HESI A2 Anatomy and Physiology Quizlet

Correct Answer: C

Rationale: The main component of the cell membrane is lipids, specifically phospholipids. They form a lipid bilayer that provides structure and acts as a barrier to regulate what enters and exits the cell. Proteins are also important in the cell membrane for various functions, but they are not the main component. Carbohydrates are found on the surface of the cell membrane for cell recognition and communication, not as the main component. Nucleic acids are not found in the cell membrane, as they are responsible for genetic information storage and protein synthesis inside the cell.

Correct Answer: B

Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouse of the cell because they are responsible for energy production through the process of cellular respiration. They produce ATP, the main energy currency of the cell. The other choices are incorrect because the nucleus is responsible for storing genetic material, ribosomes are involved in protein synthesis, and the Golgi apparatus is responsible for packaging and transporting proteins. Therefore, only the mitochondria play a direct role in energy production within the cell.

Correct Answer: C

Rationale: The correct answer is C: Medulla oblongata. The medulla oblongata is located in the brainstem and is responsible for controlling vital functions such as breathing, heart rate, and blood pressure. It contains important centers that regulate these involuntary actions, making it the correct choice. The cerebrum (A) is responsible for higher brain functions such as thinking and voluntary movement. The cerebellum (B) is involved in coordination and balance. The hypothalamus (D) regulates body temperature, hunger, and thirst, but does not directly control breathing and heart rate.

Correct Answer: B

Rationale: The correct answer is B: To fight infection. White blood cells are part of the immune system and play a crucial role in defending the body against infections by attacking and destroying pathogens such as bacteria, viruses, and other foreign invaders. They are key players in the immune response. A: White blood cells do not carry oxygen to the cells. That is the role of red blood cells. C: White blood cells do not transport nutrients. Nutrients are transported by the bloodstream and absorbed by various organs. D: White blood cells are not responsible for clotting blood. Platelets are primarily responsible for blood clotting.

Correct Answer: A

Rationale: The correct answer is A: Melatonin. Melatonin is a hormone produced by the pineal gland that plays a key role in regulating the sleep-wake cycle. It helps control the body's internal clock and signals the brain when it's time to sleep. Melatonin levels typically rise in the evening, promoting sleep, and decrease in the morning, promoting wakefulness. Summary of incorrect choices: B: Insulin - Insulin is a hormone that regulates blood sugar levels, not the sleep-wake cycle. C: Cortisol - Cortisol is a stress hormone that helps regulate metabolism and immune response, but it does not directly control the sleep-wake cycle. D: Thyroxine - Thyroxine is a hormone produced by the thyroid gland that regulates metabolism, growth, and development, but it is not directly involved in the sleep-wake cycle regulation.