as menstruation. • Progesterone as well as helping with the menstrual cycle, is more active during pregnancy when it decreases contractility of the uterine smooth muscles so an implanted embryo will not be aborted.

33. Testes • The testes are the gonads in males. They are two small, egg-shaped structures suspended in the scrotum, a loose sac of skin that hangs outside the pelvic cavity between the upper thighs. • As well as producing male sex cells, or sperm, they also produce male sex hormones, or androgens. • These hormones affect many male characteristics (for example, sexual development, growth of facial hair and pubic hair) as well as sperm production.

34. The End 