HORMONES - Chapter 18


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HORMONES - Chapter 18

  1. 1. HORMONES - Chapter 18 For the following pages, you should fill in the information for the given hormones. Much information is already given for each gland - your task is to fill in the target tissues, effects, and possible disorders for the hormones listed. I. The Pituitary Gland The pituitary gland can be divided into posterior and anterior divisions on the basis of function and developmental anatomy. Nine important peptide hormones are released by the pituitary gland—seven by the anterior pituitary and two by the posterior pituitary. All nine hormones bind to membrane receptors, and all nine use cAMP as a second messenger. A. The Anterior Pituitary (adenohypophysis) - can be subdivided into three regions: (1) a pars distalis, which is the largest portion of the entire pituitary gland; (2) an extension called the pars tuberalis, which wraps around the adjacent portion of the infundibulum; and (3) a slender pars intermedia (intermediate part), which forms a narrow band bordering the posterior pituitary. An extensive capillary network radiates through these regions, so every endocrine cell has immediate access to the circulatory system. B. Hypothalamic Control of the Anterior Pituitary - There are two classes of regulatory hormones: (1) releasing hormones and (2) inhibiting hormones. A releasing hormone (RH) stimulates synthesis and secretion of one or more hormones at the anterior pituitary, whereas an inhibiting hormone (IH) prevents the synthesis and secretion of hormones from the anterior pituitary. An endocrine cell in the anterior pituitary may be controlled by releasing hormones, inhibiting hormones, or some combination of the two. The regulatory hormones released at the hypothalamus are transported directly to the anterior pituitary by the hypophyseal portal system. The rate of regulatory hormone secretion by the hypothalamus is controlled by negative feedback. C. Hormones of the Anterior Pituitary - The hormones of the anterior pituitary are also called tropic hormones because they turn on endocrine glands or support the functions of other organs. D. Thyroid-Stimulating Hormone (TSH, or thyrotropin) - Target tissue - Effect - E. Adrenocorticotropic hormone (ACTH, or corticotropin) - Target tissue - Effect - F. The Gonadotropins - G. Follicle-Stimulating Hormone (FSH): Target tissue (males and females) -
  2. 2. Effects (males and females) - H. Luteinizing Hormone (LH): Target tissue (males and females) - Effects (males and females) - d) Prolactin (PRL, or mammotropin): Target tissue (females) - Effects (females) - e) Growth Hormone (GH, or somatotropin) - Target tissues - Effects - Disorders if GH present in excess - Disorders if GH deficient - f) Melanocyte-Stimulating Hormone (MSH) - stimulates the melanocytes of the skin, and is important in the control of skin pigmentation in fishes, amphibians, reptiles, and many mammals
  3. 3. other than primates. The pars intermedia in adult humans is virtually nonfunctional, and the circulating blood usually does not contain MSH. B. The Posterior Pituitary (neurohypophysis) - contains the axons of hypothalamic neurons. Neurons of the supraoptic and paraventricular nuclei in the hypothalamus manufacture antidiuretic hormone (ADH) and oxytocin, respectively. These products move along axons in the infundibulum to the capillaries in the posterior pituitary gland. C. Antidiuretic Hormone (ADH) – Target tissue - Effects - D. Oxytocin - Target tissue - Effects - II. The Thyroid Gland The thyroid gland curves across the anterior surface of the trachea just inferior to the thyroid cartilage. The gland produces three hormones - triiodothyronine (T3), thyroxine (T4), and calcitonin. The formation of thyroid hormones (T3 and T4) involves the use of iodide ions from the diet attached to the tyrosine molecules in the thyroid gland. A. Thyroid Hormones - Secreted in response to - Target tissues - Effects - Deficiency of thyroid hormones - Excess of thyroid hormones -
  4. 4. A. Calcitonin - produced by C cells located between the thyroid follicles. Secreted in response to - Target tissues - Effects - III. The Parathyroid Glands Two pairs of parathyroid glands are embedded in the posterior surfaces of the thyroid gland. A. Parathyroid Hormone (PTH) - secreted by the chief cells Secreted in response to - Target tissues - Effects - Deficiency of PTH - Excess of PTH - IV. The Adrenal Glands Located on the superior border of each kidney. The adrenal gland is divided into two parts: an outer adrenal cortex and an inner adrenal medulla. A. The Adrenal Cortex - The adrenal cortex produces steroid hormones, collectively called corticosteroids. Two important subcategories of corticosteroids are mineralocorticoids and glucocorticoids. B. Mineralocorticoids - produced by the outer region of the adrenal cortex, in response to a change in electrolyte composition in the blood (decreased sodium and/or increased potassium) or in response to angiotensin II (under conditions of decreased blood volume/pressure). Aldosterone is the principal mineralocorticoid produced by the human adrenal cortex. Target tissue -
  5. 5. Effects - C. Glucocorticoids - hormones which affect glucose metabolism ("glucose sparing"). Released in response to ACTH from the anterior pituitary. The most common glucocorticoid is cortisol (hydrocortisone). Affect almost every cell in the body. Target tissue - Effects - B. Adrenal Medulla - secrete epinephrine and norepinephrine in response to stimulation by the sympathetic division of the autonomic nervous system. Previously discussed. V. The Pancreas Both an endocrine and exocrine gland (exocrine portion is involved in secretion of enzymes used for digestion in small intestine, as well as bicarbonate to buffer the acidic pH of the stomach fluids entering the small intestine). The endocrine portion consists of clusters of cells called islets of Langerhans. Four cells present in islets - alpha, beta, delta and F cells. We will focus on the activities of the alpha and beta cells, which produce the hormones glucagon and insulin. A. Glucagon - produced by alpha cells. Secreted in response to - Target tissues - Effects - B. Insulin - produced by beta cells in response to an increase in blood glucose levels. Causes: Secreted in response to - Target tissues -
  6. 6. Effects - Type I Diabetes (what is it, how is it treated?) - Type II Diabetes (what is it, how is it treated?) -