Digestion and absorption Flashcards
The stimuli for the cephalic phase
Cognitive anticipation of food consumption, and sensory input (olfactory, visual, auditory)
The response to cephalic stimulation is activation of what part of the brain?
Dorsal motor nucleus in the brainstem
The salivary response is mediated via which nerve?
CN IX (glossopharyngeal)
Gastric acid secretion, pancreatic enzyme secretion, gallbladder contraction, relaxation of the sphincter of Oddi are mediated via which CN?
CN X (vagus)
The three major pairs of salivary glands
Parotid, sublingual, submandibular
Type of secretion of parotid glands
Serous
Type of secretion of sublingual glands
Mucous
Type of secretion of submandibular glands
Mixed serous and mucous
Salivary secretion is often isotonic. T/F
F
It is always hypotonic.
Control of saliva secretion: neural, paracrine, endocrine
Neural
Control of most GI secretion: neural, paracrine, endocrine
Endocrine
Primary secretion of saliva: hypotonic, isotonic, hypertonic
Isotonic
Protein ion transporters in acinar cells of salivary glands
Na,K-ATPase and NA-K-2Cl symporter
Na,K-ATPase and NA-K-2Cl symporter are located in which part of the cell membrane of salivary glands?
Basolateral membrane
In acinar cells of salivary glands, Cl and HCO3 leave the acinar cell via an anion channel in which part of the cell membrane?
Apical membrane
The only gastric secretion required
Intrinsic factor
K is higher in gastric juice or in plasma?
Gastric juice
Why may prolonged vomiting lead to hypokalemia?
Because gastric juice is high in K.
Which is the main anion of gastric juice?
Cl
The basal rate of H production is highest and lowest which part of the day?
Higher at night, lowest in the morning
The higher secretory rates of gastric juice, the higher the concentration of which ions?
H
Lower secretory rates of gastric juice (increases/decreases) Na.
Increases
At high secretory rates of gastric juice, H (increases/decreases)
Increases
At high rates of gastric juice secretion, gastric juice resemble an (hypotonic/hypertonic/isotonic) solution of HCl
Isotonic
The predominant organic constituent of gastric juice
Pepsinogen
The lower the pH, the (faster/slower) the conversion of pepsinogen to pepsin
Faster
Pepsins also act proteolytically to activate more pepsinogen. T/F
T
Why are pepsins not require for digestion?
Because their function can be replaces by that of pancreatic proteases.
Intrinsic factor is important in absorption of which vitamin?
B12 (cobalamin)
Which of the following principal control mechanisms involved in GI function regulation is represented by serotonin (syn. 5-hydroxy-trptamine)?
a. Endocrine
b. Paracrine
c. Neural
d. Combination
D
Which of the following combination is incorrect?
a. Gastrin-endocrine
b. Histamine-paracrine
c. Acetylcholine-neural
d. Cholecystokinin-paracrine
D
Xerostamia, or dry mouth, is caused by impaired salivary secretion. Which of the following is not an expected complication of this clinical correlation?
a. Tooth decay
b. Esophageal erosions
c. Difficulty swallowing
d. Gastric ulceration
D
Which of the following neurotransmitters act mainly by elevating the Ca++ concentration in the cytosol?
a. Acetylcholine
b. Cholecystokinin
c. Substance P
d. Vasoactive intestinal polypeptide (VIP)
A
The following are true statements on the regulation of gastric secretion, except:
a. Parietal cell is regulated by a combination of pathways
b. Ach directly activates parietal cells
c. Enterochromaffin cells release histamine
d. Gastrin acts via the paracrine pathway to stimulate the parietal cell.
D
Which of the following hormone is released to inhibit a meal-stimulated gastrin secretion?
a. Secretin
b. Gastrin
c. Gluco-insulinotropic peptide (GIP)
d. Somatostatin
D
Which of the following is responsible for our experiencing the “coolness of menthol” or the “sting of ammonia”
a. Olfactory cells
b. Gustatory cells
c. Common chemical sense
d. Mucus cells of the tongue
C
Which of the following is not a response in the cephalic phase of digestion?
a. Hypothermia (decreased temp)
b. Increased flow of saliva
c. Increased HR
d. Change in urine osmolarity
A
Which of the following hormones stimulates an enzyme-rich pancreatic secretion?
a. Secretin
b. CCK
c. Somatostatin
d. VIP
B
Which of the following hormones stimulates a HCO3-rich pancreatic secretion?
a. Secretin
b. CCK
c. Samatosatin
d. VIP
A
Which is the primary physiologic control for salivary secretion?
a. Sympathetic
b. Parasympathetic
c. Hormonal
d. Paracrine
B
Which of the following agonists of pancreatic acinar secretion is not mediated by an increased intracellular calcium?
a. Acetycholine
b. CCK
c. Gastrin
d. Secretin
D
Procarboxypeptidase is directly activated by
a. Chymotrypsin
b. Trypsin
c. Pepsin
d. Enterokinase
B
The digestion of the major foodstuff in the GIT is a process of:
a. Sulfation
b. Decarboxylation
c. Hydrolysis
d. Amidation
C
Phospholipids are digested into:
a. Monoglyceride and cholesterol
b. Cholesterol and lysolecithin
c. Fatty acids and lysolecithin
d. Lysilecithin and monoglyceride
C
Which of the following is responsible for apical transport of fructose in enterocytes?
a. SGLT1
b. GLUT 2
c. GLUT 4
d. GLUT 5
D
Reesterification of monoglyceride and fatty acids occur in the enterocyte:
a. Cytosol
b. Smooth ER
c. Golgi apparatus
d. nucleus
B
What digestive enzyme is necessary for the hydrolysis of phospholipids?
a. Cholesterol easter hydrolase
b. Phospholipiase A2
c. Pancreatic lipase
d. Lingual lipase
B
Extensive injury of the ileum will greatly affect the absorption of:
a. Vitamin C
b. Fructose
c. Cyanocobalamin
d. Amino acids
C
Which of the following monosaccharides will be absorbed first?
a. Pentose
b. Arabinose
c. Galactose
d. Glucose
C
Absorption of fat digestion products and fat soluble vitamins is by what transport mechanism?
a. Primary active
b. Secondary active
c. Facilitated diffusion
d. Passive diffusion
D
Dipeptides and tripeptides are absorbed by the intestines with which ion?
a. Sodium
b. Chloride
c. Hydrogen
d. potassium
C
The strongest stimulant of gastric H secretion
Parasympathetic innervation of the vagus nerve
Strongest agonist of H secretion
Histamine
The parietal cell is stimulated by the parasympathetic vagus pathway through which neurotransmitter?
Acetylcholine
Cholinergic receptors of the parietal cell: muscarinic or nicotinic?
Muscarinic
The effect of histamine to parietal cells
Stimulation of H secretion
Histamine receptors of the parietal cell
H2 receptors
Which G-cell secretion stimulates the parietal cell?
Gastrin
Gastrin stimulates the parietal cell via: neural, paracrine, endocrine mechanism
Endocrine
Parietal cell stimulation: neural, paracrine, endocrine mechanism
All
Gastrin’s effect on ECL cells
Histamine secretion
Which neurotransmitter activates G-cells?
Gastrin-releasing peptide
Gastrin receptors on the parietal cell
CCK2
Stimulation of ECL cells via gastrin: neural, paracrine, endocrine mechanism
Endocrine
ECL cells are stimulated by parasympathetic innervation through which neurotransmitter?
Acetylcholine
Cholinergic receptors on the ECL cells: muscarinic or nicotinic?
Muscarinic
Elevation of gastrin levels causes ECL cells to increase in size and number. T/F
T
Which hormone decrease the release of gastrin?
Somatostatin
Somatostatin inhibition of gastrin: neural, paracrine, endocrine mechanism
Paracrine
When do D-cells secrete somatostatin?
When acidity drops below threshold of pH 3
Pancreatic enzymes function optimally at low pH. T/F
F
They are deactivated by high levels of acidity.
Which organ is the largest quantitative contributor to the supply of bicarbonate ions needed to neutralize the gastric acid load?
Pancreas
What stimulates the intercalated ducts of the pancreas to secrete HCO3?
Secretin
What stimulates the acinar cells of the pancreas to secrete proenzymes?
CCK
Somatostatin inhibit insulin and glucagon. T/F
T