Nokea
How do vaccines work?
- A. By directly killing pathogens
- B. By introducing weakened or inactive versions of pathogens to trigger an immune response
- C. By stimulating the immediate production of specific antibodies
- D. None of the above
Correct Answer: B
Rationale: Vaccines work by introducing weakened or inactive versions of pathogens to trigger an immune response in the body. This exposure helps the immune system recognize and remember the pathogen, enabling a faster and more effective response upon future exposure. Vaccines do not directly kill pathogens but prepare the immune system for a potential encounter, enhancing protection. They also do not stimulate the immediate production of specific antibodies as the immune response takes time to develop upon vaccination. Choice A is incorrect because vaccines do not kill pathogens directly; they prime the immune system to recognize and respond to them. Choice C is incorrect because while vaccines lead to the production of specific antibodies, it is not immediate, as it takes time for the immune response to develop and produce these antibodies.
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Myelin sheath is a fatty substance that insulates and protects the long extensions of some nerve cells. It is produced by:
- A. Schwann cells
- B. Astrocytes
- C. Neurons
- D. Oligodendrocytes
Correct Answer: A
Rationale: Schwann cells are indeed responsible for producing the myelin sheath in the peripheral nervous system. These cells wrap around axons to form the myelin sheath, which enhances the speed of nerve impulse conduction. In the central nervous system, oligodendrocytes are responsible for producing the myelin sheath. Astrocytes provide support and maintenance functions for neurons, while neurons are the nerve cells themselves and do not produce myelin. Therefore, the correct answer is Schwann cells as they are specifically involved in myelin production in the peripheral nervous system.
What is the name of the condition characterized by inflammation of the small intestine?
- A. Appendicitis
- B. Celiac disease
- C. Gastritis
- D. Crohn's disease
Correct Answer: D
Rationale: A) Appendicitis is inflammation of the appendix, not the small intestine.
B) Celiac disease is an autoimmune disorder triggered by gluten consumption that damages the small intestine, but it is not characterized by inflammation alone.
C) Gastritis is inflammation of the stomach lining, not the small intestine.
D) Crohn's disease is a chronic inflammatory condition that can affect any part of the gastrointestinal tract, but it commonly involves the small intestine. Symptoms of Crohn's disease include abdominal pain, diarrhea, weight loss, and fatigue.
Where does fertilization, the fusion of sperm and egg, typically occur in the human body?
- A. Ovary
- B. Uterus
- C. Fallopian tube
- D. Vagina
Correct Answer: C
Rationale: Fertilization typically occurs in the fallopian tube. This is where the sperm and egg meet and fuse to form a zygote. The fallopian tube provides the optimal environment for fertilization as it helps in the transportation of the egg and provides a suitable site for fertilization before the resulting embryo travels to the uterus for implantation. Choices A, B, and D are incorrect. The ovary is where eggs are produced, the uterus is where the fertilized egg implants and develops into a fetus, and the vagina is the canal that leads to the cervix, but fertilization itself does not occur in these locations.
What property of a substance remains constant regardless of the amount of the substance present?
- A. Mass
- B. Weight
- C. Density
- D. Volume
Correct Answer: C
Rationale: The correct answer is C, Density. Density is a physical property of a substance that remains constant regardless of the amount of the substance present. Mass (Choice A) is the amount of matter in an object and can change depending on the amount of the substance. Weight (Choice B) is the force exerted on an object due to gravity and can vary with location. Volume (Choice D) is the amount of space occupied by a substance and can change if the amount of the substance changes.
What is the product of the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH)?
- A. NaCl + H2O
- B. NaOH + HCl
- C. Na2Cl + H2O
- D. NaClO3 + H2
Correct Answer: A
Rationale: When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), it forms sodium chloride (NaCl) and water (H2O) according to the following chemical equation: HCl + NaOH -> NaCl + H2O. Therefore, the correct answer is NaCl + H2O (Choice A). This reaction is a classic acid-base neutralization reaction where the acid (HCl) reacts with the base (NaOH) to form a salt (NaCl) and water (H2O). Choice B (NaOH + HCl) is incorrect because the order of the reactants matters in a chemical reaction, and in this case, HCl is the acid reacting with NaOH. Choices C (Na2Cl + H2O) and D (NaClO3 + H2) are incorrect because they do not represent the products of the reaction between HCl and NaOH as per the balanced chemical equation.