homeostasis and response

• what is homeostasis 


  the maintaining of internal body levels such as such blood glucose, water and body temperature
• what is the CNS made up of?

  the brain and spinal cord
• CNS

  stimulus → receptor → coordinator → effector → response
• what do receptors do?

  detect a change
• what are our effectors?

  • muscles (contract)
  • glands (release hormones)
• what is the nervous system?

  fast and precise electrical impulses through nerves
• what does the endocrine system do?

  • relies on hormones
  • focuses on the entire body
  • slower, longer lasting and more generalised
• where are hormones released?

  into the bloodstream
• neurones

  • long
  • thin
  • have dendrites
  • myelin
  • axon
• CNS

  • receptors detect a stimulus
  • sensory neurones send information to the cns
  • then to the relay neurone
  • then to the motor neurone
  • then to the effector to carry out a response
• what is the reflex arc?

  unconscious actions that happen rapidly and are automatic
• parts of the brain

  cerebral cortex → controls consciousness, intelligence, memory, language as well as sight and hearing

  cerebellum → controls balance and muscle coordination

  medulla → controls unconscious activites such as breathing and heartbeat

  hypothalamus → regulated body temperature and sendds signals ot the pituitary gland

  brain stem → connects the brain to the spinal cord
• how do scientists study the brain?

  1. study people with brain damage
  2. electrically stimulate different parts of the brain using electrodes
  3. scan the brain using CT scans , PET scan and MRI scans
• why is treating the brain difficult?

  • a wide range of things can go wrong
  • surround brain tissue is fragile
  • brain is complex
• parts of the eye

  lens → changes its shape

  cornea → its transparent, has no blood vessels, light refracts

  optic nerve → impulses generated by receptor cells

  retina → where light focuses

  sclera → white coating of the eye for protection

  ciliary muscle → controls shape of the lens

  suspensory ligaments → controls shape of the lens
• to focus on a near object:

  1. ciliary muscles contract
  2. suspensory ligaments loosen
  3. the lens becomes thicker and light rays refract strongly
• to focus on a far object:

  1. ciliary muscles relax
  2. suspensory ligaments are pulled tight
  3. lens becomes thin and only slight light rays are refracted
• myopia → short sighted

  hyperopia → long sighted
• light intensity:

  bright light → pupils constrict

  dim light → pupils dilate
• thermoregulation

  control of our internal body temperatures
• ezymes

  low temperature → slow down

  37

  high temperature → denature
• thermoregulatory centre

  • part of the hypothalamus
  • receptors in our skin and blood vessels
• when we are cold

  • our body needs to conserve heat and warm up
  • our blood vessels contract (vasoconstriction)
  • hairs stand up to trap a small layer of insulating hair
  • shivering muscles contract
• when we are too hot

  • our blood vessels dilate (vasodilation) so heat is transferred to the surroundings
  • we sweat which evaporates and takes away heat with it
  • erector muscles relax
• the endocrine system

  made up of glands that secrete hormones in the bloodstream
• what is negative feedback

  when our body tries to counteract a change
• what is part of the endocrine system

  • pituitary gland
  • thyroid gland
  • adrenal gland
  • pancreas
  • testes
  • ovaries
• Pituitary gland

  • known as the master gland
  • sends out hormones that tells the body what to do
  • tells other glands to release their hormones
  • not part of the brain but attached to it (under the hypothalamus)
• thyroid gland

  • produces thyroxine
  • regulates metabolism and growth
  • is the pituitary gland detects low levels of thyroxine it will send out TSH to stimulate the thyroid
• adrenal gland

  • fight, flight or freeze response
  • increases heart rate
• pancreas

  • produces insulin which regulates blood glucose concentration
• testes

  • only found in males
  • produces testosterone
  • releases sperm
• ovaries

  • only found in females
  • produces oestrogen
  • releases eggs
• blood glucose concentration is controlled by

  • insulin
  • glucagon
• when there is too much glucose

  • the pancreas secretes insulin which binds to receptors in the blood
  • the excess glucose is taken in by the liver and form glycogen for storage
• when there are low levels of glucose

  • the body releases glucagon which converts the glycogen into glucose so that it can e released into the bloodstream
• type 1 diabetes

  • normally occurs in childhood
  • life long condition
  • when your pancreas produces too little insulin or none
  • leads to high levels
  • could make someone ill or kill them
  • inject insulin into the abdomen or thigh
• type 2 diabetes

  • older people who have had an unhealthy diet for too long
  • when your body becomes resistant to insulin - cells wont take glucose from the bloodstream
  • to treat you need a low sugar diet or regular exercise
• the main job of kidneys

  to remove waste products and filter the blood
• what is deamination

  when excess amino acids turn into fats and carbohydrates