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. How does the integumentary system interact with the nervous system?

A. The integumentary system removes heat from the neurons in the nervous system.
B. The nervous system circulates nutrients outward to the integumentary system.
C. Touch input via the integumentary system sends messages to the nervous system.
D. Messages from the nervous system affect the color and texture of the skin.

Correct answer: C

Rationale: Touch input via the integumentary system sends messages to the nervous system. The integumentary system, comprising the skin, hair, and nails, functions as a sensory organ and a protective barrier against external threats. Specialized receptors in the skin detect stimuli like pressure, temperature, and pain, transmitting signals to the nervous system for interpretation. This communication enables the perception of touch and is vital for sensory processes, showcasing the interconnectedness between the integumentary and nervous systems. Choices A, B, and D are incorrect because the integumentary system primarily interacts with the nervous system through sensory input and communication of stimuli, rather than heat removal, nutrient circulation, or affecting skin color and texture based on nervous system messages.

3. Which of the following processes represents a different level of defense compared to the others?

A. A low pH in the stomach
B. Cilia present in the trachea
C. Body cells recognizing a pathogen
D. Mucus present in the nasal cavity

Correct answer: C

Rationale: Among the listed processes, low pH in the stomach, cilia in the trachea, and mucus in the nasal cavity serve as physical barriers that form the first line of defense against pathogens. These barriers work to block pathogens from entering the body. On the other hand, body cells recognizing a pathogen involves the immune response, which operates at a different level of defense. This process is part of the adaptive immune response, where the body's immune cells identify, target, and eliminate specific pathogens to provide a specialized defense after the pathogens have breached the physical barriers. Therefore, body cells recognizing a pathogen represent a different level of defense compared to the other listed processes.

4. What part of the eye is responsible for focusing light on the retina?

A. Cornea
B. Lens
C. Retina
D. Pupil

Correct answer: B

Rationale: The lens of the eye is responsible for focusing light on the retina. When light enters the eye, it first passes through the cornea, which helps in bending the light, and then the lens further refracts and focuses the light onto the retina at the back of the eye. The retina contains photoreceptor cells that convert light into neural signals, which are then sent to the brain for visual processing. The cornea is the transparent outermost layer of the eye that helps in focusing light, but the main responsibility lies with the lens. The retina is the layer at the back of the eye that receives the focused light and initiates the process of vision. The pupil is the opening in the center of the iris that controls the amount of light entering the eye and is not directly involved in focusing light on the retina.

5. What is the most visible part of the ear?

A. Ear canal
B. Cochlea
C. Organ of Corti
D. Pinna

Correct answer: D

Rationale: The pinna, also known as the auricle, is the most visible part of the ear. Its external shape and location make it easily noticeable on the side of the head. The pinna helps in capturing sound waves and directing them into the ear canal, where the sound transmission process begins. The other structures listed, the Organ of Corti, Cochlea, and Ear canal, are essential parts of the ear involved in hearing and sound processing, but they are not as visibly prominent as the pinna. Therefore, the correct answer is the pinna because of its external visibility and role in capturing sound waves.