Nokea
Gastrin secretion is stimulated by all but:
- A. luminal peptides
- B. vagal discharge
- C. luminal acid
- D. phenylalanine
Correct Answer: C
Rationale: Rationale: Gastrin secretion is primarily stimulated by luminal peptides and vagal discharge, which promote gastric acid secretion. Luminal acid, on the other hand, inhibits gastrin release as it acts as a negative feedback mechanism to regulate acid production. Phenylalanine does not directly stimulate gastrin secretion. Therefore, the correct answer is C as luminal acid inhibits, not stimulates, gastrin release. The other choices are incorrect because luminal peptides and vagal discharge are known stimulants of gastrin secretion, while phenylalanine does not have a direct effect on gastrin release.
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The clusters of cells in the pancreas that produce hormones are the:
- A. Nodules.
- B. Islets of Langerhans.
- C. Pancreatic medulla.
- D. Pancreatic cortex.
Correct Answer: B
Rationale: The correct answer is B: Islets of Langerhans. These are clusters of cells in the pancreas responsible for producing hormones like insulin and glucagon. The islets regulate blood sugar levels. Nodules (A) are not specific to the pancreas. Pancreatic medulla (C) and pancreatic cortex (D) do not refer to the specific clusters of cells in the pancreas that produce hormones.
Which produces the majority of salivary volume?
- A. lingual glands
- B. sublingual
- C. parotid
- D. submandibular
Correct Answer: D
Rationale: The correct answer is D, submandibular glands, as they produce the majority of salivary volume. These glands are the largest of the major salivary glands and secrete saliva rich in enzymes and mucin, contributing significantly to the total saliva volume. The lingual glands (A) are minor salivary glands located in the tongue and contribute a small portion of saliva. The sublingual glands (B) are also minor salivary glands located beneath the tongue, producing a smaller volume compared to the submandibular glands. The parotid glands (C) are another major salivary gland, but they produce a lesser volume of saliva compared to the submandibular glands.
Which is NOT produced by the citric acid cycle?
- A. NAD+
- B. CO2
- C. GTP
- D. FADH2
Correct Answer: A
Rationale: Step 1: NAD+ is a reactant in the citric acid cycle, not a product.
Step 2: NAD+ is reduced to NADH during the cycle.
Step 3: NAD+ is not directly produced as a final product in the cycle.
Step 4: Therefore, A: NAD+ is NOT produced by the citric acid cycle.
Summary: B: CO2 and D: FADH2 are produced in the cycle, while C: GTP is generated through substrate-level phosphorylation.
Antidiuretic hormone (ADH) and oxytocin:
- A. are secreted by the neurohypophysis.
- B. are mineralocorticoids.
- C. are secreted by the islets of Langerhans.
- D. stimulate the kidney to excrete Na+ and water.
Correct Answer: A
Rationale: Step-by-step rationale for choice A being correct:
1. ADH and oxytocin are peptide hormones.
2. They are synthesized in the hypothalamus.
3. They are transported and stored in the neurohypophysis.
4. Upon stimulation, they are released from the neurohypophysis.
5. Therefore, both ADH and oxytocin are indeed secreted by the neurohypophysis.
Summary of why other choices are incorrect:
B: ADH and oxytocin are not mineralocorticoids; they regulate water balance and uterine contractions, respectively.
C: Islets of Langerhans secrete insulin and glucagon, not ADH or oxytocin.
D: ADH promotes water reabsorption in the kidneys, opposite to excreting Na+ and water.
Which of the following is true of both prolactin and oxytocin? Both
- A. are concerned with lactation.
- B. are secreted by the adenohypophysis.
- C. stimulate the mammary glands to make milk.
- D. are concerned only with lactation.
Correct Answer: A
Rationale: The correct answer is A: are concerned with lactation. Both prolactin and oxytocin are hormones involved in lactation. Prolactin promotes milk production in the mammary glands, while oxytocin stimulates the release of milk from the breasts during breastfeeding. Therefore, both hormones play crucial roles in the lactation process.
Choice B is incorrect because oxytocin is secreted by the posterior pituitary gland, not the adenohypophysis. Choice C is incorrect because oxytocin specifically stimulates the contraction of the muscles around the mammary glands to release milk, not the production of milk. Choice D is incorrect because oxytocin is also involved in milk ejection, not just lactation itself.