HESI A2 Anatomy and Physiology 2023

Correct Answer: C

Rationale: The correct answer is C: Medulla oblongata. The medulla oblongata is located in the brainstem and is responsible for regulating essential functions such as heart rate and breathing. It contains vital centers that control autonomic functions, including the cardiovascular and respiratory systems. The medulla receives inputs from various sensory receptors and sends signals to the heart and lungs to maintain homeostasis. The other choices are incorrect because: A: Cerebrum is primarily responsible for higher brain functions such as thinking and voluntary movements. B: Cerebellum is involved in coordination and balance, not in regulating heart rate and breathing. D: Hypothalamus plays a role in regulating body temperature, hunger, and thirst, but not specifically in controlling heart rate and breathing.

Correct Answer: A

Rationale: The correct answer is A: Pancreas. The pancreas is responsible for producing insulin, a hormone that helps regulate blood sugar levels. It contains clusters of cells called islets of Langerhans, which specifically produce insulin. The liver (B) is involved in storing glucose and producing bile, not insulin. The gallbladder (C) stores bile produced by the liver and aids in digestion, not insulin production. The kidneys (D) filter blood and regulate fluid balance, but do not produce insulin. Therefore, the pancreas is the organ responsible for insulin production in the body.

Correct Answer: B

Rationale: The correct answer is B: Adrenaline. Adrenaline, also known as epinephrine, is released by the adrenal glands during the fight or flight response. It increases heart rate, blood flow to muscles, and alertness to prepare the body for emergency situations. Cortisol (A) is a stress hormone but not directly involved in the immediate fight or flight response. Thyroxine (C) regulates metabolism and growth, not specifically related to fight or flight. Melatonin (D) regulates sleep-wake cycles and is not involved in the fight or flight response.

Correct Answer: B

Rationale: The correct answer is B: Skin. The skin is the largest organ in the human body by surface area, covering about 20 square feet on average. It serves as a protective barrier against external elements and plays a crucial role in regulating body temperature. The liver (A), brain (C), and heart (D) are important organs, but they are not the largest in terms of size or surface area. Therefore, the correct choice is the skin.

Correct Answer: C

Rationale: The correct answer is C: Cortisol. Cortisol is a hormone released by the adrenal glands in response to stress. It helps regulate metabolism, immune response, and blood pressure during stressful situations. Insulin (A) is involved in regulating blood sugar levels, not the stress response. Adrenaline (B) is also known as epinephrine and is involved in the fight-or-flight response, which is part of the stress response. Melatonin (D) is a hormone that regulates sleep-wake cycles and is not directly related to the stress response.