Nokea
What does the P-wave in an ECG correspond to?
- A. Atrial repolarization
- B. Depolarization of SA node
- C. Ventricular depolarization
- D. Ventricular repolarization
Correct Answer: B
Rationale: The P-wave in an ECG represents the depolarization of the SA node and the atria, not atrial repolarization. Choice C, ventricular depolarization, is incorrect because the P-wave does not correspond to ventricular activity. Choice D, ventricular repolarization, is also incorrect as the P-wave does not depict ventricular repolarization. The correct interpretation is that the P-wave signifies the initiation of the electrical impulse at the SA node and subsequent atrial depolarization, making option B the correct answer.
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What is the primary function of white blood cells?
- A. To carry oxygen
- B. To fight infection
- C. To transport nutrients
- D. To transport waste
Correct Answer: B
Rationale: The correct answer is B: "To fight infection." White blood cells are primarily responsible for fighting infections and foreign invaders in the body, making them a critical component of the immune system. Choice A, "To carry oxygen," is incorrect as red blood cells are responsible for oxygen transport. Choice C, "To transport nutrients," is incorrect as this function is mainly attributed to blood plasma and other specialized cells. Choice D, "To transport waste," is also incorrect as waste removal is primarily handled by the kidneys and the lymphatic system, not white blood cells.
From which of the following germ layers does the nervous system develop?
- A. Ectoderm
- B. Endoderm
- C. Gastroderm
- D. Mesoderm
Correct Answer: A
Rationale: The correct answer is A: Ectoderm. The nervous system develops from the ectoderm, which is the outermost of the three germ layers. The ectoderm gives rise to structures such as the skin, hair, nails, and the entire nervous system. Choices B, C, and D are incorrect because the endoderm gives rise to the lining of the gut and associated organs, the gastroderm is not a recognized germ layer, and the mesoderm forms structures like muscles, bones, blood, and the circulatory system, but not the nervous system.
Which region of the small intestine is the primary site of absorption?
- A. Duodenum
- B. Jejunum
- C. Ileum
- D. Cecum
Correct Answer: B
Rationale: The jejunum is the correct answer. It is the primary site of nutrient absorption in the small intestine. The duodenum mainly facilitates digestion, the ileum is responsible for further absorption, while the cecum is part of the large intestine and not involved in nutrient absorption.
Which of the following brain structures is responsible for emotions, emotional behavior, and motivation?
- A. Amygdala
- B. Cerebellum
- C. Hypothalamus
- D. Pons
Correct Answer: A
Rationale: The correct answer is the amygdala. The amygdala is a key brain structure involved in processing emotions, emotional behavior, and motivation. It plays a crucial role in fear responses, emotional memories, and social behaviors. The cerebellum (Choice B) is primarily responsible for coordination and balance, not emotions. The hypothalamus (Choice C) regulates basic survival functions like hunger, thirst, and body temperature, but it is not primarily responsible for emotions. The pons (Choice D) is involved in functions such as sleep, respiration, and bladder control, but it is not the main center for emotions, emotional behavior, or motivation.
Which of the following does not describe a general trait of macromolecules?
- A. They can exist as single chains.
- B. They can be branched.
- C. They all contain carbon, hydrogen, and phosphorus.
- D. They are all used by the body.
Correct Answer: C
Rationale: The correct answer is C. While many macromolecules contain carbon, hydrogen, and phosphorus, not all of them do. For example, lipids, a type of macromolecule, may not contain phosphorus. Choice A and B describe structural features that macromolecules can exhibit, whether as single chains or branched forms. Choice D is incorrect as not all macromolecules are used by the body, such as synthetic polymers or certain non-digestible fibers.