The Endocrine System

Mr. HunterKennedy High School

www.mrhunterspage.blogspot.com

03/14/2013Anatomy and Physiology

• Objective(s)• SWBAT• Explain the function of the endocrine system • Understand the function of posterior pituitary

gland hormones and the hypothalamus• Bell Ringer : Where are PGs produced?

Endocrine System

• The endocrine system performs the same general function as the nervous system.• The nervous system provides a more rapid response than the endocrine system.•Nerve signals are sent via electrical impulses while the endocrine system (ES) communicates via circulating hormones.

Endocrine System

• Of the two types of glands – exocrine and endocrine, the endocrine gland is part of the endocrine system.•These ductless glands secrete hormone into the blood or into fluid surrounding cells.•Exocrine glands secrete substances through ducts to specialized regions of the body. – Sweat glands, mucous and salivary glands.

Endocrine System• Endocrine glands secrete hormones

into intercellular spaces. • Hormones can diffuse into the blood

and be carried throughout the body.• Hormones may bind to cells that have

hormone specific receptors on their surfaces.

• These cells are known as target cells. The binding of the hormone with the receptor initiates a chemical reaction.

• Hormones play an important role in homeostasis and metabolism.

• Diseases may cause a gland to secrete too much or too little hormone. – Hypersecretion or Hyposecretion

•

Hormone Classes• Two main classes of hormones are

steroid and nonsteroid type hormones.

• Nonsteriod hormones are whole proteins, shorter chains of amino acids, or versions of a single amino acid.

• Nonsteroid hormones act via a second messenger system.

• Within this system hormones are released from endocrine glands and interact with receptors on target cells. This interaction causes chemical changes to occur within the cell’s interior.

•

Hormone Classes• Within the second messenger

system ATP within side the cell is turned into cAMP. Ex cAMP causes the thyroid cells to respond to thyroid stimulating hormone by secreting the thyroid hormone thyroxine.

• Nonsteriod hormones are first messengers that act on target cells.

• The interaction of the target cell with receptors causes chemical changes to occur within the cell. This creates a second messenger within the cell that causes other reactions to take place.

•

Review 02/25/2013

1. Why does the nervous system produce a faster response than the endocrine system?

2. Of the two types of glands, exocrine and endocrine, which one is part of the endocrine system?

3. What is the difference between the two glands?4. What protein structures on the surface of cells do

hormones bind to?5. What are the names of the cells in which hormones act

upon?6. What are nonsteroid hormones and how do they act on

target cells?

Steroid Hormones • The actions of lipid soluble steroid hormones do not occur by second messenger systems.

• Because they are soluble in lipids they can pass directly through the plasma membrane of their target cells.

• Once inside the cell’s nucleus, the steroid hormone can bind to receptors – lock and key model.

• This hormone receptor complex acts on DNA which causes the formation of a new protein in the cytoplasm that produces specific effects in the target cell.

Steroid Hormones • An example of this type of hormone class would be estrogen.

• Since the steps are quite involved for steroid hormones, their hormone response times are much slower than nonsteroid hormones.

• Steriod hormones may also induce membrane receptors to produce a variety of secondary effects.

Hormonal Regulation • Negative feedback systems can regulate hormone levels within the blood.

• As you recall, positive feedback systems amplify the condition instead of reversing them to normal levels.

• Oxytocin secretion during birth increases muscle contractions for a successful delivery.

Prostaglandins (PGs) • PGs are tissue hormones that are found in a large variety of tissues.

• They perform many important functions but are not like typical hormones.

• PGs are produced within tissues and diffuse a short distance to act on cells within that tissue.

• PGs typically influence the activities of neighboring cells. Hormones can influence the activities of widely separated targets.

• PGs can be divided into separate classes – A, E and F.

Prostaglandins (PGs) • PGs can have influences on many body functions such as:

• Respiration• Blood pressure• GI secretions• Inflammation• Reproductive Systems• Most PGs regulate cells by the

production of cAMP.• Play roles in the treatment of various

conditions including high blood pressure, ulcers, and asthma.

• Aspirin cause their effects by altering the functions of PGs in the body.

Review 03/06/20131. What is the difference in the mechanism of action between nonsteroid

hormones and steroid hormones?2. Once inside the cell, what do steroid hormones interact with?3. What is produced as a result of this interaction?4. What is the name of a steroid hormone produced in substantial

quantities by females.5. Why are the response times for steroid hormones much slower than

nonsteroid hormones?6. Describe what occurs in a negative feedback system for high levels of

glucose.7. What are PGs and where are their target cells located?8. How do PGs produce effects on target cells?

Pituitary Gland• The pituitary gland is no smaller

than a pea in size but carries out very important functions.

• It consists of two glands – each of a different type.

• Anterior pituitary gland – adenohypophysis

• Posterior pituitary gland – neurohypophysis

• The anterior pituitary gland has the structure of an endocrine gland.

• The posterior pituitary gland has the structure of nervous tissue.

Pituitary Gland• Hormones released from the

adenohypohysis serve different functions from those released from the neurohypophysis.

• The pituitary gland is located in the sella turcica of the sphenoid bone.

• The pituitary stalk attaches the pituitary gland to the hypothalamus.

Anterior Pituitary Gland Hormones

• The anterior pituitary gland secretes several major hormones.

• Tropic hormones stimulates another endocrine gland to grow and secrete its hormones.

• The anterior pituitary gland was sometimes called the master gland because it exerts control over various structures including the thyroid gland and the adrenal cortex.

• Thyroid Stimulating Hormone – TSH stimulates the thyroid gland to secrete thyroid hormone.

Anterior Pituitary Gland Hormones

• Thyroid Stimulating Hormone – TSH stimulates the thyroid gland to secrete thyroid hormone.

• Adrenocorticotropic Hormone – ACTH – acts on the adrenal cortex. Stimulates the adrenal cortex to increase in size and to secrete larger amounts of cortisol.

• Follicle Stimulating Hormone – FSH stimulates the growth and estrogen secretion of primary ovarian follicles in the ovary. - In the male FSH aids in sperm production.

Anterior Pituitary Gland Hormones

• Luteinizing Hormone – LH acts with FSH to perform various functions.

• Causes estrogen production increase and ovulation.

• Stimulates the formation of the corpus luteum and its production of progesterone.

• Stimulates the interstitial cells of the testes to secrete testosterone.

• Growth Hormone – GH Speeds up the movement of amino acids out of the blood and into cells to promote anabolism of amino acids into tissue proteins.

Anterior Pituitary Gland Hormones

• GH also promotes fat catabolism and slows down glucose catabolism. Less glucose leaves the blood to enter cells. GH therefore increases blood glucose concentrations.

• Hypersecretion of insulin produces hypoglycemia.

• Hypersecretion of GH produces hyperglycemia.

• Prolactin –PRL or lactogenic hormone. Stimulates the development of the breasts for producing milk during pregnancy.

ES Review 03/07/2013

1. What are the names of the anterior and posterior pituitary glands?

2. What structure does the anterior pituitary gland have?3. What structure does the posterior pituitary gland have?4. Where is the pituitary gland located and what is it attached

to?5. What is the function of a tropic hormone?6. What are the functions of TSH, ACTH and FSH?7. How does hypersecretion of GH produce hyperglycemia?8. What is the function of PRL?

Posterior Pituitary• The neurohypophysis releases two

hormones.• Antidiuretic Hormone (ADH)• Oxytocin (OT)• ADH accelerates the reabsorption of

water from urine in the kidneys back into the blood.

• More water moves out of the kidney tubules into the blood, less water remains in the kidneys and therefore less urine is excreted from the body.

• ADH acts to decrease urine volume.• Hyposecretion of ADH results in

diabetes insipidus – large volumes of urine are produced - Dehydration

Posterior Pituitary• OT is secreted by the posterior

pituitary of a female before and after she has a baby.

• OT stimulates uterine contractions to initiate and maintain labor.

• It stimulates glandular cells of the breast to release milk into ducts from which the baby can obtain nutrients.

• Production of ADH and OT occurs in the hypothalamus.

• Two groups of neurons make the posterior gland hormones and pass them along axons to the neurohypophysis. Release is controlled by nervous stimulation.

Posterior Pituitary• The hypothalamus produces

Releasing hormones (RHs) and Inhibiting Hormones (IHs).

• They travel to the adenohypophysis via a specialized capillary system.

• They can cause the release of anterior pituitary hormones or inhibit their production and release into the general circulation.

• The hypothalamus plays a dominant role in regulating many body functions including:

• Body temperature• Appetite• Thirst

Thyroid Gland

• The thyroid gland is located in the neck just inferior to the larynx.

• The thyroid gland secretes two thyroid hormones, thyroxine – T4 and triiodothyronine – T3. It also secretes calcitonin (CT)

• T4 is the most abundant thyroid hormone.• T3 is the more potent and is considered to

be the principal thyroid hormone.

• In order for T4 to be produced, the diet must contain sufficient amounts of iodine.

• The thyroid gland can store thyroid hormone in its follicle cells until the hormone is needed and secreted into the blood.

Thyroid Gland

• Thyroid hormones help to increase cell metabolism.

• All body functions depend on thyroid secretion.

• Calcitonin decreases the amount of calcium in the blood by acting on bone to inhibit its breakdown.

• Less calcium will move out of bone into the blood. Concentration of blood Ca+ levels will decrease.

• Calcitonin helps to maintain homeostasis of blood Ca+ levels – prevents hypercalcemia.

Review 03/12/13

1. Name two hormones produced by the posterior pituitary gland.

2. What are the functions of ADH and OT?3. Hyposecretion of ADH may result in what physiological

condition?4. Where are ADH and OT produced?5. What controls the release of ADH and OT into the blood?6. What are some of the functions of the body that the

hypothalamus controls?7. Where is the thyroid gland located?8. Name and describe the functions of the hormones produced

by the thyroid gland.

Parathyroid Glands• Small glands found on the back of

the thyroid gland.• There are usually four of these

glands.• Secretion of Parathyroid Hormone

(PTH)• PTH increases Ca+ concentration in

the blood.• The opposite effect of Calcitonin. • PTH stimulates osteoclasts (bone

resorbing cells) to increase their breakdown of bone matrix. This moves Ca+ out of bone into blood.

Parathyroid Glands• Low levels of Ca+ in the blood can

cause:• Overactive nerve cells• Muscle spasms resulting from

constant nervous stimulation

• High levels of Ca+ can cause :• The death of brain and heart cells

Adrenal Glands

• The adrenal glands are located on the top of each kidney.

• The are composed of two glands :• Adrenal Cortex• Adrenal Medulla• The two glands produce different

hormones.• The adrenal cortex is divided into

three zones or layers.• Hormones secreted by all three

layers are called corticoids.• The outer zone secrete

mineralocorticoids – MCs.• Main MC is aldosterone.

Adrenal Glands

• The middle zone secretes glucocorticoids – GCs

• Hydrocortisone or Cortisol is the chief glucocorticoid.

• The innermost, deepest zone of the cortex secretes small amounts of sex hormones that resemble testosterone.

• Mineral Corticoids - Aldosterone help to control the amount of NaCl in the blood. It increases the amount of Na+ in the blood and decreases the amount of K+ in the blood. More K+ will be lost in urine.

• Aldosterone speeds up the kidneys reabsorption of water.

Adrenal Glands

• Glucocorticoids help to maintain blood glucose concentrations by the process of gluconeogenesis.

• Amino acids or fatty acids are converted to glucose within the liver.

• Glucocorticoids:• Promote the catabolism of tissue proteins

into amino acids – transported to the liver and turned into glucose and enters blood.

• Maintain normal blood pressure• Produce anti-inflammatory effect –

example: hydrocortisone cream / ointment• Production of ant-immunity or anti-allergy

effect. – Decrease in the production of antbodies.

• Responding to stress• Production of androgens in male and

females.

Review03/14/2013

1. Where are the parathyroid glands located?2. What is the function of PTH?3. Where are the adrenal glands located?4. What are the names of the two glands that the adrenal

gland is divided into?5. How many layers is the adrenal cortex divided into?6. What is the function of aldosterone?7. How do glucocorticoids help to maintain blood glucose

concentrations?

Endocrine System 03/19/2013Adrenal Medulla

• Adrenal Medulla is the inner portion of the adrenal gland.

• It secretes the hormones epinephrine and norepinephrine

• These hormones are released directly into the blood and are involved in the body’s flight or fight response.

Adrenal Medulla• In response to stress the

hypothalamus causes the anterior pituitary to release ACTH.

• This causes the adrenal cortex to release glucocorticoids. In addition, the adrenal medulla will release norepinephrine and epinephrine.

• Anti-inflammatory responses can cause blood vessel constriction and promote the spread of infections along with HBP.

Pancreatic islets – islets of Langerhans

• Glands are small clumps of cells scattered among the exocrine pancreatic cells.

• Alpha cells ( A cells ) secrete glucagon.

• Beta cells ( B cells ) secrete insulin

• Glucagon accelerates glycogenolysis in the liver

• Glycogen Glucose in liver• Increase blood glucose• Insulin decreases blood

glucose levels.

Pancreatic Islets

• Normal glucose levels = 70 to 100 mg per 100 ml of blood.

• Hyposecretion of insulin = type 1 diabetes mellitus

• Type 2 diabetes mellitus = some decrease in insulin and abnormalities in insulin target cell receptors. Blood glucose levels are increased.

Other Endocrine Glands

• Thymus gland hormone = Thymosin for development and function of immune system.

• Placenta – Temporary endocrine gland – hormone = chorionic gonadotropins-

• Secreted in urine / pregnancy Test

• estrogen and progesterone

• Pineal gland – production of melatonin – regulates onset of puberty and menstrual cycle.

• Timekeeping for the body – internal clock

• Ghrelin –secreted by stomach – boosts appetite and slows metabolism.

• ANH atrial natriuretic hormone – loss of Na+ ions and water from kidney

• Antagonist to aldosterone