Ch. 15 - Gastrointestinal Physiology

Question 1

What is the extrinsic nervous control of the GI tract?

Answer 1

Mostly Vagus CN X, parasympathetic

Question 2

What are the Intrinsic nevous controls of the GI tract?

Answer 2

• Myenteric Plexus “Auerbach’s plexus” - between outer longitudinal and middle circular muscle layers
• Submucous Plexus “Meissner’s plexus” - between the middle circular layer and the mucosa

Question 3

What is released by the small intestine in response to chime entering the duodenum?

Answer 3

• Secretin
• CCK
• GIP

Question 4

What cells release pepsinogen?

Answer 4

Chief cells - pepsinogen is converted to pepsin in presence of HCl

Question 5

What cells release Intrinsic Factor?

Answer 5

Parietal cells - binds vitamin B12 to allow for its absorption in terminal ileum

Question 6

What can peptic ulcers result from?

Answer 6

• High HCl
• Low mucous
• H. pylori

Question 7

What are the phases of Gastric Secretion?

Answer 7

• Cephalic phase
• Gastric phase
• Intestinal phase

Question 8

What phase of gastric secretion begins with smell, sight, taste or thought of food?

Answer 8

Cephalic Phase

Question 9

What increases and decreases gastric emptying?

Answer 9

• Increases
  
  • Eating, gastric distension, gastrin, vagal input (parasympathetic)
• Decreases
  
  • CCK, Secretin, GIP, duodenal distension (enterogastric reflex)

Question 10

What hormones are produced in the duodenum?

Answer 10

• CCK
• Secretin
• GIP

Question 11

What are the 3 major types of GI contractions?

Answer 11

1. Peristalsis
2. Segmentation (mixing)
3. Tonic contractions

Question 12

What is the most common type of GI contraction in the small intestine?

Answer 12

Segmentation (mixing)

Question 13

How are disaccharides absorbed?

Answer 13

Na+ cotransport (secondary actie transporters - driven by the sodium gradient)

Question 14

Where is bile made, stored and what stimulates its’ release?

Answer 14

• Made by liver
• Stored in gall bladder
• Stimulated by CCK

Question 15

What is the key enzyme of cholesterol synthesis?

Answer 15

HMG CoA Reductase

Question 16

How is cholesterol synthesis regulated in the liver?

Answer 16

Negative feedback mechanism - statin allosterically inhibits HMG CoA Reductase

Question 17

Why can’t skeletal muscle deliver glucose to the bloodstream?

Answer 17

It lacks glucose-6-phosphatase

Question 18

What are the different Glucose transporters associated with? (GLUT1-4)

Answer 18

• GLUT 1 - erythrocytes
• GLUT 2 - renal, small intestine, liver, pancreatic B cells
• GLUT 3 - neurons, placenta
• GLUT 4 - insulin regulated, adipose, striated muscle tissue

Question 19

Where does most of the gluconeogenesis occur?

Answer 19

In the liver/kidneys

In prolonged starvation - kidneys become major glucose-producing organs

Question 20

What is the role of glucokinase and where is it only found?

Answer 20

It converts glucose to glucose-6-phosphate just like hexokinase – found only in liver

Question 21

What is the first location to spot jaundice?

Answer 21

Under the tongue

Question 22

What are some prehepatic, hepatic and posthepatic causes of jaundice?

Answer 22

• Prehepatic
  
  • hemolytic anemia, malaria
• Hepatic
  
  • hepatitis, alcoholic liver disease, primary biliary cirrhosis
• Posthepatic
  
  • Choledocholithiasis (gall stones), Pancreatic head cancer

Question 23

What 2 enzymes are needed for alcohol metabolism?

Answer 23

• Alcohol dehydrogenase
• Acetaldehyde dehydrogenase (to acetate)