Chemical Coordination and Integration

• Introduction

  • Need for coordination
  • Nervous system vs. Endocrine system
  • Definition of hormones

• Endocrine Glands & Hormones

  • Hypothalamus
    • Master of master glands
    • Releasing and inhibiting hormones
    • Oxytocin and Vasopressin (stored in posterior pituitary)
  • Pituitary Gland
    • Adenohypophysis (Anterior)
      • GH (Growth Hormone)
      • PRL (Prolactin)
      • TSH (Thyroid Stimulating Hormone)
      • ACTH (Adrenocorticotropic Hormone)
      • LH (Luteinizing Hormone)
      • FSH (Follicle Stimulating Hormone)
    • Neurohypophysis (Posterior)
      • Oxytocin
      • Vasopressin (ADH)
  • Pineal Gland
    • Located on dorsal forebrain
    • Secretes Melatonin
    • Regulates diurnal rhythm / sleep-wake cycle
  • Thyroid Gland
    • Follicles and stromal tissues
    • Hormones: Tetraiodothyronine ($T_4$) / Thyroxine, Triiodothyronine ($T_3$), Thyrocalcitonin (TCT)
    • Functions: BMR, calcium regulation, physical/mental development
    • Disorders: Hypothyroidism (Goiter, Cretinism), Hyperthyroidism (Exophthalmic goiter)
  • Parathyroid Glands
    • Four glands on back of thyroid
    • Secretes Parathyroid Hormone (PTH)
    • Hypercalcemic hormone (increases blood $Ca^{2+}$)
  • Thymus Gland
    • Lobular structure near heart
    • Secretes Thymosins
    • Role in cell-mediated immunity (T-lymphocytes) and humoral immunity
  • Adrenal Gland
    • Adrenal Cortex (Outer)
      • Zona Glomerulosa: Mineralocorticoids (Aldosterone)
      • Zona Fasciculata: Glucocorticoids (Cortisol)
      • Zona Reticularis: Sex corticoids (Androgenic steroids)
    • Adrenal Medulla (Inner)
      • Secretes Catecholamines: Adrenaline (Epinephrine) & Noradrenaline (Norepinephrine)
      • Fight-or-flight hormones
  • Pancreas
    • Composite gland (Exocrine + Endocrine)
    • Islets of Langerhans
      • Alpha cells: Glucagon (Hyperglycemic)
      • Beta cells: Insulin (Hypoglycemic)
    • Disorder: Diabetes Mellitus
  • Testis
    • Primary male sex organ
    • Interstitial cells / Leydig cells
    • Secretes Androgens (primarily Testosterone)
  • Ovary
    • Primary female sex organ
    • Secretes Estrogen and Progesterone
    • Corpus luteum secretes progesterone

• Hormones of Heart, Kidney & Gastrointestinal Tract

  • Heart
    • Atrial wall secretes Atrial Natriuretic Factor (ANF)
    • Decreases blood pressure
  • Kidney
    • Juxtaglomerular cells secrete Erythropoietin
    • Stimulates erythropoiesis (RBC formation)
  • Gastrointestinal Tract
    • Peptide hormones: Gastrin, Secretin, Cholecystokinin (CCK), Gastric Inhibitory Peptide (GIP)

• Mechanism of Hormone Action

  • Hormone-Receptor Interaction
  • Cell-membrane receptor hormones (Peptide, protein, amine hormones)
    • Generate secondary messengers (Cyclic AMP, $IP_3$, $Ca^{2+}$)
    • Biochemical responses / physiological effects
  • Intracellular receptor hormones (Steriods, iodothyronines)
    • Hormone-receptor complex enters nucleus
    • Genome interaction / gene expression / protein synthesis