homeostasis

• define homeostasis

  homeostasis is the regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• whats a stimulus 


  change in environment
• whats a receptor


  receptor detects stimuli
• whats the coordination centre

  receives and processes information from receptors
• whats the effector


  produces a response which restores optimum levels

  effector is usually a muscle/gland
• role of sensory neurones

  carry information as electrical impulses form the receptors to the ins
• role of motor neurone

  carry electrical impulses from cns to effectors
• whats a synapse


  connection between two neurones is called a synapse
• how does a synapse work

  the nerve signal s transferred by chemicals which diffuse across the gap

  these chemicals then set off electrical signals in the next neurone
• reflexes are


  automatic and rapid

  do not involve the conscious part of the brain
• when a stimulus is detected by a receptor

  electrical impulses are sent along a sensory neurone to the cns
• at the end of a sensory neurone there is a

  synapse- this realises chemicals and diffuses to the relay neurone in the cns where it triggers an electrical impulse

  which then passes across a relay neurone

  ten another synapse another chemical triggered an

  electrical impulse in motor neurone

  the electrical impulse now passes down the motor neurone to an effector

  then response
• 


  stimulus receptor sensory cns motor effector response
• the brain controls?


  complex behaviour It is made of billions of interconnected neurones and has different regions that carry out different functions
• what does the cerebral cortex do

  responsible for things like consciousness

  intelligence

  memory and language
• what does the cerebellum do

  responsible for muscle coordination
• what does medulla do

  controls heat and breathing rate
• why is it hard to investigate the brain

  protected by skull

  hard to assess

  extremely delicate
• the sclera is what function of the eye


  tough supporting wall of the eye
• cornea


  transparent outer layer found at the front of the eye

  it refracts light into the eye
• iris


  contains muscles that allow it to control the diameter of the pupil
• lens


  focuses the light onto the retina

  shape of lens controlled by colliery muscles and suspensory ligaments
• optic nerve


  carries impulses from receptors on the retina to the brain
• how does the eye focus on near objects

  the Hilary muscles contract which slackens the suspensory ligaments, they get looser

  the lens is then thicker and refracts light rays strongly
• how does the eye focus on distant objects


  ciliary muscles relax

  the suspensory ligaments are pulled tight

  lens is pulled thin

  only slightly (the lens) refracts light rays
• what is long sightedness and whats the scientific name for it

  hypernopia

  when the eye cannot focus on nearby objects but can on distant objects
• what cause hypernopia


  eye ball is too short

  so the light is focused behind the retina
• what lens will help with hypernopia

  convex lens
• what is short sightedness and what is the scientific name

  myopia

  can focus on nearby objects but cannot focus on distant objects
• what causes short sightedness

  eyeball is too long

  therefore the light is focused at point in front of the retina

  also when the lens is too thick
• what lens is for myopia

  concave
• treatments for eyes


  contact lenses

  laser eye surgery

  artificial lenses
• normal human body temp

  37
• what is body temperature monitored and controlled by

  the thermoregulatory centre in the brain
• what receptors dos the thermoregulatory centre contain

  receptors sensitive to the temperature of the blood,
• the skin contains..

  temperature receptors and sends nervous impulses to the thermoregulatory centre
• if body temperature is too hight

  sweat is produced from sweat glands onto the surface of the skin

  the sweat evaporates and takes energy from the body cooling the body down
• if body temperature is too high what happens with blood vessels

  blood vessels supplying the capillaries dilate (vasodilation)

  because they are dilated this means more blood flows through the capillaries

  heat transfers out of the blood o body temperature returns to normal level
• when body temp is tooo low

  blood vessels constrict, they get narrower,

  less blood flows through less heat is lost from body

  when we shiver our skeletal; muscles contract

  this increases the rate of respiration

  and transfers energy to warm the body
• key features of the nervous system

  fast

  but the effects are short lived