Neurons and synaptic transmissions

• How many neurons are in the human nervous system?

  100 billion neurons
• What is the primary means of communication in the nervous system?

  Transmitting signals electrically and chemically
• What are the three types of neurons?

  • Sensory neurons
  • Relay neurons
  • Motor neurons
• Where are 80% of neurons located?

  In the brain
• What is the function of sensory neurons?

  To carry signals from sensory receptors
• What do relay neurons do?

  Connect sensory and motor neurons
• What is the role of motor neurons?

  To carry signals to muscles and glands
• What is the basic structure shared by all neurons?

  Cell body, dendrites, and axon
• What does the cell body (soma) contain?

  A nucleus with genetic material
• What is the function of dendrites?

  Carry nerve impulses towards the cell body
• What does the axon do?

  Carries impulses away from the cell body
• What is the myelin sheath's role?

  Protects the axon and speeds up transmission
• What are nodes of Ranvier?

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

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

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

  A gap between two neurons
• What happens when a neuron is activated?

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

  The change in charge inside the neuron
• How do neurons communicate within neural networks?

  Through electrical and chemical signals
• What triggers the release of neurotransmitters?

  The arrival of an electrical impulse
• What are neurotransmitters?

  Chemicals that transmit signals across synapses
• What happens to neurotransmitters after they cross the synapse?

  They bind to postsynaptic receptor sites
• What is the direction of neurotransmitter travel?

  One-way from presynaptic to postsynaptic neuron
• How do neurotransmitters fit into receptor sites?

  Like a lock and key mechanism
• What is the function of acetylcholine (ACh)?

  Causes muscles to contract
• What effect does serotonin have on neurons?

  Causes inhibition and makes neurons less likely to fire
• What effect does adrenaline have on neurons?

  Causes excitation and increases positive charge
• What is summation in neuron firing?

  The net effect of excitatory and inhibitory signals
• What happens if the net effect on a postsynaptic neuron is inhibitory?

  The neuron is less likely to fire
• What triggers the action potential in a postsynaptic neuron?

  When the sum of signals reaches the threshold
• What happens to the inside of a postsynaptic neuron when it fires?

  It becomes positively charged