coordination and response

• stimulus


  any change in internal/external environment
• receptors


  sense organs that detect stimulus
• effectors


  cells that carry response to correct effect of stimulus
• central nervous system


  made up of brain and spinal cord only
• neurones


  cells that make up the nervous system
• synapse


  connection between 2 neurones
• axon


  nerve fibre that carries electrical impulses away from body cell
• reflexes


  rapid, automatic response of the nervous system that doesn’t involve the brain
• reflex arc


  pathway of reflex response/electrical impulses along neurones
• cornea 


  transparent lens that refracts (bends) as light enters the eye
• iris

  controls how much light enters the pupil
• lens


  transparent disc that change shape to focus light onto retina
• retina


  contains light receptor cells
• rods


  detect black and white
• cones


  detect colour
• optic nerve


  sensory neurone that carries impulses between the eye and brain
• pupil


  hole that allows light to enter
• conjunctiva


  clear membrane that lubricates and protects eye surface
• ciliary muscle


  ring muscle that contracts/relaxes to change shape of lens
• suspensory ligaments


  connect ciliary muscles to lens
• sclera


  tough outer layer that muscles attach to move the eyeball
• fovea


  area of retina with highest concentration of cone cells (sharper vision)
• aqueous humour


  watery liquid between cornea and lens
• vitreous humour


  jelly like liquid filling the eyeball
• choroid


  tissue lining the inside of the sclera to prevent reflection of light rays inside eyeball
• blind spot


  point at which optic nerve leaves the eye - no receptor cells
• pupil constriction 


  circular and radial muscles contraction/relaxing
• accommodation of light


  fine focusing of lens by contractions/relaxation of ciliary muscles
• hormones


  chemicals that travel in the blood
• adrenaline


  readies body for 'flight or fight' response
• insulin


  control blood sugar levels
• testosterone


  main sex hormones in males
• progesterone


  maintains pregnancy
• oestrogen


  main sex hormones in females
• ADH


  controls water content
• FSH/LH


  female sex hormones
• homoestasis 


  ability to maintain constant internal environment
• thermoregulation


  optimum temperature for enzymes in metabolic reactions for respiration
• vasodilation 


  dilation of arterioles near the skins surface to increase blood flow
• vasoconstriction


  constriction of arterioles near the skins surface to decrease blood flow