Nerves + Eyes

Cards (26)

  • Stimulus - This is the change in environment which will bring about a response
  • Receptor - This detects the change in the environment it is usually one of the sense organs.
  • Effector - Brings about the response : is usually a muscle which contracts of a gland which secretes a hormone.
  • Example of Receptors:
    • Ear
    • Eye
    • Nose
    • Temperature Receptors
    • Pressure Receptors
    • Pain Receptors
  • The brain and spinal cord make up our central nervous system (CNS).
  • There are 3 types of neurones - sensory neurones, relay neurones and motor neurones.
  • Impulses from receptors pass along sensory neurones until they have reached the brain and spinal cord.
  • Relay neurones in the brain and spinal cord pass impulses from sensory neurones to motor neurones
  • Impulses pass to effectors (muscles or glands) along motor neurones.
  • A reflex action is a rapid automatic response to a stimulus (for example when a bright light shines in the eye the pupil gets smaller).
  • The brain is not involved - you cannot stop the reflex and often are not even aware it is happening
  • Reflex actions help to protect the body from damage.
  • Energy always needs to be converted to electrical energy as that is how messages are passed.
  • A synapse is a gap between two neurones.
    • Impulses arriving at a synapse cause the end of an axon to secrete a chemical, called a neurotransmitter.
    • This chemical diffuses across the gap and attaches to receptors on the membrane of the second neurone (the post-synaptic membrane).
  • Fovea - The region of the retina with the greatest number of cones.
  • Suspensory ligaments - hold the lens in place.
  • Cornea - protects the eyes’ surface and focuses light rays.
  • lens - focuses light on the retina
  • Iris - regulates the amount of light entering the eye.
  • Ciliary Muscles - Change the shape of the lens.
  • Optic Nerve - consists of many neurones which carry impulses from the retina to the brain.
  • Retina - Senses light and consist of rod and cone cells.
  • Blind spot - The region where the optic nerve leaves the eye - there is no rods and cones here ad therefore no image is formed.
  • Rod Cells:
    • Work well in dim light
    • Cannot distinguish between different colours
    • Image produced is black and white
    • Found all over the retina
  • Cone Cells:
    • Work well in bright light
    • There are 3 types that are sensitive to red, green and blue
    • Colour produced in an image
    • Found concentrated in a region of the retina called the fovea