Endocrine System Part 2
Thyroid Gland Saddle bag shaped gland Largest endocrine gland in the body 3 hormones Throxin Triiodothyronine Calcitonin Thyroid hormone
Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Copyright 2010 Pearson Education, Inc. Figure 16.1
Figure 16.8
Thyroid Hormone (TH) Actually two related compounds T 4 (thyroxin) 2 tyrosine molecules + 4 bound iodine atoms T 3 (triiodothyronine) 2 tyrosines + 3 bound iodine atoms
1) Iodide enters body Thyroid Hormone (TH) 2) Converted to iodine by thyroid gland 3) Iodine binds to thyroglobulin 4) Tyrosine added to iodized thyroglobulin, combined in vacuole with lysosomes 5) Thyroglobulin freed and recycled while T3/T4 diffuses into blood 6) T3/T4 bind to thyroxin-binding globulin in blood 7) At tissue receptor T4 converted to active T3 by tissue enzymes
Thyroid follicle cells Colloid Capillary 1 Thyroglobulin is synthesized and discharged into the follicle lumen. Golgi apparatus Tyrosines (part of thyroglobulin molecule) 4 Iodine is attached to tyrosine in colloid, forming DIT and MIT. Rough ER Iodine 3 Iodide is oxidized to iodine. DIT (T 2 ) MIT (T 1 ) Thyroglobulin colloid Iodide (I ) 2 Iodide (I ) is trapped (actively transported in). T 4 5 Iodinated tyrosines are Lysosome T 3 linked together to form T 3 and T 4. T 4 T 3 T 4 T 3 6 Thyroglobulin colloid is endocytosed and combined with a lysosome. 7 Lysosomal enzymes cleave T 4 and T 3 from thyroglobulin colloid and hormones diffuse into bloodstream. Colloid in lumen of follicle To peripheral tissues Figure 16.9
Thyroid Hormone (TH) Major metabolic hormone (catabolism) Regulates tissue growth and development Increases reactivity of mature nerve cells Regulates heart rate Regulates movement of gastrointestinal tract
Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones Target cells Stimulates Inhibits Copyright 2010 Pearson Education, Inc. Figure 16.7
Imbalances of Thyroid Hormone Goiter Cretinism Myxedema Graves disease
Copyright 2010 Pearson Education, Inc. Figure 16.10
Lowers serum calcium Inhibits bone resorption Calcitonin Stimulates uptake by the bone matrix Antagonist to parathyroid hormone (PTH) Regulated by Ca 2+ concentration in the blood Negative feedback mechanism
Parathyroid Glands 4-8 tiny glands embedded in the posterior aspect of the thyroid Parathyroid hormone (PTH) Most important hormone in Ca 2+ homeostasis
Pharynx (posterior aspect) Thyroid gland Parathyroid glands Esophagus Trachea Chief cells (secrete parathyroid hormone) Oxyphil cells Capillary (a) (b) Copyright 2010 Pearson Education, Inc. Figure 16.11
Parathyroid Hormone Functions Stimulates osteoclasts to digest bone matrix Enhances reabsorption of Ca 2+ by the kidneys Increases absorption of Ca 2+ by intestinal mucosa Negative feedback Rising Ca 2+ in the blood inhibits PTH release
Hypocalcemia (low blood Ca 2+ ) stimulates parathyroid glands to release PTH. Rising Ca 2+ in blood inhibits PTH release. Bone 1 PTH activates osteoclasts: Ca 2+ and PO 3S 4 released into blood. 2 PTH increases Kidney Ca 2+ reabsorption in kidney tubules. 3 PTH promotes kidney s activation of vitamin D, which increases Ca 2+ absorption from food. Intestine Ca 2+ ions PTH Molecules Bloodstream Copyright 2010 Pearson Education, Inc. Figure 16.12
Adrenal Glands Paired, pyramid-shaped glands atop the kidneys Essentially two glands in one Adrenal medulla Nervous tissue: part of the sympathetic nervous system NE and Epinephrine Adrenal cortex Three layers of glandular tissue Synthesize and secrete steroid hormones
Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 16.1
Adrenal Cortex Three layers that produce corticosteroids Outer layer = mineralocorticoids Middle layer = glucocorticoids Inner layer = sex hormones or gonadocorticoids
Capsule Zona glomerulosa Adrenal gland Medulla Cortex Medulla Cortex Zona fasciculata Kidney Zona reticularis Adrenal medulla (a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla Figure 16.13a
Mineralocorticoids Regulate extracellular Na + and K + Na + : affects ECF volume, blood volume, blood pressure K + : sets resting membrane potential of cells Aldosterone is most important Stimulates Na + reabsorption (and water retention) by kidneys Stimulates K + secretion
Secretion mainly controlled by blood pressure and potassium levels Primary regulators Blood volume and/or blood pressure Kidney Renin Direct stimulating effect K + in blood Stress Other factors Hypothalamus CRH Anterior pituitary Blood pressure and/or blood volume Heart Initiates cascade that produces Angiotensin II ACTH Atrial natriuretic peptide (ANP) Zona glomerulosa of adrenal cortex Enhanced secretion of aldosterone Targets kidney tubules Inhibitory effect Absorption of Na + and water; increased K + excretion Blood volume and/or blood pressure Figure 16.14
Glucocorticoids Regulate carbohydrate metabolism Keep blood sugar levels relatively constant Gluconeogenesis Suppress inflammation Vasoconstriction Vessel permeability Stabilizing lysosomes
Imbalances of Glucocorticoids Cushing s disease Addison s disease Also involves deficits in mineralocorticoids
Figure 16.15
Gonadocorticoids (Sex Hormones) Most are androgens (male sex hormones) Converted to testosterone in tissue cells or estrogens in females Supplement hormones secreted by gonads May contribute to Onset of puberty Secondary sex characteristics Sex drive
Epinephrine Adrenal Medulla Affects the metabolic rate of all cells Bronchial dilation Increased blood flow to skeletal muscles and heart Norepinephrine Increased blood pressure Increased heart rate Increased stroke volume
Short-term stress More prolonged stress Stress Nerve impulses Hypothalamus CRH (corticotropinreleasing hormone) Spinal cord Preganglionic sympathetic fibers Adrenal medulla (secretes amino acidbased hormones) ACTH Corticotroph cells of anterior pituitary To target in blood Adrenal cortex (secretes steroid hormones) Short-term stress response Catecholamines (epinephrine and norepinephrine) 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6. Increased metabolic rate Mineralocorticoids 1. Retention of sodium and water by kidneys 2. Increased blood volume and blood pressure Long-term stress response Glucocorticoids 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood glucose 3. Suppression of immune system Figure 16.16
Imbalances in Adrenal Medulla Adrenal medullary hormones not essential for life Pheochromocytoma
Activities Worksheet 3, Endocrine 24 Thyroid gland Adrenal cortex Worksheet 4, Endocrine 25 Hormone review, skip #6 Hormone origin matching
Pancreas Long, flat gland near stomach Exocrine function Produces enzyme-rich juice for digestion Endocrine function Pancreatic islets (islets of Langerhans) Alpha ( ) cells = glucagon Hyperglycemic hormone Beta ( ) cells = insulin Hypoglycemic hormone
Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 16.1
Major target is the liver Glucagon Release of glucose to the blood Hyperglycemic factor
Effects Lowers blood glucose levels Insulin Enhances membrane transport of glucose Inhibits glycogenolysis and gluconeogenesis
Stimulates glucose uptake by cells Insulin Tissue cells Pancreas Stimulates glycogen formation Glucose Glycogen Liver Blood glucose falls to normal range. Stimulus Blood glucose level Blood glucose rises to normal range. Glucose Liver Glycogen Stimulates glycogen breakdown Glucagon Pancreas Stimulus Blood glucose level Figure 16.18
Imbalances of Insulin Diabetes mellitus (DM) Due to hyposecretion or hypoactivity of insulin Vascular component Three cardinal signs of DM Polyuria = copious urine output Polydipsia = excessive thirst Polyphagia = excessive hunger and food consumption
Table 16.4
Type I Type II Gestational Diabetes Mellitus
Insulin cont. Other hormones affecting insulin levels Growth hormone (GH) Adrenocorticotropic hormone (ACTH)
Thymus Minor Endocrine Glands Pineal gland
Thymus 2 lobed organ high in chest Thymosins = lymphocytes Active during fetal development and for first two years after birth
Pineal Gland Small gland hanging from the roof of the third ventricle Melatonin Timing of sexual maturation and puberty Photoperiod Physiological processes that show rhythmic variations Body temperature, sleep, appetite Not well understood in humans
Stress Physical Psychological Strong emotional reactions Individual reactions vary
The Stress Response Changes largely mediated by hypothalamus Three stages Alarm (acute, sympathetic) Resistance (chronic, endocrine) Exhaustion Temporary change in homeostasis = General Adaptation Syndrome (GAS)
Immediate Hypothalamus Sympathetic nervous system Adrenal medulla Increased serum glucose Increased circulation Alarm Reaction
Resistance Reaction Long-term modification Hypothalamus Pituitary gland Many effects Increases energy availability Produces new proteins Improves circulation
Short-term stress More prolonged stress Fight or Flight Nerve impulses Stress Hypothalamus Resistance CRH (corticotropinreleasing hormone) Spinal cord Preganglionic sympathetic fibers Adrenal medulla (secretes amino acidbased hormones) ACTH Corticotroph cells of anterior pituitary To target in blood Adrenal cortex (secretes steroid hormones) Short-term stress response Catecholamines (epinephrine and norepinephrine) 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6. Increased metabolic rate Mineralocorticoids 1. Retention of sodium and water by kidneys 2. Increased blood volume and blood pressure Long-term stress response Glucocorticoids 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood glucose 3. Suppression of immune system Figure 16.16
Stressor too strong K + loss = cell death Exhaustion Glucocorticoid depletion = cell starvation Immune system failure
General Adaptation Syndrome (or Stress Response)
Activity Questions? Endocrine Review Worksheet