ati teas 7 science

Correct Answer: C

Rationale: The correct answer is C: Luteinizing hormone (LH). LH surge triggers ovulation by causing the mature ovarian follicle to release the egg. Estrogen and progesterone play important roles in regulating the menstrual cycle but are not the primary triggers for ovulation. FSH stimulates the growth of ovarian follicles but does not directly trigger ovulation.

Correct Answer: B

Rationale: The correct answer is B: Synapse. The synapse is the point of contact between a motor neuron and a muscle fiber where communication occurs via neurotransmitters like acetylcholine to initiate muscle contraction. A: Sarcomere is a structural unit of a muscle fiber, not the point of contact for communication. C: Tendon is a fibrous connective tissue that attaches muscle to bone, not involved in neuron-muscle communication. D: Myofibril is a cylindrical organelle within muscle fibers where muscle contractions occur, but it is not the specific point of contact for neuron communication.

Correct Answer: B

Rationale: The primary function of the small intestine is to absorb nutrients from digested food. This process involves breaking down food into smaller molecules that can be absorbed into the bloodstream for energy and growth. The small intestine has villi and microvilli that increase its surface area for efficient nutrient absorption. Choice A is incorrect because the large intestine, not the small intestine, primarily absorbs water. Choice C is incorrect as the large intestine, not the small intestine, stores waste. Choice D is incorrect because while the small intestine does produce some enzymes, its primary role is nutrient absorption.

Correct Answer: A

Rationale: The correct answer is A because the atomic number represents the number of protons in the nucleus of an atom, which determines the element's identity. The mass number is the total number of protons and neutrons in the nucleus, indicating the atom's mass. The number of electrons is not directly related to either the atomic or mass number, eliminating choices B and D. Choice C is incorrect because the atomic number specifically refers to the number of protons, not neutrons. Thus, choice A is the only accurate explanation of the difference between the atomic number and the mass number.

Correct Answer: A

Rationale: The correct answer is A: Calcitonin. Calcitonin is produced by the thyroid gland and functions to lower blood calcium levels by promoting calcium deposition in bones and inhibiting calcium reabsorption in the kidneys. This hormone opposes the action of parathyroid hormone (PTH), which increases blood calcium levels by promoting calcium release from bones and increasing calcium reabsorption in the kidneys. Thyroxine is a thyroid hormone that regulates metabolism and growth, not calcium levels. Insulin is a hormone produced by the pancreas that regulates blood sugar levels, not calcium levels. Thus, A is the correct answer as it directly regulates calcium levels in the blood through its actions on bones and kidneys.