topic 2 - brain and eye

• How do painkillers prevent you from feeling pain ?

  • neurotransmitters diffuse through the synapse as a chemical signal
  • the neurotransmitters bind to the receptors to generate electrical new impulses
  • the impulse is then sent to the brain which is what allows you to feel the pain
  • painkillers reduce pain by preventing neurotransmitters from binding with the receptor
  • then a chemical impulse cannot be generated
  • which prevents the signal from being sent to the brain as no impulse is generated.
• what do sensory neurons do?

  carries impulse from the dendrites to the cell body then from the axon to the cns
• What is the role of the reflex arc?

  • stimuli is detected by the receptor
  • sensory neurone connects to the relay neurone in the cns to and unconscious part of the brain
  • the relay neurone then connects to the motor neurone
  • the motor neurone connects to the effector which is where the result is carried out by
• what are the function of neurones?

  they carry electrical impulses from one place to another
• what do receptors do?

  detect stimuli
• what do the brain and spinal cord do?

  receive and process information from receptors
• what do effectors do?

  carry out responses
• what is the function and structure of an axon?

  it is insulated by a fatty mylein sheath, this carries messages up and down the body
• what is the function and structure of a dendron?

  dendrons branch further as dendrites and they receive upcoming impulses from other neurones
• what is the synapse?

  its the gap between where two neurones meet . In the synapse an electrical signal is turned into a chemical signal then back into an electrical signal.
• what is the function of the cerebral cortex?

  it controls intelligence , senses , personality , conscience thought and high level functions.
• what is the function of the cerebellum?

  controls balance, co-ordination and muscular activity
• what is the function of the medulla?

  controls unconscious activities such as heart and breathing rate.
• what is the function of the hypothalamus?

  it regulates the temperature and water balance in the body
• How do receptors and effectors work?

  . receptor cells detect a change in environment

  . once the change is detected, electrical signals are sent along neurones

  . these move towards the cns , which is what co-ordinates responses

  . messages are then sent back along different neurones so that the muscles either contract or relax
• what are brain tumours?

  they are cells that divide rapidly and can squash some parts of the brain and prevent them from working
• what does a PET scan show?

  during a PET scan, the patient is injected with radioactive glucose . the cells that are most active take in more glucose than the ones that aren't active.
• what happens if the spinal cord is damaged?

  it reduces the flow of information between the brain and other parts of the body.
• what does a CT scan show?

  is shows the shapes and structures of the brain.

  An x-ray beam moves in a circular motion in the head and a detector can be used to measure the absorption of the x-rays .

  A computer then uses this information to build a view inside the body as a series of slices.
• A PET scan..?

  causes specific parts of the brain to become active.
• What is the difference between CT and PT scan?

  both CT and PET scans allows us to see the structures of the brain

  CT scans use x-ray breams whilst a PET scan uses a radioactive tracer

  CT scans give and image of the brain at particular times whereas PET scan allows you to see brain activity
• What's an issue with some of these brain tumour treatments?

  they can damage the brain and the body

  sometimes, the treatment may not work because the blood barrier only allows certain substances to get from the blood to the brain.
• How to treat brain tumours?

  the cells can be treated during radiation therapy

  they can also be killed by chemotherapy - this injects drugs that kill dividing cells
• how are electrical impulses generated in the synapse?

  the electrical impulse stimulates the release of a neurotransmitter at the synapse

  • the neurotransmitter diffuses across the synapse

  • which fits into the receiving neurone

  • this stimulates an electrical impulse in the receiving neurone messenger
• cornea


  allows light to pass through, so its transparent , so oxygen diffuses into it . causes light to refract
• iris


  controls how big or small the pupil is
• lens

  refracts light, it can change its shape , controlls how strongly light is refracted
• retina

  cone cells- sensitive to colour and dont work well in low light

  rod cells- only sees black and white
• optic nerve

  takes impulses generated by receptor cells and sends it to the brain
• to see near objects ?

  lens needs to get thicker as more ray refraction is needed
• to see distant objects

  lens gets thinner as only slight refraction of rays is needed
• why is somebody short sighted

  the eyeball is too long for the strength of the lens

  or the cornea is too sharply curved

  concave curved lens
• why is somebody long sighted ?

  the eye is too short and the lens is too thick

  the cornea isn't curved enough

  convex oval lens
• what are cateracts?

  • caused by a build up of protein in the lens , making it cloudy
  • can be fixed by removing the old lens and replacing it with artificial lens
• what is colour blindness 


  a defect in the cone cell which doesn't allow you to see certain colours
• how does lazer eye surgery work?

  • cuts away the cornea and changing its shape to change the way it referacts light
• how does synaptic transmission work?

  • synapses are gaps between two neurones
  • when the impulse reaches the end of the first neuron , neurotransmitters are released into the synapse
  • the neurotransmitters then diffuse along the synapse
  • when the neurotransmitter reaches the second neurone, it triggers an impulse in the next neuron
  • different neurotransmitters have different effects on the frequency and speed
• what does the mylein sheath do?

  allows nerve transmission to travel faster
• what is the function of the retina ?

  • sends impulses to the brain which interprets the information
• what is the function of the rod cells

  converts the light to nerve impulses in the brain