Endocrine System Chapter 15-B PDF

Endocrine System Chapter 15-B Sections 15.7-15.11 Hormones produced by Glands & Tissues 15.7 – The Thyroid gland & Metabolism 15.8 – The Parathyroid glands & Calcium regulation 15.9 – The Adrenal Cortex and Medulla 15.10 – The Pineal Gland 15.11 –...

Endocrine System Chapter 15-B Sections 15.7-15.11 Hormones produced by Glands & Tissues 15.7 – The Thyroid gland & Metabolism 15.8 – The Parathyroid glands & Calcium regulation 15.9 – The Adrenal Cortex and Medulla 15.10 – The Pineal Gland 15.11 – Pancreas, Gonads and Other Tissues  15.7 Thyroid Gland Location and Structure Butterfly-shaped gland on anterior aspect of trachea Largest endocrine gland in the body Internally, the thyroid is composed of hollow, spherical follicles – The walls are lined with: Follicular cells that secrete thyroid hormone Parafollicular cells that secrete calcitonin – The central space is filled with colloid © 2016 Pearson Education, Inc.  15.7 Thyroid Gland © 2016 Pearson Education, Inc.  Thyroid Hormone (TH) Gland: Thyroid (follicular cells) Hormone: Thyroid hormone (TH) Targets: All cells Thyroid hormone enters target cell and binds to intracellular receptors within nucleus (only aa hormone) – Triggers transcription of various metabolic genes Functions: Body’s major metabolic hormone – Increases basal metabolic rate and heat production – Regulates tissue growth and development © 2016 Pearson Education, Inc.  Thyroid Hormone (TH) © 2016 Pearson Education, Inc. Thyroid Gland – Synthesis Thyroid gland stores hormone in follicle lumen until triggered by TSH to release then synthesizes to refill Stored colloid- 2-3 months of thyroid hormone Thyroid Synthesis 1. Thyroglobulin (glycoprotein) is produced by follicular cells and 2. Iodide (a form of Iodine) is actively transported by follicular cells which then converts them to iodine (I2) and moves into the lumen Lack of Iodine causes Goiter 3. In lumen, iodine is attached to tyrosine to form MIT or DIT 4. Iodinated tyrosines are linked together to form T3 and T4 5. Thyroglobulin colloid is endocytosed 6. Lysosomal enzymes split T4 and T3 from thyroglobulin and the hormones diffuse from the follicular cell into the bloodstream © 2016 Pearson Education, Inc.  Functions of Thyroid Hormone (TH) Found in two forms: Both require iodine – T4 (thyroxine): major form; “inactive” Must be converted to T3 at tissue level – T3 (triiodothyronine): active form Transport and regulation – T4 and T3 transported in blood by thyroxine-binding globulins (TBGs) Both bind to target tissue receptors, but T3 is 10 times more active than T4 Most tissues have enzyme needed to convert T4 to T3 Deiodinase- enzyme that converts T4 to T3 Type D1- body: activity decreased by stress, depression, dieting, weight gain, insulin resistance chronic fatigue, toxins, pain, chronic pain Type D2- pituitary © 2016 Pearson Education, Inc. Calcitonin Gland: Thyroid (parafollicular cells) Hormone: Calcitonin – Produced in response to high Ca2+ levels Target: Bone tissue (cells) Functions: – No known physiological role in humans at normal physiological levels, but at higher-than-normal doses decreases blood Calcium levels by: Inhibiting osteoclast activity and preventing release of Ca2+ from bone matrix Stimulating Ca2+ uptake and incorporation into bone matrix – Antagonist to parathyroid hormone (PTH) 15.8 Parathyroid Gland Gland: Parathyroid glands – Four to eight tiny yellow-brown glands embedded in posterior aspect of thyroid Hormone: Parathyroid hormone (PTH) Targets: Bone tissue, kidneys, small intestines Functions: PTH is most important hormone in Ca2+ homeostasis; Increases blood Ca2+ levels – Secreted in response to low blood levels of Ca2+ Stimulates osteoclasts to digest bone matrix – Inhibited by rising levels of Ca2+  16.8 Parathyroid Gland When PTH is released it: – Stimulates osteoclasts to digest bone matrix and release Ca2+ to blood – Enhances reabsorption of Ca2+ and secretion of phosphate (PO43-) by kidneys – Promotes activation of vitamin D by kidneys, which leads to increased absorption of Ca2+ by intestinal mucosa © 2016 Pearson Education, Inc.  15.9 Adrenal Gland Paired, pyramid-shaped organs atop kidneys Structurally and functionally it is two glands – Adrenal cortex: three layers of glandular tissue that synthesize and secrete several different hormones – Adrenal medulla: nervous tissue that is part of sympathetic division of autonomic nervous system © 2016 Pearson Education, Inc.  15.9 Adrenal Gland © 2016 Pearson Education, Inc.  Adrenal Cortex Gland: Adrenal cortex 24 different hormones collectively called corticosteroids Three layers of cortical cells produce the different corticosteroids – Zona glomerulosa — Mineralocorticoids – Zona fasciculata — Glucocorticoids – Zona reticularis — Gonadocorticoids © 2016 Pearson Education, Inc. Gland: Adrenal Cortex Hormone class: Mineralocorticoids – Function: Control the balance of minerals (primarily Na+ and K+) and water in ECF/blood Importance of Na+: affects ECF volume, blood volume, blood pressure, and levels of other ions Importance of K+: sets resting membrane potential Main Hormone: Aldosterone Target: kidney tubules Function: Stimulates Na+ reabsorption / K+ excretion by kidney tubules via Na+/K+ ATPase pump. (↑ blood volume and blood pressure) Gland: Adrenal Cortex Hormone class: Glucocorticoids – Influence cell metabolism during stress – Keeps blood glucose levels relatively constant – Help maintain blood pressure Main Hormone: Cortisol (hydrocortisone) Target: most cells Functions: In response to stress, Increases blood levels of glucose, fatty acids, and amino acids by breaking down stored fats and muscle tissue Adrenal Cortex – Glucocorticoids - Cortisol – Other functions of cortisol: Promotes gluconeogenesis- In liver, promote formation of glucose from fats and proteins and directs cells to use fatty acids for fuel so glucose is “saved” for brain Causes (vasoconstriction) rise in blood pressure to quickly distribute nutrients to cells – Too much cortisol: Suppresses cartilage and bone formation Inhibits inflammation by ↓ release of inflammatory chemicals Depresses immune system Disrupts normal cardiovascular, neural, and GI function Muscle tissue loss Gland: Adrenal Cortex Hormone class: Gonadocorticoids – Weak androgens (male sex hormones) converted to testosterone in tissue cells, some to estrogens Main Hormones: Androstenedione and Dehydroepiandrosterone (DHEA) Target: most cells Main Functions: Development of pubic/axillary hair; libido, source of estrogen for women after menopause  Adrenal Medulla Gland: Adrenal Medulla Hormones: catecholamines: Epinephrine (80%) and Norepinephrine (20%) Targets: Organs innervated by the Sympathetic ANS Function: “Fight or Flight” Response – Vasoconstriction (norepi) – Bronchodilation (epi) – Increased heart rate – Increased blood glucose levels – Blood diverted to brain, heart, and skeletal muscle © 2016 Pearson Education, Inc. Stress and the Adrenal Gland Short-term: Adrenal Long-term: Adrenal Medulla Cortex  15.10 Pineal Gland Gland: Pineal – Small gland hanging from roof of 3rd ventricle Hormone: Melatonin Targets: Hypothalamus, unknown Functions: – Day/night cycles – Physiological processes that show rhythmic variations (body temperature, sleep, appetite) – Production of antioxidant and detoxification molecules in cells – Antigonadotrophic effect in children © 2016 Pearson Education, Inc.  15.11 Other Endocrine Organs Pancreas – Triangular gland located partially behind stomach Has both exocrine and endocrine cells – Acinar cells (exocrine) produce enzyme-rich juice for digestion – Pancreatic islets (islets of Langerhans) contain endocrine cells Alpha () cells produce glucagon Beta () cells produce insulin © 2016 Pearson Education, Inc.  Pancreas Gland: Pancreas - Alpha () cells Hormone: Glucagon Target: Liver Function: Promotes Hyperglycemia (increases blood glucose) – Glycogenolysis: Break down (liver) glycogen into glucose – Gluconeogenesis: Synthesize glucose from lactic acid and other non-carbohydrates – Release glucose into blood © 2016 Pearson Education, Inc.  Pancreas Gland: Pancreas - Beta () cells Hormone: Insulin Targets: Muscle tissue, Adipose tissue, Liver, (Brain) Function: Promote Hypoglycemia (decreases blood glucose) – Lower blood glucose by promoting cellular uptake into skeletal muscle and adipose tissue – Promotes glucose oxidation and glycogen formation – Promotes protein synthesis and converting glucose into fat for storage – (Neuronal development, learning, memory) © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc.  BioFlix Video: Homeostasis © 2016 Pearson Education, Inc.  The Gonads and Placenta Gonads produce steroid sex hormones Gland: Ovaries; Hormones: Estrogen and Progesterone Targets of Estrogen: Uterus, Breast, many other cells (bone, brain) Functions of Estrogen: Maturation of reproductive organs Appearance of female secondary sexual characteristics With progesterone, causes breast development and cyclic changes in uterine mucosa/endometrium © 2016 Pearson Education, Inc.  The Gonads Gland: Testes Hormone: Testosterone Targets: Testes, Prostate, Skeletal muscle, bone, others Functions: – Initiates maturation of male reproductive organs – Causes appearance of male secondary sexual characteristics and sex drive – Necessary for normal sperm production – Increases muscle mass and bone density © 2016 Pearson Education, Inc.  Examples of Hormone Secretion by Other Organs Adipose tissue – Adipose cells release: Leptin appetite control (make you feel full); stimulates increased energy expenditure Gastrointestinal tract – Scattered endocrine cells secrete: Gastrin stimulates release of HCl Ghrelin from stomach stimulates food intake © 2016 Pearson Education, Inc.  Examples of Hormone Secretion by Other Organs Heart – Atrial natriuretic peptide (ANP) decreases blood Na+ concentration, therefore blood pressure and blood volume Kidneys – Erythropoietin increases production of red blood cells © 2016 Pearson Education, Inc.