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Flashcards in Physiology 2 Deck (108)
1

The GI Tract is all smooth muscle except?

upper 1/3 of esophagus and anal sphincter (striated)

2

Types of Smooth Muscle Contraction?

1. Phasic - parastalic
2. Tonic - can last hours

3

Chewing does?

1. breaks down food particles
2. mixes food with saliva
3. increase surface are to digest better

4

Functions of stomach?

1. storage-most in orad area
2. break down food particles in small cubic sizes
3. gastric emptying

5

GERD

-acid reflux
-heartburn
-hiatal hernia, pregnancy, failure of secondary peristalsis

6

Oxyntic Cells

Parietal Cells, in body of stomach, weak motility

7

Pyloric

antrum, very strong contractions, muscle is thicker in this area

8

accommodation

relaxation

9

Cells of Caja

-slow waves always present from these intestinal cells
"gastric pacemaker"
3-5 depolarizations/min

10

Vagal Stimulation effect on slow waves

-increase height of waves (so increase frequency of contraction)

11

What empties fastest in the stomach?

-isotonic water (everything becomes isotonic when it goes in duodenum)

12

CCK effect on emptying?

inhibits

13

Effect of acid on peristalsis?

decrease from neural reflex

14

Failure of Gastric Emptying

-fullness, loss of appetite, nausea
-obstruction-ulcer, nausea
-vagotomy

15

Increased Gastric Emptying

-inadequate regulation
-diarrhea, duodenal ulcer

16

Reason for irregular contractions in small intestine?

1. mixing
2. digesting
3. absorption

17

Peristalsis

propulsion, moves food only 4-5cm at a time, short

18

Migrating Motor Complex

-"housekeeper" reflex
-goes away when you start to eat
-# of contractions per minute except areas of extreme contractility (90min) b/c of motiline (creates wave beginning in stomach)

19

Small Intestine Motility

-must have spikes to have contraction

20

Teniae Coli

-longitudinal muscle

21

Haustra

-segmentation in colon, can disappear and reappear in different areas

22

Achalsia

food stuck in esophagus

23

rectosphinteric reflex

when rectum is distended, it will contract external sphincter
absent in paraphalgicts (rectal sphincter causes defication)
voluntary rexed for deification

24

Salivary Secretion Components

1. alpha amylase - pH 7, lingual lipase (acidic), solubilization (to taste food)
2. lubrication - needed for speech
3. protective function - allows drinking hot, dilute noxious substances, dec. cavities, sec. F, Ca, P, lysosomes to wash particles from teeth

25

Salivary Glands`

1. Parotid - watery 25-40% of output
2. Submaxilary - watery and mucus
3. Submandibular
-recieve lots of blood flow, CN nerves VII & IX both sympathetic and parasympathetic

26

Acinar cells

secretion goes unchanged in intercalated duct, then modified: abs NaCl, sec. K+ and bicarb in striated duct

27

Xerostamia

-absence of saliva

28

Ion concentration with flow rate

-hypotonic at all rates
-high K+ concentration all the time
-Na+ concentration low at low rates
-bicarb high at high rates

29

Changes in concentration as saliva moves from acinus to duct opening?

-Na+ decreases, K+ increases (secreted into duct)
-more happens the longer it stays in the gland

30

Kallikrein

salivary glands secrete it into the blood stream, acts on plasma proteins to cause secretion of Bradykinin to increase blood flow

31

What happens if you denervate salivary glands

they shrink

32

What 5 things does the stomach secrete?

1. Hydrogen Ion
2. Pepsinogens
3. Mucus
4. Intrinsic Factor
5. Water

33

Hydrogen Ion's Job in Stomach?

-activates conversion of pepsinogen into pepsin
-kills bacteria
-digests protein

***absence increases infection for small bowel

34

Pepsinogen's Job in Stomach?

-pepsin digests protein by cleaving interior peptide bonds

35

Mucus' Job in Stomach?

-lubricates food
-protects lining of stomach

36

Intrinsic Factor's Job in Stomach?

-lubricates food
-protects lining of stomach

37

Water's Job in Stomach?

-dissolves and dilutes ingested material
-secretes 1.5L per day

38

How long can the liver's stores of Vit B12 last?

5 years

39

What does the oxyntic gland mucosa secrete?

HCl

40

What does the pyloric mucosa release?

gastrin

41

What do mucus neck cells secrete?

mucus with vagal stimulation

42

What happens if you block carbanic anhydrase?

decrease acid secretion

43

How is H+ ion secreted?

down electrical gradient
against concentration gradient
into mucosa

44

What disrupts the cell membrane and cause the separation of charges across the mucosa to decrease pd?

aspirin and alcohol

45

What keeps acid from hurting stomach?

gastric mucosal barrier

46

Concentration of ions in gastric juice depending on the rate of secretion?

-Cl is constant
-H+ increases with increasing secretion
-Na+ decreases with increasing secretion
-K+ increases with increasing secretion

47

Electrolytes with chronic vomiting

hypokalemia, low Na+, loose H+
metabolic alkalosis

48

Chronic Diarrhea

metabolic acidosis

49

Non-oxyntic Fluids

-low volume with no acid production
-electrolytes like conc. in plasma
-produced continually at low rates, overwhelmed when secretion is stimulated from parietal cells

50

Increase in Oxyntic fluid due to?

acid stimulation

51

What are the 3 major stimulants of gastric acid secretion?

-gastrin: travels through circulation
-histamine: released from intracromlin like cells
stimulates acid secretion
-G cell
-Neuron

parital cell has all 3 receptors

gastrin + histamine decarboxylase activity (increased response)

52

Bile acid secretion

-independent of serum gastrin
-middle of the night
-peak is unrelated to plasmic gastrin levels

53

"fasting output"

-10% of max output of stomach

54

How much output does acid secretion peak at?

30mEq/hr

55

Cephalic Phase

-chew up food, then spit it out: 30% response of acid secretion (better the food, more acid)
-mechanisms are all in the head

56

What happens in the absence of gastrin?

vagus stimulates acid secretion
1. direct stimulation of parietal cell via Ach
2. release of gastrin via GRP

57

What part of food stimulates gastrin release?

protein (AA and peptides), lasts 1.5hr, 50-60% of acid secretion

58

What does distention do?

1. parietal cells to secrete (short intermediate reflux) - local
2. long-vaso-vagal reflux, stimulate gastric cells to release gastrin (GRP)

59

Mechanisms Regulating Gastrin Release

Vagus Nerve
-Ach at nicotenic receptor
-GR4 cell inhibits somatostatin release
Distention

60

Summary of all Mechanisms Stimulating Gastric Acid Secretion

-Cephalic: chewing, swallowing, smell, taste
-Gastric: distention, digested protein
-Intestinal: digested protein

61

Direct Inhibiters of Gastrin Release

1. somatostatin
2. secretin
3. GIP

62

pH and volume in response to a meal

meal: pH increases to 5-6 b/c of protein buffers
volume increase: stomach begins to secrete

63

Regulation of Pepsin Secretion

-Ach stimulates pepsin secretion from cell
-H+ turns pepsinogen to pepsin
-pH of 4 or less, automatic conversion
-vagus nerve stimulates pepsin secretion

64

Effect of smoking on pancreatic secretions?

decreases them

65

How much does pancreas secrete per day?

1-2L

66

What is secreted from pancreatic duct cells?

water and bicarb

67

Acinus

in pancreas
-blind system "grapes", elaborate enzymatic components

68

Ductal cells % of pancreas?

4%

69

Acinus cells % of pancreas?

80%

70

Absence of pancreatic secretion causes?

malabsorption, especially protein & fat

71

CCK with Pancreas?

major secretion regulator, triggers vago-vagal signals
-use ACh as receptor, we don't have CCK-1 receptors

72

Duct Cell in Pancreas

Cations: Na+ (water follows in aquaporin 1)
transport mechanisms are proteins
-Na+/K+ATPase
secondary transport: Na+ in/ H+ out of cell
-passive conductance: Cl- in cell more to lumen (abnormal in cystic fibrosis)

73

Electrolytes in Pancreatic Secretion and Changes with Flow?

K+ & Na+ is constant: similar to plasma conc.
Low flow: dec. HCO3- inc. Cl-
High flow: inc. HCO3- dec. Cl-

74

Anion concentration in High Pancreatic Secretion Rates?

-Na+Cl- low secretion rates
-Na+HCO3- high secretion rates
-the slower the secretion the longer the exchanges (so more Cl-) can occur

75

The steps of pancreatic enzyme secretion?

1. RER- proteins are secreted, move to smooth golgi, then condensing vacuoles (proenzymes)
2. In zymogen granules, fuze with luminal membrane
-from condensing vacuole step on, need energy

76

What determines the types of enzymes found in pancreatic secretion?

what you eat
carbs-amylase
protein-trypsin

77

What protects the pancreas from the enzymes?

1. Enzymes in membranes
2. Enzymes are "pro" inactive form
3. Trypsin responsible for activation of other enzymes
4. Cell is antitrypsin
5. Trypsin is autocatalytic

78

Pancreatic secretion after a meal?

-increase in protein
-acid secretion
-increase bicarb and volume

79

What stimulates pancreatic secretion?

vagus, from cephalic phase
-conditional stimuli, smell, taste, chewing, swallowing, hypoglycemia

-strong aciner cell stimulation
-weak duct cell stimulation

80

Secretin Release (pancreas)

-measure bicarb secretion
-threshold for release is 4.5 pH
-cells don't respond to decreasing pH past 3
-if inc. volume, get higher rates of secretion
(when fat, protein, H+ enter duodenum, H+ acts on S cells to make secretin duct & aciner, also CCK cause ACh to release on duct cells)

81

Phe + Secretin

potent release of CCK
the 2 combine have a huge response
1. conserves hormones
2. if needed lots of hormones, it would have other effects
POTENTIATION

82

Pancreatitis

-decreased volume and bicarbonate
-may impair digestion
-10% hereditary (gets rid of protective mechanisms)

83

Kwashiorkor

-a pancreatic insufficiency
-malnutrition
-decreased volume, bicarb, enzymes
-steatorrhea

84

Cystic Fibrosis

-no Cl- conductance in apical membrane
-mucus secretion
-decreased volume, bicarb, enzymes
-steatorrhea

85

Bile acids

-synthesized from cholesterol
-secreted by hepatocytes into ducts

86

Secretin Stimulates what into the Bile Ducts?

-HCO3-
-Na+
-H2O

87

Spincter of Oddi at rest?

-closed, so bile flows into gallbladder

88

CCK stimulates ACh to do what to gallbladder and sphincter of Oddi?

1. gallbladder contractions
2. relaxes sphincter of Oddi

89

% of bile acid reabsorbed due to passive diffusion?

40%

90

Amount of bile salts in the pool?

2.5g

91

% of bile acids actively reabsorbed in the ileum?

55%

92

% of bile acids lost in stool?

5%

93

4 Important Bile Acids?

Primary: synthesized by liver
1) Cholic Acid
2) Chenodeoxycolic
Secondary
3) Deoxycholic Acid
4) Lithocholic Acid

94

While have bile salt instead of bile acids?

Bile acids have pKa~7, the live conjugates them to amino acids (bile salts)
1. glycine pKa~3.7
2. taurine pKa~1.5

95

Micelle Formation

Polar Part: nucleus, hydroxyl group, ionized acidic group
Hydrophobic Part: hydrocarbon steroid body
-it solublizes products of fat digestion

96

Biliary Histology

-stuff is extracted from portal vein, secreted into bile duct, flow of bile is countercurrent from flow of blood (dec. conc. gradient)

97

How much bile aids secreted per day?

30g

98

Max synthesis of bile acids per day?

3-5g

99

Enterohepatic Circulation

bile acids actively transported into bile, stored in gallbladder, secreted in duodenum
-dehydroxylate bile salts
-if you inhibit 7 hydroxylase enzyme, stops production

100

Bile acids reabsorbed in blood

-continuous process
-secretion of bile acids osmotically drives electrolytes H20
-cholesterol and phospholipids still depend on bile acids

101

Bilirubin

-produced by metabolism of broken RBC
1. formation of Fe, chelated & disposed of
2. green-biliredin, yellow bilirubin (bound to plasma albumen in blood)
-active process that excretes bilirubin from intestine (not very effective)

102

Bilirubin Glucuronide

water soluble
bacteria converts it to bilirubin

103

Stirkobiligin

makes poop brown (pigment)

104

Secretion of Water & Electrolytes

-osmotically drive secretion of H2O & electrolytes
-liver ducts secretin inc. Na+ bicarb and H2O
-Interdigestive phase: sphincter of Oddi, filling pressure of 10-20mmHg holds 20-50mL of bile

105

CCK on Gallbladder Function

-acts through vagal stimulation
-ACh causes contraction of gall bladder and relaxes sphincter of Oddi

106

Micellar Solution

-isotonic
-all cations are osmotically inactive by being bound to bile acids

107

Cholesterol Stones

-all bile produced is supersaturated with cholesterol - 50% normal
-bile acid pool reduced 50%
-crystal formation

108

Pigment Stones

10-20%
-bile saturated with unconjugated bilirubin
-high beta glucuronidase: causes it
-gall bladder wall damaged by bacteria - E. coli
surface is damaged, physical or bacteria