Control Mechanisms in GI Physiology

Question 1

Parasympathetic effect on digestion

Answer 1

increases digestion

Question 2

Sympathetic effect on digestion

Answer 2

decreases digestion

Question 3

*** A 65-year-old woman presents to the University Hospital emergency room complaining of severe diffuse abdominal pain associated with vomiting and diarrhea. She denies any abdominal symptoms prior to this episode. Her temperature is 37.80 Celsius, BP is 178/90 mmHg, and irregular pulse rate 120/minute. Physical exam is significant for extreme diffuse tenderness with rebound and rigidity. Which of the following nerve fibers most probably carry the pain sensation from GIT to the CNS ?

Answer 3

Sympathetic

Question 4

Nerve fibers that carry pain

Answer 4

Sympathetic

Question 5

Nerve fibers that carry nausea, distension, and satiety

Answer 5

Parasympathetic

Question 6

Nerve fibers that stimulate intestinal motility and exocrine secretion

Answer 6

Parasympathetic

Question 7

Nerve fibers that inhibit intestinal motility

Answer 7

Sympathetic

Question 8

What are the inhibitory neurotransmitters in ENS?

Answer 8

Sympathetic

Norepinephrine

Question 9

What are the excitatory neurotransmitters in ENS?

Answer 9

Parasympathetic

Ach

Question 10

Hirschsprung’s Disease

Answer 10

• absence of the myenteric plexus

* distal colon

Question 11

Paralytic Ileus

Answer 11

most common cause: abdominal surgery

features: nausea and vomiting, abdominal distension, and absent bowel sounds

Question 12

Anticipatory responses

Answer 12

Cephalic Reflexes

Question 13

Vagovagal reflexes
Pain reflexes
Defecation reflexes

Answer 13

Long Reflexes

Question 14

Gastrocolic
Enterogastric
Colonoileal

Answer 14

Short Reflexes

Question 15

Peristalsis
Mixing contractions
GI secretions

Answer 15

Local Reflexes

Question 16

*** What would be the response of parietal cells if anticholinergic such as atropine is given?

Answer 16

decrease in Ach, but NOT inhibition

Question 17

Gastrin

Answer 17

G cells

• increases gastric H+ secretion

Question 18

Cholecystokinin (CCK)

Answer 18

I cells

• increases pancreatic enzyme & bicarbonate secretion
  (deals with fatty acids)

increase contraction of gallbladder

relaxation of sphincter of Oddi

Question 19

Secretin

Answer 19

S cells

• increases pancreatic bicarbonate & water secretion

increases biliary bicarbonate secretion

( low pH = high H+ )

Question 20

Somatostatin

Answer 20

(deals with SNS)

decreases secretion of other GI hormones

• decreases gastric secretion

Question 21

Histamine

Answer 21

(deals with PNS)

• increases gastric H+ secretion

Question 22

Serotonin

Answer 22

increases intestinal motility and secretion

Question 23

Carcinoid tumors

Answer 23

enterochromaffin cells (most commonly secrete serotonin)

most commonly in ileum

Question 24

Carcinoid syndrome

Answer 24

once the carcinoid tumor metastasizes to the liver

Question 25

Acrtylcholine (Ach)

Answer 25

cholinergic increases GI motility relaxes sphincters * increases H+ secretions * increases pancreatic enzyme secretion

Question 26

Norepinephrine

Answer 26

adrenergic decreases GI motility contracts sphincters increases salivary secretions

Question 27

VIP

Answer 27

decreases GI motility | * increases pancreatic bicarbonate secretion

Question 28

Substance P

Answer 28

* co-secreted with Ach | increases salivary secretions