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Name: ________________________________________ Date: _________________ BIO 210: Anatomy and Physiology Text: Fundamentals of Anatomy and Physiology 9ed.

Chapter 18—The Endocrine System We typically think of the Nervous System as being the control center for all of our bodily functions. However, very few of our cells are innervated with nerves and those that are receive short-lived commands that are very specific. It is the Endocrine System that continually controls and maintains many important functions of the body for extended periods of time. CELLULAR COMMUNICATION (Table 18-1)

• Direct communication—occurs between two cells of the ____________________; exchange of ions and molecules between ________________________; must be in ________________ with each other

o Ex.

• Paracrine communication—use of _____________________________ to transfer information from cell to cell within a _______________________; chemicals are called ________________________ or _________________________; primary effects occur within _____________________; when paracrine factors have a secondary effect in other tissues beyond the tissue of origin, it is then acting as a _____________________

o Ex.

• Hormones—chemical messengers that are released in one tissue and transported in the _____________________ to alter activities of cells in another tissue; a substance with effects outside its ____________________________

o Target cells—specific cells that can ‘read’ the message of a ______________________ and

alter its activity accordingly; need specialized ______________________ for that hormone message

FUNCTION OF A HORMONE

• Stimulate enzyme or protein synthesis • Alter transcription or translation to increase or decrease rate of protein and enzyme synthesis • Altering channel or membrane enzyme shapes thereby turning it on or off • Alter cellular activities of several tissues at the same time • Coordinate cell, tissue and organ activities on a long-term basis

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SYNAPTIC COMMUNICATION

• Chemical communication using neurotransmitters across synaptic clefts (not in bloodstream) • Target cells are close to the synapse and have specific receptors • Carries high speed messages which are quick but short-lived • Crisis management (fight or flight)

CLASSES OF HORMONES Amino Acid Derivatives

• _______________ structures related to amino acids • thyroid hormone, and catecholamines (E, NE and dopamine) are derived from the amino acid,

_________________

• melatonin derived from the amino acid, ________________________ Peptide Hormones

• thyroid stimulating hormone, LH, and FSH are _____________________ that consist of long chains of amino acids

• all hormones from the hypothalamus, heart, digestive tract, thymus, pancreas and posterior pituitary

gland are short ____________________________ Lipid Derivatives

• Eicosanoids commonly have ____________________ effects; prostaglandins, leukotrines, thromboxanes and prostacyclins

• Steroid hormones resemble ______________________; secreted by reproductive glands (androgens,

estrogens and progestins), by the adrenal glands (corticosteroids), and by the kidneys (calcitriol) DISTRIBUTION OF HORMONES

• Hormones can circulate freely, or bind to transport proteins • Freely circulating hormones are active from only a few minutes up to an hour

• Freely circulating hormones are inactivated when:

o they diffuse out of the blood stream and bind to the target cell receptor o when they are absorbed and broken down by the liver or kidneys o or when enzymes in the cell plasma break it down

• Thyroid hormones and steroid hormones remain in circulation longer than peptide hormones because

they are bound to _________________________ • The bloodstream can have a _____________________________ of bound hormones at any given time

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Thyroid and steroid hormones last in the blood longer because they attach to a transport protein. This is how hormones maintain equilibrium in the blood stream, free circulating hormones being replaced by bound hormones to a reserve of several weeks supply. MECHANISMS OF HORMONE ACTION Hormone Receptor

• Is a _______________ molecule to which a particular molecule binds strongly • Can respond to __________________________ hormones • Different tissues have different combinations of __________________ • Presence or absence of specific receptor determines hormonal _________________________

Hormones modify cellular activity. Do they affect all tissues with their receptors the same? Hormones and Plasma Membrane Receptors

• Catecholamines and Peptide Hormones—not ________________________ and cannot penetrate the plasma membrane; bind to receptor proteins on _______________________ of plasma membrane called ___________________________

• Eicosanoids—are ___________________________ so they can diffuse across plasma membrane to

reach receptor proteins on the _______________________________ of the plasma membrane called ___________________________

First and Second Messengers—Hormones that bind to receptors in the plasma membrane cannot have direct effect on activities inside target cell; they have to use intracellular intermediary to exert effects

• First Messenger— the ________________ that binds to the plasma membrane; leads to a second messenger

• Second Messengers—act as ____________________, ___________________, or _________________

resulting in change in rates of metabolic reactions; important second messengers:

o Cyclic-AMP (cAMP)—derivative of _______ o Cyclic-GMP (cGMP)—derivative of _______

o Calcium ions

• The Process of Amplification—the binding of a small number of hormone molecules to membrane

receptors which leads to thousands of ______________________ in cell; ____________________ effect of hormone on target cell

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• Down-regulation—the presence of a hormone triggers a ____________________ in number of _____________________________; when levels of particular hormone are high, cells become _______________________________ to it

• Up-regulation—the absence of a hormone triggers an __________________________ in the number of

hormone receptors; when levels of particular hormone are low, cells become ______________________ to it

• G Protein— middle man between 1st and 2nd messenger. These proteins bind to ____________ and are activated when a hormone binds to its _____________________ at the __________________________

G Proteins and cAMP (Figure 18-3)—G proteins increase or decrease cAMP (second messenger) levels in response to peptide hormones, catecholamines, and eicosanoids Increasing cAMP:

1. Activated G protein activates the enzyme adenylate cyclase 2. Adenylate cyclase converts ATP to cAMP 3. cAMP is now a 2nd messenger and activates kinase causing phosphorylation (attaching of a high-

energy phosphate group to another molecule) 4. Phosphodiesterase inactivates cAMP to AMP making increased levels of cAMP short lived

Decreasing cAMP:

1. Activated G protein stimulates phosphodiesterase activity 2. Adenylate cyclase activity is inhibited 3. cAMP levels decline 4. without phosphorylation, key enzymes remain inactive

G Proteins and Calcium Ions (Figure 18-3)—activated G proteins trigger the opening of calcium ion channels in the membrane or the release of calcium ions from intracellular stores

1. G protein activates the enzyme phospholipase C (PLC) 2. Triggers a receptor cascade allowing Ca2+ release from intracellular reserves (SER) 3. Phosphorylation of calcium channel proteins opens the channel and permits extracellular calcium

to enter the cell (positive feedback loop to increase intracellular calcium) 4. Calcium (acting as a second messenger) can bind to calmodulin which activates other enzymes

HORMONES AND INTRACELLULAR RECEPTORS (FIGURE 18-4)

• Alter rate of DNA transcription in nucleus • Change patterns of protein synthesis • Directly affect metabolic activity and structure of target cell • Include steroids and thyroid hormones

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Steroid hormones—diffuse through the plasma membrane and bind to receptors in the ________________ or ____________________; the hormone then binds to ___________ in the nucleus to activate certain genes Thyroid hormones—enter the cytoplasm and bind to receptors on the _________________________ or in the __________________; activates __________________ or accelerates _____________________________ THE PITUITARY GLAND (Figure 18-6)—also called the ________________________; lies within __________________________ isolated from cranial cavity; hangs inferior to _________________________ and is connected by the _____________________________ Facts to Know:

• Releases ______ important peptide hormones • Hormones bind to ______________________ • Use ____________ as second messenger

Anterior Lobe of the Pituitary Gland—also called ______________________________; hormones “turn on” endocrine glands or support other organs

Hypothalamic Control of the Anterior Lobe—two classes of hypothalamic regulatory hormones; rate of secretion is controlled by negative feedback:

1. Releasing hormones (RH)—stimulate synthesis and secretion of one or more hormones at anterior

lobe 2. Inhibiting hormones (IH)—prevent synthesis and secretion of hormones from the anterior lobe

HORMONES OF THE ANTERIOR LOBE (7):

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Points to Note:

• ACTH targets glucocorticoids (hormones that affect _______________________________)

• Low levels of gonadotropins causes ____________________________;

• FSH is inhibited by _____________________

• Luteinizing hormone prepares the body for ________________________ in females; in males it stimulates cells of the testes to secrete _____________________________

• Prolactin is found in males and might help regulate _________________________ production

• Growth hormone stimulates growth directly and indirectly

o Indirectly: Liver cells respond to GH by producing compounds that stimulate tissue growth;

these peptides bind to receptors on plasma membranes to increase uptake of amino acids for new protein synthesis

o Directly: stem cell division and differentiation of epithelial and connective tissues, in adipose tissue: glucose-sparing effect where fatty acids are released from adipose tissue for energy, and in the liver: stimulates the break down of glycogen into glucose from the liver increasing blood glucose levels

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The Posterior Lobe of the Pituitary Gland—also called ____________________________; contains unmyelinated axons of hypothalamic neurons; secrete Antidiuretic hormone (ADH) and Oxytocin (OXT) HORMONES OF THE POSTERIOR LOBE (2):

Points to Note:

• Antidiuretic hormone also referred to as _________________________ • ADH responds to a rise in ___________________________ in the blood or fall in blood ____________

or ___________________ by _______________________ the amount of water loss in the __________________________ and by causing ______________________________ to increase blood pressure

• ____________________ inhibits ADH • Oxytocin is responsible for the ______________________________ stimulated by a suckling infant

THE THYROID GLAND (Figure 18-10)—lies anterior to thyroid cartilage of larynx; consists of two lobes connected by narrow isthmus Points to Note:

• Thyroid follicles (Figure 18-10c)— • Thyroxine (T4)—also called tetraiodothyronine, contains __________ iodide ions

• Triiodothyronine (T3)—contains __________ iodide ions

• The absence of Thyroid-Stimulating Hormone (TSH) causes thyroid follicles to become _____________

• They bind to receptors in: ______________________ ( _______________________), surfaces of

_________________________ (_______________________________), and the _______________ (____________________________________________________________________________)

• T4 can be converted to _________ in the liver when needed

• Thyroid gland contains most of the ________________________ reserves in the body; needed to

synthesize thyroid hormones

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Functions of Thyroid Hormones (T3 and T4)—thyroid hormones enter target cells by transport system and affect most cells in body

• In children they are essential to normal development of skeletal, muscular, and nervous systems

• Responsible for ____________________________, where the cell consumes more energy resulting in increased _____________________________ and is responsible for strong, immediate, and short-lived increase in rate of ___________________________________; in ________________________, these hormones increase in _________________________________ to help them adapt

• Elevates rates of _________________ consumption and ___________________ consumption; in

children, may cause a rise in _______________________________________ • Increases __________________________ and _________________________________; generally

results in a rise in blood pressure

• Increases sensitivity to _________________________ stimulation

• Maintains normal sensitivity of respiratory centers to changes in ________ and _________ concentrations

• Stimulates ______________________ formation and thus enhances ________________ delivery

• Stimulates activity in other endocrine tissues

• Accelerates turnover of __________________________ in bone

The C Cells of the Thyroid Gland and Calcitonin (Figure 18-10c)

• C (clear) cells also called parafollicular cells • Produce _____________________ (CT) • Helps regulate concentrations of __________ in body fluids • Inhibits ________________________, which slows the rate of Ca2+ release from bone • Stimulates Ca2+ excretion by the __________________ • Most important during ______________________ to stimulate bone growth • Reduced bone loss during ______________________ and ______________________

PARATHYROID GLANDS (Figure 18-12)—four Parathyroid Glands embedded in the posterior surface of the thyroid gland

• Parathyroid Hormone (PTH) produced by parathyroid (chief) cells respond to low concentrations of ___________

• ihibits _______________________ and indirectly increases ___________________ numbers for calcium release

• enhances reabsorption of calcium by the ____________________, reducing ____________________ • increases ________________________ secretion by the kidneys which increases Ca2+, PO4

3− absorption

by ____________________________ • Antagonist for ________________________

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HORMONES OF THE THYROID AND PARATHYROID GLANDS (4):

ADRENAL GLANDS (Figure 18-14)—lie along superior border of each ________________; subdivided into the adrenal cortex and the adrenal medulla

• superficial adrenal cortex __________________________, especially cholesterol and fatty acids and manufactures ________________________________________

• Inner adrenal medulla has secretory activities controlled by sympathetic division of ANS; produces

______________________________ and _________________________________ whose metabolic changes persist for several minutes

Adrenal Cortex—(Figure 18-14c)

• outer region of adrenal cortex; produces mineralocorticoids (aldosterone)

! Aldosterone—stimulates conservation of _______ and elimination of ________

• increases sensitivity of _________________________ in taste buds to increase desire for salty foods

• Causes _____________________ of sodium ions by affecting the kidneys, sweat

glands, salivary glands, and pancreas

• Secretion responds to: drop in ______________________,

________________________, or _________________________ and a rise in __________________________________ concentration

• produces glucocorticoids (cortisol (hydrocortisone) with corticosterone)

! Glucocorticoids—accelerate ___________________________________ and

_____________________________________, show ____________________________ effects (slow phagocyte activity at injury site) and inhibit release of _________________ (cortisone creams)

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• Cortisol—liver converts to cortisone; secretion regulated by negative feedback;

has inhibitory effect on production of Corticotropin-releasing hormone (CRH) in hypothalamus and ACTH in adenohypophysis

• produces _____________________ under stimulation by ACTH—stimulate _____________________ growth in adolescents, and muscle mass, blood cell formation, and sex drive in ____________________ only

The Adrenal Medulla—contains two types of secretory cells:

• One produces epinephrine (adrenaline)—75% to 80% of medullary secretions

• The other produces norepinephrine (noradrenaline)—20% to 25% of medullary secretions Epinephrine and Norepinephrine—activation of the adrenal medullae has the following effects:

• In skeletal muscles, epinephrine and norepinephrine trigger mobilization of _____________________ reserves and accelerate the breakdown of ____________________ to provide ___________

• In adipose tissue, stored ____________ are broken down into fatty acids which are released into the

bloodstream for other tissues to use for ____________ production

• In the liver, _____________________ molecules are broken down and the resulting glucose molecules are released into the bloodstream

• In the heart, the stimulation of beta 1 receptors triggers an _________________ in the rate and force of

____________________________________________ HORMONES OF THE ADRENAL GLAND

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PINEAL GLAND (Figure 18-15)—lies in posterior portion of roof of third ventricle; contains pinealocytes and synthesizes the hormone melatonin Functions of Melatonin:

• Inhibits ______________________ functions; slows maturation of sperm, oocytes, and organs; levels decrease after ________________________

• Protects against damage by ______________________; serves as an _____________________ protecting neural tissue from ____________ and _____________________________

• Influences ______________________________ PANCREAS (Figure 18-16)—lies between inferior border of stomach and proximal portion of small intestine; contains exocrine and endocrine cells Exocrine Pancreas

• Consists of clusters of gland cells called pancreatic ______________ and their attached ducts • Takes up roughly _______ of pancreatic volume • Gland and duct cells secrete alkaline, enzyme-rich fluid called _________________________; serves as

digestive enzymes in the break down of food Endocrine Pancreas—consists of cells that form clusters known as pancreatic islets, or _________________________________________________

• Alpha cells produce ___________________ • Beta cells produce ____________________ • Delta cells produce _____________________________ identical to GH–IH • F cells secrete __________________________________

Blood Glucose Levels

• When levels rise:

• When levels decline:

Insulin—is a peptide hormone released by beta cells when glucose concentrations exceed normal levels

• Cells that have insulin receptors are _____________________________ • Cells of the brain, kidney, digestive tract lining, and RBC’s lack insulin receptors; termed

____________________________________; can take up glucose without the aid of insulin Affects on target cells:

• Accelerates __________________________ by increasing ___________________________ • Accelerates glucose utilization and enhances ____________ production • Stimulates _________________________ formation when glucose is in excess • Stimulates _____________________________ absorption and ___________________ synthesis

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• Stimulates ______________________ formation in adipose tissue and the absorption of _____________ which is used to make more tryglycerides

Glucagon—released by alpha cells; mobilizes energy reserves Affects on target cells:

• Stimulates breakdown of ___________________________ in skeletal muscle and liver cells • Stimulates breakdown of ___________________________ in adipose tissue • Stimulates production of ___________________ in liver (gluconeogenesis) • End result is the reduction in glucose use and the release of glucose into the ______________________

HORMONES OF THE PANCREAS

Hyperglycemia—abnormally __________ glucose levels in the blood in general; glucose appears in the _______________, and urine volume generally becomes excessive Diabetes Mellitus—characterized by glucose concentrations high enough to overwhelm the reabsorption capabilities of the kidneys

• Type 1 (insulin dependent) diabetes—is characterized by inadequate insulin production by the pancreatic beta cells; persons with type 1 diabetes require insulin to live and usually require multiple injections daily, or continuous infusion through an insulin pump or other device; this form of diabetes accounts for only around 5% –10% of cases; it often develops in childhood

• Type 2 (non-insulin dependent) diabetes—is the most common form of diabetes mellitus; most people

with this form of diabetes produce normal amounts of insulin, at least initially, but their tissues do not respond properly, a condition known as insulin resistance; associated with obesity; weight loss through diet and exercise can be an effective treatment

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Complications of untreated, or poorly managed diabetes mellitus include:

• Diabetic nephropathy—degenerative changes in the kidneys, can lead to kidney failure

• Retinal Damage—diabetic retinopathy ; the proliferation of capillaries and hemorrhaging at the retina may cause partial or complete blindness

• Early Heart Attacks—degenerative blockages in cardiac circulation can lead to early heart attacks; for

a given age group, heart attacks are three to five times more likely in diabetic individuals than in nondiabetic people

• Peripheral Nerve Problems—abnormal blood flow to neural tissues is probably responsible for a

variety of neural problems with peripheral nerves, including abnormal autonomic function; these disorders are collectively termed diabetic neuropathy

• Peripheral Nerve Damage—blood flow to the distal portions of the limbs is reduced, and peripheral

tissues may suffer as a result; example, a reduction in blood flow to the feet can lead to tissue death, ulceration, infection, and loss of toes or a major portion of one or both feet

ENDOCRINE TISSUE OF OTHER SYSTEMS The Intestines—produce hormones important to coordination of digestive activities The Kidneys—produce the hormones calcitriol (calcium and phosphate absorption on the digestive tract), erythropoietin (EPO) (stimulates RBC formation when oxygen levels are low), and renin (elevates blood volume by retaining water in the kidneys) The Heart—produces natriuretic peptides (ANP and BNP) when blood volume becomes excessive; action opposes angiotensin II resulting in reduction in blood volume and blood pressure; suppresses thirst The Thymus—produces thymosins (blend of thymic hormones) that help develop and maintain normal immune defenses The Testes—produce androgens in interstitial cells; testosterone is the most important male hormone; also secretes inhibin in nurse cells; supports differentiation and physical maturation of sperm The Ovaries—produce estrogens, principal estrogen is estradiol; after ovulation, follicle cells reorganize into corpus luteum and release estrogens and progestins, especially progesterone Adipose Tissue Secretions—leptin, the feedback control for appetite; controls normal levels of GnRH, gonadotropin synthesis

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HORMONES OF OTHER SYSTEMS