enteric nervous system

2. . ENTERIC NERVOUS SYSTEM-
[MINI BRAIN OF GUT]
. PARA SYMPATHETIC NERVOUS SYSTEM
. SYMPATHETIC NERVOUS SYSTEM

3. ENTERIC NERVOUS SYSTEM

5. NEUROTRANSMITTERS
Excitatory motor neurons
-ACH
-Substance P
Secreto motor neurons
-ACH
-VIP
-Histamine
Inhibitory motor neurons
-ATP
-Nitric oxide
-VIP
Others
-Norepinephrine
-Seratonin
-GABA
-Dopamine
-Somatostatin
-Leu-enkephaline
-Met-enkephaline
-Bombesin

6. TYPES OF ENTERIC NEURONS
AH-TYPE S-TYPE
-Multiple long processes
-long lasting hyper polarizing
potential
-largest population of neurons
in Myenteric Plexus
-Single long axon with multiple
short dendrites
-Exhibit nicotinic fast EPSPs
-Low RM Conductance and greater
excitability
-Max in Submucosal Plexus
Application of TETRODOTOXIN abolishes APs in S-type but not in AH-type

7. PARASYMPATHETIC INNERVATION
S2, S3, S4

9. T5
L2

10. SPLANCHNIC NERVES VAGAL FIBERS
-Mixed nerves
-Sensory afferents from gut
to spinal cord
-Sympathetic efferents to gut
-Cell bodies of sensory afferents
are in dorsal root spinal ganglia
-80% of vagal fibres are
sensory afferents
-transmit information from
gut to CNS for processing

11. SENSORY RECEPTORS
1.Mechano Receptors
2.Chemo Receptors
3.Pain Receptors/ Nociceptors
4.Mesenteric Receptors
5.Thermoreceptors

12. SYNAPTIC TRANSMISSION IN ENS
1.Slow EPSPs
2.Fast EPSPs
3.Slow IPSPs
4.Presynaptic Inhibition
5.Presynaptic Facilitation

13. -In AH-type neurons receptor is Adenylyl Cyclase & 2nd messenger is cAMP.
-In S-type neurons receptor is Phospholipase C & 2nd messenger is free
intra-neuronal Calcium.
Significance- Long-lasting responses of the gut effectors during
physiological stimuli.

14. Mediated by Acetylcholine acting on ionotropic nicotinic receptors
Significance- rapid transfer of information between elements of
enteric microcircuits.

15. Eukephalins, Dymorphine and Morphine are slow IPSP mimetics
NE-alpha 2 adrenoreceptor , Galanine, Adenosine, ATP
Significance- shunting of blood by symp. stimulation during exercise

16. PRESYNAPTIC INHIBITION
-Mechanism for selective shutdown
of a microcircuit
-Release of Histamine in response to
food allergens & infectious agents
NE-α2 adrenoreceptor- supress
fast & slow EPSPs
Seratonin supresses both fast &
slow EPSPs
Opiates supress some fast EPSPs
ACH supresses some fast EPSPs

17. PRESYNAPTIC FACILITATION
-Action of CCK on Gall Bladder
-Mechanism of action of Prokinetic drugs like TEGASEROID & CISAPRIDE

18. NEURO-MUSCULAR JUNCTION IN GIT
-Site where NTs released from axons of motor neurons act on
smooth muscle fibres & interstitial cells of Cajal.
-Simpler structers than the motor end plates of Skeletal
muscles.
-NTs are released from multiple varicosities of motor axons
which spread out along the axon.
-This structural organization is an adaptation for simultaneous
application of a chemical NT to a large number of muscle fibers
from a small number of motor axons.

20. GASTRO INTESTINAL REFLEXES
1.Local Reflexes
-control much of GI secretion, peristalisis, mixing
contractions and local inhibitory effects.
2.Short Reflexes
-Gastro-colic reflex
-Entero-gastric reflex
-Colono-ileal reflex
-Ileo-gastric reflex
-Intestino-intestinal reflex
3.Long Reflexes
-Vago-vagal reflex -Swallowing reflex
-Pain reflexes -Vomiting reflex
-Chewing reflex -Defecation reflex

21. APPLIED ASPECTS
1.Hirschprung disease/ congenital megacolon/
congenital aganglionosis
2.Cardiac Achalasia
3.Abolition of Deglutition reflex
4.Dumping syndrome after vagotomy & gastric
antrectomy for peptic ulcer
5.Idiopathic gastric stasis
6.Paralytic Ileus
7.Incontinence
8.Dysphagia- Nut cracker’s oesophagus
9.Emesis/ Vomiting