Neurons

• Neurons can be divided according to their function:

  • sensory neurons (afferent neurons) carry impulses to CNS
  • motor neurons (efferent neurons) carry impulses from CNS to effectors (muscles and glands)
  • interneurons (association neurons) provide more complex reflexes, learning and memory
• Neurons can also be divided according to their structure

  • multipolar neuron has multiple extensions from the cell body
  • bipolar neuron has exactly two extensions from the cell body
  • Unipolar neuron has only one extension from the cell body
• Basic neuron structure:

  • cell body: enlarged part containing nucleus and other organelles
  • dendrites: short, cytoplasmic extensions that receive stimuli
  • axon: single long extension that conducts impulses from cell body
• The human brain contains 100 billion neurons
• The synapse is the end of the axon where the neuron passes on the signal to another cell. They release neurotransmitters
• Dendrites are highly branched, they can take lots of signals at the same time. They receive electrical signals from the neurons or stimuli
• The axon hillock is the start of the axon, they start the signal through action potential. The axon passes on the nerve impulse