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: D

Rationale: The correct answer is D: Influenza. Influenza is caused by a virus, specifically the influenza virus. Step-by-step rationale: 1. Influenza is a contagious respiratory illness caused by the influenza virus. 2. Viruses are known to be the causative agents of influenza. 3. Asthma (A), Cystic Fibrosis (B), and Epiglottitis (C) are not caused by viruses; asthma is a chronic inflammatory disease, cystic fibrosis is a genetic disorder, and epiglottitis is usually caused by bacteria.

Correct Answer: A

Rationale: The P wave on an ECG represents atrial depolarization. During the cardiac cycle, the electrical impulse originates in the sinoatrial (SA) node, causing the atria to contract. This depolarization of the atria is reflected as the P wave on the ECG. This occurs before the ventricles depolarize (choice B), repolarize (choice D), or before the atria repolarize (choice C). Therefore, the correct answer is A because the P wave specifically represents atrial depolarization in the cardiac cycle.

Correct Answer: A

Rationale: Diastole is the correct answer because it specifically refers to the relaxation phase of the heart muscle. During diastole, the heart fills with blood before contracting in systole. Systole is the contraction phase, not relaxation. Asystole is the absence of heart contractions, not relaxation. Cardiastole is not a recognized term in relation to the heart's relaxation. Therefore, diastole is the most appropriate term for describing the relaxation of the heart muscle.

Correct Answer: A

Rationale: The correct answer is A: Meters per second. The speed of light in a vacuum is a measure of how fast light travels, which is approximately 299,792,458 meters per second. This unit is commonly used in physics to quantify the speed of light. Hertz (B) is a unit of frequency, Candela (C) is a unit of luminous intensity, and Newton (D) is a unit of force, not speed. Therefore, A is the correct unit to measure the speed of light in a vacuum.