HESI A2 Anatomy and Physiology 2023

Correct Answer: B

Rationale: The correct answer is B: Thyroxine. Thyroxine, produced by the thyroid gland, plays a key role in regulating metabolism by controlling the body's metabolic rate. It influences how fast or slow our cells use energy. Insulin (A) regulates blood sugar levels, not metabolism. Glucagon (C) raises blood sugar levels. Cortisol (D) is a stress hormone that affects various body functions but is not primarily responsible for regulating metabolism. Thyroxine is crucial for maintaining overall metabolic balance in the body.

Correct Answer: B

Rationale: The correct answer is B: Pinna. The pinna, also known as the auricle, is the most visible part of the ear located on the outside of the head. It helps collect sound waves and directs them into the ear canal. The other choices are incorrect because: A: Cochlea is a spiral-shaped organ in the inner ear responsible for hearing. C: Ear canal is the tube that connects the outer ear to the eardrum. D: Organ of Corti is a structure in the cochlea that contains sensory cells responsible for hearing.

Correct Answer: B

Rationale: The correct answer is B: Skeletal muscle. Skeletal muscle is voluntary as it is under conscious control, allowing us to move our body voluntarily. Cardiac muscle (A) is involuntary and found in the heart. Smooth muscle (C) is also involuntary and found in internal organs. Striated muscle (D) is a general term that can refer to both skeletal and cardiac muscle, but not all striated muscles are voluntary. Therefore, B is the correct answer as it specifically refers to the type of muscle tissue that is under voluntary control.

Correct Answer: B

Rationale: During the fight-or-flight response, the body needs to prepare for immediate action. Adrenaline, also known as epinephrine, is the hormone released by the adrenal glands in response to stress or danger. Adrenaline triggers physiological changes such as increased heart rate, blood flow to muscles, and heightened awareness to help the body react quickly. Insulin is involved in regulating blood sugar levels, not the fight-or-flight response. Thyroxine plays a role in metabolism, while cortisol is released in response to stress but is not the primary hormone involved in the fight-or-flight response.

Correct Answer: B

Rationale: The correct answer is B: White blood cells. White blood cells, also known as leukocytes, are primarily responsible for fighting infections by detecting and destroying pathogens. Red blood cells (A) carry oxygen, platelets (C) aid in blood clotting, and plasma (D) is the liquid component of blood carrying nutrients and waste. White blood cells play a crucial role in the immune system's defense against infections, making them the correct choice.