endocrine system

• hormones


  chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and effect other tissues
• target organs


  organs that respond to a particular hormone
• hormones control things in organs and cells that need...


  constant adjustment
• pituitary gland


  the endocrine system's most influential gland: under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands
• thyroid


  this produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature
• why is thyroxine released?

  it plays an important role in regulating basal metabolic rate - the speed at which chemical reactions in the body occur while the body is at rest. it is also important for stimulation protein synthesis for growth and development
• thyroid stimulating hormone (TSH)

  stimulates secretion of thyroxine from thyroid gland
• adrenal gland


  this produces adrenaline, which increases the supply of oxygen and glucose to the cells in the brain and muscles
• why is adrenaline released?

  released in response to stressful or scary situations - brain sends nervous impulses to adrenal glands
• pancreas


  this produces insulin, which is used to regulate blood glucose levels
• ovaries


  produces oestrogen, which is involved in the menstrual cycle
• testes


  produces testosterone, which controls puberty and spencer production in males
• difference between nerves and hormones

  nerves:

  - very fast action

  - act for a very short time

  - act on a very precise area

  
  

  hormones:

  - slower action

  - act for a long time

  - act in a more general way