reflexes

• The brain and spinal cord are apart of the central nervous system
• The nervous system:

  Enables humans to react to their surroundings and to coordinate their behaviour.

  It detects stimuli & co-ordinates a response to increase our chances of survival.
• Each SENSE ORGAN has special cells called RECEPTOR CELLS. Each receptor cell is sensitive to different things.
• How is the nervous system adapted for it’s function?

  • Made of several different types of specialised cells that are each highly adapted for their function
  • Specialised cells organised → tissues → organs → organ systems, that work together to carry out functions.
• Detecting stimuli – receptors are adapted to be able to convert energy from a stimulus into a signal that can be transmitted to the CNS.
• Reflexes are important because they allow us to respond to dangerous situations really quickly so that we are more likely to survive
• The brain may not always be involved in a reflex because reflex arcs always use the nearest co-ordinator. This helps to make the response really fast
• Neuroscientists study the brain by:

  • Studying patients with brain damage, electrically stimulating different parts of the brain and by using MRI scanning techniques
• Cornea - transparent + convex
• Iris - Pigmented muscle tissue; 2 types of muscle (circular & radial) allows the iris to change the size of the pupil
• Lens - Transparent, biconvex flexible disc; attached to ciliary muscle by suspensory ligaments which allows the thickness of the lens to be changed
• Retina - Lining of tissue at the back of the eye; contains 2 types of light receptors, the rods (work even in dim light but only detects intensity of light) & cones (only work in bright light, but detects different wavelengths/colours of light)
• Optic nerve - Bundle of sensory neurons at the back of the eye
• Sclera - Tough white outer layer of eye
• What is the function of rod cells?

  • Detect intensity of light (black/white vision)
  • Work in dim light → night vision.
• What is the function of rod cells and why do they have lots of mitochondria?

  • Detect intensity of light (black/white vision)
  • Work in dim light → night vision.
  • To release energy from respiration for generating a signal
• How can we see things?

  Light reflected from objects enters the eye & is focused onto the retina.
• What does a beam of light pass through to get to the retina?

  Conjunctiva; cornea; aqueous humour; pupil; lens; vitreous humour.
• Where can the beam change direction?

  Cornea & lens.
• Aqueous humour - The fluid in the outer cavity adding to the eye’s strength
• Vitreous humour - The fluid in the inner cavity adding to the eye’s strength