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GI 6+7
SMP
44
Medical
Graduate
01/29/2012

Additional Medical Flashcards

 


 

Cards

Term
What part of the brain regulates thirst and hunger behaviors?
Definition
Hypothalamus
Term
Describe how the thirst reflex works when the body is dehydrated.
Definition
If the extracellular fluid volume decreases, plasma osmolality will rise. This increase is detected by hypothalamic osmoreceptors, which shrink as water leaves them to maintain homeostasis. Hypothalamus senses this shrinking of osmoreceptors.
Term
Which hormones are released to retain water?
Definition
Aldosterone, angiotensin II, and antidiuretic hormone.
Term
How sensitive is the thirst response?
Definition
It can detect a 2% increase in plasma osmolality.
Term
Describe which hormones are active during the fasting state.
Definition
The oxnytic cells of the stomach release ghrelin into blood. Ghrelin reaches arcuate nucleus of hypothalamus, which stimulates a release of neuropeptide y (NPY), which stimulates hunger.
Term
What happens once food is ingested? How is the hunger reflex repressed?
Definition
Upon eating, Peptide YY and Glucagon-Like Peptide-1 (GLP-1) are released from the jejunum, and these two supress NPY. Leptin is also secreted by adipose cells, and this also acts to supress NPY.
Term
What's odd about leptin and ghrelin levels in obese people?
Definition
In obese people, leptin levels are elevated, and ghrelin levels are decreased. This indicates that some hormone desensitization may be occurring.
Term
Why do you sometimes get full, even after you have eaten less food?
Definition
If you eat the food slowly, it'll have time to get to the jejunum, allowing a release of GLP-1 and Peptide YY, which supress hunger.
Term
What do each of the three salivary glands release?
Definition
Parotid glands release serous fluid with amylase. Sublingual glands release mucous. The submaxillary glands release both.
Term
What determines the final tonicity of saliva?
Definition
As saliva flows through the ducts, electrolytes are reabsorbed. Tonicity is thus dependent on the flow through the ducts. Saliva will ALWAYS be hypotonic to the plasma, but higher flow rates = higher tonicity (less time for electrolytes to be reabsorbed). And vice versa.
Term
What are the differences in the electrolyte content of saliva vs blood plasma?
Definition
Saliva is hypotonic, it has a HIGHER potassium concentration, and more bicarbonates than chlorides.
Term
What are the effects of chronic vomiting?
Definition
Loss of protons resulting in alkalosis, and a loss of potassium leading to hypokalemia.
Term
What are the three products in saliva, and what are their functions?
Definition
Alpha- salivary amylase, which digests starches. Lingual lipase, secreted by the tongue, which helps start the lipid digestion process. And R protein binders, which attach to vitamin B12, protecting it from breaking down in the stomach.
Term
What controls the rate of salivary flow through the ducts?
Definition
The parasympathetic nervous system. But NOT the vagus nerve. The glossopharyngeal and facial nerves provide the innervation, and they increase flow rate of saliva.
Term
Sympathetic innervation doesn't do much for salivary flow rate, but there is an initial uptick in flow rate. What's causes this?
Definition
Sympathetic innervation causes contraction of the myoepithelial cells surrounding the acinar cells, causing a quick, short release of fluid.
Term
Which glands are the lingual lipases released from?
Definition
von Ebner's glands in the tongue.
Term
What are some factors that increase salivary flow? Decrease it?
Definition
Increases flow: PNS (ACh), CNS (anticipating food coming in), nausea (to get ready for vomiting), esophageal distension. Decrease flow rate: Sympathetics (NE), hormones that retain water (ADH, Angiotensin 2, aldosterone), sleep, dehydration (obvi), aging.
Term
What's the difference between mucous, mucus, and mucin?
Definition
Mucous glands secrete mucus, which is a bicarbonate rich buffer. Mucins are glycoproteins that help form the viscosity of the mucus.
Term
What are the esophageal secretions?
Definition
The esophagous justhas minor serous and mucous glands, mostly in the lower segment. They lubricate the bolus.
Term
Which cells release HCl in the stomach? What does HCl do?
Definition
Parietal cells. It breaks down bacteria, aids in digestion by breaking stuff down.
Term
In addition to HCl, what do parietal cells release?
Definition
Intrinsic factor, which protects vitamin B12.
Term
Where is pepsin released from and what does it do?
Definition
It's released as pepsinogen from chief cells, and once it's broken down to pepsin, it breaks down protein.
Term
What's the role of gastrin?
Definition
Gastrin is a hormone released from G-cells in the antrum. It's released into the blood, and it causes a further increase in HCl production. It also causes mass movements in the large intestines (Gastrocolic reflex).
Term
Where is gastric lipase secreted from and what's it role?
Definition
It's also secreted from chief cells (as is pepsinogen), and it continues the lipid breakdown.
Term
What other two local hormones affect HCl production in the parietal cells?
Definition
Somatostatin inhibits HCl production and histamine increases it.
Term
How does mucus protect the stomach epithelium?
Definition
It creates a bicarbonate layer right next to the epithelial cells, and it acts as a buffer.
Term
What factors regulate HCl secretion, directly and indirectly?
Definition
Gastrin (more HCl) and GIP (gastrin inhibitory protein) act directly on parietal cells to recruit more H/K pumps. Secretin and peptide YY act indirectly to reduce HCl levels by supressing gastrin.
Term
Why is the blood leaving the parietal cells alkayltic?
Definition
Once CO2 is comes into the parietal cells, it's converted to bicarbonate and a proton. The proton stays in (and gets pumped into the lumen of stomach), but the bicarbonate gets transported back to blood, as a chloride ion comes into the parietal cell.
Term
Describe the morphological change that occurs to parietal cells during stimulation and de-stimulation.
Definition
If a parietal cell is stimulated, it forms canaliculi to increase surface area. This allows more proton pumps to become activated.
Term
Of the inhibitors of HCl secretion, which ones act directly on parietal cells?
Definition
Somatostatin and prostaglandins.
Term
Wat are the three phases of neural control of acid secretion?
Definition
1. Cephalic -> anticipation of food increases HCl production via vagal stimulation.
2. Gastric: Once chyme reaches stomach, vagal effects, and gastrin increase HCl production.
3. Intestinal: Once chyme gets to duodenum, there's a decrease in HCl production via secretin.
Term
How can chronic use of NSAIDs/aspirin lead to ulcers?
Definition
NSAIDs and aspirin block prostaglandins, which promote mucus secretion and HCl inhibition. With prostaglandins blocked, you get a decrease in mucus and increased HCl levels which obviously isn't good.
Term
Which bacteria is the most common cause of gastric ulcers? And how do they survive and do work?
Definition
Helicobacter pyolori. It survives by secreting urease, which produces NH3 that can neutralize the acid around it. Ammonia is also toxic to epithelial cells of the stomach.
Term
What are the differences between the brush border cells and the crypts of lieberkuhn?
Definition
The crypts secrete chloride ions, and thus water and sodium as well. Via the CFTR protein. The brush border cells have villi/microvilli, so they're used for absorption of nutrients. They have a lot of brush border hydrolases. They absorb water instead of secreting it.
Term
What cells make up the pancreatic duct? What do they secrete?
Definition
Acinar cells release digestive enzymes, centroacinar and extralobular cells secrete electrolytes, bicarbonate, and water.
Term
What are acinar cells and centroacinar/extralobular cells stimlated by?
Definition
CCK stimulates acinar cells, and secretin stimulates centroacinar/extralobular cells.
Term
What are pancreatic enzymes secreted as?
Definition
Zymogens, so they don't eat up the pancreatic cells, leading to pancreatitis.
Term
How is trypsinogen activated in the duodenum? What does it go on to do?
Definition
It's activated by enterokinase to trypsin. Trypsin activates all the other zymogens.
Term
What is the primary hormone released if the chyme in the duodenum consists mostly of peptides and amino acids?
Definition
Gastrin from G-cells. Gastrin's effects: increase in HCl at parietal cells, increases antral and intestinal motility.
Term
What is the primary hormone released if the chyme is a long fatty acid chain?
Definition
Secretin, from S-cells. Secretin increases pancreatic, biliary, and intestinal electrolyte secretions. Reduces HCl levels and Gastric emptying.
Term
What's the primary hormone released if the chyme in the duodenum is mostly peptides and fats?
Definition
CCK. Increases pancreatic enzyme secretion, gall bladder contraction, relaxes sphincter of oddi, reduces gastric emptying, and causes increased motility in small and large intestines (mass movements).
Term
If the chyme in the duodenum consists of fatty acids, protein, and sugars, what hormone is released?
Definition
Gastrin inhibitory peptide. This increases insulin secretion, lowers gastric emptying and motility.
Term
What does the Ileum secrete? In exhange for what?
Definition
Ileum secretes protons in exchange for sodium ions, and bicarbonate in exchange for chloride ions.
Term
What's secreted/absorbed in the colon? What happens during diarrhea?
Definition
Potassium ions and bicarbonate are secreted, while sodium (and thus water) is absorbed. With diarrhea, we can get hypokalemia (as with vomiting), and acidosis (unlike with vomiting).
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