Which organ is responsible for synthesizing ANP?

Correct Answer: A

Rationale: The correct answer is A: the heart. Atrial Natriuretic Peptide (ANP) is synthesized and released by the atrial cells of the heart in response to stretching of the atrial wall due to increased blood volume or pressure. ANP functions to regulate blood pressure and fluid balance by promoting natriuresis and vasodilation. The kidney (choice B) is responsible for filtering blood and regulating electrolyte balance, but it does not synthesize ANP. The skin (choice C) is involved in thermoregulation and vitamin D synthesis, not ANP production. The spleen (choice D) plays a role in immune function and blood storage, but it does not synthesize ANP.

Correct Answer: C

Rationale: The correct answer is C: cAMP and calcium. Peptide hormones bind to their receptors on the cell surface, activating G-proteins which then trigger the production of cAMP as a second messenger. cAMP then further activates protein kinases to initiate various cellular responses. Calcium is also a common second messenger in peptide hormone signaling pathways, regulating processes like muscle contraction and gene expression. Choice A is incorrect because peptide hormones themselves are not second messengers. Choice B is incorrect as glucose is not a common second messenger for peptide hormones. Choice D is incorrect as sodium is not typically involved in peptide hormone signaling pathways.

Correct Answer: B

Rationale: Step 1: The hormones produced by the hypothalamus and secreted by the posterior pituitary are ADH (vasopressin) and oxytocin. Step 2: ADH regulates water balance by increasing water reabsorption in the kidneys. Step 3: Oxytocin is involved in uterine contractions during childbirth and milk ejection during breastfeeding. Step 4: Therefore, choice B (ADH and oxytocin) is correct. Summary: - Choice A (ADH and aldosterone) is incorrect because aldosterone is produced by the adrenal glands, not the posterior pituitary. - Choice C (oxytocin and prolactin) is incorrect because prolactin is produced by the anterior pituitary. - Choice D (cortisol and aldosterone) is incorrect because cortisol is produced by the adrenal glands, not the posterior pituitary.

Correct Answer: C

Rationale: The correct answer is C: myxedema. Hypothyroidism in adults is commonly caused by an underactive thyroid gland, leading to decreased production of thyroid hormones. Myxedema is the term used to describe severe hypothyroidism, characterized by symptoms such as fatigue, weight gain, cold intolerance, and swelling of the face and hands. Graves disease (choice A) is actually a cause of hyperthyroidism, not hypothyroidism. Diabetes insipidus (choice B) is a disorder related to the kidneys and has no direct connection to thyroid function. Acromegaly (choice D) is caused by excess growth hormone production, unrelated to thyroid function. Therefore, the correct choice is C as it accurately describes hypothyroidism in adults.

Correct Answer: A

Rationale: The correct answer is A: adrenal cortex. Cortisol is a glucocorticoid hormone produced by the adrenal cortex. The adrenal cortex is responsible for the synthesis and secretion of cortisol in response to stress. The adrenal medulla produces catecholamines like adrenaline and noradrenaline, not cortisol. The anterior pituitary produces adrenocorticotropic hormone (ACTH), which stimulates cortisol production by the adrenal cortex. The pancreas produces insulin and glucagon, not cortisol. Therefore, the adrenal cortex is the correct choice for the production of cortisol.