regarding autonomic nervous system and its anatomy and clinical tests

1. AUTONOMIC NERVOUS SYSTEM
ANATOMY AND TESTS
Arvind kulkarni

2. Introduction
• Autonomous – self driven .
• Usually self driven up to the point that they
may not involve conscious control .
• Highly integrated with other neural circuits.
• It is the system that controls non striated
muscles and glands .
• The boundary between autonomic and non-
autonomic systems is blurry .

3. • Central autonomic centers- hypothalamus,
amygdala, basal forebrain , ventral striatum ,
brainstem and spinal cord .
• Peripheral autonomic system- sympathetic
and parasympathetic divisions .

4. Divisions
• Sympathetic ( thoracolumbar ) system
• Parasympathetic ( craniosacral ) system
• Enteric system .

5. Sympathetic Parasympathetic
Preganglionic fibers arise from IML
column of T1-L3
Cranial outflow – GVE of 3rd ,7th , 9th ,10th ,
bulbar portion of 11th
Sacral outflow- fibers from S2-S4 of SC.
Preganglionic fibers are short terminate
on ganglia some distance away from
viscera
Preganglionic fibers are long – end in
peripheral ganglia near or on the viscera
One Preganglionic fibers synapse with
many post ganglionic -
One Preganglionic fiber synapse with only
one post ganglionic
Prevertebral ganglia-viscera of abdomen
and pelvis.
Para vertebral sympathetic chain
Collateral ganglia
Terminal ganglia.
e.g.- E-W nucleus-ciliary , sup salivatory
nucleus- submandibular and inf salivatory
nucleus-otic ,lacrimal- pterygopalatine, n
ambiguus.
Pelvic splanchnic nerves

10. Adrenergic Synaptic Transmission
• Transmission at these synapses is called
adrenergic:
Norepinephrine
released by most postganglionic sympathetic
nerve fibers.
Epinephrine,
released by the adrenal medulla
• Collectively called Catecholamines

11. Responses to Adrenergic Stimulation
• Beta adrenergic receptors:
Produce their effects by stimulating production of
cAMP
NE binds to receptor
G-protein dissociates into
a subunit or
bg- complex

12. Responses to Adrenergic Stimulation
• Depending upon tissue, either a subunit or
bg-complex produces the effects
•Alpha subunit-
Activates adenylate cyclase
 Producing cAMP
cAMP activates protein kinase
Opening ion channels

13. Responses to Adrenergic Stimulation (continued)
• Has both excitatory and inhibitory effects.
• Responses due to different membrane
receptor proteins.
a1 : constricts visceral smooth muscles.
a2 : contraction of smooth muscle.
b1 : increases HR and force of contraction.
b2 : relaxes bronchial smooth muscles.
b3: adipose tissue, function unknown

14. Anatomy of the chain
• Rami communicantes from the spinal nerves
connect to the chain

16. A closer look at spinal nerves

17. Routes of Preganglionic Axons
• Cell bodies of neurons #1 lie in the lateral gray
horns of the spinal cord
• The axons of neurons #1 leave the spinal cord
via the ventral root
• These axons pass to the spinal nerve
• Axons leave the spinal nerve via the white
branches (rami communicantes)
• Connect with the sympathetic chain ganglia

18. Routes of Preganglionic Axons
• There are 3 possible routes that sympathetic
neurons may follow
• Possibility #1: synapses within the ganglion at
that level and
– Second neuron leaves at that level via the gray
ramus communicans, exits to the visceral effector

20. Routes of Preganglionic Axons
• Possibility #2: neuron #1 goes up or down the
chain and synapses at some other level.
– Second neuron: leaves at that other level via the
gray ramus communicantes, and exits to the
visceral effector.

21. Routes of Preganglionic Axons
• Possibility #3: neuron #1 does not synapse in
the chain (exception!!) but exits and synapses
in a collateral ganglion near a major blood
vessel.
– Neuron #2 travels from that ganglion to the
visceral effector.

23. Where are the Collateral Ganglia ?
• Location –Near a major blood vessel
– Celiac ganglion
• Innervates upper abdominal viscera
– Superior mesenteric
• Innervates middle abdominal viscera
– Inferior mesenteric
• Innervates lower abdominal & pelvic organs

24. The Adrenal Medulla
• Yet another type of innervation:
– Going to the adrenal medulla
– No synapse in ganglia
– No synapse in collateral ganglia
– YES synapse in the adrenal medulla

26. Adrenal Medulla
• Only Preganglionic neurons are in this
pathway
• Neuron #1 stimulates the medulla,
• The medulla releases norepinephrine and
epinephrine (adrenaline) to blood

27. Human Anatomy 5th ed. 2005
Benjamin Cummings
Adrenal Medulla
Figure 17-06

28. Parasympathetic system
• Rest and digest system .

29. Parasympathetic division
• Cell bodies are in the brain or in the gray
matter of the spinal cord (sacral region)
• Neurons #1 exit the cranial region through
cranial nerves 3, 7, 9, & 10 or
• Neurons #1 exit the spinal cord through the
sacral spinal nerves

30. Parasympathetic
• Neurons #1 are long and synapse with
neurons #2 (short) in ganglia
• Ganglia are found on, or
–near the visceral effector

32. Central autonomic network
• Peripheral ANS is under the control of higher
centers in cerebral cortex.
• hypothalamus, amygdala, basal forebrain ,
ventral striatum , brainstem and spinal cord .
• Most important of these is hypothalamus

33. hypothalamus
• Ventral diencephalon – lies just below the
thalamus and above pituitary
• Wt- 4 gm
• Autonomic pathways  I/l brainstem
tegmentum  ant fasciculus in SC  widely
distributed mainly in Reticulospinal tract 
terminate at appropriate level at IML level of
SC.

35. Tests of assessment
• Bedside tests –
• General physical and neurological examination-
acromegaly , dwarfism , s/o endocrine imbalance,
sexual immaturity – hypothalamic .
• Dryness of skin- spoon test , sweat droplets at
papillary ridges +20 ophthalmic lens , changes in
skin temperature ,color, alopecia , hypertrichosis,
thickening or fragility of nails ,absent piloerection
, decreased hand wrinkling in water and skin
atrophy.

36. • Tests for OH- BP changes in supine and
standing . 1,3,5 min .
• HR Changes - > 30 bpm on standing. Or > 120
bpm
• Absent reflex tachycardia .
• POTS- >30 bpm or >120 bpm without fall in BP.
• Sustained hand grip, mental stress , cold
pressor test- DBP at least 15 mm hg/
HR >10 bpm

37. • Resting tachycardia – parasymp dysfunction .
• Bladder- palpation for distention, anal wink
and bulbocavernous reflex . internal anal
sphincter reflex.
• Lacrimal gland tear production- schirmer test-
place a strip of sterile filter paper in lower
conjuctival sac – measurement of degree of
wetting over 5 min.

38. • vagal tone- beat to beat variability of HR–
deep breathing, standing , valsalva.
• HR- DB sinus arrhythmia , pulse variability ,
R-R interval on ECG
• HR – standing- ( 30:15 ratio) ratio of R-R
Interval at beat 30 /R-R at beat 15.
• Normal > 1.04
•

39. • Valsalva-
• Phase 1- increased IT pressure  rise in BP
• Phase 2- gradual fall in BP due to impaired
venous return
• Phase 3- brief fall due to release of pressure
• Phase 4 – normal  overshoots BP for 1 min
 absence indicates early autonomic
dysfunction .

41. • Tilt table test – neurocardiogenic syncope
• Thermoregulatory and sudomotor function-
• SSR- peripheral sympathetic function
• QSART- quantitative sudomotor axon reflex test.-
postganglionic sudomotor fibers- sweat output
iontophoresis into the skin of acetylcholine
• Thermoregulatory sweat test ( TST )- both central
and peripheral sympathetic function- sweat
response in response to changes in body
temperature.

42. • Thank you.