Chapter 15: Autonomic Nervous System

1
Chapter 15 Autonomic Nervous System
2
Overview of ANS

• Main input to ANS comes from autonomic sensory
  neurons that are associated with interoceptors.
• Chemoreceptors that monitor pH
• Mechanoreceptors that monitor stretch
• Pain receptors produce conscious sensations
• Autonomic motor neurons regulate visceral
  activities.
• Limited conscious control of autonomic responses

3
ANS vs SNS
4
Sympathetic and Parasympathetic
5
Sympathetic and Parasympathetic
6
ANS anatomy

• Motor neurons
• Preganglionic neuron
• Cell body in CNS
• Type B myelinated axon that extends to autonomic
  ganglion.
• Postganglionic neuron
• Cell body in autonomic ganglion
• Forms synapses with preganglionic neuron
• Type C unmyelinated fiber that terminates on
  visceral effector

7
Preganglionic neurons

• Sympathetic division has cell bodies in the
  lateral horns of the gray matter in T1-12 and
  L1,2 and sometimes 3.
• Axonal output referred to as thoracolumbar
  outflow
• Parasympathetic division has cell bodies in
  cranial nerves III, VII, IX, and X and in the
  gray horns of S2-4.
• Axonal output referred to as craniosacral
  outflow.

8
(No Transcript)
9
(No Transcript)
10
Sympathetic ganglia

• Sympathetic trunk ganglia lie in a vertical row
  close to both sides of the vertebral column from
  the base of skull to coccyx
• Superior, middle and inferior cervical ganglia
• Postganglionic neurons innervate organs above
  diaphragm.
• Prevertebral ganglia lie anterior to vertebral
  column and close to abdominal arteries.
• Celiac, superior and inferior mesenteric ganglia
• Postganglionic neurons innervate organs below the
  diaphragm.

11
Parasympathetic ganglia

• Terminal ganglia are located close to area within
  wall of the visceral organ.
• Ciliary ganglion
• Pterygopalatine ganglion
• Submandibular ganglion
• Otic ganglion
• Axons are longer than those found in the
  sympathetic division.

12
Sympathetic postganglionic neurons

• Preganglionic neurons connect to postganglionic
  neurons in the following ways
• Preganglionic neuron synapses with postganglionic
  neuron in first ganglion it reaches
• Preganglionic neuron ascends or descends to
  another ganglion along sympathetic chain before
  synapsing with postganglionic neuron.
• An axon may project through a ganglion and
  synapse with a postglanglionic neuron in one of
  the prevertebral ganglia.
• Preganglionic sympathetic fibers synapse on the
  adrenal medulla.
• Preganglionic neurons can have numerous branches.

13
Parasympathetic postganglionic neurons

• Axons of preganglionic neurons project to
  visceral effectors and synapse on 4-5
  postganglionic neurons supplying a single
  visceral organ.

14
Autonomic plexuses

• Made up a tangled web of ganglia and axons found
  close to major arteries.
• Cardiac plexusheart
• Pulmonary plexuspulmonary branches
• Celiac plexusceliac and mesenteric arteries,
  liver, gall bladder, pancreas, stomach, spleen,
  and kidneys
• Mesenteric plexuslarge and small intestines
• Hypogastric plexuspelvic viscera
• Renal plexuskidneys and ureters

15
(No Transcript)
16
Structure of sympathetic division

• Cervical portion
• Superior cervical ganglion postganglionic neurons
  project to head and heart
• Middle and inferior cervical ganglia project to
  heart.
• Thoracic portionpostganglionic neurons project
  to thoracic viscera
• Lumbar portion

17
Structure of parasympathetic division

• Ciliary ganglion
• preganglionic nerves are in the oculomotor (III)
  nerve
• postganglionic neurons go to smooth muscles of
  the eye.
• Pterygopalatine
• Preganglionic neurons from facial (VII) nerve
• Postganglionic neurons project to nasal mucosa,
  palate, pharynx, and lacrimal glands.

18
Structure of parasympathetic division

• Submandibular ganglion
• preganglionic nerves from facial (VII) nerve
  postganglionic neurons go to sublingual and
  submandibular salivary glands
• Otic ganglia
• Preganglionic neurons from glossopharyngeal (IX)
  nerve
• Postganglionic neurons project to parotid
  salivary glands.

19
Cholinergic neurons and receptors

• Cholinergic neurons release ACh
• Cholinergic receptors
• Nicotinic receptors are present in postganglionic
  neurons and motor endplate
• Muscarinic receptors are present in membrane of
  all effectors (smooth muscle, cardiac muscle, and
  glands)

20
Cholinergic neurons and receptors
21
Cholinergic neurons and receptors
22
Cholinergic neurons and receptors
23
Adrenergic neurons and receptors

• Adrenergic neurons release norepinephrine (NE)
• Adrenergic receptors
• Alpha and beta receptors are on visceral
  effectors
• a1 and b1 are excitatory
• a1 and b2 are inhibitory
• b3 is on brown adipose tissue and is involved in
  thermogenesis

24
Adrenergic neurons and receptors
25
Physiological effects of ANS

• Autonomic tonethe balance between both
  sympathetic and parasympathetic activity.
• Sweat glands, arrector pili muscles, kidneys,
  spleen, and most blood vessels only get
  sympathetic input.
• Sympathetic response supports vigorous activity
  and rapid production of ATP
• Parasympathetic response supports functions that
  conserve and restore energy.

26
Sympathetic responses Fight or flight

• Pupils dilate
• Heart rate and blood pressure increase
• Airways dilate
• Blood vessels that supply kidneys and GI tract
  constrict
• Blood vessels that supply muscles, liver and
  adipose tissue dilate
• Liver cells break down glycogen to glucose and
  adipose tissue breaksdown triglycerides

27
Parasympathetic responses rest and digest

• SLUDDsalivation, lacrimation, urination,
  digestion, defecation
• Decreased heart rate
• Decreased diameter of airways
• Decreased diameter of the pupils

28
Autonomic reflexes

• Regulate controlled conditions in the body
• Blood pressure
• Digestion
• Defecation
• Urination
• The reflex arc organizes the response.
• Receptor
• Sensory neuron
• Integration center
• Motor neuron
• Effector

29
Autonomic reflexes

• Receptordistal end of the sensory neuron
• Sensory neuron--projects to CNS
• Integration centerhypothalamus and brain stem
  and spinal cord
• Motor neurons project from CNS through one or two
  synapses
• Effectoreffects on smooth muscle, cardiac
  muscle, and glands.

30
Autonomic control in CNS

• Hypothalamus is major control and integrator
• Receives sensory input
• Is connected to both ANS divisions
• Posterior and lateral parts control the
  sympathetic division.
• Anterior and medial parts control the
  parasympathetic division