The Endocrine System

• The endocrine system is a chemical (hormonal) system
• the ability to detect change and to respond is called sensitivity
• response is a form of defense that allows organisms to survive
• exocrine glands are glands that release their products into ducts or tubes eg. sweat glands and ovaries
• endocrine glands are ductless glands that release hormones into the bloodstream eg. pancreas and ovaries
• a hormone is a chemical messenger produced by an endocrine gland and carried in the bloodstream to another part of the body where it has a specific effect
• hypothalamus - found in the brain and releases Growth Hormone releasing hormone (GHRH)
• Pituitary gland - many of its hormones trigger other glands to release theirs
• too much growth hormone often due to a tumor - gigantism - may require surgery
• too little GH - dwarfism - GP can give GH to children to prevent it
• pineal gland - secretes melatonin which helps to control sleep patterns
• the pancreas is both an exocrine and an endocrine gland
• pancreas - endocrine function - Islets of Langerhans are a special group of cells that make insulin which controls blood glucose levels
• pancreas - exocrine function - most of the cells in the pancreas produce enzymes which pass into the pancreatic duct and become active in the duodenum
• the adrenal glands - function - fight or flight hormone - produce adrenaline which increases the flow of blood to the brain, lungs, heart and skeletal muscle
• testes - produce testosterone
• ovaries - produce oestrogen and progesterone
• thyroid gland - produces thyroxine which controls matebolism