a & p exam 3

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a & p exam 3
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2010-11-07 22:43:42
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endocrine system TRACS handout
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hormones
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  1. Anterior Pituitary Hormones
    • • Growth hormone (GH)
    • • Thyroid-stimulating hormone (TSH) or thyrotropin
    • • Adrenocorticotropic hormone (ACTH)
    • • Follicle-stimulating hormone (FSH)
    • • Luteinizing hormone (LH)
    • • Prolactin (PRL)
  2. Growth Hormone (GH)
    • • Produced by somatotrophs
    • • Stimulates most cells, but targets bone and skeletal muscle
    • • Promotes protein synthesis and encourages use of fats for fuel
    • • Most effects are mediated indirectly by insulin-like growth factors (IGFs)
    • • GH release is regulated by
    • • Growth hormone–releasing hormone (GHRH)
    • • Growth hormone–inhibiting hormone (GHIH) (somatostatin)
    • • Direct action of GH
    • • Stimulates liver, skeletal muscle, bone, and cartilage to produce insulin-like growth
    • factors
    • • Mobilizes fats, elevates blood glucose by decreasing glucose uptake and
    • encouraging glycogen breakdown (anti-insulin effect of GH)
  3. Thyroid-Stimulating Hormone (Thyrotropin)
    • • Produced by thyrotrophs of the anterior pituitary
    • • Stimulates the normal development and secretory activity of the thyroid
  4. Adrenocorticotropic Hormone (Corticotropin)
    • • Secreted by corticotrophs of the anterior pituitary
    • • Stimulates the adrenal cortex to release corticosteroids
  5. Gonadotropins
    • • Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
    • • Secreted by gonadotrophs of the anterior pituitary
    • • FSH stimulates gamete (egg or sperm) production
    • • LH promotes production of gonadal hormones
    • • Absent from the blood in prepubertal boys and girls
  6. Prolactin (PRL)
    • • Secreted by lactotrophs of the anterior pituitary
    • • Stimulates milk production
    • • Blood levels rise toward the end of pregnancy
    • • Suckling stimulates PRH release and promotes continued milk production
  7. Oxytocin
    • • Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-
    • Ca2+ second-messenger system
    • • Also triggers milk ejection (“letdown” reflex) in women producing milk
    • • Plays a role in sexual arousal and orgasm in males and females
  8. Antidiuretic Hormone (ADH)
    • • Hypothalamic osmoreceptors respond to changes in the solute concentration of the
    • blood
    • • If solute concentration is high
    • • Osmoreceptors depolarize and transmit impulses to hypothalamic neurons
    • • ADH is synthesized and released, inhibiting urine formation
    • • If solute concentration is low
    • • ADH is not released, allowing water loss
    • • Alcohol inhibits ADH release and causes copious urine output
  9. Thyroid Hormone (TH)
    • • Actually two related compounds
    • • T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms
    • • T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms
    • • Major metabolic hormone
    • • Increases metabolic rate and heat production (calorigenic effect)
    • • Plays a role in
    • • Maintenance of blood pressure
    • • Regulation of tissue growth
    • • Development of skeletal and nervous systems
    • • Reproductive capabilities
  10. Calcitonin
    • • Produced by parafollicular (C) cells
    • • Antagonist to parathyroid hormone (PTH)
    • • Inhibits osteoclast activity and release of Ca2+ from bone matrix
  11. Parathyroid Hormone
    • • Functions
    • • Stimulates osteoclasts to digest bone matrix
    • • Enhances reabsorption of Ca2+ and secretion of phosphate by the kidneys
    • • Promotes activation of vitamin D (by the kidneys); increases absorption of Ca2+ by
    • intestinal mucosa
  12. Adrenal Cortex
    • • Three layers and the corticosteroids produced
    • • Zona glomerulosa—mineralocorticoids
    • • Zona fasciculata—glucocorticoids
    • • Zona reticularis—sex hormones, or gonadocorticoids
  13. Mineralocorticoids
    • • Regulate electrolytes (primarily Na+ and K+) in ECF
    • • Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of
    • other ions
    • • Importance of K+: sets RMP of cells
    • • Aldosterone is the most potent mineralocorticoid
    • • Stimulates Na+ reabsorption and water retention by the kidneys
  14. Glucocorticoids (Cortisol)
    • • Keep blood sugar levels relatively constant
    • • Maintain blood pressure by increasing the action of vasoconstrictors
    • • Cortisol is the most significant glucocorticoid
    • • Released in response to ACTH, patterns of eating and activity, and stress
    • • Prime metabolic effect is gluconeogenesis—formation of glucose from fats and
    • proteins
    • • Promotes rises in blood glucose, fatty acids, and amino acids
  15. Gonadocorticoids (Sex Hormones)
    • • Most are androgens (male sex hormones) that are converted to testosterone in tissue
    • cells or estrogens in females
    • • May contribute to
    • • The onset of puberty
    • • The appearance of secondary sex characteristics
    • • Sex drive
  16. Adrenal Medulla
    • • Chromaffin cells secrete epinephrine (80%) and norepinephrine (20%)
    • • Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to
    • skeletal muscles and the heart
    • • Norepinephrine influences peripheral vasoconstriction and blood pressure
  17. Pineal Gland
    • • Small gland hanging from the roof of the third ventricle
    • • Pinealocytes secrete melatonin, derived from serotonin
    • • Melatonin may affect
    • • Timing of sexual maturation and puberty
    • • Day/night cycles
    • • Physiological processes that show rhythmic variations (body temperature, sleep,
    • appetite)
  18. Pancreas: Glucagon
    • • Major target is the liver, where it promotes
    • • Glycogenolysis—breakdown of glycogen to glucose
    • • Gluconeogenesis—synthesis of glucose from lactic acid and noncarbohydrates
    • • Release of glucose to the blood
  19. Pancreas: Insulin
    • • Effects of insulin
    • • Lowers blood glucose levels
    • • Enhances membrane transport of glucose into fat and muscle cells
    • • Participates in neuronal development and learning and memory
    • • Inhibits glycogenolysis and gluconeogenesis
  20. Ovaries and Placenta
    • • Gonads produce steroid sex hormones
    • • Ovaries produce estrogens and progesterone responsible for:
    • • Maturation of female reproductive organs
    • • Appearance of female secondary sexual characteristics
    • • Breast development and cyclic changes in the uterine mucosa
    • • The placenta secretes estrogens, progesterone, and human chorionic gonadotropin
    • (hCG)
  21. Testes
    • • Testes produce testosterone that
    • • Initiates maturation of male reproductive organs
    • • Causes appearance of male secondary sexual characteristics and sex drive
    • • Is necessary for normal sperm production
    • • Maintains reproductive organs in their functional state
  22. Other Hormone-Producing Structures
    • • Heart
    • • Atrial natriuretic peptide (ANP) reduces blood pressure, blood volume, and blood
    • Na+ concentration
    • • Gastrointestinal tract enteroendocrine cells
    • • Gastrin stimulates release of HCl
    • • Secretin stimulates liver and pancreas
    • • Cholecystokinin stimulates pancreas, gallbladder, and hepatopancreatic sphincter
    • • Kidneys
    • • Erythropoietin signals production of red blood cells
    • • Renin initiates the renin-angiotensin mechanism
    • • Skin
    • • Cholecalciferol, the precursor of vitamin D
    • • Adipose tissue
    • • Leptin is involved in appetite control, and stimulates increased energy expenditure
    • • Skeleton (osteoblasts)
    • • Osteocalcin prods pancreatic cells to divide and secrete more insulin, improving
    • glucose handling and reducing body fat
    • • Thymus
    • • Thymulin, thymopoietins, and thymosins are involved in normal development of the
    • T lymphocytes in the immune response

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