What two effects does PTH exert on the kidneys?

Correct Answer: B

Rationale: The correct answer is B because PTH (Parathyroid Hormone) acts on the kidneys by increasing calcium reabsorption and increasing the excretion of phosphate in the urine. PTH stimulates the kidney to reabsorb more calcium to maintain normal blood calcium levels. It also enhances the excretion of phosphate in the urine, helping to lower blood phosphate levels. Option A is incorrect because PTH does not block sodium reabsorption or increase water excretion in the kidneys. Option C is incorrect as PTH does not decrease the reabsorption of both calcium and phosphate. Option D is incorrect because PTH does not increase the excretion of H+ or bicarbonate.

Correct Answer: C

Rationale: The correct answer is C: rapid acting effects. Endocrine properties involve hormones reaching targets through the blood, causing slow and cyclic effects. Rapid acting effects are more characteristic of the nervous system, not the endocrine system. Endocrine effects are caused by chemicals, so choice D is incorrect.

Correct Answer: A

Rationale: The correct answer is A: Negative feedback mechanism. This is because most hormones in the endocrine system are regulated by a negative feedback loop, where the release of a hormone is inhibited once a certain level of that hormone is reached in the body. This helps maintain homeostasis. Incorrect choices: B: Positive feedback mechanism - This is less common in hormone regulation as it leads to amplification of a response rather than maintaining balance. C: Hormone-receptor complex - While hormones bind to receptors to exert their effects, this is not the primary mechanism of hormone regulation. D: Hormone-gene complex - While hormones can affect gene expression, this is not the primary mechanism of hormone regulation in the endocrine system.

Correct Answer: D

Rationale: The correct answer is D: Nervous system. The nervous system works closely with the endocrine system to regulate and coordinate the body's functions through the release of neurotransmitters and hormones. The nervous system controls rapid responses, while the endocrine system controls slower, long-term processes. The cardiovascular system (A) primarily transports blood and nutrients, the respiratory system (B) is involved in gas exchange, and the reproductive system (C) is responsible for reproduction, none of which directly coordinate with the endocrine system.

Correct Answer: B

Rationale: The correct answer is B: Insulin. Insulin is a protein hormone produced by the pancreas that regulates blood sugar levels. Proteins are large molecules made up of amino acids, and insulin fits this definition. Oxytocin (A) is a peptide hormone, not a protein. TSH (C) and ADH (D) are both peptide hormones as well, not proteins. In summary, insulin is the only option that fits the criteria of being a protein hormone.