Neuron Structure and Function

• The dendrites are the receptive region of the neuron.
• The cell body is the part of the neuron that contains the nucleus and is responsible for receiving and sending signals.
• The axon is the part of the neuron that is responsible for generating, conducting, initiating action potentials.
• The axon hillock is the connection between the cell body and the axon.
• The axon myelin sheath is made of fat and protein, and functions to insulate the axon.
• In the CNS, the myelin sheath is made of oligodendrocytes. In the PNS, the myelin sheath is made of Schwann cells.
• The Nodes of Ranvier are gaps in the myelin sheath, and are needed for Saltatory conduction.
• Telodentria are the branches at the end of the axon. At the end of the axon is where the axon terminals are, they contain neurotransmitters.
• The synapse is the extracellular space where neurotransmitters are released. The three structures of the synapse are the presynaptic neuron (neurotransmitter), synaptic cleft, and postsynaptic cell (receptors).
• The four characteristics of neurons are:

  1. Extreme longevity
  2. Amitotic - nonregenerative
  3. High metabolic rate
  4. Irritability - able to respond to stimuli
• Saltatory conduction involves the Nodes of Ranvier and Schwann cells in the PNS. It speeds up the delivery of action potential.
• Action potential is another way to say nerve impulse.
• Neurons are the functional units of nervous tissue, while neuralgia are the supporting cells.
• Resting membrane potential is -70mV, with lots of K+ inside and Na+ outside.
• Voltage gated channels are found on the axon, and open due to a change in voltage (threshold). Chemically gated channels are found on the cell body and dendrites.
• Graded potentials, or local potentials, involve chemical gated channels which are activated by neurotransmitters.
• Depolarization is when the cell interior becomes more positive.

  Hyperpolarization is when the cell interior becomes more negative.
• The threshold level is -55mV for the action potential to occur.
• Action potential involves voltage gated channels, and can conduct in two ways; local/graded conduction and saltatory conduction.

  Local conduction happens on unmyelinated neurons, and saltatory is only on myelinated.
• Action potential involves two stages; depolarization and repolarization.

  Depolarization is when voltage gated channels allow Na+ to enter the axon, making the charge more positive.

  Repolarization is when voltage gated channels allow K+ to leave the axon, returning the charge to resting potential.
• After action potential, the sodium potassium pump brings Na+ and K+ concentrations back to normal by using ATP in active transport.
• The three types of neurons are the sensory neurons, interneurons, and motor neurons.

  • Sensor neurons carry info to CNS.
  • Interneurons are found only in CNS.
  • Moto neurons carry info away from CNS.