Neurons

• How many neurons are there in the human nervous system?

  About 100 billion
• Where are 80% of neurons located in the human body?

  In the brain
• What is the primary function of neurons in the nervous system?

  To transmit signals electrically and chemically
• What is the general structure of a neuron?

  1. Dendrite receives a signal
  2. Signal carried towards the cell body
  3. Signal travels along the axon
  4. Terminal boutons pass the signal to the next neuron
• What are the components of a neuron?

  Cell body, dendrites, axon, myelin sheath, terminal buttons
• What is the function of the myelin sheath?

  To protect the axon and speed up transmission
• What are nodes of Ranvier?

  Segments in the myelin sheath that speed up transmission
• What is the role of terminal buttons in a neuron?

  To communicate with the next neuron across a synapse
• What are the three main types of neurons based on their function?

  1. Sensory neurons: Transmit information from senses to the CNS
  2. Motor neurons: Transmit information between CNS and organs/muscles
  3. Relay neurons: Connect neurons to other neurons within the CNS
• What do sensory neurons do?

  Transmit information from the senses to the central nervous system
• What is the function of motor neurons?

  Transmit information between the central nervous system and organs/muscles
• What do relay neurons do?

  Connect neurons to other neurons and transmit information within the CNS
• What is the charge of a neuron in its resting state?

  Negatively charged inside compared to the outside
• What happens when a neuron is activated by a stimulus?

  The inside of the cell becomes positively charged, causing an action potential
• What does the electrical impulse do once it travels down the axon?

  It travels towards the end of the neuron
• What is synaptic transmission?

  The process that enables the signal to pass to the next neuron
• What are the key features of synaptic transmission?

  • Neurons communicate in neural networks
  • Each neuron is separated by a synapse
  • Signals within neurons are transmitted electrically
  • Signals between neurons are transmitted chemically
• What is the process of synaptic transmission?

  1. Impulse travels down the axon
  2. Impulse reaches presynaptic terminal
  3. Neurotransmitter is released and diffuses across the synapse
  4. Neurotransmitter fits into postsynaptic receptor site
  5. Neurotransmitter is taken up by the receiving neuron
  6. Neurotransmitter has excitation or inhibition effects
• What are neurotransmitters?

  Chemicals that transmit signals across synapses
• Name two examples of excitatory neurotransmitters.

  Acetylcholine and adrenaline
• Name an example of an inhibitory neurotransmitter.

  GABA and serotonin
• What effect does adrenaline have on the post-synaptic neuron?

  It causes excitation by increasing its positive charge
• What effect does serotonin have on the receiving neuron?

  It causes inhibition, making the neuron less likely to fire