which muscle is responsible for breathing

HESI A2

Anatomy HESI A2 Practice Test

1. Which muscle is responsible for breathing?

A. Diaphragm
B. Intercostal muscles
C. Rectus abdominis
D. Pectoralis major

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 organ in the digestive system absorbs nutrients?

A. Stomach
B. Small intestine
C. Large intestine
D. Esophagus

Correct answer: B

Rationale: The small intestine is the primary site for nutrient absorption in the digestive system. It plays a crucial role in absorbing digested food into the bloodstream, where the nutrients are then circulated to the body's cells for energy and other functions. The stomach primarily breaks down food through the action of acids and enzymes, while the large intestine absorbs water and salts, not nutrients. The esophagus is a muscular tube that connects the mouth to the stomach and does not participate in nutrient absorption.

3. Which hormone is involved in the body's stress response?

A. Insulin
B. Adrenaline
C. Cortisol
D. Melatonin

Correct answer: C

Rationale: The correct answer is C: Cortisol. Cortisol, produced by the adrenal glands, is involved in the body's stress response. It helps regulate metabolism, immune function, and the body's response to stressors by increasing blood sugar levels, suppressing the immune system, and aiding in the metabolism of fats, carbohydrates, and proteins. Choice A, Insulin, is a hormone that regulates blood sugar levels and is not primarily involved in the stress response. Choice B, Adrenaline, is also known as epinephrine and is involved in the fight-or-flight response, which is related to stress but is not the main hormone in the body's stress response. Choice D, Melatonin, is a hormone that regulates sleep-wake cycles and is not directly involved in the stress response.

4. Which cellular structure is responsible for producing energy?

A. Nucleus
B. Mitochondria
C. Ribosome
D. Golgi apparatus

Correct answer: B

Rationale: Mitochondria are the organelles responsible for producing energy in the cell through a process called cellular respiration. They are often referred to as the powerhouses of the cell due to their role in generating ATP, the cell's energy currency. The nucleus is not involved in energy production but houses the cell's genetic material. Ribosomes are responsible for protein synthesis, not energy production. The Golgi apparatus is involved in processing and packaging proteins for secretion, not energy production.

5. The arteries are part of which system?

A. Nervous system
B. Endocrine system
C. Lymphatic system
D. Cardiovascular system

Correct answer: D

Rationale: The correct answer is D, Cardiovascular system. Arteries are blood vessels that carry oxygen-rich blood away from the heart to various parts of the body. They are a key component of the cardiovascular system, which is responsible for transporting blood, nutrients, and oxygen throughout the body. The other options (A, B, and C) are incorrect because arteries are not part of the nervous system, endocrine system, or lymphatic system.