HESI A2 Anatomy and Physiology 2023

Correct Answer: A

Rationale: The correct answer is A: Cerebellum. The cerebellum is responsible for balance and coordination as it receives sensory information from the inner ear and muscles to control movement. It coordinates muscle actions and maintains posture. The cerebrum (B) is responsible for higher brain functions, the medulla oblongata (C) controls basic life functions like breathing and heart rate, and the hypothalamus (D) regulates body temperature, hunger, and thirst. Thus, the cerebellum is the most appropriate choice for balance and coordination.

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.

Correct Answer: A

Rationale: Insulin is the correct answer because it is secreted by the pancreas in response to high blood glucose levels. Insulin helps to lower blood glucose levels by promoting the uptake of glucose into cells for energy storage. Glucagon, on the other hand, is secreted by the pancreas to increase blood glucose levels. Somatostatin regulates the release of insulin and glucagon but does not directly lower blood glucose levels. Cortisol is a stress hormone secreted by the adrenal glands and does not play a direct role in lowering blood glucose levels.

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: 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.