8 Endocrine system

• Endocrine organs


  • PINEAL GLAND
  • THYROID GLAND
  • PITUITARY GLAND
  • ADRENAL GLANDS
  • PANCREAS
  • OVARIES
  • TESTES
  • HYPOTHALAMUS
• Pineal gland


  Regulated by the hypothalamus
• Melatonin


  Regulates the sleep-wake cycle
• Thyroxine


  Increases rate and contractility of the heart
• Serotonin


  The 'happy hormone', increases rate of cellular metabolism
• Epinephrine/Adrenaline


  Increases blood flow to skeletal muscles, constricts arterioles, elevates blood pressure, increases heart rate, stimulates breakdown of glycogen
• Norepinephrine/Noradrenaline


  Increases blood flow to skeletal muscles
• Cortisol


  Controls metabolism of carbohydrates, proteins and fats
• Insulin


  Decreases blood glucose levels if high
• Glucagon


  Increases blood glucose levels if low
• Testosterone


  Promotes development of male sex characteristics
• Estrogen and Progesterone


  Promote development of female sex characteristics
• Growth Hormone Releasing Hormone (GHRH)


  Stimulates production of Growth Hormone
• Growth Hormone (GH)


  Stimulates growth in children and adolescents, maintains normal body structure in adults
• Somatostatin (GHIH)


  Growth hormone inhibiting hormone, inhibits production of GH
• Thyrotropin Releasing Hormone (TRH)


  Stimulates production of Thyroid Stimulating Hormone
• Thyroid Stimulating Hormone (TSH)


  Stimulates thyroid gland to secrete hormones
• Corticotropin Releasing Hormone (CRH)


  Stimulates production of Adrenocorticotropic Hormone
• Adrenocorticotropic Hormone (ACTH)


  Stimulates adrenal gland to secrete hormones
• Follicle Stimulating Hormone (FSH)


  Stimulates gonads (testes and ovaries) to secrete hormones
• Gonadotropin Releasing Hormone (GnRH)


  Stimulates production of FSH and LH
• Luteinizing Hormone (LH)


  Stimulates gonads (testes and ovaries) to secrete hormones
• Dopamine


  Prolactin releasing hormone (PRH)/prolactin inhibiting hormone (PIH)
• Prolactin (PRL)


  Controls release of prolactin, milk production
• Anti Diuretic Hormone (ADH)


  Regulates the amount of water excreted by the kidneys, promotes water reabsorption by the kidneys
• Oxytocin


  Controls contraction of the uterus, milk secretion
• Hormones


  • Secreted by endocrine glands
  • Regulate and coordinate a range of bodily functions
  • Affect specific target cells when they bind to receptors
  • Most are secreted quickly and in a short burst, some are secreted over longer periods for permanent changes
• Local hormones


  Act on the same cell (autocrine) or neighbouring cells (paracrine)
• Circulating hormones


  Travel around the body in the bloodstream
• Regulation of circulating hormones

  1. Nervous system signals

  2. Chemical changes in the blood

  3. Other hormones
• Blood glucose levels increase

  Insulin released from pancreas, stimulates uptake of glucose by cells
• Blood glucose levels decrease


  Glucagon released from pancreas, stimulates breakdown of glycogen into glucose
• During exercise


  Insulin not released, adrenaline and glucagon released, more glucose available for body cells
• Body temperature increases


  Hypothalamus starts cooling mechanisms like sweating and vasodilation
• Body temperature decreases


  Hypothalamus starts warming mechanisms like shivering and vasoconstriction
• Blood water levels increase

  Hypothalamus stimulates posterior pituitary to release less ADH, kidney reabsorbs less water
• Blood water levels decrease


  Hypothalamus stimulates posterior pituitary to release more ADH, kidney reabsorbs more water
• Positive feedback loops


  Accelerate change, drive systems towards a new stage (e.g. blood clotting, breastfeeding, childbirth contractions)
• Hypothalamus and pituitary gland

  • Responsible for homeostasis, maintaining a constant internal environment
  • Pituitary gland is located below the hypothalamus, connected via nerves and blood supply
  • Hypothalamus controls the pituitary gland, which influences other glands
  • Hypothalamus releases hormones that stimulate the anterior pituitary to release other hormones
  • Hypothalamus also controls the posterior pituitary, sending signals to release hormones stored there