Eyes, brain and nervous system

• Define homeostasis?

  regulation of internal conditions of a cell or organism to maintain optimum conditions for function
• What is homeostasis in response to?

  internal or external changes
• Why is homeostasis important?

  to maintain optimum conditions for enzyme action and cell functions
• Give 3 examples of conditions regulated in the body?

  blood glucose levels, body temp and water levels
• Describe how internal conditions are regulated?

  receptor detect a stimulus, the coordination system receives and processes information and the effectors bring responses to restore optimum levels
• What is a stimulus?

  a change in environment
• Give some examples of coordination centres?

  brain, spinal chord and pancreas
• Give 2 examples of an effector?

  muscle or gland
• Suggest why body temp should not be allowed to increase much?

  enzymes became denatured at high temperatures so they can't catalyse reactions
• What does the nervous system enable organisms to do?

  react to changes in surroundings and coordinate their behaviour
• Describe the overall structure of the human nervous system?

  central nervous system which is the brain and spinal cord, other nerves to run to and from the CNS
• Describe how information passes along neurones?

  as electrical impulses
• Define the term synapse?

  small gap between two neurones
• Describe how information passes across a synapse?

  when electrical impulse reaches end of neurone, a chemical is released which diffuses across synapse and attaches to next neurone triggering another electrical impulse
• What is a reflex action?

  an automatic and rapid response as it doesn't involve conscious part of the brain
• Why is a reflex action important?

  protective as helps minimise damage to body
• Why does a conscious action take longer than a reflex action?

  impulse has to travel to brain and back so pathway is longer and more synapses
• The brain controls complex behaviour and is made of billions of interconnected neurones
• Where is the cerebral cortex located?

  outer layer of the brain
• What is the function of the cerebral cortex?

  consciousness, intelligence, memory and language
• How does the cerebral cortex work?

  receives sensory input from the skin
• Where is the cerebellum located?

  back of brain below cerebral cortex
• What is the function of the cerebellum?

  movement, balance and muscle coordination
• Where is the medulla located?

  bottom of brain, connects to spinal chord
• What is the function of the medulla?

  regulates unconscious activities e.g. heartbeat and breathing
• What are the three methods used by neuroscientists to map regions of brain to particular functions?

  studying patients with brain damage, electrically stimulating parts of the brain, MRI techniques
• Explain the difficulties of investigating brain function and treating brain damage and disease?

  brain is very delicate so surgery could cause damage, complex so difficult to work out what performs each function
• Finish the statement.... the eye is a sense organ that contains?

  receptors which are sensitive to light intensity and colour
• How is the structure of the retina related to its function?

  contains receptors sensitive to light intensity and colour sends impulses to optic nerve
• How is the structure of the optic nerve related to its function?

  made of many neurones which carry electrical impulses from retina to brain
• How is the structure of the sclera related to its function?

  tough white outer layer which protects the eye
• How is the structure of the cornea related to its function?

  transparent and curved layer at front of eye which refracts light into eye
• How is the structure of the lens related to its function?

  flexible and transparent biconvex disc which focuses light on retina
• How is the structure of the iris related to its function?

  ring of muscle which controls pupil diameter so how much light enters eye
• How is the structure of the ciliary muscle related to its function?

  muscles connected to lens which contract to change lens shape
• How is the structure of the suspensory ligament related to its function?

  connects lens to ciliary muscles which help control lens shape
• Explain the response of the eye to dim light?

  pupil dilates because iris radial muscles contract and circular muscles relax, increasing amount of light entering eye
• Explain the response of the eye to bright light?

  pupil constricts because in the iris circular muscles contract and radial muscles relax, this decreases amount of light entering eye
• What is accommodation?

  the changing shape of lens to focus on near or distant objects
• What is myopia?

  short sightedness so can't focus on distant objects