The Nervous System

• What is the overall function of the nervous system?

  - Control and coordination

  - Detect stimuli in the environment
• What is the main organ in the nervous system?

  The brain
• What type of cells is the nervous system mostly made of? And what is its job?

  Neurones

  Its job is to carry messages/impulses very fast
• How are neurones adapted to their function?

  1. Long; can transmit electrical impulses over long distances.

  2. Have myelin sheath; insulates the impulse so it travels faster.

  3. Have dendrites (branched endings); can connect to lots of other neurones.
• Which direction do motor neurones carry electrical impulses?

  From the CNS to a muscle or a gland.
• Where are the nerve endings of motor neurones found?

  On an effector.
• Effector meaning

  Muscle or gland
• Which direction do sensory neurones carry electrical impulses?

  From sense organs to the brain.
• Where do sensory neurones have their dendrites?

  In receptors
• What are receptors?

  Cells that detect stimuli
• What do ears detect?

  Sound waves, positioning and balance.
• What do eyes detect?

  Light
• What does the nose detect?

  Chemicals in the air.
• What does skin detect?

  Pressure, pain and temperature.
• What does the tongue detect?

  Chemicals in food and soluble chemicals.
• How does information get sent to the brain?

  Stimulus

  Receptor

  Coordinator

  Effector

  Response
• What do relay neurones help with?

  Reflex actions
• Where are relay neurons located?

  CNS
• What is the size of relay neurones?

  Short
• What is the myelin sheath made of?

  Schwann cells
• Is the myelin sheath continuous?

  No
• How does the myelin sheath change the speed of transmission of an electrical impulse?

  It increases the speed.
• What could happen if the myelin sheath breaks?

  The impulse might not be carried properly.
• Name a medical condition in which the myelin sheath degenerates.

  Multiple Sclerosis