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Chapter 20, sp 10


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  • 1. Human Anatomy, Second Edition McKinley & O'Loughlin Chapter 20 Lecture Outline: Endocrine System
  • 2. Endocrine System
    • Endocrine system and the nervous system often work together to bring about homeostasis.
    • Both use specific communication methods and affect specific target organs.
    • Their methods and effects differ.
  • 3. Differences
    • Communication Method
      • NS: Nerve impulses and neurotransmitters
      • ES: Hormones
    • Target of Stimulation
      • NS: Other neurons, muscles cells, and gland cells
      • ES: Any cells with receptors for hormone
    • Effect of Stimulation
      • NS: Stimulates or inhibits muscle contraction +/- gland secretion
      • ES: Changes in metabolic activities
    • Response time
      • NS: Quick action: msec or minutes (sometimes minutes)
      • ES : Slower response: sec to hours to days
  • 4. Differences
    • Range of Effect
      • NS: Localized
      • ES: Widespread
    • Duration of Response
      • NS: Short term effects generally
      • ES: Long-term effects generally
    • Recovery Time
      • NS: rapid
      • ES : Slow
  • 5. Similarities
    • Release chemicals that bind to receptors
    • Many of the same chemical messengers
    • Regulated mainly by negative feedback
    • Common goal: coordinate and regulate
    • Interlocking systems: neuroendocrine system
  • 6.
  • 7. Endocrine Glands & Hormones
    • Exocrine glands
      • secretions released into ducts opening onto an epithelial surface
    • Endocrine glands
      • ductless organs that secrete their molecules directly into the bloodstream
    • All endocrine cells are located within highly vascularized areas to ensure that their products enter the bloodstream immediately.
  • 8. Overview of Hormones
    • Molecules that have an effect on specific organs.
    • Only cells with specific receptors respond to that hormone.
      • Receptors are large proteins or glycoproteins
      • About 2000-100,000 receptors/target cell
      • Combination of hormone and receptor activates a chain of events in the target cell leading to physiological effects
      • Increasing the hormone levels leads to a decrease in the number of receptors
      • Amount of hormone released regulated by need
  • 9. Overview of Hormones
    • Cell with receptors are called target cells , and the organs that contain them are called target organs .
      • The response to a hormone depends on both the hormone and the target cell
      • Various target cells respond differently to the same hormone
    • Organs, tissues, or cells lacking the specific receptor do not respond to its stimulating effects.
  • 10. Blocking Hormone Receptors
    • RU-486 blocks the receptor for progesterone and, thereby, blocks the effects of progesterone in maintaining the uterine lining and abortion of the embryo
  • 11. Classification of Hormones
    • Peptide hormones (water soluble)
      • formed from chains of amino acids
      • most of our body’s hormones are peptide hormones
      • longer chains are called protein hormones
      • Examples: all hormones of the hypothalamus and the anterior pituitary
    • Biogenic amines (water soluble)
      • small molecules produced by altering the structure of a specific amino acid
      • Examples: thyroid hormone, catecholamines
    • Steroid hormones (lipid soluble)
      • derived from cholesterol
      • Examples: hormones of the reproductive organs and adrenal cortex
  • 12. Classification of Hormones
    • Circulating hormones
      • Act on distant target cells
      • Inactivated by liver in time
      • Most common
    • Local hormones
      • Act on nearby target cells or same cell
      • Inactivated quickly
  • 13. Negative Feedback Loop
    • A stimulus starts a process, and eventually either the hormone that is secreted or a product of its effects causes the process to slow down or turn off.
    • Many hormonal systems work by negative feedback mechanisms.
  • 14.
  • 15. Positive Feedback Loop
    • Accelerates the original process, either to ensure that the pathway continues to run or to speed up its activities.
    • Only a few positive feedback loops occur in the human endocrine system.
      • one example is the process of milk release from the mammary glands
  • 16.
  • 17. Control of Hormone Secretions
    • Most hormones released in short bursts
    • When endocrine gland stimulated, then more frequent bursts
    • Three regulatory mechanisms
      • Humoral (ex., blood levels of a nutrient)
      • Neural
      • Hormonal
  • 18. Hypothalamic Control of the Endocrine System
    • The hypothalamus is the master control center of the endocrine system and oversees most endocrine activity.
      • the hypothalamus secretes regulatory hormones that regulate the secretion of most of the anterior pituitary hormones
    • The hypothalamus has indirect control over these endocrine organs.
    • It is the major integrating link between the nervous and endocrine systems
    • The hypothalamus and pituitary gland have important roles in all aspects of growth, development, metabolism, and homeostasis
  • 19. Hypothalamic Control of the Endocrine System
    • Hypothalamus produces two hormones that are transported to and stored in the posterior pituitary.
      • oxytocin
      • antidiuretic hormone (ADH) or vasopressin
    • Hypothalamus directly oversees the stimulation and hormone secretion of the adrenal medulla.
      • An endocrine structure that secretes its hormones in response to stimulation by the sympathetic nervous system.
    • Some endocrine cells are not under direct control of hypothalamus.
  • 20.
  • 21. Pituitary Gland (Hypophysis)
    • Called the “master gland” but it is controlled in two ways by the hypothalamus
    • Partitioned both structurally and functionally into an anterior pituitary and a posterior pituitary.
      • Anterior pituitary (adenohypophysis) is glandular tissue that produces hormones
      • Posterior pituitary (neurohypophysis) is neural tissue
  • 22.
  • 23. Control of Anterior Pituitary Gland Secretions
    • Anterior pituitary gland is controlled by regulatory hormones secreted by the hypothalamus.
      • Releasing hormones
      • Inhibiting hormones
    • Hormones reach the anterior pituitary via hypothalamo- hypophyseal portal system .
      • a “shunt” that takes venous blood carrying regulatory hormones from the hypothalamus directly to the anterior pituitary before the blood returns to the heart
  • 24.
  • 25. Tropic Hormones
    • Most hormones from the anterior pituitary are tropic hormones or tropins and activate other endocrine glands
  • 26.
  • 27. Anterior Pituitary Hormones
    • TSH - thyroid stimulating hormone
    • PRL - prolactin develops the breast and milk production in pregnant women
    • ACTH - adrenocorticotropic hormone
    • Gonadotropins: FSH and LH - regulate hormone synthesis by gonads and production and maturation of gametes
    • MSH - melanocyte stimulating hormone has little effect on humans and production ceases prior to adulthood except in specific diseases
    • GH - growth hormone (somatotropin) stimulates growth of the entire body by increasing protein production and growth of the epiphyseal plates
  • 28. Disorders of Growth Hormone Secretion
    • Pituitary dwarfism
      • Lack of GH in a child
      • Very short and often have periodic low blood sugar
      • Injections of GH helps
    • Pituitary gigantism
      • Excess GH in a child
      • Very tall and leads to increased levels of blood sugar (untreated can lead to diabetes and heart failure) and large internal organs
    • Acromegaly
      • Excess GH in an adult
      • Bones of hands, feet and face increase in size
      • Diabetes and large internal organs
      • Cause: lack of feedback or pituitary tumor
  • 29. Hypophysectomy
    • Historically, used to treat advanced breast and prostate cancer to remove the hormone stimulation for their growth. Medications used now.
    • Currently, used to treat pituitary tumors. Radiation may also be used.
  • 30. Posterior Pituitary Hormones
    • Made by the hypothalamus, stored in the posterior pituitary
    • Oxytocin (OT)
      • stimulates contraction of smooth muscle of the uterus and ejection of milk in females
      • leads to prostate gland secretion in males
      • regulated by positive feedback!
      • makes us want to cuddle, groom, and pair bond
    • Antidiuretic hormone (ADH) or vasopressin
      • stimulates water reabsorption by the kidneys and arteriole constriction
      • secretion inhibited by alcohol
      • Lack: diabetes insipidus (normal urine output of 1-2 liters/day increases to about 20 liters/day)
  • 31. Thyroid Gland
    • Inferior to the thyroid cartilage of the larynx and anterior to the trachea.
    • “ Butterfly” shape due to its left and right lobes connected by a narrow isthmus.
    • The thyroid gland is highly vascularized, giving it an intense reddish coloration.
    • Regulation of thyroid hormone secretion depends upon a complex thyroid gland–pituitary gland negative feedback process.
  • 32. Thyroid Gland Hormones
    • Follicular cells produce thyroxine (T4) and triiodothyronine (T3)
      • Regulate the rate of metabolism
      • Most cells are targets
      • Needed for normal growth and development (including the brain)
      • Iodide is oxidized to iodine and then combines with tyrosine to produce these hormones - occurs within a large glycoprotein molecule, thyroglobulin, which is secreted into follicle
      • Scalloping of edges of thyroglobulin indicates active secretion
  • 33. Thyroid Gland Hormones
    • Parafollicular cells (Clear or C cells) produce calcitonin which reduces blood calcium levels in children and deposits calcium in the bones. Opposes actions of parathyroid hormone.
  • 34.
  • 35.
  • 36.
  • 37. Disorders of Thyroid Gland Secretion
    • Hyperthyroidism
      • Increased metabolic rate, weight loss, hyperactivity and heat intolerance
      • Causes: ingestion of T4, excessive stimulation by the pituitary, loss of feedback control by the thyroid (Graves disease)
      • Graves disease
        • Autoimmune
        • Exophthalmos
        • Goiter
      • Treatment: removal or radioactive iodine
  • 38. Disorders of Thyroid Gland Secretion
    • Hypothyroidism
      • Lack of thyroid hormone
      • Low metabolic rate, lethargy, feel cold, weight gain some times, photophobia
      • Causes: decreased iodine intake, loss of pituitary stimulation, post-therapeutic hypothyroidism, autoimmune
      • Treatment: oral replacement
      • Cretinism - severe form
      • Myxedema - adult form
    • Goiter
      • Enlargement of the thyroid
      • Endemic from lack of iodine
      • Surgical removal to decrease size may be required
  • 39. Parathyroid Glands
    • Small, brownish-red glands on the posterior surface of the thyroid gland.
    • Usually four small nodules, but some may have as few as two or as many as six.
    • The chief cells are the source of parathyroid hormone (PTH).
      • stimulates osteoclasts to resorb bone and release calcium ions from bone matrix into the bloodstream
      • stimulates calcitriol hormone synthesis in the kidney
      • promotes calcium absorption in the small intestine
      • prevents the loss of calcium ions during the formation of urine
    • The function of oxyphil cells is not known.
  • 40.
  • 41.
  • 42.
  • 43. Disorders of Parathyroid Gland Secretion
    • Hyperparathyroidism is most common
      • Bones depleted of calcium (fractures)
      • Extra urinary calcium leads to kidney stones
      • High blood calcium leads to decreased GI motility and constipation
      • High blood calcium leads to psychological changes
    • Hypoparathyroidism is rare
      • Most of the symptoms are neuromuscular and in severe cases, convulsions may occur
      • Due to accidental removal or damage during thyroid surgery usually or, less common, autoimmune disorder
      • Therapy is dietary vitamin D/calcium supplementation
  • 44. Adrenal Glands (suprarenal)
    • Paired, pyramid-shaped endocrine glands anchored on the superior surface of each kidney.
    • Retroperitoneal and embedded in fat and fascia to minimize their movement.
    • Outer adrenal cortex and an inner adrenal medulla secrete different types of hormones
  • 45. Adrenal Cortex
    • Yellow color due to stored lipids in its cell.
    • Synthesize more than 25 different steroid hormones, the corticosteroids.
      • corticosteroid synthesis is stimulated by the ACTH produced by the anterior pituitary
      • corticosteroids are vital to our survival; trauma to or removal of the adrenal glands requires corticosteroid supplementation
    • Divided into the zona glomerulosa, the zona fasciculata, and the zona reticularis.
    • Different functional categories of steroid hormones are synthesized and secreted in the separate zones.
    • Regulates salt, sugar, and sex!
  • 46.
  • 47.
  • 48.
  • 49.
    • Mnemonic device for adrenal cortical hormones:
        • Salt
        • Sugar
        • Sex
  • 50. Zona glomerulosa (salt)
    • Mineralocorticoids (ex., aldosterone)
    • Increase Na + (and water) reabsorption and K + loss from kidneys
    • Control salt/water balance (and, therefore, blood pressure)
    • Lack: Addison disease
    • Excess: hypertension, edema, loss of K +
  • 51. Zona fasciculata (sugar)
    • Glucocorticoids (ex., cortisone)
    • Acts on most cells
    • Help regulate blood nutrient levels (energy sources)
    • Increase blood sugar by increasing liver glucose and glycogen formation
    • Anti-inflammatory
    • Helps resist long-term stress
    • Lack: Addison disease
    • Excess: Cushing syndrome
  • 52. Zona reticularis (sex)
    • Gonadocorticoids or sex hormones
    • Most androgens from testes in adult males
  • 53. Disorders in Adrenal Cortex Hormone Secretion
    • Cushing syndrome
      • Excessive glucocorticoids (usually from taking corticosteroids but may be from too much production)
      • Immunosuppressant, but have side effects: osteoporosis, muscle weakness, redistribution of body fat and salt retention
      • Symptoms: body obesity (“moon face” and “buffalo hump”), hypertension, excess hair growth, kidney stones, and menstrual irregularities
  • 54. Disorders in Adrenal Cortex Hormone Secretion
    • Addison disease
      • Chronic shortage of glucocorticoids and sometimes mineralocorticoids
      • Symptoms: weight loss, general weakening, hypotension (can be deadly), and darkening (“bronzing”) of the skin
      • Treat with oral corticosteroids
      • President Kennedy had it
  • 55. Disorders in Adrenal Cortex Hormone Secretion
    • Adrenogenital syndrome (androgen insensitivity syndrome or congenital adrenal hyperplasia)
      • Starts in embryo and fetus
      • Inability to synthesize corticosteroids so body releases massive amounts of ACTH
        • Results in hyperplasia of the adrenal cortex and causes release of intermediary hormones that have a testosterone-like effect, virilization in newborn girls and enlarged penis and premature puberty in males. Most have salt-losing problem.
        • Treat with oral corticosteroids to inhibit release of ACTH
  • 56. Adrenal Medulla
    • Red-brown color due to its extensive vascularization.
    • Primarily clusters of large, spherical cells called chromaffin cells.
    • When innervated by the sympathetic division of the ANS, one population of cells secretes the hormone epinephrine and the other population secretes the hormone norepinephrine.
    • Hormones work with the sympathetic nervous system to prepare the body for an emergency or fight-or-flight situation.
  • 57. Disorder in Adrenal Medulla Hormone Secretion
    • Pheochromocytoma
      • Benign tumor of chromaffin cells
      • Episodic secretion of large amounts of epinephrine and norepinephrine
      • Marked swings in blood pressure
      • Prolonged fight or flight symptoms
      • Metabolic problems: hyperglycemia and glycosuria
      • Untreated: fatal brain hemorrhage or heart failure
      • Treatment: surgery to remove tumor
  • 58. Pancreas
    • Elongated, spongy, nodular organ between the duodenum of the small intestine and the spleen and posterior to the stomach.
    • Both exocrine and endocrine activities.
    • Mostly composed of cells called pancreatic acini that produce an alkaline pancreatic juice that aids in digestion
    • Scattered among the acini are small clusters of endocrine cells called pancreatic islets (islets of Langerhans) composed of four types of cells
  • 59. Pancreas
    • Alpha cells secrete glucagon when blood glucose levels drop.
    • Beta cells secrete insulin when blood glucose levels are elevated.
    • Delta cells are stimulated by high levels of nutrients in the bloodstream.
      • synthesize somatostatin, also described as growth hormone-inhibiting hormone, or GHIH, which slows the release of insulin and glucagon and slows the rate of nutrient entry into the bloodstream
    • F cells are stimulated by protein digestion.
      • secrete pancreatic polypeptide to suppress and regulate somatostatin secretion from delta cells
    • Pancreatic hormones provide for orderly uptake and processing of nutrients.
  • 60.
  • 61.
  • 62. Diabetes Mellitus (“sweet urine”)
    • General
      • Inadequate uptake of glucose from blood
      • Glucose spills over into the urine
      • “ Starving in the midst of plenty”
      • Chronically high blood glucose damages blood vessels especially smaller arterioles
        • Retinal blindness
        • Kidney failure
        • Leg amputations
      • Increases incidence of heart disease and stroke
  • 63. Diabetes Mellitus (“sweet urine”)
    • Type 1 diabetes
      • Insulin-dependent DM
      • Usually in children and young individuals - not related to obesity
      • Autoimmune - trigger event may be viral
      • Beta cells are destroyed
      • New monitoring instruments and automated delivery of insulin have helped treatment and lifestyle
  • 64. Diabetes Mellitus (“sweet urine”)
    • Type 2 diabetes
      • Insulin-independent DM
      • Decreased insulin release or decreased insulin effectiveness at peripheral tissues
      • Formerly, adult-onset DM but it is being seen in the young increasingly
      • Obesity plays a major role in its development
      • Treatment: For most, diet, exercise, and medications that enhance insulin release or increase its sensitivity at the tissue level. More severe cases, insulin injections.
  • 65. Diabetes Mellitus (“sweet urine”)
    • Gestational diabetes
      • Occurs in some pregnant women esp. towards end of pregnancy
      • Untreated: risk to fetus and increases complications of delivery
      • Risk: overweight, African American, Native American, or Hispanic, or those with a family history
      • Usually resolves after birth, but 20-50% chance of type 2 DM within 10 years
  • 66.
    • Pancreas transplants have many risks
    • Islet cell transplants less invasive but still many complications
    New Treatments for Severe DM 20-
  • 67.
    • May result from too much insulin
    • Quickly leads to insulin shock
    • If not sure if diabetic coma or insulin shock, treat for insulin shock
    Hypoglycemia Danger 20-
  • 68. Metabolic Syndrome
    • According to the American Heart Association, almost 25% of Americans have metabolic syndrome.
  • 69. Metabolic Syndrome
    • Metabolic syndrome increases the risk of:
      • Coronary artery disease
      • Stroke
      • Diabetes
  • 70. Metabolic Syndrome
    • Risk factors (must have 3)
      • Obesity (waist greater than 35 in. for women and 40 in. for men)
      • High blood pressure (greater than 130/85 mm Hg)
      • High blood glucose (110 mg/dL or greater)
      • Abnormal cholesterol profile (dyslipidemia)
        • Triglycerides (greater than 150 mg/dL)
        • HDL (less than 50 mg/dL for women and less than 40 mg/dL for men)
  • 71. Metabolic Syndrome
    • Treatment requires long-term management of the risk factors
      • Lose weight
      • Exercise
      • Eat a heart healthy diet
  • 72. Pineal Gland (body)
    • A small, cone-shaped structure attached to the posterior region of the epithalamus.
    • Secretes melatonin.
      • helps regulate a circadian rhythm (24-hour body clock)
      • also appears to affect the synthesis of the hypothalamic regulatory hormone responsible for FSH and LH synthesis
      • role in sexual maturation is not well understood
  • 73. Thymus
    • Bilobed - within the mediastinum superior to the heart and posterior to the sternum.
    • Size varies
      • always relatively large in infants and children
      • as with the pineal gland, the thymus decreases in size and activity with age, especially after puberty
    • Functions principally in association with the lymphatic system to regulate and maintain body immunity.
    • Produces complementary hormones thymopoietin and thymosins.
      • act by stimulating and promoting the differentiation, growth, and maturation of T-lymphocytes (thymus-derived lymphocytes)
  • 74. Endocrine Functions of the Kidneys, Heart, GI Tract, and Gonads
    • Organs of the urinary, cardiovascular, digestive, and reproductive systems contain their own endocrine cells, which secrete their own hormones.
      • help regulate electrolyte levels in the blood
      • red blood cell production, blood volume, and blood pressure
      • digestive system activities
      • sexual maturation and activity
  • 75. Aging and the Endocrine System
    • Secretory activity of endocrine glands decreases, especially secretion of growth hormone and sex hormones.
    • Reduction in GH levels leads to loss of weight and body mass.
    • Testosterone or estrogen levels decline