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Which of the following describes one difference between skeletal and cardiac muscles?
- A. Cardiac muscles are involuntary, whereas skeletal muscles are voluntary
- B. Skeletal muscles are not autorhythmic, whereas cardiac muscles are
- C. Skeletal muscles are found in the limbs, whereas cardiac muscles are found in the heart
- D. Skeletal muscles are not autorhythmic
Correct Answer: A
Rationale: The correct answer is A because cardiac muscles are involuntary, meaning they are not under conscious control, while skeletal muscles are voluntary, allowing conscious control over their movement. Option B is incorrect as skeletal muscles are not autorhythmic, unlike cardiac muscles. Option C is inaccurate as skeletal muscles are primarily found in the limbs, while cardiac muscles are predominantly located in the heart. Option D is false as skeletal muscles are not autorhythmic; instead, cardiac muscles possess autorhythmicity due to their ability to generate and conduct electrical impulses independently.
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Which of the following respiratory structures is affected by a disease that disrupts gas exchange, such as emphysema?
- A. Trachea
- B. Alveoli
- C. Secondary bronchi
- D. Primary bronchi
Correct Answer: B
Rationale: Emphysema is a condition that primarily affects the alveoli in the lungs. Alveoli are tiny air sacs where the exchange of oxygen and carbon dioxide occurs. In emphysema, the walls of these air sacs break down, reducing the surface area available for gas exchange. This leads to impaired respiratory function, making it harder for oxygen to enter the bloodstream and for carbon dioxide to be removed. Therefore, the correct answer is the alveoli (Choice B).
A student makes a solution that simulates stomach acid. Which of the following would be true of this solution, compared to distilled water?
- A. It has a higher pH.
- B. It has more hydrogen ions.
- C. It contains more hydroxyl ions.
- D. It has more hydroxyl ions.
Correct Answer: B
Rationale: The correct answer is B. A solution that simulates stomach acid is acidic, which means it has a higher concentration of hydrogen ions compared to distilled water, which is neutral. Stomach acid is characterized by its high hydrogen ion concentration, which is responsible for its acidic nature. Hydroxyl ions are associated with bases, not acids, so options C and D are incorrect. Option A is incorrect as well because stomach acid would have a lower pH compared to distilled water due to its high acidity.
Which component of an atom has relatively little mass that is considered negligible when calculating the atomic mass number?
- A. Neutron
- B. Proton
- C. Electron
- D. Quark
Correct Answer: C
Rationale: The correct answer is C: Electron. Electrons have significantly less mass compared to protons and neutrons, making their contribution to the atomic mass number negligible. When calculating the atomic mass, the mass of electrons is typically not factored in due to their minimal mass compared to the other components of the atom. While protons and neutrons contribute significantly to the atomic mass number, electrons, due to their much smaller mass, are considered to have a negligible impact on the overall calculation. Therefore, electrons can be disregarded when determining the atomic mass of an atom.
Where are the tibia and fibula located in the body?
- A. Coxal
- B. Antecubital
- C. Crural
- D. Tarsal
Correct Answer: C
Rationale: The tibia and fibula are located in the crural region of the body. The crural region, also known as the lower leg, is situated between the knee and the ankle. The tibia and fibula are the two bones found in this region and play a crucial role in the skeletal structure of the lower limb. The coxal region refers to the hip, the antecubital region is located at the front of the elbow, and the tarsal region pertains to the ankle area. Therefore, the correct answer is C, crural, as it specifically refers to the location of the tibia and fibula in the lower leg.
Which of the following actions contributes to the repolarization of a neuron?
- A. Inhibition of sodium and potassium pumps to stop all ion movement into the neuron.
- B. Opening of potassium channels to allow potassium to leave the neuron.
- C. Closing of both sodium and potassium channels to restrict the movement of ions into and out of the neuron.
- D. Opening of sodium channels to allow sodium to enter the neuron.
Correct Answer: B
Rationale: Repolarization is the phase where the neuron returns to its resting membrane potential after depolarization. Opening of potassium channels is crucial during repolarization as it enables potassium ions to move out of the neuron, helping restore the negative charge inside the cell. This outward movement of positively charged potassium ions is necessary for repolarization, countering the sodium influx that occurred during depolarization. Therefore, the correct answer is the opening of potassium channels to allow potassium to leave the neuron.