Biology Paper 2

• Homeostasis is the regulation of conditions to maintain an optimum internal environment in response to internal or external change
• homeostasis controls:

  • body temperature
  • blood glucose levels
  • water levels
• homeostasis is important to maintain for enzyme and cell function
• homeostasis is controlled by the nervous system and the hormonal system
• receptors detect changes in the environment
• information is sent via hormones or nervous impulses
• The CNS processes information
• factors respond to a stimulus
• stimulus > receptor > coordinator > effector > response
• nerves transmit electrical impulses to send information
• nerves are bundle of nerve cells
• CNS is the brain and the spinal cord
• reflex actions:

  • Immediate and automatic
  • only use three neurones
  • Don’t involve the brain
  • Keep body safe
• reflex actions happen by:

  stimulus > receptor > sensory neurons > relay neurones > motor neurone > effector
• synapse is a gap between two neurones which neuro transmitters pass
• measuring reaction time practical:

  • meter ruler held above non dominant hand
  • ruler dropped randomly
  • catch ruler as fast as possible
  • table to convert cm into reaction time
• when the body is too cold:

  • reduce heat loss by radiation
  • vasoconstriction to reduce blood flow - narrow lumen
  • muscle contraction to increase respiration
  • hairs stand up
• when the body is too hot:

  • increase heat loss by radiation
  • vasodilation increased blood flow - wider lumen
  • hairs lie flat and sweating increases
• the endocrine system is made up of glands that secrete hormones directly into blood steam
• endocrine system compared to the nervous system:

  • chemicals not electrical impulses
  • blood not nerves
  • slower response time
  • longer effects
• pituitary (master) gland - secretes hormones that control other glands
• thyroid gland - produces thyroxine, regulates metabolism
• adrenal gland - produces adrenaline
• pancreas: produces insulin and glucagon, regulates blood glucose
• ovaries - produce oestrogen and progesterone
• testes - produce sperm and testosterone
• blood glucose level is monitored and controlled by the pancreas
• blood glucose levels increase after digesting a meal when insulin is released
• controlling blood glucose levels increasing is negative feedback has changed as being reversed
• Receptor > coordinator > insulin > effector > response
• when blood glucose levels are too low after exercise, glucagon is released
• glucagon being released causes cells to break down Glucose into the blood
• release of glucose:

  receptors > coordinators > glucagon > effector > response
• diabetes is caused when the blood glucose levels are not being controlled properly
• diabetes can cause high blood glucose levels
• type 1 diabetes: not enough insulin produced by the pancreas

  treatment: insulin injections to help lower blood glucose
• type 2 diabetes: insulin receptors do not respond to insulin anymore

  treatment: low carb diet and more exercise
• risk factor for type 2 diabetes is obesity
• pituituary gland is in the head
• throid gland is in the neck