Endocrine System

• How do hormones trigger a response?

  Glands are stimulated which causes hormones to secrete

  The hormones diffuse directly into the blood, and then they're taken around the body by the circulatory system

  They then diffuse out of the blood all over the body, but each hormone will only bind to specific receptors, found on the membranes of target cells, for that hormone

  The hormones trigger a response in the target cell
• Examples of major glands?

  Pituitary gland - releases hormones to control other glands in the endocrine system

  Adrenal gland - produces adrenaline. Responsible for 'fight or flight'

  Thyroid gland - produces thyroxine. Responsible for the body's metabolic rate

  Pancreas - releases insulin and glucagon. Responsible for regulating blood sugar level
• Why is the endocrine system slow?

  They aren't released directly onto their target cells, they must travel in the blood to get there.

  They aren't broken down quickly, so the effects of hormones can last much longer.

  Hormones are transported all over the body, so the response may be widespread if the target cells are widepsread.
• How does the hypothalamus help coordinate the 'fight or flight' response?


  In the initial shock response, the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system.

  This stimulates the adrenal medulla within the adrenal glands.

  This releases adrenaline and noradrenaline into the bloodstream.

  These hormones affect the body.

  The result of these changes is that the body is ready to use energy to deal with the stressful situation
• In what way does the 'fight or flight' response affect the body?


  Blood pressure and heart rate are increased to get blood quickly to areas of the body that needs activity

  Digestion decreases so that blood can be direction to the brain and muscles.

  Pupils dilate so more light can enter to eye to allow for clearer vision.

  Breathing rate increases so that more oxygen can be sent to the muscles.