Hormones help balance the body’s reactions differently than nerve impulses in that:

Correct Answer: D

Rationale: The correct answer is D: All of the above. Hormones balance the body's reactions differently than nerve impulses because: - A: Hormonal responses are slower compared to nerve impulses due to the time it takes for hormones to travel through the bloodstream. - B: Hormones can target specific target cells located in different parts of the body, making their effects more targeted and widespread. - C: Hormonal effects can last longer than the quick, temporary effects of nerve impulses, contributing to sustained physiological changes. Therefore, D encompasses all these aspects, highlighting how hormones differ from nerve impulses.

Correct Answer: A

Rationale: The correct answer is A: Pineal gland. Melatonin is a hormone that regulates sleep-wake cycles and is primarily secreted by the pineal gland located in the brain. The pineal gland responds to darkness by releasing melatonin, which helps to induce sleep. The other choices, B: Thyroid, C: Thymus, and D: Adrenal, do not secrete melatonin. The thyroid gland produces hormones that regulate metabolism, the thymus gland is involved in immune function, and the adrenal glands secrete hormones like cortisol and adrenaline. Therefore, the pineal gland is the correct answer for melatonin secretion.

Correct Answer: A

Rationale: The correct answer is A because endocrine glands release hormones directly into the bloodstream to reach target organs and regulate various physiological processes. This allows for systemic effects on the body. Choices B and C are incorrect as hormones are not released directly into tissues or skin. Choice D is also incorrect as endocrine glands release hormones directly into the bloodstream, not through ducts.

Correct Answer: A

Rationale: Rationale for Choice A: 1. The hypothalamus produces oxytocin and antidiuretic hormone (ADH). 2. These hormones are transported via the hypothalamic-pituitary portal system to the posterior pituitary for storage. 3. When needed, the posterior pituitary releases these hormones into the bloodstream. 4. Oxytocin is involved in labor and milk ejection, while ADH regulates water balance by increasing water reabsorption in the kidneys. Summary of other Choices: B. Incorrect - ADH, when released, causes urine volume to decrease and blood volume to increase by increasing water reabsorption. C. Incorrect - Luteinizing hormone triggers ovulation and stimulates progesterone production but is released by the anterior pituitary, not the hypothalamus. D. Incorrect - Hyposecretion of FSH or LH can lead to infertility, not necessarily sterility, and the effects differ between males and females.

Correct Answer: A

Rationale: The correct answer is A: parathyroid hormone. Parathyroid hormone is responsible for regulating calcium levels in the blood by increasing calcium release from bones, enhancing calcium absorption in the intestines, and promoting calcium reabsorption in the kidneys. This hormone acts to elevate blood calcium levels when they are low. B: Aldosterone is a hormone that regulates sodium and potassium levels, not calcium. C: Calcitonin is involved in lowering blood calcium levels by inhibiting the breakdown of bone tissue, but it is not the primary hormone responsible for regulating calcium levels in the blood. D: Thyroid hormone plays a role in metabolism regulation, growth, and development, but it is not directly involved in the regulation of calcium levels in the blood.