which muscle is responsible for breathing
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HESI A2

Anatomy HESI A2 Practice Test

1. Which muscle is responsible for breathing?

Correct answer: A

Rationale: The diaphragm is the primary muscle responsible for breathing. It is a large, dome-shaped muscle located at the base of the chest cavity. When it contracts, it flattens, increasing the volume of the chest cavity and causing inhalation. When it relaxes, it returns to its dome shape, decreasing the volume of the chest cavity and causing exhalation. The intercostal muscles, located between the ribs, assist the diaphragm in breathing by expanding and contracting the chest cavity. The rectus abdominis and pectoralis major are not directly involved in the process of breathing.

2. Which brain part is responsible for regulating heart rate and blood pressure?

Correct answer: B

Rationale: The medulla oblongata, situated in the brainstem, plays a crucial role in controlling essential functions like heart rate, blood pressure, and breathing. It contains vital cardiovascular and respiratory centers, making it the correct choice for the regulation of heart rate and blood pressure. The cerebellum is primarily involved in coordinating movement and balance, not in regulating heart rate and blood pressure. The hypothalamus is responsible for maintaining homeostasis, regulating body temperature, hunger, and thirst, but not specifically heart rate and blood pressure. The pons is involved in functions like sleep, respiration, and bladder control, not primarily in regulating heart rate and blood pressure.

3. What is the primary role of the stomach in the digestive system?

Correct answer: B

Rationale: The primary role of the stomach in the digestive system is to break down food. It accomplishes this through the action of gastric acid and digestive enzymes, which work together to break down food into a semi-liquid mixture known as chyme. Option B, 'To break down food,' is the correct answer. Option A, 'To absorb nutrients,' is incorrect because absorption mainly occurs in the small intestine. Option C, 'To secrete digestive enzymes,' is partially correct as the stomach does secrete digestive enzymes, but its primary function is to break down food. Option D, 'To store glucose,' is incorrect as glucose storage primarily occurs in the liver and muscles, not the stomach.

4. Which hormone is produced by the adrenal cortex?

Correct answer: B

Rationale: The correct answer is B, Cortisol. Cortisol is the hormone produced by the adrenal cortex. It plays a crucial role in regulating metabolism, immune response, and managing stress. Insulin is produced by the pancreas, thyroxine by the thyroid gland, and glucagon by the pancreas. Therefore, choices A, C, and D are incorrect as they are not hormones produced by the adrenal cortex.

5. What is the role of the stomach in digestion?

Correct answer: B

Rationale: The correct answer is B: To break down food. The stomach's primary function in digestion is to mechanically and chemically break down food. It achieves this by utilizing gastric acid and digestive enzymes to convert food into chyme, a semi-liquid mixture. The chyme is then passed to the small intestine for further processing and absorption of nutrients. Choices A, C, and D are incorrect because the stomach's main role is not to absorb nutrients, secrete digestive enzymes, or transport nutrients; instead, it primarily focuses on breaking down food.

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