AQA GCSE Biology - Paper 1

• Homeostasis


  process by which organisms maintain a relatively stable internal environment
• Receptors


  Detect changes in stimuli
• Coordinators


  Receives information from receptors
• Effectors

  Bring about responses
• Sensory neurones


  Carry impulses from the receptors to the CNS
• Relay neurone


  Carry impulses from the sensory to motor neurone
• Motor neurone


  Carry impulses from CNS to effectors
• Reflex action


  Automatic, rapid responses
• Conscious part of brain


  Not used in a reflex action
• Cerebrum

  Controls memory, language, and thought
• Cerebellum


  Balance and coordination
• Hypothalamus


  Regulatory centre for temperature and water balance
• Retina


  light-sensitive tissue lining the back of the eyeball
• optic nerve


  carries neural impulses from the eye to the brain
• Sclera


  White of the eye
• Cornea


  The transparent tissue that covers the front of the eye.
• Iris


  colored part of the eye
• ciliary muscle


  Changes the shape of the lens
• suspensory ligaments


  hold the lens in place
• Contract to focus on nearly object

  Ciliary muscles (causing lens to become thicker)
• Suspenseful ligaments tighten


  When focussing on distant object
• short sighted


  When light focuses before the retina
• Concave lens


  Lens used to correct shortsightedness
• long sighted


  When light not focuses by time it reaches retina
• Convex lens


  Used to correct longsightedness
• Circular muscles


  Contract to make pupil constrict
• Radial muscles


  Contract to make pupil dilate
• Thermoregulatory centre


  Monitors temperature of blood and receives impulses from skin receptors
• Vasodilation


  Blood vessels widening to lose heat
• Vasoconstriction


  Blood vessels narrow to reduce heat loss
• Sweating


  Takes heat from body to evaporate
• Shivering


  Contraction and relaxation of muscles to generate heat
• Endocrine systems


  Glands that produce hormones
• Hormones


  Travel in blood to affect target organs
• pituitary gland


  Master gland that produces hormones to stimulate other glands to secrete hormones
• Pancreas


  Monitors and controls blood glucose levels
• Insulin


  Produced by pancreas when blood glucose levels are too high
• Glucagon


  Produced by pancreas when blood glucose levels fall
• Glucagon causes

  Glycogen to break down to release glucose into blood
• Insulin causes

  The liver to take up glucose and store as glycogen