Chpt 20: Stomach Acid production & Mech. movement

What is to note about Pepsinogen and stomach acid production? Why does this happen?

They are secreted at the same time; bc pepsinogen needs acid to activate

How is stomach acid produced? (1st step)

In parietal cell CO2 and H20 bind to make Carbonic acid which dissocates to bicarb and H+

How is stomach acid produced? (2nd step)

H+/K+ pump, pumps out H+ AND takes in K+. THEN bicarb diffuses out while Cl- comes in

How is stomach acid produced? (3rd step)

OUTSIDE OF PARIETAL CELL Cl- and H+ bind to form HCL

What are the three phases to stomach acid production?

Cephalic phase, Gastric phase, & Intestinal phase

What happens in the cephalic phase?

BEFORE eating food thru thinking, seeing, or smelling food

How does the cephalic phase stimulate stomach acid production? (2 ways)

Indirect: parasymp stimulates

direct: stimulate pepsinogen & acid secretion

What happens in the gastric phase?

Food in the stomach causes DISTENSTION (which always stimulates)

How does the gastric phase stimualte stoamch acid production?

directly with pepsinogen and stomach acid OR indirectly using Gastrin

How is pepsin regulated by positive feedback? How does this affect stomach acid production too?

Once one pepsinogen in turned to pepsin it INCREASES production of pepsin WHICH increase stomach acid too.

How can the gastric phase be INHIBITED?

when food exits stomach neg feedback take control and stops all secretions OR too much acid stops secretion

What happens in the intestinal phase?

Food enters duodeunum & DISTENSION stimulates lipid digestion.

Pancreatic Digestive enzymes are secreted by what 2 cells?

Acinar cells and Duct cells

WHAT do DUCT cells secrete, what abt Acinar cells

Duct cells secrete bicarb

acinar secretes digestive enzymes

How are the 2 pancreatic digestive enzymes stimulated to secrete in the first place?

CCK and secrotin

Which hormone (CCK or Secretin) stimulates Acinar and how?

CCK stimulates Acinar cells from fat & amino Acids in Duodenum

What OTHER function do CCK and secretin possess in the GI TRACT? WHy do they do this and from where?

Both secrete bile into the duodenum to decrease acidity or break down fat

(CCK from gall bladder & secretin from liver)

What is the function of mechinal digestion in the GI tract?

to mix food and move it from mouth to anus

What is peristalsis?

Moves food from A to B by rhythmic contractions

What is segmentation? What is it MOST important for (in sm intestine)..?

Mixes food by alternating contractions; mixiing chyme toward the mucus of intestine to increase absorption

Which mechanical movement does the stomcach use?

peristalsis to move chyme towards pyloric sphincter but moves BACK & segmentation mixes it

What is it called when the stomach uses mechanical movement to empty it?

Migrating Motility complex

How do the smooth muscle, which is throughout the GI tract stimulate contractions?

thru pacemaker cells which activate AP on their own

What is the difference between stomach contractions and intestinal?

Stomach does NOT need AP to start contracting (if there is any conctraction are stronger), intestines NEED AP to start contraction

Masication is both what?

involutnary and voluntary

What is to note abt Gastrin as it relates to stomach contractions AND the activation of the Sm intestine how it affects stomach contr?

Gastrin increases stomach conctracts and activation of sm intesinte inhibits stomach contractions

Once food (chyme) reaches sm intestine, DISTENSION stimulates contractions of WHAT 3 reflexes?

intestino-intestinal, illeumgastric, & gastroileal

What are the 2 reflexes of the LG intestine?

colonocolic: Distention in1 are of colon RELAXES another

gastrocolic: chyme in stomach stimulate LG intestine movement

What are the two movements ONLY found in LG intestine?

Haustration (like segmentation BUT slower)

mass movement (like peritalsis BUT contractions are longer)

What do the 3 relfexes of sm intestine do?

intestino-intestinal: severe damage to sm intestine stops contraction,

ileumgrastric: when illeum distention inhibited stomach contractions

gastroileal: chyme in stomach increases ms movement of illeum ileum

in the anus WHICH sphincter is smooth muscle and skeletal?

External anal sphincter is skeletal and internal anal sphincter is smooth

Which hormone (CCK/Secrotin) stimulates duct cells?

Secretin stimulates Duct cells when there is high acidity in the duodenum