peripheral nervous system - nerves, ganglia

• nerve - collections of axons (myelinated/unmyelinated)
  • separates into motor/sensory parts at origin
  • dorsal root - sensory axons
  • ventral root - motor axons
• ganglia - groups of neuron cell bodies outside the central nervous system
  • dorsal root ganglia - contains cell bodies of sensory neurons
  • motor neuron cell bodies found inside spinal cord
• somatic motor neurons stimulate skeletal muscles to contract
  • for each muscle stimulated to contract, its antagonist must be inhibited by hyperpolarizing the motor neuron

autonomic nervous system - contains sympathetic/parasympathetic areas, medulla oblongata 

• autonomic neurons control smooth muscles, cardiac muscles, glands
• medulla oblongata - controls the system
• 2 neurons used for each pathway (1 has cell body in central nervous system, other has cell body in autonomic ganglion)
• preganglionic neuron - 1st neuron, releases Ach at synapse
• postganglionic neuron - releases Ach in parasympathetic division, norepinephrine in sympathetic division
• sympathetic division - stimulates the adrenal gland to secrete epinephrine
  • prepares the body for fight or flight
  • norepinephrine released at postganglionic neuron synapses
• parasympathetic division - slows down heart, increases secretions
  • regulates organs by releasing Ach
  • ACh causes G proteins to open up ion channels >> hyperpolarization >> slows down cell

neuroglia - cells that support neurons

• supplies neurons w/ nutrients, gets rid of waste, provides immunity
• Schwann cells - produce myelin sheaths in peripheral nervous system
• oligodendrocytes - produce myelin sheaths in central nervous system