Which is true of dark (red) muscle?

Correct Answer: a

Rationale: The correct answer is A: This muscle is optimized for endurance training. Dark (red) muscle contains more myoglobin, which stores oxygen and enhances endurance performance. This muscle type is rich in mitochondria, allowing for sustained energy production. Choice B is incorrect because dark muscle actually has more mitochondria. Choice C is incorrect because dark muscle contains more slow-twitch fibers, which are fatigue-resistant and contribute to endurance. Choice D is incorrect because dark muscle predominantly consists of slow-twitch fibers, making it optimized for endurance rather than speed.

Correct Answer: C

Rationale: Estrogen, progesterone, and testosterone are indeed secreted by the gonads. Estrogen and progesterone are primarily produced by the ovaries in females, while testosterone is mainly produced by the testes in males. These hormones play crucial roles in reproductive functions and secondary sexual characteristics. Choices A and B are incorrect because testosterone induces virilization (masculinizing effects) while estrogen and progesterone are more associated with feminizing effects. Choice D is incorrect because estrogen, progesterone, and testosterone are not secreted by the adenohypophysis, which mainly produces and releases other hormones such as growth hormone and prolactin.

Correct Answer: B

Rationale: Rationale: 1. Testosterone is an androgen hormone primarily produced in the testes. 2. Androgens are responsible for male characteristics and reproductive functions. 3. Progesterone is a female sex hormone, not an androgen. 4. Estrogen is also a female sex hormone, not an androgen. 5. Aldosterone is a mineralocorticoid hormone, not an androgen. Summary: Testosterone is the correct answer as it is a male sex hormone with androgenic properties. Progesterone, estrogen, and aldosterone are not androgens and do not exhibit the same functions as testosterone.

Correct Answer: D

Rationale: The correct answer is D because obesity can lead to insulin resistance, which antagonizes insulin, causing elevated blood glucose levels. Additionally, obesity is associated with increased risk of hypertension, leading to increased blood pressure. Therefore, all choices are applicable in describing the effects of obesity on the body.

Correct Answer: C

Rationale: Step-by-step rationale for why Choice C is correct: 1. The pancreas secretes hormones like insulin and glucagon. 2. Insulin lowers blood glucose levels, while glucagon raises them. 3. These hormones play a crucial role in regulating blood glucose levels. 4. Disruption in their secretion can lead to diseases like diabetes. Summary: Choice A is incorrect because the pancreas does not secrete steroids related to sugar, salt, and sex. Choice B is incorrect because the pancreas is not controlled by the adenohypophysis. Choice D is incorrect because the pancreas does not secrete iodine-containing hormones that regulate the basal metabolic rate.