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Flashcards in Physiology Deck (122)
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1

1. 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.

2

2. 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).

3

3. 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.

4

4. 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).

5

5. What is eructation?

A) burping
B) vomiting
C) farting
D) gurgling noises in the stomach

A) Burping

6

6. 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.

7

7. 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.

8

8. 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')

9

9. 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.

10

10. 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.

11

11. 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.

12

12. 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

13

13. 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

14

14. 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

15

15. 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.

16

16. 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).

17

17. 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.

18

18. 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.

19

19. 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.

20

20. 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)

21

21. 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.

22

22. 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.

23

23. 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.

24

24. 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.

25

25. 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.

26

26. 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).

27

27. 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.

28

28. 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.

29

29. 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.

30

30. 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).