Chemical integration

• Endocrine glands lack ducts and are called ductless glands
• Hormones are non-nutrient chemicals that act as intercellular messengers and are produced in trace amounts
• Invertebrates have simple endocrine systems with few hormones, while vertebrates have many chemicals acting as hormones
• The human endocrine system includes pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads
• The hypothalamus regulates a wide spectrum of body functions and produces releasing hormones and inhibiting hormones
• The pituitary gland consists of adenohypophysis and neurohypophysis, producing various hormones like GH, PRL, TSH, ACTH, LH, FSH, MSH, oxytocin, and vasopressin
• Over-secretion of GH can lead to gigantism, while low secretion can result in pituitary dwarfism
• Prolactin regulates the growth of mammary glands and milk formation
• TSH stimulates the synthesis and secretion of thyroid hormones
• ACTH stimulates the synthesis and secretion of glucocorticoids from the adrenal cortex
• LH and FSH stimulate gonadal activity and are called gonadotrophins
• MSH regulates pigmentation of the skin
• Oxytocin stimulates uterine contractions and milk ejection, while vasopressin stimulates water resorption in the kidney
• Melatonin from the pineal gland regulates the body's diurnal rhythm
• Thyroid gland synthesizes thyroxine and triiodothyronine, essential for metabolism and red blood cell formation
• Iodine deficiency can lead to hypothyroidism and goitre
• Hyperthyroidism can result in exopthalmic goitre and Graves' disease
• Parathyroid gland secretes PTH to regulate blood calcium levels
• Thymus gland secretes thymosins for immune system development
• Adrenal medulla secretes adrenaline and noradrenaline as emergency hormones
• Adrenal cortex produces corticoids like glucocorticoids and mineralocorticoids
• Cortisol is the main glucocorticoid involved in carbohydrate metabolism and anti-inflammatory reactions
• Aldosterone is the main mineralocorticoid that regulates water and electrolyte balance
• Cortisol produces anti-inflammatory reactions and suppresses the immune response
• Cortisol stimulates the production of RBC
• Aldosterone acts mainly at the renal tubules and stimulates the reabsorption of Na+ and water
• Aldosterone stimulates the excretion of K+ and phosphate ions
• Aldosterone helps in the maintenance of electrolytes, body fluid volume, osmotic pressure, and blood pressure
• Small amounts of androgenic steroids are secreted by the adrenal cortex
• Androgenic steroids play a role in the growth of axial hair, pubic hair, and facial hair during puberty
• Pancreas acts as both an exocrine and endocrine gland
• The endocrine pancreas consists of 'Islets of Langerhans'
• Islets of Langerhans contain α-cells and β-cells
• α-cells secrete glucagon
• Glucagon plays a role in maintaining normal blood glucose levels
• Glucagon stimulates glycogenolysis and gluconeogenesis
• β-cells secrete insulin
• Insulin regulates glucose homeostasis
• Insulin stimulates cellular glucose uptake and utilization
• Insulin stimulates conversion of glucose to glycogen