Outline flashcards for the ANS

• ANS


  • Generally not consciously controlled, though meditation/biofeedback can influence via somatic/special senses > limbic system > ANS
• Autonomic Motor System


  1. Preganglionic neuron (SC > autonomic ganglion)

  2. Postganglionic neuron (autonomic ganglion > effector)

  
• Preganglionic neuron


  • Cell body in lateral horn of SC or brainstem, myelinated
• Postganglionic neuron


  • Cell body in autonomic ganglion, unmyelinated, has varicosities instead of axon terminal
• Effectors (muscle/glands)


  • Most have dual innervation - parasympathetic & sympathetic which oppose each other
• Sympathetic division


  "Fight or flight" - dilates pupils, dilates bronchioles, vasodilation to skeletal muscle, vasoconstriction to smooth muscle not involved with "fight/flight", increases heart rate/contractility
• Parasympathetic division


  "Rest and digest" - mostly opposes sympathetic, focused on smooth muscle and glands
• Sympathetic division


  1. Preganglionic neurons from T1-L2/3 via white rami communicantes

  2. Postganglionic neurons return via grey communicating rami to anterior ramus of spinal nerve, or join nerve branches to heart/neck/shoulder, or follow blood vessels to abdomen/pelvis

  
• Sympathetic trunk ganglia


  • Paired ganglia lining in a row on either side of spinal cord (3 cervical, 11-12 thoracic, 4-5 lumbar, 4-5 sacral, 1 coccygeal)
• Prevertebral ganglia


  • Anterior to vertebral column, close to large abdominal arteries
• Sympathetic neurotransmitters


  Preganglionic - acetylcholine (ACh), Postganglionic - norepinephrine (NE) (mostly, with some epinephrine)
• Parasympathetic division


  1. Preganglionic neurons from nuclei of CN III, VII, IX & X and lateral grey horns of S2-S4

  2. Preganglionic neurons from brainstem are part of CN III, VII, IX, & X

  3. Preganglionic neurons from S2-S4 join to form parasympathetic splanchnic nerves

  
• Parasympathetic ganglia


  • Located close to the organs innervated (long preganglionic neuron, short postganglionic neuron), called terminal ganglia

  
• Vagus nerve (CN X)


  One of the most important parasympathetic nerves, innervates heart, lungs, stomach, intestines, liver/GB, pancreas, other viscera
• Parasympathetic neurotransmitter


  Acetylcholine (ACh)
• Cholinergic neurons


  • All sympathetic and parasympathetic preganglionic neurons
  • All postganglionic parasympathetic neurons
  • Sympathetic postganglionic neurons going to sweat glands
• Nicotinic receptors


  Excitatory to post synaptic cell, found on dendrites & cell bodies of sympathetic & parasympathetic postganglionic neurons & motor end plates

  
• Muscarinic receptors


  Can either excite or inhibit effector (e.g. pupil constriction, inhibits sphincters in GI system), found on plasma membranes of all parasympathetic effectors (cardiac/smooth muscle, glands) & sympathetic sweat glands
• Adrenergic neurons


  • Sympathetic postganglionic (most)

  
• Adrenergic receptors


  α1 & β1 - excitatory (vasoconstriction, increased HR/contractility)

  α2 & β2 - inhibitory (bronchodilation, pupil dilation, vasodilation in vessels going to skeletal muscle)

  β3 - brown adipose > thermogenesis (heat regulation)