Homeostasis

• homeostasis is maintaining a stable internal bodily environment
• negative feedback counteracts changes in your body in order to keep it stable
• a stimulus is a change in the environment
• homeostasis in the body includes the control of:

  • blood glucose concentration
  • temperature
  • water levels
• the Nervous System consists of:

  • The Central Nervous System - the brain and spinal chord
  • The peripheral nervous system - nerve cells that carry information to or from the CNS
• The coordination centre (such as the brain, spinal chord and pancreas) receives and processes information from the receptors
• Effectors bring responses to the body, such as muscles and glands.
• there are three main types of neurone - sensory, motor and relay

  
• information from receptors passes along neurones as electrical impulses to co-ordinators such as the CNS
• Stimulus → receptor → coordinator → effector → response

  
• skin detects -

  • touch
  • temperature
  • pain
• tongue detects -

  • chemicals (in food or drink)
• nose detects -

  • chemicals (in air)
• eyes detect -

  • light
• ears detect -

  • sound
  • position of head
• neurotransmitters are release across the synapse
• Nervous reaction -

  • very fast action
  • act for a very short time
  • act on a very precise area
• Hormonal reaction -

  • slower action
  • act for a long time
  • act in a more general way
• the endocrine system is a network of glands that secrete hormones into the bloodstream
• Pituitary gland -

  • produces many hormones that regulate bodily conditions
  • these hormones act on other glands, directing them to release hormones that bring about change
• Thyroid -

  • produces Thyroxine
  • regulates metabolism, heart rate and temperature
• Adrenal gland -

  • produces Adrenaline
  • prepares body for 'fight or flight'
• Pancreas -

  • produces Insulin
  • regulates blood glucose levels
• Ovaries -

  • produces Oestrogen (involved in the menstrual cycle)
• Testes -

  • produces Testosterone
  • controls puberty and sperm production
• Type 1 Diabetes -

  • the Pancreas produces little or no Insulin
  • meaning a persons blood glucose levels can rise to a level that can kill them
  • Insulin shots can be used to regulate blood glucose levels
• Type 2 Diabetes -

  • a person becomes resistant to their own Insulin
  • can also cause blood glucose to rise to a deadly level
  • being overweight can increase chances of developing it
  • can be controlled by exercise and by having a carbohydrate-controlled diet
• Menstrual cycle stages -

  1. menstruation starts, uterus lining breaks down
  2. uterus lining builds up, getting ready to receive fertilised egg
  3. egg develops and is released, this is called Ovulation
  4. the wall is then maintained, the cycle repeats