Endocrine System, Kidneys, Negative Feedback

• During exercise the skin appears red, what is this cause?

  dilation of blood vessels in skin
• What is the endocrine system?

  system of glands which secrete hormones directly into bloodstream
• What is a hormone?

  chemical messenger secreted by a gland that travels in blood to target organ
• What does the thyroid gland secrete?

  thyroxine
• What does the adrenal gland secrete?

  adrenaline
• What does the pancreas gland secrete?

  insulin and glucagon
• What does the ovary gland secrete?

  oestrogen and progesterone
• What does the testes gland secrete?

  testosterone
• Why is the pituitary gland referred to as the master gland?

  secretes several hormones into blood which act on other glands to stimulate release of other hormones
• Describe how coordination by the endocrine system is different from coordination by the nervous system?

  endocrine system effects are slower but longer lasting, endocrine uses hormones in blood while nervous system uses electrical impulses in neurons
• What organ monitors and controls blood glucose concentration?

  pancreas
• Explain how pancreas responds when blood glucose conc. is too high?

  pancreas secretes insul, insulin causes glucose to diffuse from blood to liver and muscle cells where excess glucose is converted to glycogen for storage so blood glucose conc. decreases
• Explain how the pancreas responds when blood glucose conc. is too low?

  pancreas secretes hormone glucagon which triggers breakdown of glycogen into glucose in liver cells, glucose diffuses into blood so blood glucose conc. increases
• How is blood glucose conc. controlled using negative feedback?

  when blood glucose conc. rises or falls below optimum, a hormone is secreted by pancreas which returns conc. to normal
• What is type 1 diabetes and how is it treated?

  pancreas doesn't produce enough insulin and treated by insulin injections
• What is type 2 diabetes and how is it treated?

  body cells stop responding to insulin and treated by controlled carbohydrates and regular exercise
• What is a risk factor for type 2 diabetes?

  obesity
• Explain why water and ions need to be balanced in the body?

  if body fluid too concentrated cells lose too much water by osmosis and shrink but if too dilute, cells gain too much water by osmosis and burst
• how are water, ions and urea lost from the body?

  water via lungs during exhalation, water, ions and urea from skin in sweat, excess water, ions and urea removed via kidneys in urine
• What causes excess amino acids in the body and how are the excreted safely?

  digestion of proteins in diet, excess amino acids deaminated in liver to form ammonia which is toxic so converted into urea, urea excreted via urine
• What are the 2 ways a healthy kidney produces urine?

  filtration of blood and selective reabsorption
• Describe filtration of blood?

  water, glucose, ions and urea pass through filter into kidney tubules, proteins too large to pass through
• Describe sselective reabsorption?

  all glucose, some ions and water, no urea reabsorbed
• Describe how the water level in body is controlled?

  higher concentration of blood causes ADH release from pituitary gland, ADH increases permeability of kidney tules so more water reabsorbed, small volume of more concentrated urine controlled by negative feedback
• Explain the consequences of kidney failure?

  toxic substances build up like urea and incorrect water balance and ion concentration which damages cells by osmosis
• What are the two main ways of treating kidney failure?

  kidney dialysis and kidney transplant
• Describe the basis principles of dialysis?

  blood passes over partially permeable membrane, dialysis fluid contains same conc. of glucose and ions as healthy blood but no urea
• Explain the role of the hormone adrenaline in the body?

  increases heart rate to boost delivery of oxygen and glucose to brain and muscles so more energy can be released via respiration to prepare body for fight or flight
• When and where is adrenaline produced?

  adrenal glands in times of fear or stress
• Describe the role of thyroxine in the body?

  stimulates basal metabolic rate which plays an important role in growth and development
• Describe what happens in negtive feedback?

  receptors detect levels are too low/high, effectors respond to counteract change, levels restored to normal
• Describe how thryoxine is controlled by negative feedback when levels are low?

  pituitary gland secretes more TSH stimulating thyroid to release more thyroxine so levels in blood rise
• Describe how thyroxine is controlled by negative feedback when levels are higher?

  thyroxine stops secretion of TSH from pituitary gland so less thyroxine releases and level decreases