CH 19 Autonomic Nervous System

• ANS consists of

  1.Input

  2.Integrating centers

  3.Output

  4.Enteric division
• Input:

  autonomic (visceral) sensory neurons
• Interoreceptors-

  From inside body: chemoreceptors, mechanoreceptors, proprioceptors
• Integrating centers-

  interneurons in CNS
• Output:

  Autonomic motor nerves
• in the somatic nervous system we saw

  One neuron
• In Autonomic nervous system (ANS), we are going to see

  two neurons
• These neurons in ANS

  Effect HR, contractility, pupil size, BP
• outputs are going to be some type of a

  Neuron
• Two seperate systems that manage the ANS include

  Sympathetic & parasympathetic systems
• Enteric division consists of

  Specialized nerves/ganglia in GI tract
• generally, effects of the ANS are not

  Consciously controlled
• Somatic nervous system (SNS) has

  Just 1 lower motor neuron (LMN)
• Autonomic nervous system (ANS) has

  2 motor neurons in sequence
• The 2 motor neurons in sequence that the ANS contains include

  1.Preganglionic neuron

  2.Postganglionic neuron
• Ganglion is

  a collection of cell bodies outside of the CNS
• Nuclei:

  collections of cell bodies in the CNS (brain or SC)
• Preganglion neuron

  •SC lateral horn to autonomic ganglion

  •Cell body in lateral horn (SC/BS)

  •myelinated
• Postganglionic neuron

  •autonomic ganglion to effector (smooth/cardiac ms or gland)

  •cell body in autonomic ganglion

  •unmyelinated

  •varicosities
• Varicosities (in postganglionic neuron) are

  Numerous swellings to release NT
• Adrenal gland is

  a gland that sits ontop of the kidney
• Adrenal glands secrete

  Hormones
• Remember, sympathetic is

  “fight or flight”
• Rememeber, parasympathetic is

  “Rest & digest”
• Preganglionic neuron

  Goes directly to adrenal medulla
• Postganglionic neuron

  releases hormones epinephrine & norepinephrine
• Modified postganglionic neuron=

  Chromaffin cell
• Most effectors (ms/glands) have dual innervation-

  parasympathetic & sympathetic which oppose each other
• Sympathetic 


  “Fight or flight”

  dilates pupils, increases HR contractility
• Parasympathetic 


  “Rest & digest”

  mostly opposes sympathetic, focused on smooth ms & glands
• Sympathetic & Parasympathetic

  •often go to same organs

  •often oppose each other
• Sympathetic “Fight or Flight”

  •T1-L2/3

  •increases HR/contractility

  •relaxes bronchioles (lungs) & GI smooth ms‘s

  •vasodilation-sk ms

  •vasocontriction-other glands, restrains salivation, secretes epinephrine
• Vasodolation (sympathetic)


  A widening of blood vessels, leading to increased blood flow with flushing or warmth.
• Vasoconstriction (sympathetic)


  Vasoconstriction is the narrowing (constriction) of blood vessels 
• Parasympathetic “Rest & Digest”

  does opposite of sympathetic (fight or flight)

  •slows HR, stimulates flow of saliva, constricts bronchi, constricts pupil etc, contacts bladde, constricts breathing
• Both parasympathetic & sympathetic goes to

  Smooth ms, cardiac m, & glands
• Cranial nerves are part of the

  Parasympathetic system
• Sympathetic nervous system has 2 groups of ganglia

  •sympathetic trunk ganglia

  •Prevertebral ganglia
• sympathetic trunk/chain ganglia

  •line both sides of SC, runs up and down
• sympathetic trunk/chain ganglia (SNS)

  •3 cervical

  superior-head & heart

  middle & inferior-heart

  •11-12 thoracic

  •4-5 lumbar

  •4-5 sacral

  •1 coccygeal (R & L fused)