Chemical Coordination and Integration

SYNOPSIS

• Endocrine System

• Exocrine Glands: These are the glands with ducts. They discharge their secretions on the body surface or in body cavities.
• Endocrine Glands: These are ductless glands. Their secretions are directly poured into the blood.
• Heterocrine Glands: They are a mixed type of glands. They have exocrine as well as endocrine parts.

• A hormone, also called a chemical messenger, is a secretion from some glandular part of the body which is poured into the blood and which acts on the target organs or cells of the same individual.

• Hypothalamus and its Hormones
  The hypothalamus is a part of the brain which consists of several masses of grey matter called hypothalamic nuclei.
  
  

  Hypothalamic Hormone	Response of Pituitary	Target Organ
  Thyrotropin-releasing hormone (T-RH)	Secretion of TSH	Thyroid
  Adrenocorticotropin-releasing hormone (A-RH)	Secretion of adrenocorticotropic hormone (ACTH)	Adrenal cortex
  Follicle-stimulating hormone-releasing hormone (FSH-RH)	Secretion of FSH	Ovary/Testis
  Luteinising hormone-releasing hormone (LH-RH)	Secretion of LH	Ovary/Testis
  Growth hormone-releasing hormone (GH-RH)	Secretion of GH or STH	Most tissues
  Somatostatin	Inhibition of the secretion of growth hormone	—
  Prolactin-releasing hormone (P-RH)	Secretion of LTH or prolactin hormone	Mammary glands

• Endocrine Glands and their Hormones
  
  

  Gland	Hormones	Functions	Disorders
  Adrenal glands	Adrenaline	Prepares the body for the fight and flight mechanism	Addison’s disease Cushing syndrome
  Thyroid gland	Thyroxine	Regulates carbohydrate, protein and fat metabolism Increases the basal metabolic rate (BMR) Regulates ossification of bones and mental development	Simple goitre Ophthalmic goitre Cretinism
  Parathyroid glands	Parathormone	Controls metabolism and maintains blood calcium level	Tetany Demineralisation of bones
  Pituitary gland
  Anterior pituitary	Growth hormone	Essential for normal growth	Dwarfism Gigantism
  	Thyroid-stimulating hormone (TSH)	Controls the synthesis and secretion of thyroid hormones from the thyroid gland	____
  	Follicle-stimulating hormone (FSH)	Stimulates the growth and development of ovarian follicles in females Promotes spermatogenesis in males	____
  	Luteinising hormone (LH)	Stimulates ovulation, formation of the corpus luteum and secretion of progesterone in females Stimulates the secretion of androgens in the testes in males	____
  	Adrenocorticotropic hormone (ACTH)	Regulates the synthesis and secretion of glucocorticoids from the adrenal cortex	____
  Intermediate lobe	Melanocyte-stimulating hormone (MSH)	Stimulates melanocytes present in the skin and hence controls pigmentation	____
  Posterior pituitary	Oxytocin	Stimulates the contraction of uterine muscles during childbirth Stimulates ejection of milk from the mammary glands after delivery	____
  	Vasopressin/anti-diuretic hormone	Stimulates the resorption of water and electrolytes by DCT in the kidneys	____
  Pineal gland	Melatonin	Regulates the 24-hour diurnal rhythm of the body and body temperature	____
  Thymus	Thymopoietin Thymosin	Controls the maturation and distribution of lymphocytes Stimulates the production of antibodies	____
  Pancreas	Insulin	Regulates the blood glucose (sugar) level	Diabetes mellitus Hyperglycemia
  Testes in males	Testosterone	Controls the development of male sex organs and secondary sexual characters during puberty	____
  Ovaries in females	Oestrogen	Controls the development of female sex organs and secondary sexual characters during puberty	____

• Hormones of the Heart, Kidneys and Gastrointestinal Tract
  
  

  Organ	Hormones	Functions
  Heart	Atrial natriuretic factor (ANF)	Causes dilation of blood vessels which results in decrease in blood pressure
  Kidney	Erythropoietin	Stimulates erythropoiesis
  Stomach	Gastrin	Stimulates the gastric glands to secrete gastric juice
  Intestine	Secretin	Stimulates the secretion and release of bicarbonate ions and water from the exocrine pancreas
  	Cholecystokinin	Stimulates the pancreas to release its enzymes Stimulates the gall bladder to release bile in the duodenum
  Liver	Angiotensinogen	Stimulates the adrenal cortex to produce aldosterone