Lab 06-Endocrine-System complete

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May 6, 2024

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Lab 6 : Endocrine System Learning outcomes of the lab exercises : 1. Identify and locate the major endocrine glands. 2. Associate the hormones produced and secreted by the major endocrine glands with their target organ and their function. " You may never have thought of it this way, but when you send a text message to two friends to meet you at the dining hall at six, you’re sending digital signals that (you hope) will affect their behavior— even though they are some distance away. Similarly, certain cells send chemical signals to other cells in the body that influence their behavior. This long-distance intercellular communication, coordination, and control is critical for homeostasis, and it is the fundamental function of the endocrine system." OpenStax A&P pg. 732 GLANDS OF THE ENDOCRINE SYSTEM A. ANTERIOR PITUITARY GLAND (which hangs from the base of the brain and sits in sella turcica may then secrete 6 different hormones: 1. Human Growth Hormone (HGH) a. controls growth of the body; b. targets bone, muscle and adipose tissue. 2. Prolactin (PRL) a. stimulates the production of milk by the mammary glands; b. targets the mammary glands. 4. Thyroid stimulating hormone (TSH) a. controls the secretion of hormones by the thyroid gland; b. targets thyroid gland. 4. Adrenocorticotropic Hormone (ACTH) a. controls the secretion of hormones by the adrenal cortex; b. targets the outer portion of the adrenal gland (cortex). 5. Follicle Stimulating Hormone (FSH) a. response depends upon sex: o In females, maturation of an ovarian follicle and ovum; o In males, maturation of sperm in the testes; 6. Luteinizing Hormone (LH) a. response depends upon sex: o In females, LH causes ovulation; o In males, LH causes secretion of testosterone. B. POSTERIOR PITUITARY GLAND 1. is located behind the anterior pituitary gland; 2. is continuous with nerve fibers (supraopticohypophyseal tract) of the hypothalamus; 3. does not actually produce hormones (they are produced by the hypothalamus), but stores them until it is stimulated to release them; 4. secretes 2 hormones: a. Antidiuretic Hormone (ADH) : o targets distal convoluted tubules (of kidney); o causes DCT’s to reabsorb water back into the bloodstream, and therefore increases blood pressure. b. Oxytocin (OT) : 174
o targets uterine smooth muscle and breasts; o causes uterine muscle contraction and milk production. OpenStax A&P Fig. 17.11 Major Pituitary Hormones C. THYROID GLAND : 1. is located below larynx and around trachea; 2. is involved in iodine uptake (in order to produce thyroxine (T 4 ) & triiodothyronine (T 3 ) below); 3. produces 3 hormones when stimulated by TSH: a. Thyroxine (T 4 ) & Triiodothyronine (T 3 ) : increase basal metabolic rate by stimulating cellular oxygen use to produce ATP; b. Calcitonin : o release is triggered by an increase in blood calcium levels; o targets bone cells (stimulates osteoblast activity and inhibits osteoclast activity) & distal convoluted tubules (causes secretion of excess calcium into urine); 175
o Therefore, causes a decrease in blood calcium (and phosphate) levels back to normal. D. PARATHYROID GLANDS : 1. consist of 4 small glands; 2. are located within the thyroid gland; 3. produce a hormone called Parathyroid Hormone (PTH) : a. release of PTH is stimulated by decreased blood calcium levels; b. PTH targets bone cells (activates osteoclasts to resorb bone), proximal convoluted tubules (causes PCT’s to reabsorb calcium back into bloodstream), and small intestine (promotes calcium absorption). c. Therefore, PTH causes an increase in blood calcium (and phosphate) levels back to normal. 4. PTH and calcitonin together maintain the homeostasis of Ca ++ in the blood. E. ADRENAL GLANDS 1. are located atop the kidneys; 2. are divided into an outer adrenal cortex and an inner adrenal medulla . a. Hormones of the Adrenal Medulla : o is located in the central portion of the adrenal glands; o produces 2 closely related hormones, which function in the sympathetic division of the autonomic nervous system: 1. epinephrine; 2. norepinephrine . These hormones target: 1. the heart (SA Node to increase heart rate); 2. smooth muscle: peripheral arterioles (vasoconstriction, which increases blood pressure); terminal bronchioles (bronchodilation, which increases depth of breathing) 3. the diaphragm (increased breathing rate). b. Hormones of the Adrenal Cortex : o is located in the outer portion of the adrenal glands; o produces many steroid hormones when stimulated by ACTH: 1. Aldosterone targets proximal convoluted tubules, causing reabsorption of water and electrolytes back into the blood (increases blood pressure). 2. Cortisol targets all cells, where it regulates glucose metabolism (along with T 3 and T 4 ). 3. Supplemental sex hormones (estrogens and androgens) that target secondary sex organs. 176
OpenStax A&P Fig. 17.17 Adrenal Glands F. PANCREAS : a. is located behind the stomach on the left side of abdomen; b. functions as a mixed gland. (i.e. both an exocrine gland (digestion) and endocrine gland (see below); c. Hormones of the Pancreatic Islets (of Langerhans) 1. Glucagon : o is produced by Alpha cells (α-cells) in Islets of Langerhans; o Secretion is stimulated by decreased blood glucose levels (i.e. fasting), glucagon increases blood glucose levels (i.e. causes breakdown of glycogen and release of glucose into bloodstream). 2. Insulin : o is produced by Beta cells (β-cells) in Islets of Langerhans; o Secretion is stimulated by increased blood glucose levels (i.e. after eating), insulin decreases blood glucose levels (i.e. moves glucose from bloodstream into cells and promotes glycogen formation in liver and skeletal muscle). d. Review how these two hormones regulate glucose homeostasis in blood. G. THYMUS GLAND : 1. is located in the mediastinum region behind sternum; 2. produces a hormone called thymosin that affects the maturation of lymphocytes (T-cells); 3. plays an important role in lymphatic system and immunity; 4. decreases in size as we age. H. PINEAL GLAND : 1. is attached to the thalamus of the brain stem; 2. secretes a hormone called melatonin : a. production is stimulated by daylight (circadian rhythm); b. affects moods, emotions, etc. I. OVARIES: 1. An ovarian follicle (and ovum) start to mature each month following puberty under the influence of follicle stimulating hormone (FSH). a. The developing follicle secretes estrogen : o Estrogen develops female secondary sexual characteristics (at puberty) and maintains them throughout life. 177
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