Physiology Flashcards
- Choose the INCORRECT statement. Absorption of water/fluid…
A) occurs largely in the small intestine
B) occurs as a simultaneous process to secretion in the small intestine
C) is driven by the electrolyte movement, usually anions, across the luminal membrane
D) is aided by the large surface area provided by the folds, villi and microvilli
E) may occur in the small intestine in the villi
C) is driven by the electrolyte movement, usually anions, across the luminal membrane
Absorption is driven by electrolyte movement across the luminal membrane, but usually the absorption of Na ions or positive ions - CATIONS, not Anions which are negatively charged.
- Regulation of gastric acid secretion…
A) also regulates intrinsic factor secretion
B) mostly involves enteroendocrine secretions in the cephalic phase
C) is mediated by the effect of acetylcholine (released by the PNS) on G cells thereby stimulating gastrin secretion
D) mostly increases acid production in the intestinal phase
A) also regulates intrinsic factor secretion
The factors which stimulate gastric acid secretion also stimulate Intrinsic Factor secretion. In the cephalic phase, acid production is stimulated through the vagal nerve and in the intestinal phase is mostly inhibited by enteroendocrine mechanisms. The PNS stimulates G cells via gastrin-releasing peptide (not acetylcholine).
- Phase II of the MMC is characterised by motility which is…
A) quiet and minimal
B) submaximal and irregular
C) maximal and regular
B) submaximal and irregular
Phase I is quiet, Phase II submaximal and irregular and Phase III is maximal and regular.
- The final secretion of the salivary glands is…
- hypotonic/isotonic/hypertonic?
- rich in…?
Hypotonic and bicarbonate-rich.
The initial secretion of the salivary glands is isotonic and during ductal modification, it becomes hypotonic and rich in bicarbonate (as Na & Cl are reabsorbed to a greater extent than K & HCO3 are secreted).
- What is eructation?
A) burping
B) vomiting
C) farting
D) gurgling noises in the stomach
A) Burping
- Which of the following will pass most slowly through the stomach?
A) Croissant with peanut butter
B) Skim flat white
C) water
D) Low fat yoghurt
A) Croissant with peanut butter.
Croissants and peanut butter have a high fat content and this will slow the gastric emptying.
- What is the name of the motility pattern that occurs for short periods of time in the large intestine and is responsible for the distension of the rectum and the feeling of urgency?
A) peristalis
B) segmentation
C) haustrations
D) mass movements
D) Mass movements.
Mass movements are multi-haustral contractions that move the fecal matter along - usually into the rectum, causing distention and a feeling of urgency. Peristalsis is similar but it is given a different name here as the matter in the large intestines is not just a bolus but a larger volume which continues to fill large portions the intestines. Segmentation is the main motility pattern of the small intestine in the digestive phase and haustrations are the equivalent in the large intestine and allow fluid to be absorbed from the fecal matter.
- Vomiting of gastric contents can cause…
A) metabolic alkalosis
B) metabolic acidosis
A) Metabolic alkalosis.
As gastric contents do not enter the small intestine, the alkaline tide is maintained. Think deeply about this. (no acidic stomach contents to stimulate somatostatin from the D cells in the pyloric gland area; no somatostatin to negatively feedback on G cells to reduce acid production and hence elevated HCO3- entering the blood, the ‘alkaline tide’)
- Bile…
A) is stored and concentrated in the liver
B) is used to excrete toxic substances
C) is acidic in nature
D) contains substances that are required for the digestion of proteins and carbohydrates
B) is used to excrete toxic substances
Bile is stored and concentrated in the gallbladder (not liver). It is an alkaline secretion, rich in bicarbonate that contains bile salts and lecithin which aid in the digestion of lipids (not proteins or carbohydrates). It is a vehicle which allows the excretion of toxic substances from the body.
- Which of the following is NOT found in saliva in large concentrations and plays little role in digestion?
A) Lipase
B) Amylase
C) Protease
D) Mucus
C) Protease
There is always mucus in the GIT. Lingual lipase and salivary amylase….remember? Although lingual lipase also doesn’t do that much. The saliva also contains small amounts of kallikreins (proteases) but they are not significant in digestion. Best answer here is protease.
- To achieve the final pancreatic secretion exchange of which two ions takes place during ductal modification?
A) Na and Cl B) K and Cl C) HCO3 and Cl D) Na and K E) HCO3 and PO4 F) Na and HCO3
C) HCO3 & Cl
The process of ductal modification allows exchange of chloride & bicarbonate producing a bicarbonate rich pancreatic solution.
- Which of the following gives the correct order of the gut wall layers starting innermost?
A) submucosa, muscularis externa, mucosa, serosa
B) mucosa, submucosa, muscularis externa, serosa
C) muscularis externa, mucosa, submucosa, serosa
D) serosa, muscularis externa, submucosa, mucosa
B) mucosa, submucosa, muscularis externa, serosa
- Which of the following is NOT a mechanism stimulating acid secretion?
A) distention of the antrum => local ENS reflex
B) amino acids in stomach antrum => stimulating G cells
C) low pH in stomach => stimulating D cells
D) sight of food => stimulating vagal outflow
C) low pH in stomach => stimulating D cells
Stimulation of D cells increases somatostatin secretion which inhibits acid secretion
- Which of the following does not relate to smooth muscle properties or function within the GIT?
A) unitary smooth muscle
B) functions as a syncytium
C) has gap junctions (low resistance pathways)
D) has a flat resting membrane potential
D) has a flat resting membrane potential
Smooth muscle in the gastrointestinal tract has a slow wave potential - undulating membrane potential which can generate action potentials when it reaches threshold
- Which of the following has the lowest volume of secretion per day?
A) stomach B) pancreas C) liver D) small intestine E) large intestine
E) large intestine
The large intestine secretes very small volumes per day - almost neglible and mostly mucus. The other options secrete quite large volumes - go check the lecture notes.
- Which of the following occurs when parietal cells are stimulated?
A) tubulovesicles fuse with the luminal membrane
B) tubulovesicles are snipped off the luminal membrane
C) mitochrondrial activity decreases
D) luminal surface area decreases
A) tubulovesicles fuse with the luminal membrane
When parietal cells are stimulated, the tubulovesicles (containing proton pumps) fuse with the luminal membrane increasing its surface area and capacity for acid production. Acid production requires energy and mitochondrial activity would increase (not decrease).
- Which of the following motility patterns is characteristic during fasting?
A) peristalsis
B) segmentation
C) mass movements
D) migrating motor complex
D) migrating motor complex
The MMC occurs during fasting and has three characteristic phases. It occurs approximately every 90 minutes starting at the stomach and continuing through to the ileum. The MMC can be disrupted by feeding.
- Vitamin B12 absorption…
A) is increased in patients who have had gastric bypass surgery
B) occurs in the duodenum
C) requires complex formation with bile salts
D) may decrease if acid production is decreased
D) may decrease if acid production is decreased
Vitamin B12 absorption requires formation of the VitB12/Intrinsic Factor complex. IF is secreted by parietal cells and under the same conditions as acid secretion. If acid secretion decreases, IF secretion will decrease and vitamin B12 absorption will decrease. Additionally a decrease in acid secretion may affect the liberation of vitamin B12 from food (maldigestion) which will affect absorption. Bypass surgery produces low levels of acid secretion in the small proximal stomach pouch.
- If there is a 15 ul/cm/min secretory flux and a 50 ul/cm/min absorptive flux occurring simultaneously, then what is the net flux result?
A) 60 ul/cm/min secretion
B) 60 ul/cm/min absorption
C) 35 ul/cm/min secretion
D) 35 ul/cm/min absorption
D) 35 ul/cm/min absorption
Secretion and absorption are separate processes that occur at the same time. The net effect is the balance of the two individual components. If 50 is being absorbed whilst 15 is being secreted then the combined effect is 50-15 = 35 absorption.
- Which of the following is true with regard to the summed volumes being secreted into the gastrointestinal tract in a typical day?
A) saliva + small intestine < gastric juice + pancreatic secretions + bile
B) gastric juice < small intestine
C) saliva > gastric juice
D) small intestine > bile + pancreatic secretions
A) saliva + small intestine < gastric juice + pancreatic secretions + bile
Whilst you don’t need to know the exact numbers it helps to know their relative amounts. Small intestine (~1000ml), saliva (~1500ml), bile + pancreatic secretions (~2000ml) and the gastric juice (~2500ml)
- In the jejunum the following are absorbed:
A) sugars, amino acids, NaHCO3
B) glucose, amino acids, calcium, bile salts
C) sugars, NaCl, vitamin B12
D) amino acids, intrinsic factor, iron
A) sugars, amino acids, NaHCO3
Bile salts, vitamin B12 and intrinsic factor are all absorbed in the ileum. Sugars and amino acids are absorbed co-transported with Na in the jejunum and NaHCO3 is absorbed preferentially to NaCl. HCO3 being absorbed in the form of CO2 and H20 not as HCO3.
- The following are fat soluble vitamins:
A) A, D, B1
B) B1 & B2 (does that remind you of a song?)
C) A, D, E, K
D) B5, A, K, D
C) A, D, E, K
Vitamins B & C are water soluble.
- What is the function of aldosterone?
Aldosterone levels are influenced by Na & K levels in the body. Aldosterone increases to aid Na conservation by allowing Na to be reabsorbed through the ENaC (epithelial sodium channels) in the colon. Aldosterone also increases the number of Na/K pumps on the basolateral membrane in the same cells as the combination of the Na/K pumps & the ENaC increases the Na absorption from the lumen of the large intestine.
This is the same process which occurs to stimulate Na reabsorption in the late distal tubule & collecting duct of the renal tubule.
- Which one of the following is NOT TRUE of Cholecystokinin (CCK):
A) stimulates production of a more alkaline pancreatic secretion
B) is released from I cells in response to luminal amino acid/fat content
C) stimulates secretions of the acinar cells in the pancreas
D) relaxes the Sphincter of Oddi
A) Stimulates production of a more alkaline pancreatic secretion.
CCK is released from I cells in response to the presence of amino/acids or fats in the duodenal lumen and via an endocrine action stimulates the ACINAR (not DUCT) cells. Acinar cells produce digestive enzyme content whilst duct cells modify the secretion making it more alkaline.
SECRETIN from S cells responding to increased luminal acidity stimulates the production of a more alkaline pancreatic secretion.
- With respect to salivary secretion:
A) the final secretion will be alkaline even at high flow rates
B) the initial secretion is hypotonic with respect to plasma
C) the saliva is saltier [contains more NaCl] at low flow rates compared to high flow rates
D) it is primarily under endocrine control
A) the final secretion will be alkaline even at high flow rates
The primary salivary secretion from the acinar cells is isotonic & plasma-like in electrolyte composition. As the secretion travels through the duct cells it undergoes modification so that Na & Cl are absorbed (making the final secretion less salty) and K & HCO3 are secreted (making the final secretion more alkaline). Absorption occurs to a greater extent than secretion so the final secretion will be hypotonic. While less modification takes place at high flow rates, bicarbonate secretion is maintained and the final secretion will be alkaline. Salivary secretion is primarily under neural (not endocrine) control.
- The intestinal phase of gastric acid secretion is largely regulated by…
A) the parasympathetic nervous system
B) the enteroendocrine secretions of the GIT
C) a combination of the parasympathetic nervous system and the enteroendocrine secretions of GIT
B) the enteroendocrine secretions of the GIT
Once food enters the intestines it is mainly the enteroendocrine cells responding to the composition of the chyme in the lumen that feeds back to inhibit gastric acid secretion (& gastric motility/emptying).
- Which of the following is INCORRECT about Bile
A) It is produced by hepatocytes
B) It is stored in the gallbladder
C) It contains bile salts
D) It is recycled
D) It is recycled.
Bile SALTS are recycled. Bile salts are just one component of Bile - so Bile as such is not recycled. Bile is produced by the hepatocytes & stored and concentrated in the gallbladder.
- The cephalic phase of gastric secretion:
A) is mediated by the vagus nerve
B) begins when food is tasted
C) accounts for about 80% of the total acid secretion
D) involves secretions from enteroendocrine cells in the duodenum
A) is mediated by the vagus nerve.
The cephalic phase of acid secretion is responsible for about 30% of the total acid secreted & is initiated with the sight & smell of food (even before it is tasted). It is mediated entirely through the vagus nerve.
- Glucose is an end product of the reaction catalyzed by
a) Sucrase
b) Lactase
c) Maltase
d) Lipase
e) Amylase
c) Maltase
Know your disaccharides &monosaccharides. Maltose is composed of 2 glucose molecules so maltase breaks this down into glucose. Maltose also digests malto-triose to glucose molecules. Sucrose is composed of a fructose & a glucose and is broken down by sucrase. Lactose is glucose & galactose digested by lactase. Lipases digest lipids. Amylase is an endo-enzyme so can’t produce individual glucose molecules. Dextrinase can produce glucose molecules but it wasn’t an option.
- Removal of the proximal small bowel will have which one of the following effects:
A) decreased gastric acid secretion
B) increased gastric acid secretion
B) increased gastric acid secretion
Inhibitory feedback on gastric acid secretion is largely initiated by the enteroendocrine cells in the duodenal & jejunal mucosa. Without this feedback, gastric acid secretion would be increased (as in, inhibition would be lost).
- The transporter (on the basolateral membrane) that is important for chloride secretion in the crypts is:
A) Na/H pump
B) H/K exchanger
C) HCO3/Cl exchanger
D) NaK2Cl symporter
D) NaK2Cl symporter
The NaK2Cl symporter brings in chloride ions that can then leave via the chloride channels on the luminal membrane. Na follows the Chloride and water follows by osmosis giving a largely NaCl secretion.
- Causes of diarrhoea include:
A) loss of absorptive mucosa B) infections e.g. cholera C) secretagogue secreting tumours D) osmotically induced mechanisms E) all of the above
E) all of the above
Lactose intolerance is an example of an osmotically induced diarrhoea. Some tumours secrete high concentrations of hormones/peptides that are secretagogues (that is they cause secretion). Cholera etc stimulate the opening of the chloride channels in the crypts causing fluid secretion and losing absorptive mucosa is a problem as the SI needs to absorb around 7 litres per day otherwise the absorptive capacity of the LI is overwhelmed.
- Net electrolyte secretion in the large intestine occurs for:
A) Na and Cl
B) HCO3 and Cl
C) HCO3 and K
D) K and Na
C) HCO3 and K
This is why diarrhoea can produce a loss of HCO3 and K - producing metabolic acidosis and hypokalemia.
- Intestinal calcium absorption is increased by:
A) increased vitamin D levels
B) increased vitamin A levels
C) increased vitamin B levels
D) increased vitamin C levels
A) increased vitamin D levels
Increased vitamin D causes an increase in the brush border Ca binding proteins and so increases calcium aborption
- The following is a feedback reflex
A) gastro-gastric reflex
B) gastro-ileal reflex
C) gastro-colic reflex
D) entero-gastric
D) entero-gastric
Feedback means the stimulation occurs more distally in the GIT and the response ealier (feeding back to slow down the progress of the chyme through the system). The entero gastric reflex is stimulated in the intestines and provides a response to slow the stomach (gastric) motility.
- Amylase produces…
a) alpha-limit dextrins
b) glucose & fructose
c) dissacharides
d) glucose and galactose
e) none of the above
f) a & c
f) a & c
it doesn’t produce any of the monosaccharides
- Na absorption in the small bowel:
A) occurs by secondary active transport
B) decreases with glucose absorption
C) occurs by active transport at the apical membrane
D) occurs with chloride, both moving through tight junctions
A) occurs by secondary active transport
Na absorption occurs across the luminal, apical membrane (not through tight junctions w chloride) by secondary active transport - i.e. secondary to the Na gradient set up by the Na/K pump on the basolateral membrane. So the active transport is on the basolateral membrane not apical. As Na is cotransported with glucose, Na absorption increases w glucose absorption.
- After a fatty meal, most of the fat would be:
A) absorbed into the portal circulation & transported to the liver
B) absorbed into the portal vein & transported to the hepatic artery
C) absorbed as chylomicrons into the lymphatics
D) absorbed as triglycerides into the portal vein & bypass the liver
C) Absorbed as chylomicrons into the lymphatics
Most of the fats are packaged as chylomicrons & absorbed into the central lacteal of the villi (not the capillaries and so not entering the portal circulation).
- Release of which one of the following increases the pH of the duodenal contents:
A) Secretin B) Gastrin C) Intrinsic factor D) Cholecystokinin E) Gastrin Releasing Peptide F) Pepsin
A) Secretin
Secretin stimulates BICARBONATE SECRETION & therefore makes the duodenal contents more alkaline. Intrinsic factor & pepsin have no effect on pH. Gastrin & Gastrin Releasing Peptide (neurotransmitter from the vagus innervating G cells) both stimulate acid secretion so decrease pH. Cholecystokinin can increase pH but only in that it augments the effects of Secretin.
- Gastric acid secretion is decreased by:
A) Vagal inhibition
B) Luminal peptides and amino acids
C) Histamine release from ECL cells
D) Distention of the stomach wall
A) Vagal inhibition
Vagal stimulation increases acid secretion so vagal inhibition will decrease acid secretion. Luminal peptides and amino acids stimulate gastrin release from G cells and increase acid secretion. Distension of the stomach wall stimulates acid secretion by short (ENS) and long (Vagal) reflexes. Histamine stimulates H2 receptors on parietal cells and stimulates acid secretion via cAMP pathway.
- In the small intestine, glucose is absorbed:
A) passively
B) in combination with sodium
C) by facilitated diffusion
D) cotransported with chloride
B) in combination with sodium
Glucose is absorbed via secondary active transport in combination with sodium via the SGLT transporter on the apical membrane. Sodium also co-transports amino acids & other solutes (via other transporters).
- Following ingestion of a meal:
A) Digestion of fat & carbohydrate begin in the mouth whilst protein digestion begins in the stomach
B) Digestion of protein begins in the mouth & fats and carbohydrates begin in the stomach
C) Most fluid & electrolytes are absorbed in the large bowel
D) Composition of the food has no effect on transit time through the bowel
A) Digestion of fat & carbohydrate begin in the mouth whilst protein digestion begins in the stomach.
Lingual lipase and salivary amylase begin the digestion of fats and carbohydrates (respectively) in the mouth whilst pepsin begins the digestion of proteins. The lipase and amylase action are minimal but the enzymes are present. Protein digestion does not occur in the mouth unless we are talking manual breakdown through chewing. Most fluids and electrolytes are absorbed in the small (not large) bowel and transit time is affected by the composition of the food - for example, high fat meals slow emptying from the stomach - so increase the transit time through the bowel.
- Retropulsion refers to:
A) the mixing of the gastric contents
B) the emptying of the stomach
C) Harry & Ron transiting the barrier at Platform 9 and 3/4
D) the frequency of the slow wave in the Interstitial Cells of Cajal
A) the mixing of the gastric contents.
Retropulsion refers to the “throwing back” effect that occurs when gastric contents are propelled against a closed pyloric sphincter causing a mixing of the gastric contents. Retropulsion is similar to Harry & Ron NOT being able to transit the barrier at platform 9 & 3/4 (because Dobby had magically sealed it). Whilst the frequency of the slow wave potential in the stomach will determine the highest rate of peristaltic wave activity & hence the amount of gastric mixing it is not what “retropulsion” is referring to.
- In the fasting state, the type of motility occurring in the small intestine is:
A) peristalsis
B) migrating motor complex
C) segmentation
D) mass movements
B) migrating motor complex
What are 4 of its features?
- What are the four basic processes of the gastrointestinal tract?
A) Digestion, elimination, chewing, fasting
B) Secretion, digestion, elimination, absorption
C) motility, secretion, ruminating, elimination
D) Digestion, absorption, secretion, motility
D) Digestion, absorption, secretion, motility
The four basic processes are digestion (of foodstuffs), absorption (into the blood or in the case of fats into the lymphatic system), secretion (of acid, mucus, digestive enzymes, water, electrolytes etc.) & motility (just to keep things moving along!).
- The four layers of the gut wall in no specific order are: submucosa, serosa, muscularis externa & mucosa
True or False?
True!
The mucosa is the innermost layer where absorption and section take place followed by the submucosa which contains veins & arteries & connective tissue & such like. The muscularis externa is made up of 2 muscle layers - the inner circular layer & the outer longitudinal layer. They provide for all types of movements such as grinding, mixing, peristalsis, mass movements, expulsion, swallowing etc. Lastly there is the serosal layer.
- The four anatomical areas of the stomach are:
A) Trunk, head, body, legs
B) Cardiac, body, funny, antral
C) Fundus, cardia, corpus, antrum
D) Fungus, body, corpus, antrum
C) Fundus, cardia, corpus, antrum
The cardia is the area around the junction of the lower oesophagus and the stomach. The fundus is the area which is at the top of the stomach (usually above the level of the cardia). The corpus (or body) of the stomach makes up most of the stomach with the antrum being the last third or so just prior to the pylorus.
- The mucosa in the corpus is called the oxyntic mucosa.
True or False?
True!
Oxyntic mucosa is mucosa that produces acid. The corpus and the fundus have oxyntic mucosa. The cardia and the antrum generally don’t produce acid.
