Week 4

• Iris


  Controls how much light enters the pupil.
• Retina


  Made of receptor cells called rods and cones which detect light and changes it into electrical impulses.
• Fovea


  Area of the retina with highest concentration of cone cells that provides sharp vision.
• conjunctiva


  Protects and lubricates eye from dust and microorganisms and keeps eye moist.
• Suspensory Ligaments


  Attaches the lens to the ciliary muscles. Used in accommodation.
• Cornea


  It refracts the light and protects the eye. The cornea is transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface.
• Ciliary Muscles


  Contract and relax to change the shape of the lens in accommodation.
• Sclera


  Tough outer layer that protects the eye
• Pupil


  Hole in the center of the eye that lets light in.
• lens


  Focuses light onto the retina.
• Optic nerve


  The bundle of sensory neurones that carry the impulses to the brain.
• Choroid


  Dark layer containing many pigment cells. Stops light being reflected around inside of eye.
• Blind Spot


  Where the optic nerve leaves the back of the eye (no receptors)
• Vitreous humour


  A black jelly-like substance which helps to maintain the shape of the eye and absorbs the light so it doesn't reflect in you eye
• Iris Reflex


  Very bright light can damage the retina — so you have a reflex to protect it.

  1) Very bright light triggers a reflex that makes the pupil smaller, allowing less light in (in this case, light receptors detect the bright light and send a message along a sensory neurone to the brain. The message then travels along a relay neurone to a motor neurone,

  which tells giroular muscles in the iris to contract, making the pupil smaller.)

  2) The opposite process happens in dim light. This time, the brain tells the radial muscles to contract, which makes the pupil bigger.
• Distant objects


  1)The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight.

  2) This makes the lens go thin (less curved).

  3) So it refracts light by a smaller amount.
• Near objects


  1). The ciliary muscle contracts, which slackens the suspensory ligaments

  2). The lens becomes fat (more curved)

  3). This increases the amount by which it reflect light
• Short-sighted people


  Short-sighted people are unable to focus on distant objects. This occurs when the cornea or lens bends the light too much or the eyeball is too long. The images of distant objects are brought into focus in front of the retina.
• Long-sighted people


  Long-sighted people are unable to focus on near objects.

  This occurs when the cornea or lens doesn't bend the light enough or the eyeball is too short. The images of near objects are brought into focus behind the refing.
• What is A?


  Conjuntiva

  
• What is B?


  Lens

  
• What is C?


  Iris

  
• What is D?


  Sclera

  
• What is E?


  Ciliary Muscles

  
• What is F?


  Vitreous Humor

  
• What is G?

  
• Definition of stimuli?


  Change in environment
• What are receptors?


  specialised cells that are adapted to detect stimuli
• Where are receptors found?

  Organs
• What do receptors do?

  they communicate with effectors via the nervous system and/or hormonal system.
• What is in the CNS ( Central Nervous system)?

  Brain and Spinal Cord
• What are the 3 types of neurones?

  Sensory, motor and relay