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BSC 216 Both Lectures on Endocrine System

by: Vanessa Notetaker

BSC 216 Both Lectures on Endocrine System BSC 216

Marketplace > University of Alabama - Tuscaloosa > Biology > BSC 216 > BSC 216 Both Lectures on Endocrine System
Vanessa Notetaker
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Class notes on the Endocrine system
Anatomy & Physiology II
Austin Hicks
Class Notes
Endocrine system, Anatomy & Physiology II
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This 10 page Class Notes was uploaded by Vanessa Notetaker on Sunday September 18, 2016. The Class Notes belongs to BSC 216 at University of Alabama - Tuscaloosa taught by Austin Hicks in Fall 2016. Since its upload, it has received 6 views. For similar materials see Anatomy & Physiology II in Biology at University of Alabama - Tuscaloosa.


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Date Created: 09/18/16
Endocrine System Lecture on 9/13 and 9/15 Introduction  The nervous system and the endocrine system have similar goals in the body (to maintain homeostasis) but, go about it in different ways o The endocrine system is a slower and more long term solution to homeostatic imbalances  Adaptation to stress  Also uses neurotransmitters and hormones o The nervous system responds to homeostatic balances almost immediately but, the result is short lived as well  Uses neurons and neurotransmitters and hormones In Depth Comparison of Nervous vs. Endocrine System  Similarities o Both serve for internal communication o Some chemicals can function in both systems as neurotransmitters and hormones o Neuroendocrine cells exist as a combination of both systems  Neurons that secrete things like oxytocin and catecholamines into the bloodstream o Overlapping effects on same target cell o Systems regulate each other o Target organs or cells  Differences o Nervous system uses electrical and chemical internal communication  Endocrine only uses chemical o Nervous system reacts quickly and stops quickly  Endocrine reacts slowly and effects may last for weeks o Nervous system adapts quickly to long term stimuli  Endocrine takes a long time to adapt o Nervous system has targeted and specific area of effect  The endocrine system has widespread, general effects Exocrine vs. Endocrine Glands  Exocrine glands have ducts that carry secretions to a duct or hollow space o Secretion of chemicals into the stomach which has an epithelial surface  Endocrine glands have no ducts and are secreted into the blood stream from fenestrated capillaries  Liver cells have traits of both but is neither o Release hormone, release bile into ducts, release albumin and blood clotting factors into blood Key Mechanisms of Communications Between Cells  Gap junctions o Pores embedded in the plasma membrane that allow signaling molecules, nutrients and electrolytes to move from cell to cell  Neurotransmitters o Released from neurons to travel across the synaptic cleft  Paracrine hormone o Secreted into tissue fluids to affect nearby cells  Hormones o Chemical messengers that travel in the bloodstream to other tissues and organs Types of Chemical Signals  Endocrine cells affect different cell types  Paracrine pathway has tissue cells secreting paracrine chemicals that affect different kinds of nearby cells  Autocrine pathway has a specialized cell secreting autocrine chemicals to affect a same cell or near cell Overview of the Endocrine System  Endocrine system- a collection of glands, tissues and cells that secrete hormones  Endocrinology- the study of the endocrine system and the diagnosis and treatment of its disorders  Endocrine Organs-organs that are traditional sources of hormones o Primary- only perform endocrine functions  Pituitary, thyroid and parathyroid o Secondary- have endocrine and other functions  Heart, kidneys and small intestine o Neuroendocrine Organs  Consist of nervous tissue, yet secrete hormone-like chemicals (neurohormones)  Hypothalamus, pineal gland and adrenal medulla  Hormone- chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ usually a considerable distance away o Hypothalamus and pituitary hormones (brain) usually affect organs in lower abdomen Classes of Hormones  Can be either amino acid based or steroid o Amino acid- may be one to multiple amino acids long and typically hydrophilic o Steroid- cholesterol derivatives and hydrophobic  The way the hormone reacts with water affects how it acts o Hydrophobic molecules can pass through the cell membrane  Enters cell and initiates the creation of proteins (takes longer) o Hydrophillic molecules cannot pass through the cell membrane and need help of transmembrane protein to enter  Secondary messenger initiates signal application to turn on already existing proteins (quicker) Effects of Hormone Actions  Stimulate secretions from endocrine or exocrine cells  Activating or inhibiting enzymes  Stimulating or inhibiting cellular division  Opening or closing ion channels  Activating or inhibiting DNA transcription Hormone Secretion  Hormone secretion can be activated via hormonal, humoral, or neural stimuli o Hormonal stimulation  Growth hormone- releasing hormone (GHRH) stimulates growth hormone(GH) from anterior pituitary cell  To inhibit GH secretion somatostatin is released from an anterior pituitary cell  This occurs in the anterior pituitary but the hormones are secreted by the hypothalamus o Humoral stimulus  Response to the concentration of ions in the blood  Glucose uptake by a pancreatic cell triggers insulin secretion o Neural stimulus  Cells response to signals from the nervous system  Sympathetic neurons stimulate secretion of epinephrine and norepinephrine from an adrenal medulla cell Regulation of Secretion  If homeostatic balance is upset receptors on endocrine cells detect the deviation of the variable  The stimulated control center increases or decreases the secretion of a particular hormone  The hormone triggers a response in its target cells that moves conditions towards the normal range Anatomy  Hypothalamus o Regulates primitive functions of the body from water balance and thermoregulation to sex drive and childbirth o It creates the hormones but, the functions are carried out by the pituitary gland o Releasing and inhibiting hormones travel in hypophyseal portal system from hypothalamus to anterior pituitary  Infendibulum- Passage of blood vessels and neuroendocrine cells originate in hypothalamus but, extend into pituitary  Pituitary gland o Adenohypophysis (Anterior) o Neurohypophysis (Posterior) Hypothalamic Hormones  Eight hormones produced in hypothalamus o Six releasing and inhibiting hormones stimulate or inhibit the anterior pituitary  Two other hypothalamic hormones are oxytocin (OT) and antidiuretic hormone (ADH) o Both stored and released by posterior pituitary  Posterior pituitary does not synthesize them, the neuroendocrine cells in hypothalamus do Posterior Pituitary Hormones  Produced in hypothalamus o Transported by hypothalamo-hypophyseal tract via infundibulum to posterior lobe o Releases hormones when hypothalamic neurons are stimulated o Hormones are stored in axon terminals in the posterior pituitary o Hormones are secreted into the blood when the hypothalamic neurons fire action potentials  ADH (antidiuretic hormone)/Vasopressin o Increases water retention (decreases urine output) and prevents dehydration o Hypersecretion of ADH causes diabetes insipidus  Oxytocin (OT) o Surge of hormone released during sexual arousal and orgasm o Promotes feelings of sexual satisfaction and emotional bonding between partners  And also promotes bonding between infant and lactating mother o Stimulates labor contractions during childbirth and stimulate flow of milk during lactation Anterior Pituitary Hormones  Two gonadotropic hormones are produced in anterior pituitary that target the gonads and are stimulated from hypothalamic releasing hormone GnRH o Follicle stimulating hormone (FSH)  Stimulate secretion of ovarian sex hormones, development of ovarian follicles and sperm production o Luteinizing Hormone (LH)  Stimulates ovulation, stimulayes corpus luteum to secrete progesterone, stimulates testes to secrete testosterone  Thyroid stimulating hormone (TSH) o Stimulates secretion of thyroid hormone  Triggered by hypothalamic releasing hormone thyrotropin releasing hormone (TRH)  Adrenocorticotropic hormone (ACTH) o Stimulates adrenal cortex to secrete glucocorticoids o Secretion stimulated by corticotopin releasing hormone  Prolactin (PRL) o After birth, stimulates the mammary glands to synthesize milk; enhances secretion of testosterone by testes o Secretion stimulated by infant suckling and prolactin releasing hormone  Growth Hormone (GH) o Stimulates mitosis and cellular differentiation o Secretion stimulated by growth hormone releasing hormone (GHRH) and inhibited by somatostatin Growth Hormone  GH has widespread effect on the body tissues especially cartilage, bone, muscle and fat  Induces liver to produce very important growth stimulants o Insulin -like growth factors (IGF-I) or somatomedins (IGF-II)  Stimulate target cells in diverse tissues  IGF-I prolongs the action of GH  Increases the half life from 6-20 minutes to 20 hours Mechanisms of GH-IGF action  Increase protein synthesis o Boost DNA transcription, mRNA production, amino acid uptake into cells o Suppresses protein catabolism  Increase lipid metabolism o Fat is catabolized by adipocytes which provides energy for growing tissues  Creates a glucose sparing effect in carbohydrate metabolism o Mobilizes fatty acids o Reduces the dependence of most cells on glucose  Promotes Na+, K+, Cl- retention by kidneys and enhances Ca2+ absorption by small intestine Short term effects of Growth Hormone  Inhibits uptake of glucose by skeletal muscle, stimulates gluconeogenesis in liver and stimulates lipolysis in fat  Leads to increased blood glucose concentration and increased blood fatty acid concentration Long term effects of Growth Hormone  Insulin-like Growth Factor is released by the liver, muscle, bone and other tissues  Stimulates glucose uptake by cells, stimulates cell division, stimulates protein synthesis  Leads to decreased blood glucose concentration, increased growth of bone and other tissues and increased mass of muscle and other tissues Effects of Growth Hormone  In Childhood – Influences bone, cartilage and muscle growth o Growth occurs at the epiphyseal plates in the bones  In adulthood- Thickens and remodels bones  Secretion of GH is the highest during the first 2 hours of sleep, during vigorous exercise, and in younger crowds  Levels of GH decrease with age o Lack of protein synthesis leads to the aging of tissues and wrinkling of skin o At age 75, average adult body is 8% bone, 15% muscle and 40% fat Disorders Involving GH  Hyposecretion of GH during adolescence leads to dwarfism  Hypersecretion of GH during adolescence results in gigantism  Once there are no longer epiphyseal plates in the bone past adolescence a hypersecretion of GH results in acromegaly where the bones widen instead of growing longer Control of Pituitary Secretion  Secretions are regulated by hypothalamus, other brain centers and feedback from target organs  There is hypothalamic and cerebral control o Anterior lobe control consists of hypothalamus releasing hormones and inhibiting hormones  FUN FACT: cold weather stimulates the hypothalamus to release TSH leads to generation of body heat to keep you warm  Neuroendocrine reflex- hormone release in response to nervous system signals and higher brain centers o Milk ejection reflex can be triggered by suckling infant or an infant’s cry o Emotional stress can affect secretion of gonadotropins, disrupting ovulation, menstruation and fertility Anatomy of Thyroid Gland  Located in the anterior part of the neck just superficial to the larynx  Butterfly shaped with two lobes connected by an isthmus  Secretes thyroid hormones and calcitonin Anatomy of Parathyroid Glands  Glands embedded in the posterior surface of the thyroid gland  Chief cells secrete parathyroid hormone o Maintains calcium ion concentration in the extracellular fluid Structure of Thyroid and Parathyroid Glands  Composed of thyroid follicles (multiple sphere shaped sacs) o Follicular cells are simple cuboidal epithelial cells and produce thyroid hormones o Colloid fills the follicle and is protein rich and stores precursor of thyroid hormone  Parafollicular cells are in between follicles and produce calcitonin Thyroid Hormones  Triiodothyronine (T3)- three iodine atoms bound to an amino acid core o Has higher physiological activity  Thyroxine (T4)- 4 iodine atoms bound to amino acid core  Thyroid hormones enter by crossing the plasma membrane freely since they are nonpolar  Effects of thyroid hormone o Regulation of the metabolic rate and thermoregulation o Promotion of growth and development o Synergism with the sympathetic nervous system Thyroid Hormone Production  Iodine ions and thyroglobulin are secreted into the colloid  Iodide ions are converted to iodine atoms that attach to thyroglobulin  Iodinated thyroglobulin enters the follicle cell by exocytosis and is converted to T3 and T4 by lysosomal enzymes Thyroid disorders  Graves’ disease o Hyperthyroidism that leads to abnormal production of proteins that mimic TSH o Signs are weight loss, heat intolerance, goiter and exophthalmos(bulging eyes) o Treated by drugs or removal of gland  Hypothyroidism o Iodine deficiency as a cause of autoimmunity o Signs are weight gain, cold intolerance and goiter o Treated by drugs Parathyroid Hormone  Produced by chief cells in parathyroid glands and maintains blood calcium ion concentration o Raises Ca by stimulation of osteoclasts, activation of Vitamin D to Vitamin D3 or increases the reabsorption of calcium ions from the fluid in the kidneys o Calcitonin opposes Parathyroid hormone and is produced by thyroid’s parafollicular cells and combats hypercalcemia by blocking osteoclast activity Anatomy of the Adrenal Gland  Pyramid shaped glands located on the superior end of the kidney  Composed of the outer cortex and the inner medulla  Produces steroid hormones and catecholamines Adrenal Cortex  Made of different layers of cells  Zona glomerulosa o Most Densely packed cells of the three layers o Mineral corticoids  Zona fasciculata o Largest area of cells and more organized than zona glomerulosa o Glucocorticoids & androgenic steroids  Zona reticularis o Not as dense as zona glomerulus but, about the same size and not as disorganized o Glucocorticoid & androgenic steroids Mineralcorticoids  Regulate the concentration of minerals in the body  Work to maintain the concentrations of extracellular sodium and potassium ions within their normal ranges, regulate EC fluid volume, maintain BP and maintain acid-base homeostasis o Aldosterone Glucocorticoids  Produced in zona fasciculate and zona reticularis  Mediate the body’s response to stress and regulate blood glucose levels  Stimulate gluconeogenesis in the liver, release of amino acids from muscles, release of fatty acids from adipose tissue  Works as anti-inflammatory agent  Androgenic steroids: produced largely as a bi-product of cortisol synthesis Cushing’s Syndrome  Over-secretion of cortisol  Releases fatty acids from limbs and redeposits them in torso and face, wastes muscles, hyperglycemia, weight gain Hormones of the Adrenal Medulla  Made up of chromaffin cells that are stimulated by the neurotransmitter acetylcholine o When stimulated they release catecholamines (epinephrine and norepinephrine)  Epinephrine and norepinephrine both increase heart rate, dilate the brachioles, dilate the pupils and decrease digestive function Anatomy of the Pancreas  Consists of a tail that has a point and the rest is the body o The body is adjacent to the duodenum o Pacreatic cells consist of the alpha, beta and gamma cells in the pancreatic islet and have adjacent acinar cells Pancreatic Islets  Insulin is secreted by the beta cells in the pancreatic islet o Insulin lowers blood sugar by converting glucose to glycogen to be stored in the liver or the glucose is metabolized o Inaction of insulin leads to diabetes Diabetes Mellitus  Disruption of metabolism due to hyposecretion or inaction of insulin  Symptoms include polyuria, polydipsia and polyphagia o Elevated blood glucose, glucose and ketones in urine o Transport maxium-limit of how much glucose can be reabsorbed before excreted by urine  With diabetes the transport maximum is exceeded  Type I Diabetes- Autoimmune disease that causes destruction of beta cells o Glucose uptake is not possible so individual is always hungry o Treated with insulin ALWAYS o Genetic o Pathogenesis- Cells cannot absorb glucose and must rely on protein and fat for energy needs; Leads to ketonuria and ketoacidosis  Type 2 Diabetes- Insulin resistance leads to lack of responsiveness o Genetic, over 40, obese, and native American, Hispanic and Asian are all risk factors o Treated with weight loss and exercise, or oral medications o Pathogenesis- leads to neuropathy and cardiovascular damage from atherosclerosis and microvascular disease  Arterial dmage in retina and kidney (Type I), atherosclerosis leads to heart failure (Type II)  Diabetic neuropathy- nerve damage from impoverished blood flow  Erectile dysfunction, incontinence, poor wound healing and loss of sensation from area


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