Chapter 25 and 26 Endocrine to print
Page 1: Chapter 25/26: Endocrine System Endocrine Regulation
Compare endocrine structure and function with nervous structure and function.
Endocrine system and nervous system both function to achieve and maintain homeostasis.
Identify the different ways to classify hormones.
Differentiate between the mechanisms of action of steroid and nonsteroid hormones.
Describe endocrine reflexes and up- and down-regulation.
Discuss the chemical nature, classification, and mechanism of action of eicosanoids (prostaglandins, thromboxane, and leukotrienes).
Discuss the mechanisms of hypersecretion and hyposecretion.
Page 2: ORGANIZATION OF THE ENDOCRINE SYSTEM
The endocrine and nervous systems function to achieve and maintain homeostasis.
When the two systems work together, referred to as the neuroendocrine system, they perform the same general functions: communication, integration, and control.
In the endocrine system, secreting cells send hormone molecules by the blood to specific target cells contained in target tissues or target organs.
Page 3: Mechanisms of Endocrine and Nervous Signals
Endocrine signals are slow and target cells through the bloodstream.
Nervous signals are fast and target cells through neurotransmitters.
Page 4: ORGANIZATION OF THE ENDOCRINE SYSTEM
Hormones are carried to almost every point in the body and can regulate most cells.
Endocrine glands are "ductless glands" made of glandular epithelium that manufacture and secrete hormones.
Glands of the endocrine system are widely scattered throughout the body.
Page 5: HORMONES
Tropic hormones target other endocrine glands and stimulate their growth and secretion.
Sex hormones target reproductive tissues.
Anabolic hormones stimulate anabolism in target cells.
Hormones can be classified by general function and chemical structure.
Page 6: Hormones
Steroid hormones: synthesized from cholesterol, lipid soluble, examples include cortisol, aldosterone, estrogen, progesterone, testosterone.
Nonsteroid hormones: synthesized primarily from amino acids, can be protein hormones, glycoprotein hormones, peptide hormones, or amino acid derivative hormones.
Page 7: HORMONES: CLASSIFICATION - Steroid hormones
Steroid hormones are synthesized from cholesterol.
They are lipid soluble and easily pass through the phospholipid plasma membrane of target cells.
Page 8: HORMONES: CLASSIFICATION - Nonsteroid hormones
Nonsteroid hormones are synthesized primarily from amino acids.
They can be protein hormones, glycoprotein hormones, peptide hormones, or amino acid derivative hormones.
Page 9: Structure of Nonsteroid Hormones
Protein hormones have long, folded chains of amino acids.
Glycoprotein hormones are protein hormones with carbohydrate groups attached to the amino acid chain.
Peptide hormones have a short chain of amino acids.
Amino acid derivative hormones are derived from a single amino acid molecule.
Page 10: HORMONES
Hormones signal a cell by binding to the target cell's specific receptors in a "lock and key" mechanism.
Different hormone receptor interactions produce different regulatory changes within the target cell.
Combined hormone actions can have synergistic, permissive, or antagonistic effects on target cells.
Page 11: Lock-and-Key Model
Hormones bind to specific receptors on target cells in a lock-and-key mechanism.
Page 12: HORMONES
Most hormones have primary effects that directly regulate target cells and secondary effects that influence other regulatory mechanisms.
Endocrine glands produce more hormone molecules than are needed, and the unused hormones are excreted or broken down.
Page 13: HORMONES
Regulation of hormone secretion is usually part of a negative feedback loop called endocrine reflexes.
Endocrine gland secretion may be regulated by physiological changes produced by target cells, hormones produced by other glands, or nervous system input.
Page 14: HORMONES - Regulation of target cell sensitivity
The sensitivity of target cells depends on the number of hormone receptors.
Up-regulation increases the number of hormone receptors and increases sensitivity.
Down-regulation decreases the number of hormone receptors and decreases sensitivity.
Page 15: Eicosanoids
Eicosanoids are a unique group of lipid hormones that serve important integrative functions in the body.
They are called tissue hormones because their secretion is produced in a tissue and diffuses only a short distance to other cells within the same tissue.
Eicosanoids tend to integrate activities of neighboring cells.
Page 16: PROSTAGLANDINS
Prostaglandins have diverse physiological effects.
Different classes of prostaglandins have been identified, each with specific functions.
Page 17: PROSTAGLANDINS
Prostaglandin F is especially important in the reproductive system and affects uterine contractions, intestinal motility, and peristalsis.
Many tissues are known to secrete prostaglandins.
Pituitary and Pineal Glands
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Discuss the size, location, and anatomical components of the pituitary gland.
List the hormones of the adenohypophysis, describe their general functions, and identify the primary locations of their target cells.
Identify the actions of the hormones stored and released by the neurohypopysis.
Discuss the structure, location, functions, and hormones of the pineal gland.
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The pituitary gland is composed of two separate glands: the adenohypophysis (anterior pituitary gland) and the neurohypophysis (posterior pituitary gland).
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The adenohypophysis (anterior pituitary) is composed of irregular clumps of secretory cells supported by fine connective tissue fibers and surrounded by a rich vascular network.
Three types of cells can be identified in the adenohypophysis: chromophobes, acidophils, and basophils.
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There are five functional types of secretory cells in the pituitary gland.
These include somatotrophs, corticotrophs, thyrotrophs, lactotrophs, and gonadotrophs.
Tropic hormones target other endocrine glands and stimulate their growth and secretion.
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The pituitary gland secretes various hormones, including growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, oxytocin, and gonadotropic hormones.
These hormones have different target organs and functions.
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Growth hormone promotes growth of bone, muscle, and other tissues.
It stimulates fat metabolism and tends to shift cell chemistry away from glucose catabolism.
Growth hormone functions as an insulin antagonist and helps maintain blood glucose levels.
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Prolactin is produced by acidophils in the pars anterior.
Prolactin promotes breast development during pregnancy and stimulates milk production after childbirth.
Tropic hormones stimulate the growth and development of other endocrine glands.
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Follicle-stimulating hormone stimulates the growth of follicles in females and the development of seminiferous tubules in males.
Luteinizing hormone stimulates the formation and activity of the corpus luteum in females and the secretion of testosterone in males.
Both hormones are called gonadotropins because they stimulate the growth and maintenance of the gonads.
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The hypothalamus secretes releasing hormones into the blood, which are carried to the adenohypophysis through the hypophyseal portal system.
Releasing hormones influence the secretion of hormones by acidophils and basophils in the adenohypophysis.
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The pituitary gland serves as a storage and release site for antidiuretic hormone and oxytocin, which are synthesized in the hypothalamus.
The release of antidiuretic hormone and oxytocin into the blood is controlled by nervous stimulation.
Antidiuretic hormone prevents the formation of a large volume of urine and helps conserve water.
Oxytocin causes milk ejection from the lactating breast and stimulates uterine muscle contractions during childbirth.
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The pineal gland is a tiny, pine cone-shaped structure located on the dorsal aspect of the brain.
It is a member of both the nervous system and the endocrine system.
The pineal gland supports the body's biological clock and secretes hormones.
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The thyroid gland is composed of lobes and a narrow connecting isthmus.
It is located in the neck, on the anterior and lateral surfaces of the trachea, just below the larynx.
The thyroid gland is composed of follicles filled with thyroid colloid that contains thyroglobulins.
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Epiglottis, hyoid bone, thyroid follicle, sterno hyoid muscle, larynx, thyrohyoid muscle, pyramidal lobe, internal jugular vein, thyroid gland, lateral lobe, isthmus, common carotid artery, trachea, thyroid follicle, follicular cells, parafollicular cells, thyroid colloid, lumen, epithelium.
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Thyroid gland produces triiodothyronine (T3) and tetraiodothyronine (T4).
T3 is the principal thyroid hormone and binds efficiently to nuclear receptors in target cells.
T4 is more abundant than T3 and serves as a precursor to T3.
T3 and T4 are attached to globulin molecules before being stored in the colloid of follicles.
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T3 and T4 detach from globulin and enter the bloodstream.
T3 and T4 attach to a plasma protein called thyroid-binding globulin and travel as a hormone-globulin complex.
Thyroid hormone helps regulate the metabolic rate of all cells and cell growth and tissue differentiation.
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Step 1: Iodide ions enter thyroid cells and move into the follicle.
Step 2: Tyrosine amino acids enter the follicle.
Step 3: Tyrosine amino acids combine with iodine to form thyroglobulin.
Step 4: Some of the thyroglobulin is released into the follicle.
Step 5: Iodine attaches to the polypeptide backbone of thyroglobulin.
Step 6: When needed, follicular cells endocytose thyroglobulin and release "free" T3 and T4.
Step 7: Thyroid hormones enter the bloodstream.
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Calcitonin is produced by the thyroid gland in the parafollicular cells.
Calcitonin may influence the processing of calcium by bone cells and decrease blood calcium levels.
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Parathyroid glands are embedded in the posterior surface of the thyroid's lateral lobes.
Parathyroid glands are tiny, rounded bodies within thyroid tissue.
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Parathyroid hormone is an antagonist to calcitonin and maintains calcium homeostasis.
Parathyroid hormone causes bone to be dissolved, yielding calcium and phosphate.
Parathyroid hormone causes phosphate to be secreted by the kidney cells into the urine.
Parathyroid hormone increases the absorption of calcium by stimulating the kidney to produce active vitamin D.
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Adrenal glands are located on top of the kidneys.
Adrenal glands are composed of two portions: adrenal cortex and adrenal medulla.
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Adrenal gland structure: capsule, zona glomerulosa, zona fasciculata, zona reticularis, medulla.
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Adrenal cortex secretes corticosteroids, including mineralocorticoids, glucocorticoids, and gonadocorticoids.
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Adrenal hormones: mineralocorticoids, glucocorticoids, gonadocorticoids, and catecholamines.
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Aldosterone, a mineralocorticoid, maintains sodium homeostasis in the blood by increasing sodium reabsorption in the kidneys.
Aldosterone also increases water retention and promotes the loss of potassium and hydrogen ions.
Secretion of aldosterone is controlled by the renin-angiotensin-aldosterone system and blood potassium concentration.
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Glucocorticoids secreted by the adrenal cortex, such as cortisol, cortisone, and corticosterone, affect every cell in the body.
Glucocorticoids are involved in protein mobilization, gluconeogenesis, and lipid catabolism.
Glucocorticoids help maintain normal blood pressure and aid in the effects of norepinephrine and epinephrine.
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Adrenal gland secretion increases with stress and is controlled by a negative feedback mechanism involving hormone from the adenohypophysis.
Gonadocorticoids, sex hormones (androgens), are released from the adrenal cortex.
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Hypersecretion of glucocorticoids can cause upper body obesity, thin arms and legs, round and red face, slow growth rate in children, acne or skin infections, purple marks on the skin, thin and red skin with easy bruising.
Hyposecretion of glucocorticoids causes weakness and dehydration, and severe cases can lead to coma and death.
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Adrenal medulla secretes epinephrine and norepinephrine, which are part of the class of nonsteroid hormones called catecholamines.
Epinephrine and norepinephrine bind to receptors of sympathetic effectors to enhance the effects of sympathetic stimulation.
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Epinephrine and norepinephrine reach target cells and are released by the adrenal medulla.
They bind to adrenergic receptors of sympathetic effectors to prolong and enhance the effects of sympathetic stimulation.
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Pancreatic islets are the endocrine portion of the pancreas.
Pancreatic acini are the exocrine portion and secrete digestive enzymes into ducts draining into the small intestine.
Page 54: PANCREATIC ISLETS
Each islet contains four primary types of endocrine glands joined by gap junctions
Alpha cells (A cells) secrete glucagon
Beta cells (B cells) secrete insulin; ~ 75% of all islet cells
Delta cells (D cells) secrete somatostatin
Page 55: PANCREATIC ISLETS
Work as a team to maintain homeostasis of food molecules
Glucagon tends to increase blood glucose levels; stimulates gluconeogenesis in liver cells
Insulin lowers blood concentration of glucose, amino acids, and fatty acids and promotes their metabolism by tissue cells
Primary role of delta cells is regulating the other endocrine cells of the pancreatic islets
Page 56: Regulation of Blood Glucose Levels
Feedback loop regulates blood glucose levels
Low blood glucose level increases glucagon secretion by pancreatic islets
High blood glucose level decreases glucagon secretion by pancreatic islets
Low blood glucose level decreases insulin secretion by pancreatic islets
High blood glucose level increases insulin secretion by pancreatic islets
Glucose release by liver increases blood glucose level
Glucose release by liver decreases blood glucose level
Glucose uptake by cells decreases blood glucose level
Glucose uptake by cells increases blood glucose level
Tissue cells play a role in maintaining normal blood glucose level
Page 57: GONADS
Gonads are paired organs within the scrotum in males
Testosterone is produced by interstitial cells in the gonads and responsible for the growth and maintenance of male sexual characteristics
Testosterone secretion is mainly regulated by gonadotropin levels in the blood
Page 58: GONADS
Ovaries are the primary sex organs in females
Ovaries produce several types of sex hormones
Estrogens: steroid hormones secreted by ovarian follicles; promote development and maintenance of female sexual characteristics
Progesterone: secreted by corpus luteum; maintains the lining of the uterus necessary for successful pregnancy
Ovarian hormone secretion depends on the changing levels of follicle-stimulating hormone and luteinizing hormone from the adenohypophysis
Page 59: PLACENTA
Placenta is a temporary endocrine gland that forms on the lining of the uterus
Placenta produces hormones such as progesterone, estrogens, and human chorionic gonadotropin (hCG)
Page 60: THYMUS
Thymus is a gland located just beneath the sternum
Thymus is large in children but atrophies at puberty and becomes a vestige of fat and fibrous tissue in old age
Thymus is considered primarily a lymphoid organ, but the hormone thymosin has been isolated from thymus tissue
Thymosin stimulates the development of T lymphocytes
Page 61: GASTRIC AND INTESTINAL MUCOSA
The mucous lining of the stomach and intestines contains cells that produce both endocrine and exocrine secretions
Gastrointestinal hormones such as gastrin, secretin, and cholecystokinin play regulatory roles in coordinating the secretory and motor activities involved in the digestive process
Ghrelin, a hormone secreted by endocrine cells in the gastric mucosa, stimulates the hypothalamus to increase appetite, slows metabolism and fat burning, and may contribute to obesity
Page 62: HEART
The heart has a hormonal role
Hormone-producing cells in the heart produce several atrial natriuretic peptides, including atrial natriuretic hormone
Atrial natriuretic hormone opposes increases in blood volume or blood pressure and acts as an antagonist to antidiuretic hormone and aldosterone
Page 63: OTHER ENDOCRINE GLANDS AND ORGANS
Major endocrine glands produce more hormones than are outlined in this text
Many tissues, including adipose tissue, produce hormones such as leptin and resistin
Page 64: CYCLE OF LIFE: ENDOCRINE SYSTEM
Endocrine regulation begins in the womb
Hormones related to reproduction begin at puberty
Secretion of male reproductive hormones is continuous from puberty, with a slight decline in late adulthood
Secretion of female reproductive hormones declines in middle adulthood
Page 65: THE BIG PICTURE: THE ENDOCRINE SYSTEM AND THE WHOLE BODY
Nearly every process in the human organism is kept in balance by the intricate interaction of different nervous and endocrine systems
The endocrine system operates with the nervous system to finely adjust the many processes they regulate
The neuroendocrine system adjusts nutrient supply
Calcitonin, parathyroid hormone, and vitamin D balance calcium ion use
The nervous system and hormones regulate reproduction
Page 66: Mechanisms of Disease
Hyperthyroidism, hypothyroidism, hyperpituitarism, hypopituitarism, and type I and II diabetes are mechanisms of disease related to the endocrine system.