2. Gi Motility And Secretion

Front 1

What are the 3 major characteristics of GI smooth muscle motility?

Back 1

1. Smooth muscle is primarily single unit
2. Pacemaker cells allow for spontaneous depolarization.
3. Areas of hyperpolarization stop waves of depolarization.

Front 2

What makes single unit smooth muscle unified?

Back 2

Gap junctions - they couple the cells electronically.

Front 3

What controls the stopping of depolarization?

Back 3

Norepinephrine - released over areas where hyperpolarization is intended to occur.

Front 4

What controls the release of norepinephrine?

Back 4

-SNS or ENS

Front 5

What are the 3 patterns of "GI motor behavior?"

Back 5

1. Peristalsis
2. Mixing
3. Sphincters

Front 6

What type of movement is caused by peristalsis?

Back 6

Propulsive - it pushes the GI contents forward

Front 7

In what 2 structures does peristalsis occur?

Back 7

1. Esophagus
2. Intestines

Front 8

What 2 types of muscular contraction allows for peristaltic movement?

Back 8

1. Circular muscle Contraction
2. Longitudinal musc contraction

-But in adjacent segments.

Front 9

What are the 2 adjacent segments in peristaltic muscle named?
What muscle is contracting in each?

Back 9

1. Propulsive segment - circular muscle contracts here
2. Receiving segment - longitnl. muscle contracts here.

Front 10

What does Circular contraction do?

Back 10

Decreases the diameter of the GI tract and causes forward movement.

Front 11

What does longitudinal contraction do?

Back 11

Shortens the GI tract and increases the diameter.

Front 12

How does vomitting occur?

Back 12

By reverse peristalsis - the small intestine forces contents to stomach, then Ab contraction forces food out.

Front 13

If Longitudnl muscle contracts, what does circular do?

If circular muscle contracts, what does longitud do?

Back 13

-is inhibited.

-relaxes.

Front 14

Where does MIXING motor muscle occur?

Back 14

in the intestines - accounts for their wound up, bumpy, messiness.

Front 15

What are the segments in mixing?

Back 15

-Propulsive - bidirectional
-Receiving - where mixing occurs

-They flip back and forth, take turns being each other.

Front 16

If food is being pushed back and frth w/out forward movement, how does it move thru intestines?

Back 16

Usually there is a combination of mixing and peristalsis.

Front 17

What are Sphincters?

Back 17

Muscles that close off the GI tract.

Front 18

What are the 2 types of sphincters?

Back 18

1. Involuntary (smooth muscle)
2. Voluntary (skeletal muscle)

Front 19

What 4 things must we consider regarding the mouth and esophagus?

Back 19

1. Motility
2. Secretions
3. Secretion regulation
4. Functions of saliva

Front 20

In what state are the upper and lower esophageal sphincters normally?

Back 20

Closed;
-upper to prevent air entry into the esophagus
-lower to prevent acid reflux

Front 21

What 2 types of actions occur in swallowing?

Back 21

1. Voluntary
2. Involuntary

Front 22

What does voluntary action accomplish re: motility during swallowing?

Back 22

it pushes saliva to the back of the mouth.

Front 23

What does Involuntary action accomplish/cause?

Back 23

1. Upper sphincter relax/opens
2. Primary peristalsis in esophagus
3. Lower sphincter relax/food enters stomach

Front 24

What triggers 2ndary peristalsis?

Back 24

Food remaining in the esophagus after swallowing.

Front 25

What are the main secretions in the mouth and esophagus?

Back 25

From the salivary glands in the mouth.

Front 26

Where is saliva formed, and what three cell types add to it?

Back 26

-In the saliva glands.
1. Serous cells
2. Myoepithelial cells
3. Mucus cells

Front 27

What is the function of serous cells?

Back 27

Line salivary gland; contain zymogen granule vesicles.
Zymogen grans release amylase

Front 28

what is the function of amylase?

Back 28

breaks down carbs

Front 29

What do Myoepithelial cells do?

Back 29

Contract and force out saliva from the gland and increase its flow.

Front 30

What do mucus cells do?

Back 30

Secrete mucus into saliva.

Front 31

Is Saliva just saliva, or can it be altered? How?

Back 31

It can be altered - as it flows through the duct, duct cells add HCO3- for acid neutralization, and remove some Na and Cl so the saliva is hypotonic.

Front 32

What 2 things regulate saliva secretion?

Which is more important?

Back 32

-SNS
-PNS -> the main actor

Front 33

How does SympNS control salivary secretion?

Back 33

It causes a small transient increase in salivary flow.

Front 34

How does ParaNS control salivary secretion?

Back 34

It causes a LARGE increase in salivary flow!

Front 35

What stimulates PNS activation of salivary flow, and how does it work (2 things)?

Back 35

Stimuli: thinking/smelling, tasting/chewing. Result:
1. Vasodilation of vessels near salivary glands.
2. Increased capillary permeability so more fluid enters saliva glands.

Front 36

What are the 3 enzymes in saliva?

Back 36

1. Salivary amylase
2. Lingual lipase
3. Mucins

Front 37

What does Salivary amylase do? What's another name for it?
What happens to it in the stomach?

Back 37

Ptyalin; begins carb breakdown but is inactivated in the stomach by acid.

Front 38

What does lingual lipase do? Does it work very well?

Back 38

Begins fat breakdown; no - there are no bile salts around to emulsify the fats.

Front 39

What are mucins?

Back 39

Glycoproteins found in mucus.

Front 40

So what are the 5 functions of saliva?

Back 40

1. Begin carb breakdown
2. Begin fat breakdown
3. Put mucus in mixture
4. Solvent for tasting
5. Aid in speach

Front 41

What are the anatomical components of the stomach?

Back 41

1. Fundus/cardia
2. Body
3. Antrum
4. Pyloric sphincter
5. Pylorus
then the duodenum.

Front 42

What is the function of
-Fundus/body
-Antrum

Back 42

Fundus/body are for storage.
Antrum is for mixing - lots of smooth muscle here (why its smaller)

Front 43

What type of motility occurs in the stomach?

Back 43

Mixing, which increases the rate of stomach emptying.

Front 44

What stimulates mixing?

Back 44

Gastrin and the PARA NS

Front 45

What type of meal has the slowest rate of emptying?

Back 45

A fatty meal - it increases CCK which inhibits gastric motility and secretion.

Front 46

What is the most potent inhibitor of stomach motility?

Back 46

Cholecystokinin.

Front 47

What is "Receptive Relaxation"?

Back 47

Phenomenon where a full stomach is relaxed, and an empty stomach contracts.

Front 48

What stimulates receptive relaxation?

Back 48

The full stomach stimulates the PARASNS to stimulate the ENS, which inhibits stomach smooth muscle.

Front 49

What 4 things get secreted into the stomach? From which glands?

Back 49

1. Mucus - oxyntic gland
2. HCl - oxyntic gland
3. Pepsinogen - oxyntic gland
4. Gastrin - pyloric gland

Front 50

What secretes mucus, and why?

Back 50

Mucus cells; to protect the stomach from acid.

Front 51

What do the Parietal cells secrete?

Back 51

HCl and intrinsic factor

Front 52

what do Chief cells contain?

Back 52

Zymogen granules; which secrete pepsinogen.

Front 53

What does pepsinogen do, and why does it have to be in granules?

Back 53

Breaks down protein; in granules to protect the cells.

Front 54

What does the Pyloric gland contain?

Back 54

G cells, which secrete Gastrin (a hormone!!)

Front 55

What is the oxyntic gland structurally?

Back 55

A folding of the stomach that contains exocrine glands.

Front 56

What is the mechanism of HCl secretion from parietal cells?

Back 56

1. CO2 diffuses in parietal cells from the blood.
2. CO2 combines w/ H2O = H+ and HCO3-
3. H+ goes to stomach
4. HCO3- goes back to blood in exchange for CL-.
5. Cl- diffuses to stomach.

Front 57

What is "Alkaline Tide"?

Back 57

The increase in pH of blood passing the stomach because a lot of bicarb enters in exchange for Cl-.

Front 58

What are the 3 phases of gastric secretions?

Back 58

1. Cephalic
2. Gastric
3. Intestinal

Front 59

What 3 things regulate gastric secretions?

Back 59

1. Autonomic NS
2. Enteric NS
3. Hormones

Front 60

When does the cephalic phase occur?

Back 60

Before food enters the stomach; while thinking/smelling/tasting, chewing..

Front 61

What does the cephalic phase stimulate?

Back 61

Increase in HCl and pepsinogen secretions.

Front 62

When does the Gastric phase occur?

Back 62

When food is in the stomach.

Front 63

What does the gastric phase stimulate?

Back 63

Increase in HCl, and Pepsinogen secretions. BY THE ACTION OF GASTRIN.

Front 64

When does the intestinal phase occur?

Back 64

When food is in the duodenum

Front 65

What does the intestinal phase stimulate?

Back 65

Decrease in HCl and Pepsinogen secretions. BY THE ACTION OF ENTEROGASTRONES.

Front 66

When does Gastrin work?
When do CCK/Secretin/GIP work?

Back 66

-During GASTRIC phase.
-During INTESTINAL phase.

Front 67

How many functions of gastric juice are there?

Back 67

3 :) keep going you can do it.

Front 68

What functions are gastric juice involved with?

Back 68

1. Stimulate Digestion
2. Bactericidal action
3. Supply of intrinsic factor

Front 69

How does gastric juice stim digestion?

Back 69

It has HCl; HCl catalyzes activation of pepsinogen to pepsin; pepsin breaks down proteins.

Front 70

Does HCl control the continuous activation of pepsin?

Back 70

No; only the beginning; then by autocatalysis pepsin activates formation of itself.

Front 71

How does gastric juice have bactericidal action?

Back 71

The low ph kills most ingested bacteria

Front 72

What bacteria does gastric juice not kill?

Back 72

Helicobacter pylori - often a cause of peptic ulcers.

Front 73

How does gastric juice supply intrinsic factor?

Back 73

The parietal cells secrete it, and it allows for Vit B12 absorption/ RBC production.

Front 74

What important juice does the liver secrete?

Back 74

Bile

Front 75

Where is bile stored and concentrated?

Back 75

In the gallbladder.

Front 76

What hormone stimulates release of bile again?

Back 76

Cholecystikinin - causes gall bladder contraction

Front 77

What is Bile made up of? (three things)

Back 77

1. HCO3-
2. Bilirubin
3. Bile salts

Front 78

What are bile salts and what do they do?

Back 78

Derived from cholesterol, they emulsify fat.

Front 79

of the stuff in the duodenum, what gets absorbed into the bloodstream and transported to the liver?

Back 79

only glucose and protein; not fat.

Front 80

What happens to glucose at the liver?

Back 80

-If high serum glucose, makes glycogen.
-If low serum glucose, keep it in the blood.

Front 81

What happens to protein at the liver?

Back 81

1. May convert to other amino acids
2. Make plasma proteins
3. Convert to glucose via gluconeogenesis.
4. Remain in blood.

Front 82

Bile salts have 2 distinct regions; what are they?

Back 82

1. Cholesterol-derived region which is nonpolar, lipophilic.
2. Amino acid chain which is polar, neg charged, lipophobic.

Front 83

Which region of the bile salt is stuck in the fat droplet?
Which is in the water?

Back 83

cholesterol region - lipid

amino acid chain - water

Front 84

How do large fat droplets get broken into smaller ones?

Back 84

by MIXING

Front 85

What happens to small fat droplets?

Back 85

Bile salts stick their cholesterol tails into them.

Front 86

How do bile salts function as emulsifiers?

Back 86

Their negative charges surrounding the fat repel each other and prevent reformation of the large fat droplets.

Front 87

What 2 things DONT bile salts do?

Back 87

-Don't break apart large fat droplets
-Don't break down fat

Front 88

What are Micelles composed of?

Back 88

1. Fat
2. Bile salts
3. Cholesterol
4. Fat soluble vitamins A/D/E