The Endocrine System Unit 7

Transcription

1 General Functions of the Endocrine System Coordinating and regulating body cells, tissues, organs, and systems to maintain homeostasis by secreting chemicals (hormones) The Endocrine System Unit 7 Effects are sustained and work for longer periods of times than the nervous system Works primarily on negative feedback mechanisms Refresher: Negative Feedback vs. Positive Feedback Negative Feedback Mechanisms (Inhibitory) The response counteracts the input The most common feedback mechanism Examples: Blood pressure Blood sugar regulation Cardiac output Temperature regulation Positive Feedback Mechanisms (Stimulatory) The response is intensified by the input Example: Breastfeeding Childbirth Blood clotting What is a hormone? Chemical messengers released by one tissue (gland) and transported by the bloodstream to reach the target tissues The target tissue is where the effect of the hormone actually occurs Gland Bloodstream Target Tissue Over 50 different hormones Most only affect a few, specific types of cells Hormone Function Hormone Function (cont.) Regulates chemical and volume of the body s internal environment Regulates metabolism and energy balance Regulates contraction of cardiac and smooth muscle Regulates certain activities of the immune system Maintains homeostasis despite emergency environmental interruptions Infection Dehydration Emotional stress Trauma Hemorrhage Temperature extremes starvation Plays a role in normal growth and sequential development Contributes to the process of reproduction 1

2 Endocrine Glands Glands and Organs of the Endocrine System Glands that secrete their products (hormones) into extracellular spaces around cells. The hormones then enter into the bloodstream by diffusing into the capillaries located next to the glands. Hypothalamus Pituitary Thyroid Parathyroid Thymus Pancreas Adrenal Gonads Testes Ovaries Pineal Thalamus Kidneys Liver Stomach Lungs Heart Small Intestines Skin Placenta Endocrine Glands Endocrine Glands And The Hormones they Secrete Pituitary Gland (Hypophysis) Hormones of the Pituitary Gland Growth hormone Thyroid stimulating hormone Adrenocorticotropic hormone 2

3 Pituitary Gland Growth Hormone (GH) Found in the brain (attached to the hypothalamus by a small stalk called the infundibulum Sits in the sella turcica of the sphenoid bone! (yes, I m really excited about that) Often called the master gland Produces or stores 9 hormones Structurally divided into two parts: Anterior pituitary gland (adenohypophysis) Posterior pituitary gland (neurohypophysis) Also called human growth hormone (hgh) The most abundant anterior pituitary hormone Stimulates growth of body cells Stimulates protein synthesis by helping in the use of amino acids in making new proteins Inhibits protein breakdown Stimulates lipolysis (fat breakdown) Inhibits the use of glucose as a fuel for metabolism Affects nearly every tissue of the body Thyroid Stimulating Hormone (TSH) Also called Thyrotropin Influences the body s metabolic rate Target tissue is the thyroid gland Stimulates the secretion of: T3 Triiodothyronine T4--Thyroxine Adrenocorticotropic Hormone (ACTH) Target tissues are the adrenal glands Stimulates the release of steroid hormones Glucocorticoids (cortisol) Thyroid Gland Thyroid Gland Located just below the thyroid cartilage (Adam s apple) of the larynx Has a bow-tie shape Reddish-brown in color Has two lobes connected to each other by the isthmus The only gland that can store its secretory product in large quantities Normally about 100 day supply 3

4 Hormones of the Thyroid Gland Thyroxine (T4) Contains 4 iodine atoms Requires mineral iodine to be made Targets most body cells and acts to increase metabolism by improving energy utilization, O2 consumption, growth and development Most is converted to T3 by the removal of an iodine atom Actions of the Thyroid Hormones (T3 and T4) Regulates oxygen utilization and basal metabolic rate Regulates cellular metabolism Increases protein synthesis Increases lipolysis Increases glucose use in ATP production Works in conjunction with hgh to regulate growth and development catecholamines Enhances the actions of Epinephrine Norepinephrine Parathyroid Gland Parathyroid Gland Four tiny glands located on the posterior surface of the thyroid gland Control the body s calcium levels Produces parathyroid hormone Parathyroid Hormone (PTH) Parathyroid Hormone (PTH) Raises blood calcium levels by: Breaking down bone Increasing body s ability to absorb calcium from food Increasing the kidney s ability to hold on to calcium that would otherwise be lost in urine Negative feedback 4

5 Adrenal (Suprarenal Glands) Adrenal (Suprarenal Glands) Glands located superior to each kidney Structurally divided into two regions: Adrenal cortex Outer region Adrenal medulla the inner portion of the gland Adrenal Medulla The inner portion of the gland Reddish-brown in color due to the large number of blood vessels Contains two sets of hormone producing cells Under the direct control of the autonomic nervous system (ANS) Contains many sympathetic nerve cells Functions with the sympathetic division of the nervous system Hormone production and release can occur almost immediately Hormones of the Adrenal Medulla Epinephrine (adrenaline) Fight or flight Raises the heart rate Constricts blood vessels Dilates pupils Suppresses the immune system Norepinephrine (noradrenaline) Fight or flight Raises the heart rate Causes glucose to be released as energy Causes blood to flow to the muscles Epinephrine and Norepinephrine Epinephrine accounts for 80% and norepinephrine accounts for 20% of secretions from the adrenal medulla Target tissues include skeletal muscles, adipose tissue, and the liver Effects: Breakdown of glycogen to form glucose to provide more ATP (energy) Increased muscular power and endurance Increased heart rate and force of contraction (contractility) Increases blood flow to the vital organs such as the brain, lungs, and heart Increased mental alertness Enlarged airways Increased breathing rate OVERALL: helps the body cope with emergency and stress situations Adrenal Cortex Outer region of the adrenal glands Makes up the majority of the gland Appears yellow due to the presence of lipids Produces more than 2 dozen steroid hormones known as corticosteroids 5

6 Hormones of the Adrenal Cortex Glucocorticoids Regulate metabolism Influence resistance to stress Regulated by the secretion of ACTH Cortisol (hydrocortisone) Makes up 95% of glucocorticoids Primary role is that of gluconeogenesis Synthesis of glucose and destruction of glycogen in the liver which provides body with adequate glucose to produce ATP Promotes normal metabolism Provides resistance to stress (back up for stress response by the adrenal medulla) Acts as an anti-inflammatory compound Inhibits allergens Pancreas Pancreas Located just posterior and slightly inferior to the stomach Pink organ with a nodular appearance Both an endocrine and exocrine gland Exocrine produce digestive enzymes Endocrine produce hormones Cell Types of the Islets of Langerhans Alpha Cells Secrete Glucagon Raises blood sugar Beta Cells Secrete Insulin Lowers blood sugar Endocrine tissue of the pancreas is called the Pancreatic Islets or Islets of Langerhans Secreted by Alpha Cells Glucagon Increases blood sugar when it falls below normal ranges Main target tissue is the liver Accelerates the conversion of glycogen into glucose (glycogenolysis) Promotes the formation of glucose from lactic acid (lactate) and certain amino acids (gluconeogenesis) Suppresses appetite Secreted by the Beta Cells Decreases blood glucose levels if it gets too high Insulin Accelerates the transfer of glucose from the blood into the body s cell Accelerates the conversion of glucose to glycogen (glycogenesis) Accelerates the entry of amino acids into cells and the synthesis of proteins Accelerates the conversion of glucose or other nutrients into fatty acids (lipogenesis) Inhibits glycogenolysis Inhibits gluconeogenesis Primarily influenced by blood glucose levels Also influenced by increased levels of certain amino acids and hormones hcg and ACTH stimulate insulin release 6

7 Insulin Decreases blood glucose Blood Glucose Regulation Pineal Gland Glucagon Increases blood glucose Pineal Gland Melatonin Behind the 3 rd ventricle in between the two hemispheres of the cerebrum Named because of its shape Pine cone Function is linked to the light detection function of the eye Light sensitive in sub-mammals (frogs, fish, birds) Sometimes called the third eye Some believe it s the gate to higher consciousness What is actually does: Produces melatonin Helps maintain circadian rhythm (sleep cycles) Helps regulate reproductive hormones Derivative of the amino acid tryptophan Production of melatonin is influenced by the detection of light and dark by the retina Inhibited when retina detects light Stimulated in the absence of light Thymus Thymus Located behind the sternum and between the lungs Only active until puberty Important for T-cell production (immune system) Lymphatic AND Endocrine function Produces thymosin 7

8 Thymosin Gonads Stimulates and controls the production and maturation of T-cells White blood cells pass through the thymus where thymosin triggers the transformation into T-cells Ovaries Produce estrogen Testes Produce testosterone Metabolic Diseases and Disorders of the Endocrine System Diabetes Mellitus A group of disorders that leads to an elevation of blood glucose (hyperglycemia) Symptoms include: polyuria - polydipsia polyphagia - glucosuria Two Types or Categories of Diabetes Type I Diabetes - Insulin Dependent Diabetes Mellitus (IDDM) Type II Diabetes - Non Insulin Dependent Diabetes Mellitus (NIDDM) Type I Diabetes (IDDM) Pancreas does not produce insulin due to the destruction of beta cells in the Islets of Langerhans Requires regular injections of insulin to prevent death Most commonly develops in individuals younger than 20 years old (Juvenile Onset Diabetes Mellitus) Appears to be an autoimmune disorder atherosclerosis heart disease Complications from Diabetes peripheral vascular disease severe kidney damage Glaucoma and/or blindness gangrene ketoacidosis weight loss neuropathy 8

9 Treatments for Diabetes Regular insulin injections Artificial pancreas Transplantation of the pancreas transplantation of clusters of islet cells Injection of fetal islet cells Type II Diabetes (NIDDM) Also called Maturity Onset Diabetes Much more common type of Diabetes (over 90% of Diabetes cases) Most often occurs in individuals over 40, but seeing more often now in children Most individuals are overweight or clinically obese Blood glucose levels can usually be controlled by medications, diet, exercise, and weight loss and control High and Low Blood Sugars Dwarfism Caused by a hyposecretion of hgh during the growth years resulting in a small person who has a body frame of normal proportions Slow bone growth Epiphyseal plates close before normal height is reached Other organs of the body may also fail to grow and develop Treatment requires administration of hgh during childhood Dwarfism Giantism Due to a hypersecretion of hgh during childhood resulting in a person who grows to a very large size Abnormal increase in bone length and size of other organs The person is very tall with normal body proportions 9

10 Giantism Acromegaly Caused by hypersecretion of hgh in adulthood May be caused by steroid and hgh use Bones of hands, feet, and skull thicken Eyelids, lips, and tongue enlarge Skin thickens and develops furrows Prominent forehead and large nose are typical features Acromegaly Cretinism Caused by hyposecretion of thyroid hormones during fetal development, infancy, and childhood Low metabolism Retarded growth Individuals usually are severely mentally impairments Exhibit dwarfism because the skeleton fails to grow Delayed/slowed sexual development Yellowish skin color Treated with synthetic hormones which prevent the onset of symptoms Cretinism Myxedema Caused by hypothyroidism during the adult years Causes facial tissue to swell and look puffy About 5 times more common in females Other symptoms: Bradycardia Lethargy Dry skin and hair Sensitivity to cold Low body temperature Muscle weakness Easily gains weight Hypersensitive to medications 10

11 Myxedema Graves Disease Caused by hyperthyroidism An autoimmune disorder resulting in: Increased metabolism Increased sweating Weight loss Tremors of hands Heat intolerance Insomnia Nervousness May have a slightly enlarged thyroid gland (goiter) Causes eyes to protrude (exophthalmos) Graves Disease Cushing s Syndrome Goiter Exophthalmos Occurs when your body is exposed to high levels of the hormone cortisol for a long time. Overuse of glucocorticoid medications Prednisone Dexamethasone Prednisolone Body s own overproduction of cortisol Cushing s disease Tumor of the adrenal gland Tumors that produce ACTH Cushing s Syndrome Cushing s Syndrome Signs and Symptoms Round, red, full face (moon face) Slow growth rate in children Weight gain with fat accumulation on the trunk (central obesity) Fat accumulation in the shoulders (buffalo hump) Fat loss from the arms, legs, and buttocks Striae (stretch marks) on abdomen, thoughs, breasts Thin skin with easy bruising Bone pain and tenderness Excessive hair growth in women 11

12 Hyperparathyroidism Hyp0parathyroidism Too much PTH Most patients do not have symptoms when diagnosed Too little PTH Rare Possible symptoms and dangers Osteoporosis Kidney stones Peptic ulcers Insomnia Symptoms: Tingling in hands, fingers, and around mouth Muscle cramps Tetany (severe muscle cramping of the entire body) Convulsions 12