Ch17

• Endocrine system


  Control system which maintains homeostasis, regulates energy use, metabolism, growth and reproduction among other body processes
• Types of Hormones

  • Amino acid derivatives
  • Peptide hormones
  • Lipid derivatives
• Amino acid derivative hormones

  • T4, T3, epinephrine, norepinephrine
• Peptide hormones


  • ADH, oxytocin, insulin, GH, PRL, TSH, LH, FSH
• Lipid derivative hormones


  • Eicosanoids, steroid hormones (testosterone, estrogen, progesterone, corticosteroids)
• Steroid hormones


  Lipid-soluble, pass easily through target cell membrane
• Non-steroid hormones


  Water-soluble, require receptor on target cell membrane
• Pathways of Hormone Action

  1. Steroid hormones: Enter cell by diffusion, bind to protein receptor, newly formed hormone-receptor complex alters gene expression, new proteins carry out function

  2. Non-steroid hormones: Hormone binds outside of cell and acts as first messenger, result is increase or decrease in some second messenger, G-protein regulated using cyclic AMP as the second messenger
• Regulation of Hormone Secretion

  • Hormonal control by tropic hormones of hypothalamus
  • Nervous control by Autonomic nervous system
  • Humoral control by regulating blood levels
• Anterior Pituitary


  • Secretes HGH, PRL, TSH, ACTH, FSH, LH
• Human Growth Hormone (HGH)


  Controls growth of the body, targets bone, muscle and adipose tissue
• Prolactin (PRL)


  Stimulates the production of milk by the mammary glands, targets the mammary glands
• Thyroid stimulating hormone (TSH)


  Controls the secretion of hormones by the thyroid gland, targets thyroid gland
• Adrenocorticotropic Hormone (ACTH)


  Controls the secretion of hormones by the adrenal cortex, targets the outer portion of the adrenal gland (cortex)
• Follicle Stimulating Hormone (FSH)


  In females, maturation of an ovarian follicle and ovum; In males, maturation of sperm in the testes; A gonadotropin, which targets primarily ovaries & testes
• Luteinizing Hormone (LH)


  In females, LH causes ovulation; In males, LH causes secretion of testosterone; A gonadotropin, which targets ovaries & testes
• Posterior Pituitary


  • Located behind the anterior pituitary gland, continuous with nerve fibers (supraopticohypophyseal tract) of the hypothalamus, secretes ADH and oxytocin
• Antidiuretic Hormone (ADH)


  Targets distal convoluted tubules (of kidney), causes DCT's to reabsorb water into the bloodstream, increases BP
• Oxytocin (OT)


  Targets uterine smooth muscle and breasts, causes uterine muscle contraction and milk production
• Pituitary Dwarfism = hyposecretion of GH during growth years, slow bone growth & closing of epiphyseal plates before normal height is reached, treated with oral GH therapy
• Pituitary Gigantism = hypersecretion of GH during growth years, abnormal increase in the length of long bones
• Acromegaly = hypersecretion of GH during adulthood, bones of hands, feet, cheeks, and jaw thicken, soft tissues also grow
• Diabetes insipidus = hyposecretion of ADH, diuresis, dehydration, thirst, treated with ADH in nasal spray
• Thyroid Gland


  • Located below larynx and around trachea, involved in iodine uptake to produce T4 and T3, produces T4, T3, and calcitonin
• Thyroxine (T4) & Triiodothyronine (T3)


  Increase basal metabolic rate by stimulating cellular oxygen use to produce ATP
• Calcitonin


  Release is triggered by an increase in blood calcium levels, targets bone cells (stimulates osteoblast activity and inhibits osteoclast activity) & DCT's (causes secretion of excess calcium into urine), causes a decrease in blood calcium (and phosphate) levels back to normal
• Cretinism = hyposecretion of T3/T4 during fetal life and infancy, dwarfism & mental retardation, prevented by newborn testing, treated with oral thyroid therapy
• Myxedema = hyposecretion of thyroid hormones during adulthood, edema, slow heart rate, low body temp, dry hair & skin, muscular weakness, lethargy, weight gain, treated with oral thyroid hormones
• Grave's Disease = an autoimmune disorder that causes growth of thyroid and hypersecretion of thyroid hormones, with no negative feedback, enlarged thyroid, peculiar edema of the eyes, increased metabolic rate, heat intolerance, increased sweating, weight loss, insomnia, tremor, and nervousness, treated by surgical removal, use of radioisotopes, and anti-thyroid drugs
• Goiter = low thyroid hormones due to iodine deficiency, thyroid is overstimulated and enlarges, but still functions below normal levels
• Parathyroid Gland


  • Consist of 4 small glands embedded in the posterior of the thyroid, produce Parathyroid Hormone (PTH)
• Parathyroid Hormone (PTH)


  Release is stimulated by decreased blood calcium levels, 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), causes an increase in blood calcium (and phosphate) levels back to normal
• Hyperparathyroidism = usually due to tumor in thyroid, loss of bone tissue, bone fracture & pain, hypercalcemia (excess Ca), may deposit in soft tissues
• Hypoparathyroidism = less common, in past due to accidental removal of glands with surgery, hypocalcemia, weakness, faulty muscle contractions
• Adrenal Gland


  • Located on top of the kidneys, divided into an outer adrenal cortex and an inner adrenal medulla
• Hormones of the Adrenal Medulla


  Epinephrine and norepinephrine, function in the sympathetic division of the autonomic nervous system, target the heart (increase heart rate), smooth muscle (vasoconstriction, bronchodilation)
• Hormones of the Adrenal Cortex


  Aldosterone (targets PCT, causes reabsorption of water and electrolytes, increases BP), cortisol (regulates glucose metabolism), supplemental sex hormones (estrogens and androgens)
• Addison's Disease = hyposecretion of adrenal cortical hormones due to autoimmunity or disease, symptoms include mental lethargy, anorexia, nausea, vomiting, weight loss, hypoglycemia, muscle weakness, electrolyte imbalances, dehydration, arrhythmias, skin pigmentation
• Cushing's Syndrome = hypersecretion of adrenal cortical hormones due to pituitary tumor or steroid administration, symptoms include redistribution of fat, thin limbs due to wasting of muscles, "moon face", "buffalo hump", bruises, poor wound healing, hyperglycemia, osteoporosis, weakness, hypertension, susceptibility to infection, resistance to stress, mood swings
• Pineal Gland


  • Attached to the thalamus of the brain stem, secretes melatonin, production is stimulated by daylight (circadian rhythm), affects moods and emotions