Exam 3 - LECTURE 18 Autonomic Nervous System

Question 1

What are chracteristics of the Autonomic nervous system?

Answer 1

• Sympathetic
  
  • originates from spinal cord levels T1 - L2
• Parasympathetic
  
  • Originates from CN 3,7,9,10 and S2 - S4
• Entirely motor
• Dual innervation for most structures
  
  • innervated by both sympathetic and parasympathetic structures

Question 2

What are the two neuron pathways?

Answer 2

• Preganglionic neuron
  
  • always myleinated
  • synapses with postganglionic neuron
  • USES ACETYLCHOLINE
• Postganglioninc Neuron
  
  • Originates from ganglion
  • Never Myleinated
  • USES NOREPINEPHRINE

Question 3

How do parasympathetic nerves and sympathetic nerves compare?

Answer 3

• Parasympathetic nerves
  
  • synapse on microscopic ganglionic cells embedded in walls of targets organs
  • Primarily responsible for maintaining and coordinating gut function
    
    • secretion of digestive fluids
    • peristaltic contraction
• Sympathetic Nerves
  
  • Synapse on cells located in large visible ganglia located in dorsal wall of coelom, typicall anterior to abdominal aorta
  • Involved in responses to anger,fear and anxiety
    
    • Inhibits digestive fluid secretion
    • inhibits peristalsis
    • closes involuntary sphincters
    • contricts blood flow to gut

Question 4

What is the Thorarcic sympathetic chain?

Answer 4

• Cervical ganglia
  
  • superior
  • middle
  • inferior
• Lies against neck of ribs and costovertebral junctions
• 12 thoracic ganglia pairs
  
  • first one often fused with inferior cervical ganglion
  • referred to as stellate ganglion collectively
• Preganglion sympathetic supply to thoracic biscera are from t1 to 5
• post ganglionic are from
  
  • superor, middle, and inferior cervical ganglia
  • t1- t5
• They exit the chain as direct fibers and travel downwards to enter the thorax as cardiopulmonary splanchnic nerves travel on their own and do not accompany other nerves or vesels
  
  • function
    
    • cornary artery dilation
    • increased heart rate
    • bronchodilation

Question 5

Question 6

How are the abdominal organs sympathetically innervated ?

Answer 6

• Preganglioninc sympathetic fibers that supply the organs follow same initiatlly as those that follow the skin and thoracic structures
  
  • preganglioninc fibers do not synapse in the paravertebral ganglia but pass medially to synapse on ganglion cells located around the aorta (preaortic ganglia)
  • splanchic nerve is a bundle of preganglionic fibers traveling to preaortic ganglia
  • located near origins of mahor arterial branchies from abdominal aorta
  • Postganglionic fibers travels form the preaortic ganglia to their target organs by following the arterial banches

Question 7

What are splanchnic nerves?

Answer 7

• Composed of preganglionic fibers and visceral sensory fibers
• supply abdominal viscera
• synapse in prevertbral ganglia
• Greater
  
  • t5 -t9
  • synapse in the celiac ganglion
• lesser
  
  • t10 - t11
  • synapses in the superior mesenteric ganglion
• least
  
  • t 12
    
    • synapse in the aorticorneal ganglion

Question 8

What is the abdominal synpathetic trunk?

Answer 8

• paravertebral
  
  • continous with thoracic symathetic trunk
  • lumbar splanchnic nerves (t11 - l2)
  • Inferior mesenteric ganglion (prevertebral)
  • Superior and inferior hypogastric plexuses
    
    • sympathetic innervation to
      
      • descending colon and sigmoid colon
      • rectus, pelvic structures

Question 9

What is the vagus nerve?

Answer 9

• Cranial nerve X
• Major parasympathetic supply to thoracic and abominal viscera
• Branches into
  
  • cardiac branches to cardiac plexus
  • pulmonary branches to pulmonary plexus
  • esophageal branches to esophageal plexus
  • left recurrent laryngeal nerve form left vagus
    
    • hooks around arc of aorta to left of ligamentum arteriosum
  • Right reccurent laryngeal nerve from right vagus
    
    • hooks around subclavian artery
    • arises neck, not thorax

Question 10

How does the vagus nerve run?

Answer 10

• Parallel to esophagus
  
  • innervates esophagus
• left vagus nerve
  
  • becomes anterior vagal trunk
• Right vagus nerve
  
  • becomes posterior vagal trunk
• passes posterior to root of lung on each side
• pierces diaphragm with esophagus
• becomes gastric nerve
• supplies viscera thoracic cavity