ati teas 7 science

Correct Answer: C

Rationale: The correct answer is C: Control sleep-wake cycles. Melatonin is primarily responsible for regulating our sleep-wake cycles, also known as the circadian rhythm. This hormone is released by the pineal gland in response to darkness, signaling to the body that it is time to sleep. Melatonin helps to synchronize our internal body clock with the natural day-night cycle. Choice A (Regulate blood pressure) is incorrect because melatonin does not play a direct role in regulating blood pressure. Choice B (Stimulate the digestive system) is incorrect as melatonin is not involved in stimulating the digestive system. Choice D (Maintain bone density) is also incorrect as melatonin's primary function is not related to bone density regulation.

Correct Answer: A

Rationale: The correct answer is A: Axon. The axon is responsible for transmitting signals away from the cell body towards other neurons or muscles. It is a long, slender projection of the neuron that carries electrical impulses known as action potentials. The axon is covered by the myelin sheath, which helps to speed up the transmission of signals. Summary: - B: Dendrite receives signals from other neurons and transmits them towards the cell body. - C: Synapse is the gap between neurons where neurotransmitters are released to communicate signals. - D: Myelin sheath insulates and speeds up signal transmission along the axon, but it is not responsible for transmitting signals itself.

Correct Answer: A

Rationale: The primary function of the digestive system is to break down food into nutrients for absorption by the body. This process involves mechanical and chemical digestion to convert food into molecules that can be absorbed by the intestines. Option A is correct as it describes this essential function. Option B is incorrect because the absorption of oxygen primarily occurs in the respiratory system. Option C is incorrect as the production of energy is mainly attributed to the metabolic processes within cells. Option D is incorrect as the regulation of body temperature is primarily controlled by the thermoregulatory system, not the digestive system.

Correct Answer: B

Rationale: The correct answer is B: Autoimmune disease. In autoimmune diseases, the immune system mistakenly targets healthy cells and tissues, causing inflammation and damage. This is due to a breakdown in self-tolerance mechanisms. Immunodeficiency (A) is the opposite, where the immune system is weakened. Allergy (C) is an immune response to harmless substances, not attacking healthy tissues. Cancer (D) involves uncontrolled cell growth, not immune system attacking healthy tissues.

Correct Answer: B

Rationale: The correct answer is B: Thyroxine. Thyroxine is a hormone produced by the thyroid gland that plays a key role in regulating metabolism. It controls the body's metabolic rate, impacting energy levels and weight. Adrenaline (A) is produced by the adrenal glands and is involved in the fight-or-flight response. Cortisol (C) is produced by the adrenal glands and is known as the stress hormone. Insulin (D) is produced by the pancreas and regulates blood sugar levels, not metabolism. Thyroxine directly influences metabolism, making it the correct choice.