NAS WK8 - ENTERIC

Question 1

FUNCTION OF ENTERIC NS

Answer 1

• digestion but in abnormal conditions can lead to disease of GI tract
• innervates GI tract

Question 2

WHAT IS ENS

Answer 2

• 3rd division of autonomic system (along with parasympathetic & sympathetic)
• intrinsic (as has everything it needs all inside of the GI tract (all neurones, effectors etc))

Question 3

WHERE IS ENS

Answer 3

• two major plexuses of ganglion cells & fibre bundles all interconnected
• submucosal plexus (in stomach & intestines only) & myenteric plexus (full length of GI tract)

Question 4

WHAT DO ENTERIC REFLEXES CONTROL

Answer 4

• secretory reflex - by submucosal plexus
• motor reflex - by myenteric plexus e.g. peristalsis
• blood flow (by both myenteric & submucosal plexus)

Question 5

HOW MOTOR REFLEX WORKS

Answer 5

sensory receptors (mechano & chemo) detect contents (food) of lumen & send signal to myenteric plexus which sends signals to effector using interneurons

Question 6

HOW GI TRACT WORKS (PERISTALSIS)

Answer 6

we contract the part behind food in GI tract (by activating excitatory efferent from myenteric plexus in ENS) & relaxing parts in front of food

Question 7

SECRETORY REFLEX

Answer 7

mechano/chemo receptors send info to submucosal plexus through sensory neurones & then it uses interneurons to interact with effector muscles to control gland secretion & it increases secretion of mucus, enzymes & acid

Question 8

HOW ENS CONTROLS BLOOD FLOW

Answer 8

• efferent neurones can innervate blood vessels & release neurotransmitters which control vascular state of blood vessel (dilated or constricted) due to poor interactivity between enteric neurones & brain)
• usually, ENS interacts with brain by sending info via afferents to SNS/PNS & then they send to CNS (this can happen in reverse direction too)

Question 9

ENS DYSFUNCTIONS

Answer 9

• higher age = decreased ENS function (less neurones as they die over time)
• ENS targeted by pathogens, leading to changes in enteric neurones

Question 10

CHAGA’S DISEASE

Answer 10

insect bit releases trypanosome parasite –> neurone death

Question 11

ACHALASIA

Answer 11

loss of inhibitory neurones in myenteric plexus of oesophagus leads to difficulty swallowing

Question 12

HIRSCHSPRUNG’S DISEASE IN BABIES

Answer 12

baby is born with missing ENS neurones in distal reaches of colon so distal colon can’t do peristalsis so faeces builds up –> halted faeces movement –> colitits & can’t open sphincter to let food out

Question 13

PARKINSON’S DISEASE

Answer 13

pathogen enters nervous system by enteric neurones

Question 14

MYASTHENIA GRAVIS

Answer 14

usually somatic NS as is antibodies to nACh receptors on skeletal muscles BUT can be enteric as antibodies to ACh receptors on smooth muscle

Question 15

ENS DRUG TARGETS

Answer 15

endogenous opioids targets opioid receptors to change function of ENS & GI tract (e.g. anti-diarrhoeal drugs act on opioid receptors)