Chapter 51: Endocrine System. 51-1 Hormones. 51-2 Endocrine Glands. 51-3 Feedback Mechanisms. 51-1 Hormones. I. Types of Glands (2 TYPES in our body). A GLAND secretes materials into BLOODSTREAM. (1) Exocrine Glands (e.g., sweat glands, mucous glands, salivary glands).
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Chapter 51: Endocrine System 51-1 Hormones 51-2 Endocrine Glands 51-3 Feedback Mechanisms
51-1 Hormones I. Types of Glands (2 TYPES in our body) • A GLAND secretes materials into BLOODSTREAM.
(1) Exocrine Glands (e.g., sweat glands, mucous glands, salivary glands) • Secrete NON-hormonal substances into DUCTS transport these inside AND outside body.
(2) Endocrine Glands (e.g., pituitary gland, thyroid gland, adrenal gland) • Ductless glands dump HORMONES directly into bloodstream.
II. Types of Hormones (TWO classes) • Chemicals that in SMALL amounts INFLUENCE activity of DISTANT cells (using our bloodstream as the MEDIUM).
(1) Amino Acid (Peptide) Hormones (e.g., epinephrine, adrenaline) • PROTEIN hormones that attach directly to cell membrane.
(2) Steroid Hormones (e.g., estrogen, testosterone) • LIPID hormones derived from cholesterol (diffuse through cell membrane).
III. Hormone Action • When a hormone BINDS to a receptor on (or INSIDE) its TARGET CELL, it triggers a SERIES of events leading to CELL CHANGES.
(1) Target Cells (e.g., testosterone works on SKELETAL muscle cells) • Cells that have receptors SPECIFIC to a SPECIFIC type of HORMONE.
(2) Receptors • Proteins BOTH INSIDE cytoplasm and ON SURFACE of a target cell.
(A) Amino Acid Hormones (CANNOT diffuse needs a MESSENGER) • ID target cells by SURFACE RECEPTORS embedded in cell membrane.
(1) First Messenger (i.e, the HORMONE) • HORMONE 1ST messenger by BINDING to target cell receptor.
(2) Hormone-Receptor Complex (HRC) • Complex formed BETWEEN hormone and RECEPTOR protein—the HRC activates a 2nd messenger INSIDE target cell.
(3) Second Messenger (i.e., cyclic AMP or simply cAMP—gets ACTIVATED) • cAMP initiates a SERIES of events that LEADS to CHANGES within target cell (NOTE: Different ORGANS may respond differently to cAMP).
(B) Steroid Hormones (fat soluble, easily PASS THROUGH cell membrane) • Diffuse THROUGH membrane, bind to a receptor INSIDE cell—the HRC then ENTERS nucleus and CHANGES cell activity.
IV. Prostaglandins (stimulate LABOR contractions & blood CLOTTING) • A group of LIPIDS (i.e., NOT hormones, NO glands) produced by cells ALL OVER the body, AND only act LOCALLY.
51-2 Endocrine Glands I. Pituitary Gland (i.e., “MASTER gland,” links nervous WITH endocrine) • Releases hormones that AFFECT other glands and organs (BUT is regulated by HYPOTHALAMUS).
Critical Thinking (1)Why might damage to the PITUITARY gland be considered far MORE SERIOUS that damage to one of the other endocrine glands?
(1) Neurosecretory Cells (located in HYPOTHALAMUS) • Makes hormones that REGULATE pituitary’s activity. (releasing OR inhibiting hormones)
(A) Posterior Pituitary (back of pituitary) • Secretes OXYTOCIN and ADH.
(1) Oxytocin (TARGETS mammary glands AND uterine muscles) • Initiates uterine CONTRACTIONS during childbirth; stimulates SECRETION of breast milk.
(2) Antidiuretic Hormone (ADH—TARGETS kidney nephrons) • Stimulates REABSORPTION of WATER by kidneys, concentrates urine.
(B) Anterior Pituitary (TOP of pituitary, regulated by hypothalamus) • Secretes GH, PROLACTIN, TSH, LH and ACTH.
(1) Releasing Hormones (TARGET anterior pituitary) • STIMULATES secretion of AP hormones. (2) Release-Inhibiting Hormones (TARGET anterior pituitary) • INHIBITS secretion of AP hormones.
Critical Thinking (2)Severe structural abnormalities result from gigantism, a condition of extremely rapid growth, and from pituitary dwarfism, a condition of slowed growth. Based on your understanding of the endocrine system, suggest what causes these inherited disorders.
(3) Growth Hormone (GH, targets growth tissue) • Regulates GROWTH of muscle AND bone tissue.
(4) Prolactin (TARGETS mammary glands) • Stimulates and sustains MILK PRODUCTION in breasts before AND during lactation.
II. Thyroid Gland (TWO lobes, near larynx) • Regulated by TSH; secretes thyroxine, triiodothyronine, and calcitonin.
(1) Thyroid-Stimulating Hormone (TSH, TARGETS thyroid gland) • Secreted by AP, REGULATES thyroid gland. (2) Thyroxine and Triiodothyronine (TARGETS various tissues) • MAINTAIN heart rate, blood pressure, temperature, and metabolism.
(3) Calcitonin (TARGETS osteoblasts of BONE tissue) • Stimulates DEPOSIT of CALCIUM IONS (Ca ++) from BLOOD TO BONE.
(4) Hyperthyroidism (OVER-production of thyroid hormones) • OVER-activity, weight LOSS, HIGH blood pressure, an ELEVATED heart rate and temp. (treated w/medicine)
(5) Hypothyroidism (UNDER-production of thyroid hormones) • SLOWED-growth, lethargy, weight GAIN, DECREASED heart rate AND temp. (treated with thyroxine)
(6) Cretinism (can result from a HYPOthyroidism, a DEFICIENCY) • A form of mental IMPAIRMENT during fetal and childhood development.
(7) Goiter (if there is an IODINE deficiency, a NUTRIENT for thyroid) • A SWELLING of thyroid gland treated with IODINE and THYROXINE.