Nursing Elites

1. What is the small repeating unit in the contractile apparatus of skeletal muscle?

• A. Myofibril
• B. Actin
• C. Sarcomere
• D. Myosin

Correct answer: C

Rationale: The correct answer is 'Sarcomere.' The sarcomere is the smallest repeating unit within myofibrils and is responsible for muscle contraction in skeletal muscle. It consists of overlapping actin and myosin filaments arranged in a highly organized structure that allows for the sliding of filaments during muscle contraction. 'Myofibril' (choice A) is incorrect because it is a larger structure composed of sarcomeres. 'Actin' (choice B) and 'Myosin' (choice D) are incorrect as they are individual proteins that are components of the sarcomere, not the smallest repeating unit itself.

2. What happens when the diaphragm contracts?

• A. Air is expelled from the lungs.
• B. The lungs expand to allow air intake.
• C. The vocal cords vibrate to produce sound.
• D. The trachea narrows to control airflow.

Correct answer: B

Rationale: When the diaphragm contracts, it moves downward, creating more space in the chest cavity. This expansion of the chest cavity causes the lungs to expand as well, allowing air to be drawn into the lungs during inhalation. Therefore, the correct answer is that the lungs expand to allow air intake when the diaphragm contracts. Choices A, C, and D are incorrect because when the diaphragm contracts, it does not expel air from the lungs, cause the vocal cords to vibrate, or narrow the trachea to control airflow.

3. What is the name for the sac-shaped structures in which carbon dioxide and oxygen exchange takes place?

• A. Kidneys
• B. Medulla oblongata
• C. Alveoli
• D. Bronchioles

Correct answer: C

Rationale: The alveoli are the tiny sac-shaped structures in the lungs where gas exchange occurs. Oxygen from the air we breathe diffuses into the bloodstream through the alveoli, while carbon dioxide, a waste product produced by cells, is removed from the blood and exhaled out of the body through the alveoli. Choices A, B, and D are incorrect. Kidneys are organs responsible for filtering waste from the blood, the medulla oblongata is a part of the brain responsible for autonomic functions, and bronchioles are smaller airway passages in the lungs that branch off from the bronchi.

4. Which structure is the largest part of the airway?

• A. Alveoli
• B. Bronchi
• C. Bronchioles
• D. Trachea

Correct answer: D

Rationale: The correct answer is the trachea. The trachea is the largest part of the airway and serves as the main passageway for air to enter and exit the lungs. It connects the larynx to the bronchi and is an essential component of the respiratory system. The alveoli, although crucial for gas exchange, are tiny air sacs in the lungs and not the largest part of the airway. Bronchi and bronchioles are smaller airway passages that branch off from the trachea, making them smaller in size compared to the trachea.

5. Which statement confirms that the cell membrane is selectively permeable?

• A. Receptors are found on a cell's surface.
• B. Cells communicate with each other using cell signals.
• C. Environmental changes can cause a cell to expand or shrink.
• D. Sodium ions must travel through ion channels to enter the cell.

Correct answer: D

Rationale: The correct answer is D because selective permeability is demonstrated by the fact that specific ions, such as sodium, require ion channels to cross the cell membrane. This process allows the cell to control what substances can enter or exit, highlighting the selective nature of the cell membrane. Choices A, B, and C do not directly relate to the concept of selective permeability of the cell membrane. Receptors on a cell's surface (Choice A) are involved in cell signaling rather than selective permeability. Cell communication through signals (Choice B) and environmental changes affecting cell size (Choice C) are not directly related to the selective permeability of the cell membrane, which specifically refers to the regulation of substances passing through the membrane.

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