Structure+function of neurons

• How many neurons are in the human nervous system?

  100 billion
• What are the three types of neurons?

  • Sensory neurons
  • Relay neurons
  • Motor neurons
• What percentage of neurons are located in the brain?

  80%
• How do neurons communicate within the nervous system?

  By transmitting signals electrically and chemically
• What is the function of sensory neurons?

  They carry signals from sensory receptors
• What is the role of relay neurons?

  They connect sensory and motor neurons
• What do motor neurons do?

  They carry signals to muscles and glands
• What is the basic structure of a neuron?

  • Cell body (soma) with a nucleus
  • Dendrites for receiving impulses
  • Axon for transmitting impulses
  • Myelin sheath for protection and speed
  • Terminal buttons for communication
• What is the function of the cell body in a neuron?

  It contains the nucleus and genetic material
• What do dendrites do?

  They carry nerve impulses towards the cell body
• What is the role of the axon?

  It carries impulses away from the cell body
• What is the myelin sheath's function?

  It protects the axon and speeds up transmission
• What happens if the myelin sheath is continuous?

  It slows down the electrical impulse
• What are nodes of Ranvier?

  Gaps in the myelin sheath
• How do nodes of Ranvier affect impulse transmission?

  They speed up transmission by forcing jumps
• What are terminal buttons?

  They communicate with the next neuron
• What is the synapse?

  A gap between neurons for communication
• Where are the cell bodies of motor neurons located?

  In the central nervous system (CNS)
• Where are sensory neurons located?

  Outside of the CNS in the PNS
• What percentage of neurons are relay neurons?

  97%
• What is the resting state of a neuron?

  The inside is negatively charged
• What happens when a neuron is activated by a stimulus?

  The inside becomes positively charged
• What is an action potential?

  An electrical impulse traveling down the axon
• What does the electrical impulse do?

  It travels down the axon towards the end