26: Stomach Flashcards by Ryley Tegler

Parietal cell function: the players

HCL dissociate in to hydrogen and bicarb

proton pump (hydrogen potassium)
potassium and chloride channles
carbonic anhydrase
bicarb/chloride antiporter

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Parietal cell function

hydrogen out, sodium in
potassium goes out and recycles continuously
so we get rid of H ions

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Parietal cell function 2

Bicarb/cholride antiporter:
chloride comes in, and exits. like K
bicarb stays and diffuses into blood vessle

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stomach is like a

washing machiene/grinder

to produce chyme and finish what mouth didn’t

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mechanical digestion

gentle waves in stomach to mix bolus with juices
more vigours from body to stomach to pyloric region to move chyme
intense near pyloriys to opening of pyloric sphincter to squirt out teaspoons (1-2 per wave)

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protein digestion

starts in stomach
HCl denatures protein molecs
HCl activates pesinogen to pepsin to break peptide bonds to A.As

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Fat digestion

continues in stomach

gastric lipase splits triglycercides (but most effective at pH 5-6) (infant stomach)

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HCl also

kills microbes

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Mucous

keeps stomach walls from being digested

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Things stomach absorbs

water
electrolytes
drugs (asprin)
fat (to slow passage of alcohol to intestine where it is quicker)
alcohol (more slowly if fat taken in too)

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Cephalic Phase

anticipation 
prepare mouth and stomach 
sight, smell, memories, thoughts of food
salivation (facial and Glossopharyngeal)
gastic glands secrete gastric juices (Vagus)

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Gastric Phase

breakdown of material

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Intestinal Phase

controlled release of chyme

entry into duodenoum slows gastic activity, inc intestinal activity

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Neural influence on Gastric Phase

strech receptors and chemoreceptors–> signal bolus entry
vigorous peristalsis and gastric gland secretions
chyme periodically released into duodenum

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Endocrine influences on Gastric Phase

distention and pressure of food= G cells secrete gastrin

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gastrin

inc gastric gland secretions and motillity

causes pyloric sphincter relaxation

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Neural influence on Intesinal Phase

distension of duodenum and chem contents of chyme= activated symp nerves
this slows gastric activity

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Endocrine influnce on Intesinal Phase

distension of duodenum and contents of chyme= hormonal release from dnteroendocrine cells here
secretin
cholecystokinin (CCK)

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secretin

dec stomach secretions

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CCK

dec stomach emptying

gatric emptying

inc as bolus enters stomach

distension of stomach and presence of food in it causes

secretion of gastric and vagaal nerve impulses

secretion of gastric and vagaal nerve impulses stimulates

contraction of lower esophogeal spincter and stomach

relaxation of pylorc sphincter for emptying

Enterogastric reflex regulates

regulate amount of chyme released into duodenum

CCK and secretin relases

CCK and secretic both

stim symp impulses and inhibit gastric emptying

Enterogastric reflex initiated by

distension of duodenum and contents of chyme | sensory impulses sent to medulla to inhibit parasymp stim of stomach

2 types of influence for intestinal and gastric phases

neural | endocrine

smooth muscle control

involuntary mostly ANS ACH and norepi membrane potential -50 to -60

smooth muscle types

single/unitary multiunit categorized by manner of excitation

unitary SM

walls of GI tract gall baldder walls walls of urinary bladder may not be in contact with motor neuron

Unitar SM is

autorythmic connect via gap junction: transmit APs from one fiber to another adhering to eachother=transmission of force slow synched graded contraction

conexons

entire unit and channels between cells

conexens

the individual cells that make up the unit

genotypes and phenotypes

want conexons that have same numbers so that channels work most efficiently

function syncytium

a group of cells that get one nervous system input. react as a group!

how smooth and skeletal muscle differ (smooth described)

SR poorly developed (SM) thick filaments of SM have actin grabbing heads entire lengthen thick and thin filaments arranged diagonally within cell for twisting motion

circular muscle

contracting at right angles to each other

smooth muscle varicosities

little bumps | release neurotransmitters into diffuse junctons of SM fiber

special features of SM (about contraction)

can sustain contraction for a long time without tiring at small NRG cost maintains low level of tone even w/o APs stress relaxation response

Stress relaxation in SM

stretch causes inc in tension tension decs w/in 1-2 minutes allows SM to change length but maintain ability to contract (important for storage organs) never goes down to zero!

Length-tension relationship

SM operate over wider range of resting lengths | generally broader length-tension relationships in SM compared to skeletal muscle

proton pump of parietal cell

pushes H out of cell | H+/K+ ATPase

antiporter

Cl-/HCO3-

why do we cross parietal cell?

to get into blood stream

where do CO2 and H2O come from

CO2: metabolism | H2O just in cell

carbonic anhydrase in parietal cell

major in disposing of cellular waste

Goal of parietal cell

to secrete HCl!

what makes CA?

H2O and CO2 make carbonic anhydrase

CA dissociates into

bicarb and H... we need to get rid of this