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RUSVM Physiology II > GI3 > Flashcards

GI3 Flashcards

(66 cards)

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1
Q

What occurs to proteins in the stomach?

A

Partly denatured and hydrolyzed by pepsin

Proteins and polypeptides

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2
Q

What is required for the breakdown of proteins and polypeptides to oligopeptides and amino acids in the small intestine?

A

Pepsin’s

Pancreatic polypeptides

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3
Q

How are oligopeptides reabsorbed across the intestinal wall

A

Oligopeptides have to be broken down by animopeptidases and oligopeptidases in the brush border to make tri- and di- peptides

Tri and di peptides are absorbed with the H+ gradient

Tertiary transport

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4
Q

How are amino acids absorbed in the intestinal lumen?

A

With sodium gradient

Secondary active transport

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5
Q

Amino acids are important precursors to?

A

Serotonin (tryptophan)
Melatonin (tryptophan->serotonin)
Dopamine (tyrosine)
Histamine (histidine)

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6
Q

What are peptides? What are important physiological peptides?

A

Short chains of amino acids linked by peptide bonds

Oxytocin
ADH
Bradykinin
Angiotensin II

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7
Q

What are important polypeptides?

A

Gastrin
CCK
Glucagon
ANP

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8
Q

What occurs in the duodenum to breakdown lipid droplets and increase surface area

A

Emulsification by bile acids

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9
Q

What is the structure of bile acids?

A

Sterol ring with amino acid side chain

Amphiphatic

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10
Q

What enzyme partially digests lipids in the stomach?

A

Gastric lipase

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11
Q

After emulsification, what enzyme is required to breakdown lipids further? What does it produce?

A

Pancreatic lipase

Triglycerides -> free fatty acid and monoglycerides

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12
Q

How are free fatty acids and monoglycerides absorbed across the intestinal wall?

A

FFA, monoglycerides, and vitamins form mixed micelles

Micelles are absorbed by enterocytes

Go to ER for re-esterification (MAG+free fatty acid=TAG)

Triglycerides are surrounded by phospholipid =chylomicrons which are excocytosed into the lymphatic vessels

(Bile acids are reabsorbed at the ileum

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13
Q

How does short chain fatty acid absorption differ from long chan?

A

Can be absorbed across the apical membrane directly (do not required micelle)

Do not have to be resynthesized to TAG -> directly released to portal system where they bind albumin

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14
Q

How is lipid digestion controlled?

A

CCK synthesized when lipids enter duodenum
-> stimulates bile acid secretion and pancreatic enzyme secretion

Secretin-> stimulates HCO3 secretion from pancreas

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15
Q

What happens to TAGs at skeletal muscle and adipose tissue

A

Lipoprotein lipase in capillaries converts TAG -> FFA and MAG

FFA enter muscle cells or adipocytes

Storage
Muscle makes glycerol
Adipose tissue makes TAG

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16
Q

What occurs to the remnants of chylomicrons?

A

Liver absorbs components in receptor-mediated endocytosis

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17
Q

What are fatty acids used for?

A

Energy
Structural :phospholipid and glycolipid
Hormone precursors : prostaglandin
Energy reserve :TAG in adipose tissue

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18
Q

De-novo synthesis of fatty acids occurs in the liver, mammary gland, and adipose cells. Describe the process

A

Carbohydrates and proteins –> ACoA –> malonyl CoA–> Palmitate (fully saturated fatty acid)

Stored as mono-, di- and triacylglycerols

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19
Q

Mobilization of fats from their storage tissue requires what enzyme?

A

Hormone-sensitive lipase (stimulated by epi and glucagon )

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20
Q

____________________ of fatty acid produces AcetylCoA, NADH, FADH2

A

B oxidation

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21
Q

1 palmtoyl CoA can produce ______ATP

A

131 (minus 2 needed) = net 129ATP

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22
Q

Excess Acetyl CoA can be converted in the liver to ketone bodies, what are the three ketone bodies?

A

Acetoacetate
Acetone
3-hydroxybutyrate

Can be used in for energy in peripheral tissues-> converted back to Acetyl CoA -> Krebs cycle

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23
Q

Reabsorption of water in the intestine is highest in the ________________ and lowest in the _______________

A

Jejunum; colon

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24
Q

How is Na+ absorbed in the intestines?

A

Apical:
Na/H+ exchanger
Na/Glucose cotransporter
Na/Amino acid cotransporter

Basolaterally
Na/K+ ATPase

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25
How is K+ absorbed in the small intestine?
Paracellular
26
How is Ca2+ reabsorbed in the intestine?
Calcitoriol (PTH stimulates release from the kidney) - > increase apical Ca2+ channels - >increase Calbindin-synthesis - > increase Ca2+ ATPase (basolateral)
27
How is Mg2+ absorbed in the intestine?
Mg2+ channels | Paracellular
28
How is phosphate absorbed in the intestine?
Na+/phosphate symporter
29
How is B12 absorbed in the GI tract?
B12 within a food protein HCl and pepsin separates B12 from food protein B12 binds to HC Trypsin cleaves B12 from HC in duodenum B12 combines with IF (intrinsic factor) IF with B12 binds to receptor in ileum and is absorbed
30
Absorption of iron uses ____________ transporter at the apical membrane which cotransports Fe with _______
Ferroportin; H+
31
The smooth muscles of the GI tract are connected by _________________ so they function as a syncytium
Gap junctions
32
What are the intrinsic control mechanisms of the GI tract?
Nerves- Enteric nervous system Endocrine- secretin, gastrin, CCK, GIP, Motilin
33
What are the extrinsic control mechanisms of the GI tracts?
Nerves- Vagus and Splanchnic nerves Endocrine -aldosterone
34
What are the two plexus of the enteric nervous system and where are the located?
Plexus myentericus - between longitudinal and circular muscle -> controls muscular activity Plexus submucosus - between submucosa and circular muscle -> control mucus secretin and reabsorption
35
Enteric neurons contain _______________ which are bulge like structures which allows it to affect a wide area
Varicosities (containing neurotransmitter )
36
Enteric neurons are classified into what three types?
Dogiel type 1 - small cell body with short dendrites (motor) Dogiel type 2 - large cell body with one or two long dendrites (sensory) Dogiel type 3 - multiple shapes, motor and sensory
37
What types of receptors detect changes int he GI and conveys these changes to the Enteric nervous system and CNS?
Mechanoreceptor- detect stretch Chemoreceptors- nutrient, osmolarity, pH
38
What are the three types of motor neurons from the ENS and where are they located?
Muscle motor neuron - plexus myentericus Secretory motor neuron - plexus submucosus Vaso motor neurons - both plexus (control blood perfusion)
39
What two types of neurotransmitter are secreted by enteric neurons?
Conventional (norepi and ACh) Non-noraderenergic, non-cholinergic (NANC) NO VIP (vasoactive intestinal polypeptide Substance P
40
How does the CNS regulate the enteric NS?
PSNS - ACh-> stimulators> increase secretion SNS - NA -> inhibits ACh release
41
What parasympathetic nerve innervates the decsending colon and the distal GI tract?
Pelvic nerve - from the sacral spinal cord
42
What parasympathetic nerve innervates the esophagus, stomach, sm intestine, ascending colon, pancreas, gallbladder, and liver?
Vagus nerve - from medulla oblongata
43
Sympathetic nerves exit the spinal cord in the __________________ region
Thoracolumbar
44
What are slow waves of the GI tract?
Rhythmic contractions of smooth muscle, slow undulating changed in membrane potential no action potential, does not reach threshold
45
What cells are the electrical pacemakers for smooth muscle cells and maintain the slow waves of the GI tract?
Interstitial cells of Cajal Ion channels periodically open to produce current
46
What is a spike potential in the GI tract
True action potential Resting membrane potential becomes greater than -40mV The higher the slow wave potential the more frequently there will be a spike potential -> these AP cause contractions of the smooth muscle
47
What are the three GI reflexes essential to GI control?
Within gut wall From gut to prevertebal sympathetic From gut to spinal cord or brain stem
48
What do reflexes within the gut wall control?
GI secretion, peristalsis , mixing contractions, and local inhibitory effects
49
What type of reflex transmits signals from one part of the GI tract to another?
Gut to preverterbral sympathetic ganglia Eg Gastrocolic- from stomach causing evacuation of the colon Enterogastric - colon to sm intestine to inhibit motility Colonoileal -colon to inhibit ileal emptying
50
Reflexes for pain to inhibit the GI tract, or the defecation reflex must travel to the _____________ before going back to the GI system
Spinal cord
51
During peristalsis, stretch in the intestinal wall is recognized by mechanoreceptors. What is the feedback neuronal feedback to the smooth muscle around the site of distention?
Proximal to distention -> excitatory motor neuron -> ACh and SP -> smooth muscle contraction Distal to distention -> inhibitory motor neuron -> NO, ATP, VIP -> smooth muscle relaxation
52
The _________________reflex is the GI circuits of afferent and efferent fibers bringing gut stimuli to the dorsal vagal complex in the brain
Vasovagal via vagal nerve
53
During swallowing of food and entering of food into the stomach the vasovagal reflex causing ______________ of the stomach.
Relaxation of the smooth muscle
54
There are three relaxations of the stomach, what are they and what initiates them?
Receptive relaxation(vasovagal) - mechanical stimulation of pharynx Adaptive relaxation (gastro-gastric)- food expanding stomach Feedback relaxation (CCK)- nutrients
55
What is the motoric of the stomach
Tonic contraction of the fundus (gastric store) Strong peristaltic wave in the antrum (grinder) Passage into the grinder and the pylorus Emptying of fluid and pre-digested particles into the duodenum. (Fluid empty faster than solid particles)
56
What are the functions of intestinal motility
Mixing of food with digestive juices (GI secretions) Enhancing contact between intestinal wall and food Peristalsis, propulsive movement of chyme
57
During the digestive period, there are propulsive and non propulsive patterns of peristalsis in the small intestine/ What is the function of each of these patterns?
Propulsive: aboral migrating (movement of food) Non-propulsive : small segmental contractions along intestine (mixing and distribution of nutrients)
58
What is the migrating motoric complex?
Series of contractions occurring between meals that helps to push undigested material out of the intestine and controls bacterial population 3 phases: rest, intermittent contractions, strong peristaltic contractions
59
Mixing activity in the colon is present in all species but is more pronounced in pigs and horses due to the formation of sacculations called _______
Haustra
60
What are pathological contractions of the intestine.
Vomiting | Diarrhea
61
What stimuli can cause vomiting?
Before food intake (color, smell, emotion, appearance ) After food intake ->food particles-> visceral afferent -> vomiting center After absorption -> particle in blood ->chemoreceptor trigger zone
62
What is the sequence of events of vomiting?
Antiperistaltic wave originate in duodenum Propulsion toward stomach Contraction of abdominal musculature increases intraabdominal pressure Expansion of chest cavity - lower intrathoracic pressure Relax lower esophageal sphincter Open upper esophageal sphincter
63
Diarrhea is due to increased frequency for fecal volume. Fecal volume often is increased to to increased water. This increased water in the gut can result from?
Ingested water Water secreted by glands of GI tract Water secreted or lost through mucosal epithelium
64
What are the two types of diarrhea?
Malabsorptive - does not recover all secreted water (viral/ bacterial/ protozoan destruction of villi-> less SA for absorption ) Secretory - rate of secretion is greater than absorptive capacity (Bacteria produce enterotoxins stimulating adenylyl cyclase -> cAMP -> Cl- channel open -> H2O outflow)
65
Describe the retrosphicteric reflex
Feces accumulate in rectum -> peristaltic movement -> PSNS -> relax internal anal sphincter -> urge to deficate -> Somatic voluntary-> pudendal nerve -> maintain contraction or relaxation of external anal sphincter
66
The internal anal sphincter constriction is caused by ________________ stimulation and relaxation is caused by ____________________ stimulation
Sympathetic; parasympathetic

RUSVM Physiology II (11 decks)

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