Crash Course Sympathetic and Parasympathetic

• The sympathetic nervous system responds to stress by prioritizing functions needed for immediate survival and suppressing less urgent functions
• Neurotransmitters


  Chemicals released by neurons to communicate across synapses
• Hormones


  Chemicals secreted by glands that circulate in the bloodstream
• Sympathetic nervous system signaling

  1. Brain sends action potentials down spinal cord

  2. Preganglionic neurons release acetylcholine in ganglia

  3. Postganglionic neurons release norepinephrine at effectors
• Acetylcholine (ACh)


  Neurotransmitter used in sympathetic ganglia and throughout the peripheral and central nervous systems
• Norepinephrine


  • Neurotransmitter released by postganglionic sympathetic neurons
  • Hormone released by adrenal glands
• Alpha receptors


  Receptors on smooth muscle that cause contraction when bound by norepinephrine or epinephrine
• Beta receptors


  Receptors on smooth muscle that cause relaxation when bound by norepinephrine or epinephrine
• Norepinephrine and epinephrine

  Can have opposite effects on smooth muscle depending on the type of receptors present
• The parasympathetic nervous system counteracts the sympathetic stress response, promoting rest and recovery
• Parasympathetic nervous system


  Calms the body, allows digestion, reproduction, waste excretion, fighting infections
• Parasympathetic and sympathetic systems have different structures - ganglia locations, neurotransmitters used
• Cranial nerves


  • Olfactory
  • Optic
  • Oculomotor
  • Trochlear
  • Trigeminal
  • Abducens
  • Facial
  • Auditory
  • Glossopharyngeal
  • Vagus
  • Spinal accessory
  • Hypoglossal
• Mnemonic for remembering cranial nerve names

  Oh, Oh, Oh, To Touch And To Feel Very Good Velvet- Ah Heaven
• Mnemonic for remembering cranial nerve types

  Some say marry money, but my brother says big brains matter more
• Vagus nerve


  • Stretches from brainstem to visceral organs, carries both sensory and motor functions, regulates automatic functions like heart rate, digestion
• Parasympathetic system is required for sexual function - provides relaxation and blood flow, while sympathetic system provides excitement
• Beta-2 receptors


  When norepinephrine and epinephrine bind to beta-2 receptors on smooth muscle, they cause the muscle to relax, leading to vasodilation and decreased blood pressure.
• Alpha-1 receptors


  When norepinephrine and epinephrine bind to alpha-1 receptors on smooth muscle, they cause the muscle to contract, leading to vasoconstriction and increased blood pressure.
• Smooth muscle


  A type of muscle that is found in the walls of various organs and structures in the body, including blood vessels, the digestive tract, and the respiratory system.
• Norepinephrine and epinephrine


  Hormones and neurotransmitters that are part of the body's sympathetic nervous system, which is responsible for the "fight or flight" response.