Physiology 4.4

Front 1

What is the functional unit of intestinal absorption?

Back 1

Villus

Front 2

Describe the 3 regions of the Intestinal Villus.

Back 2

Crypt => Mitosis and Secretion

Tip => Absorption (upper 1/3)

Zone of Maturation => cell differentiation

Front 3

The mucosal epithelium possesses ? on the luminal side and ? between cells.

Back 3

Microvilli (brush border)


Tight Junctions

Front 4

What is the layer of fluid that separates the well-mixed bulk phase of intestinal contents in the lumen from the mucosal cell surface?

Back 4

Unstirred Layer

Front 5

99% of the water that enters the GI tract is absorbed transcellularly and paracellularly by the ? and ?

Back 5

Jejunum

Duodenum

Front 6

The tight junctions between enterocytes consists of transmembrane proteins called ?

Back 6

Claudins

Front 7

? determine the selective size, charge, and conductance properties of the Paracellular (between cells) Pathway.

Back 7

Claudins ---(tight junctions)

Front 8

Transcellular Absorption of water is linked to the absorption of nutrients through the ? transporter.

Back 8

SGLT-1

transport together -- Na+ and 1 Glucose --H20 Follows

Front 9

? exchange results in net absorption of Na+ during the Interdigestive (between meals) Period.

Back 9

Na-H Exchange

Front 10

? is the major mechanism for the Post Prandial (after meal) absorption of sodium.

Back 10

Cotransport of Na+ with Glucose and Amino Acids

Front 11

What is the only primary active transport mechanism for Na+ in its transport in the gut lumen across apical membranes?

Back 11

Basolateral Na+ / K+ ATPase

Front 12

True or False

Voltage-Dependent Absorption of Chloride includes passive diffusion across Tight Junctions (paracellular) and through Cl- Channels.

Back 12

True

Front 13

True or False

Cl - HCO3 exchange during the INTERDIGESTIVE period results in net Cl- Absorption

Back 13

True

Front 14

Potassium absorption is passive except for the ?

Back 14

Distal Colon

Front 15

PostPrandial removal of K+ from the blood is stimulated by ?, ? and ?

Renal excretion into the urine helps prevents HyperKalemia from occurring.

Back 15

Insulin

Aldosterone

Epinephrine

Front 16

True or False

Passive absorption of Ca2+ occurs paracellularly throughout the small intestines and exceeds active absorption.

Back 16

True

Front 17

Active Absorbed free Ca2+ in the cytosol binds to ?

? helps stimulate the active absorption of Ca2+ as it promotes protein synthesis of the protein in the previous question.

Back 17

Calbindin


Vitamin D

Front 18

How is Ca2+ exported out of the enterocyte?

2 methods

Back 18

Ca2+ ATPase

3Na+ in // Ca2+ out exchanger

Front 19

Mg2+ that is Actively absorbed occurs in the ?

Passively absorbed Mg2+ occurs in the ?

Back 19

Ileum


rest of the small intestines

Front 20

Most non-heme iron in the diet is presented as ?

An enterocyte Iron Reductase reduces it to ? which is then transported by ?

Back 20

Fe3+

converted to Fe2+

DCT1 transport

Front 21

DCT1 transporter is most optimal when the pH of the intestinal lumen is ?

What is responsible for decrease in Lumen pH of small intestines?

Back 21

Less than intracellular pH



Na-H channel

Front 22

How does Heme Iron enter the enterocyte?

? cleaves the heme and allows Fe3+ to be STORED bound to ? OR transported to the basolateral membrane via ?

Back 22

HCP1

Heme Oxygenase

Ferritin =>storage


Mobilferrin =>transport to basolateral membrane

Front 23

Iron bound to ? is brought to the ? transport to be taken across the basolateral membrane.

The transporter is associated with a ?

Back 23

Mobilferrin

transported by IREG1

-->associated with a copper containing oxidase

Front 24

Fe3+ is transported in PLASMA bound to ?

Back 24

Transferrin

Front 25

The rate of absorption of iron increases with demand--

When ? levels in Plasma are low --enterocyte cytosol levels of iron DECREASE and ? in the cytosol bind to mRNA that code for synthesis of iron transport proteins.

When levels are HIGH in the plasma -- ? binds to IRP which inhibits translation of iron transport and thereby decreases iron absorption

Back 25

Transferrin-Iron


Iron Regulatory Proteins (IRP)


Fe3+ (binds and inhibits IRP)

Front 26

Vitamin C is only actively (contransport with Na+) absorbed in the ?

Vitamin B12 (cobalamin) is only actively (contransport with Na+) absorbed in the ?

Back 26

Ileum


distal Ileum

Front 27

At low pH, protein-bound Vit B12 (cobalamin) is released and rapidly binds to ? present in saliva and gastric secretions.

Pancreatic proteases then hydrolyze the complex and VitB12 is then bound to ? which allows it to be absorbed in the ileum.

Transport of VitB12 out of enterocytes into portal blood is performed by ?

Back 27

Haptocorrin

Intrinsic Factor

Transcobalamin II

Front 28

Skipped to Clinical correlations pg12

fill in later

Back 28

Skipped to Clinical correlations pg12

fill in later

Front 29

Enterocytes possess a transporter that pumps xenobiotics from the cell back into the intestinal lumen. ? actively metabolize numerous xenobiotics and can affect the efficacy of certain medications.

Back 29

Cytochrome P450

Front 30

Where is lactase found?

Back 30

in the apical domain of the enterocyte

brush border

Front 31

? is due to toxic effects of dietary gluten. Atrophy of villi results in malabsorption and produces a wide spectrum of nutritional deficiencies.

Back 31

Celiac Disease

Front 32

Active transport of electrolytes into the intercellular space of the colon creates an ? gradient.

Tight junctions are less "leaky" than those in the small intestines.

Back 32

Osmotic gradient --draws water into the space

Front 33

Active electrogenic absorption of Na+ in the colon is done through ? and is not linked to glucose and amino acid transport.

Back 33

ENAC

Front 34

? stimulate Na+ absorption and K+ secretion in the colon by INCREASING membrane PERMEABILITY to Na+ and K+ and increasing Na/K ATPase activity.

Back 34

Mineralocorticoids (and some glucocorticoids)

Front 35

How do you treat --

Osmotic Diarrhea?

Secretory Diarrhea?

Back 35

fasting => osmotic diarrhea


oral administration of Glucose-Saline solutions => secretory diarrhea

Front 36

Constipation will affect cardiovascular return how?

(think valsalva maneuver)

Back 36

initial pressure increase

then followed by--

decreased venous return

>>causes decreased cardiac output and stroke volume

>>cause stroke, fainting, hemorrhoids etc.

Front 37

Bacterial overgrowth are problems because of the competition for the uptake of ?

and the deconjugation of ? that results in poor digestion and absorption of fat.

Back 37

Vit B12 (cobalamin)

Deconjugation of bile acids

Front 38

V. cholera stimulates ?

Rotavirus stimulates ?

Why are these effects bad?

Back 38

activate cAMP dependent secretion of Cl- =>Cholera


stimulates Ca2+ activated secretion of Cl-
inhibits cotransport of glucose and amino acids with Na+ into enterocytes

increase particles causes water to be pulled into the lumen of intestines causing diarrhea.

Front 39

The ? receives neural signals from GI trac, chemical signals from nutrients in the blood, signals from GI hormones, adipose tissue, and neural signals from the cerebral cortex relating to sight, taste, smell.

Back 39

Hypothalamus

Front 40

activation of ? neurons in the ? stimulates secretion of ? which stimulates synthesis of cocaine/amphetamine-related transcripts.

Back 40

POMC neurons

Arcuate Nuclei

secretion of α-MSH

Front 41

α-MSH acts on ? receptors present in the ? of the hypothalamus.


Activation of these receptors will cause?

Back 41

Melanocortin Receptors 3 and 4

Paraventricular Nuclei of the hypothalamus


decreases food intake and increases energy expenditure

Front 42

Activation of ? neurons stimulates food intake by inhibiting the effects of α-MSH on MCR 3 and 4.

Back 42

NPY / AGRP neurons

Front 43

For short term control of regulating food intake -- ? signals from gastric filling and oral factors of chewing, tasting and swallowing have a "meter" effect on regulation of food intake

Back 43

VAGUS SENSORY SIGNALS

Front 44

What are the 3 short term controls of food intake regulation?

Back 44

Vagal Sensory signals --suppresses hunger

CCK --suppresses hunger
PYY
Glucose-dependent insulinotropic peptide

Ghrelin --stimulates food intake

Front 45

? is a product of PARIETAL CELLS primarily and rises in blood during a FAST.

Stimulates food intake

Back 45

Ghrelin

Front 46

? comes from primarily from the ileum and colon is secreted in proportion to calories ingested.

Back 46

Peptide YY (PYY)

Front 47

The concentration of glucose, amino acids and lipids in blood modulate food intake. Elevated blood glucose stimulates increased firing rates of glucoreceptor neurons in the satiety center in ? and ? of the hypothalamus

Back 47

Ventromedial nuclei

Paraventricular nuclei

Front 48

? from adipocytes stimulates receptors found in the HYPOTHALAMUS. The effect is to INHIBIT ? neurons and STIMULATE ? neurons and INCREASE production of ?

Stimulate Sympathetic nerve activity
Decrease secretion of insulin

Back 48

Leptin

inhibit NPY/AGRP neurons

stimulate POMC neurons

increase production of CRH

Front 49

Describe Leptin signaling pathway

Back 49

Leptin + Leptin Receptor

=> activate JAK2

=> phosphorylation of tyrosine residues

=> activates transcription of leptin targets and protein synthesis

Front 50

Name the neurotransmitters and hormones INHIBITING food intake. (7)

CLAPIGS

Back 50

CCK
Leptin
α-MSH
PYY
Insulin
Glucagon-like peptide
Serotonin (5-HT)

Front 51

Name the neurotransmitters and hormones stimulating food intake. (5)

GGONE (cause you're so hungry!)

Back 51

Ghrelin
Glucocorticoids
Orexins A and B
Neuropeptide Y
Endogenous opioids

Front 52

True or False

Oligosaccharides and polysaccharides must be first hydrolyzed to MONOSACCHARIDES prior to absorption?

Back 52

True

Front 53

True or False

Hydrolases expressed by certain colon bacteria convert Dietary fiber to short-chain fatty acids.

Back 53

True

Front 54

Where are Disaccharidases that facilitate complete hydrolysis of oligosaccharides found?

Back 54

Enterocyte brush border


monosaccharides are they only ones that can be absorbed

Front 55

Glucose and Galactose absorption is done via ? which is Na+ dependent at the apical brush border.

What happens if the Na/K+ pump fails?

Back 55

SGLT1


if Na/K pump fails --SGLT1 will not work anymore since it requires the Na+ gradient to function.

Front 56

Fructose crosses the enterocyte APICAL membrane via ?

All three monoglycerides (glucose galactose fructose) are transported across the BASOLATERAL MEMBRANE by ?

Back 56

GLUT 5 ---fructose across APICAL


GLUT 2 ---all monosugars across basolateral membrane

Front 57

True or False

Pepsin plays a relatively MAJOR role in the hydrolysis of dietary protein.

Back 57

FALSE

plays a MINOR role

Front 58

Proteins are hydrolyzed to oligopeptides or single amino acids by ? and ? enzymes.

Back 58

Pancreatic enzymes

Apical membrane enzymes

Front 59

Cytosolic peptidases hydrolyze ? to ?


Apical Brush border endopeptidase and ectopeptidase convert ? to ?

Back 59

Oligopeptides
to
Free Amino acids

(same with apical brush border)

Front 60

What is the main contributor to protein digestion?

Back 60

Pancreatic Proteases

Trypsin
Chymotrypsin
Elastase
Carboxypeptidase A and B

Front 61

What is the major transporter of amino acids in enterocytes?


? Cotransports SMALL PEPTIDES (di and tri-peptides) with H+

Back 61

Na+ and Neutral Amino Acid Cotransporter B


PepT1 => small peptides with H+

Front 62

? are found above Peyer's patches and replace typical enterocytes.

has DEEP basolateral membrane pocket invagination

-->helps transport Ag to APC and help initiate immune response

Back 62

M Cells

Front 63

? cells in the crypts of intestine secrete antimicrobial substances:

Defensin-5
RegIIIy
CARD15

Back 63

Paneth cells

Front 64

By products of lipid hydrolysis (long-chain fatty acids and 2-monoglyceride) are solubilized in ? which diffuse across the unstirred layer to reach the brush-border membranes.

Back 64

Mixed Micelles

Front 65

Products of fat hydrolysis in the enterocyte make their way to the SER via a fatty acid-binding protein. Re-esterfication of lipids occur and are packaged in ?

Back 65

Chylomicrons

Front 66

During fasting, endogenous lipids are processed and secreted in ?

Back 66

VLDL

Front 67

True or False

VLDL and Chylomicrons permeate villus LACTEAL capillaries.

Back 67

TRUE

they DO NOT permeate villus blood capillaries

Front 68

Conjugated Bile Acids are ACTIVELY ABSORBED in the ? by a ? transporter and by a ? transporter.

Back 68

terminal Ileum

Na+ dependent Bile Acid Transporter


Organic Salt Transporter (OST)

Front 69

Bile acids that are not extracted by Hepatocytes are filtered by the ? and reabsorbed in the Proximal Tubules.

Back 69

Renal Glomeruli

Front 70

Cholesterol lowering drugs work by either ? or ?

Back 70

bind to bile acids

or

inhibit de novo synthesis of cholesterol via STATINS

Front 71

Vitamin A, D, E, K are lipid soluble and are present in ? in the intestinal lumen.

They are incorporated into ? and ? prior to entering lymph.

Back 71

Mixed miscelles


chylomicrons
VLDL

Front 72

What happens to blood flow during PostPrandial?

Back 72

blood flow increases 8x

response to production of Vasodilator metabolites and Vasoactive GI hormones

Front 73

Where do long-chain fatty acids, 2 monoglyceride and fat soluble vitamins enter into?

? removes absorbed nutrients, minerals and water soluble vitamins.

Back 73

Lacteal Vessels


Venous blood

Front 74

? shunts oxygen from arteriole to venule.

Pathophysiological states can exaggerate hypoxia at the villus tip causing massive necrosis of the intestinal villus.

Back 74

Countercurrent Oxygen Exchange