Nervous System

• What does the nervous system enable humans to do?

  React to surroundings and coordinate behavior
• How does the nervous system communicate?

  Using electrical impulses very quickly
• What are the basic components of the nervous system?

  Billions of neurones
• What are the two ways conditions inside the body are controlled?

  • Chemical responses
  • Nervous responses
• What are receptors in the nervous system?

  Cells that recognize and respond to stimuli
• What is a stimulus?

  Something that sets off a reaction
• What do receptors detect?

  Changes in the environment
• What is the plural of stimulus?

  Stimuli
• What is the role of the coordination centre?

  Receives and processes information from receptors
• What are effectors?

  Organs, tissues, or cells that produce a response
• What responses can effectors bring about?

  Muscle contractions or hormone release
• What are nerve cells called?

  Neurones
• What do neurones carry?

  An electrical message or impulse
• What is a bundle of neurones called?

  A nerve
• What is the function of the axon in a neurone?

  To carry electrical signals quickly
• What is the myelin sheath?

  A fatty insulation around the axon
• What are dendrites?

  Tiny branches that receive incoming impulses
• What is a synapse?

  A tiny gap between two nerve cells
• What happens at a synapse?

  The electrical signal converts to a chemical signal
• What are neurotransmitters?

  Chemicals that pass nerve impulses across synapses
• How do neurotransmitters function across a synapse?

  They diffuse and bind with receptor molecules
• What do receptor molecules on the second neurone bind to?

  Specific neurotransmitters from the first neurone
• What initiates the transmission of an electrical impulse in the second neurone?

  Binding of neurotransmitters to receptor molecules
• What is the flow of information in the nervous system?

  • Stimulus → receptor
  • Coordinator (CNS)
  • Effector → response
• What are sense organs?

  Groups of receptors that respond to stimuli
• What stimuli do different sense organs respond to?

  • Skin: Touch, temperature
  • Tongue: Chemicals
  • Nose: Chemicals
  • Eye: Light
  • Ear: Sound
• What is an example of an effector response?

  A muscle contracting to move an arm
• What is another example of an effector response?

  A gland releasing a hormone into the blood
• What organ collects information from the environment?

  Eye
• What do the response cells in our eyes respond to?

  Wavelengths of visible light
• Where are the receptor cells in our eyes located?

  Retina
• How many types of receptor cells are in the eye?

  Two types
• What do rods detect?

  Low light intensity
• What are cones sensitive to?

  Bright, colored light
• What colors are cones sensitive to?

  Blue, green, and red
• What do rods and cones contain that makes them photosensitive?

  Photosensitive chemicals
• Which type of receptor cell is more numerous in the eye?

  Rods
• Where are cones concentrated in the retina?

  Fovea
• What is the function of the lens in the eye?

  Refracts (bends) light
• What do ciliary muscles do to the lens?

  Change its shape