Endocrine System

• Endocrine System


  the endocrine influences metabolic activity by means of hormones

  = chem messengers secreted by cells into the extracellular fluids

  these messengers travel thru the blood + regulate the metabolic function of ther cells in the body

  binding of a hormone to cellular receptors initiates responses
• Hormonal Control


  reproduction

  growth + development

  maintenance of electrolyte, water + nutrient balance of blood

  regulation of cellular metabolism + energy balance

  mobilisation of body defences
• Exocrine Glands


  produce nonhormonal substances, like sweat + saliva

  have ducts that carry thses substances to a membrane surface
• Endocrine Glands


  ductless glands

  produce hormones, which releases into the surrounding tissue fluid

  typically have a rich vascular + lymphatic drainage that receives their hormones

  most of the hormone-producing cells in endocrine glands r arranged in cords/branching networks, which maximises contact between them + surrounding capillaries
• Glands of the Endocrine System

  the endocrine glands inc:

  pituitary

  thyroid

  parathyroid

  adrenal

  pineal

  
• Endocrinal Organs


  the hypothalamus, along w its neural functions, also produces + releases hormones = neuroendocrine organ

  in addition, several organs like pancreas, gonads (ovaries + testes) + placenta contain endocrine tissue
• Chemical Messengers - Hormones

  hormones = long-distance chemical signals that travel in blood/lymph thru out the body
• Chemical Messengers - Autocrines

  autocrines = short-distance chem signals that exert their effects on the same cells that secrete them

  e.g. certain prostaglandins released by smooth muscle cells cause those muscle cells to contract
• Chemical Messengers - Paracrines

  paracrines r also short-distance chem signals

  act locally (w in the same tissue) but affect cell types other than those releasing the paracrine chems

  e.g. somatostatin released by one pop of pancreatic cells inhibits the release of insulin by a diff pop of pancreatic cells