Physiology

Question 1

Meissner’s plexus (submucosal) and myenteric plexus function?

Answer 1

Comprise enteric nervous system

Integrate and coordinate motility, secretory, endocrine GI functions

Question 2

Function of Myenteric plexus?

Answer 2

Motility

Question 3

Function of Submucosal (Meissener’s) plexus?

Answer 3

Secretion and blood flow–> receives sensory info form chemo + mechano receptors in GI tract

Question 4

What are the four official GI hormones?

Answer 4

Gastrin
Cholecystokinin (CCK)
secretin
Glucose-dependent-insulinotropic peptide (GIP)

Question 5

What is the site of secretion, stimulus, and action of Gastrin?

Answer 5

G cells of Stomach
Peptides, Vagus, stomach distention
Increases Gastric H+ secretion (parietal cells)+ stimulate mucosal growth

Question 6

What inhibits Gastrin?

Answer 6

H+ in stomach

Somatostatin

Question 7

What is site of secretion (soc), stimulus, and actions of CCK?

Answer 7

I cells of duodenum and jejunum
Peptides + AA + fatty acids
Gallbladder contraction + relax spincter of Oddi + increase pancreatic HCO3 secretion + Growth of pancreas/gallbladder + inhibits gastric emptying

Question 8

What is soc, stimulus, and actions of Secretin?

Answer 8

S cell of duodenum
H + fatty acids in duodenum
Increases pancreatic and biliary HCO3 + decreases Gastric H+ secretion

Question 9

What is soc, stimulus, and actions of GIP?

Answer 9

duodenum and jejunum
FA + AA + oral glucose
Increases Insulin secretion + decreases Gastric H+ secretion

Question 10

What are the most potent gastrin stimulating AA?

Answer 10

phenylalanine

tryptophan

Question 11

Zollinger-Ellison syndrome (GASTRINOMA)?

Answer 11

Gastrin secreting non-Beta-cell tumor in pancreas

Question 12

Meals containing FAT stimulate release of what to slow down gastric emptying to allow more time for digestion/absorption?

Answer 12

CCK

Question 13

What are the GI paracrines?

Answer 13

Somatostatin

Histamine

Question 14

Somatostatin secretion stimulant/ inhibitor and function?

Answer 14

Stimulated by H+ in lumen
Inhibited by Vagal stimulation
Functions to: inhibit ALL GI hormone release + Gastric secretion

Question 15

Function of histamine in GI tract?

Answer 15

Increases gastric H+ secretion directly by potentiating effects of gastrin and Vagus

Question 16

GI neurocrines are?

Answer 16

Vasoactive intestinal peptide (VIP)
GRP (bombesin)
Enkephalins

Question 17

VIP soc and actions?

Answer 17

Neurons in mucosa and smooth muscle cells
GI smooth muscle + lower esophageal relaxation
Stimulates pancreatic HCO3 secretion
Inhibits Gastric H+ secretion

Question 18

Pancreatic islet cell tumor secreting VIP?

Answer 18

Mediates Pancreatic Cholera

Question 19

GRP (bombesin) soc, actions?

Answer 19

Released from Vagus nerve innervating G cells

Stimulates Gastrin releases from G cells

Question 20

Enkephalins soc and actions?

Answer 20

1. Secreted from nerves in mucosa of SM and GI tract
2. Stimulates GI sm muscle contraction (lower esophageal, pyloric, and ileocecal sphincters.
3. Inhibits intestinal secreting of fluid and electrolytes-> Opiates can treat Diarrhea

Question 21

What parts of the GI tract are striated muscle?

Answer 21

Pharynx
Upper 1/3 esophagus
External anal sphincter

Question 22

Oscillating membrane inherent to smooth muscle cells of parts of GI tract?

Answer 22

Slow waves–> occurs spontaneously + not APs but do determine pattern of APs/ contractions

Question 23

What are the pacemakers cells of the GI smooth muscles?

Answer 23

Interstitial cells of Cajal

Question 24

Mechanism involved in Slow wave productions?

Answer 24

Depolarization by Ca++ influx

Repolarization by K+ efflux

Question 25

What affects the frequency of slow waves?

Answer 25

1. Varies–> LOWEST stomach + HIGHEST duodenum but otherwise CONSTANT
2. Neural or hormal inputs only affect the APs that occur on top of Slow waves NOT slow waves

Question 26

Steps of swallowing coordinated in the Medulla?

Answer 26

1. Nasopharynx closes + breathing is inhibited
2. Laryngeal muscles contract to close glottis elevate larynx
3. Peristalsis begins in the pharynx to propel bolus, upper esophageal sphincter relaxes to permit food

Question 27

What mediates Esophageal sphincter relaxation?

Answer 27

Vagus–> via VIP

Question 28

Condition when lower esophageal sphincter does not relax during swallowing and accumulates in the esophagus?

Answer 28

Achalasia

Question 29

Receptive relaxation?

Answer 29

Vagovagal reflex which along with CCK help relax orad region to accompany newly swallowed food

Question 30

Migrating myelectric complex?

Answer 30

Contraction that occur during fasting @ 90 min intervals to empty the stomach–> MOTILIN mediated

Question 31

Gastric emptying is fastest when?

Answer 31

Stomach contents are ISOTONIC

Question 32

What inhibit gastric emptying?

Answer 32

FAT–> stimulate CCK

H+ in duodenum–> direct neural reflex

Question 33

Gastrocolic reflex?

Answer 33

Food in the stomach increases motility of COLON and increases frequency of mass movement–> Mediated by Parasympathetics + CCK/gastrin

Question 34

Absence of colonic enteric nervous system–> resulting in severe constipation and dilation

Answer 34

Megacolon

Question 35

Composition of of Saliva?

Answer 35

High volume
High K+ and HCO3
Low Na+ and Cl-
HYPOtonic 
alpha amylase, lingual lipase, kallikrein

Question 36

What increases the amount of saliva produced?

Answer 36

BOTH sympathetics and parasympathetics

(CN VII + IX)

Question 37

Parasympathetic stimulation of saliva?

Answer 37

Muscarinic receptors on acinar and ductal cells–> increase IP3 and inctracellular Ca++–> increase saliva production

Atropine–> anticholincergic causes dry mouth

Question 38

Sympathetic saliva stimulations?

Answer 38

Increases production + gland growth

Act on Beta receptors on acinar/ ductal cells