Nokea
Through which aspect do afferent fibers enter the spinal cord?
- A. Through the anterior aspect
- B. Through the dorsal aspect
- C. Through the ventral aspect
- D. Through the lateral aspect
Correct Answer: B
Rationale: Afferent fibers, responsible for carrying sensory information, enter the spinal cord through the posterior (dorsal) aspect. Specifically, they enter through the dorsal roots, located on the back (posterior) side of the spinal cord. This route allows sensory information to be transmitted to the central nervous system for processing and integration. Choices A, C, and D are incorrect because afferent fibers do not enter the spinal cord through the anterior, ventral, or lateral aspects.
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What controls muscles by sending electrical impulses to the muscles?
- A. Blood vessels
- B. Nerves
- C. Hormones
- D. Neurons
Correct Answer: B
Rationale: Nerves control muscles by transmitting electrical impulses that initiate muscle contractions. Blood vessels are responsible for transporting blood, not controlling muscles. Hormones are chemical messengers produced by glands to regulate bodily functions, not specifically controlling muscles. Neurons are the basic building blocks of the nervous system that transmit signals, but nerves are the specific structures that control muscles by sending electrical impulses.
Which of the following produces the first heart sound ('lub')?
- A. The closing of the aortic and pulmonary valves
- B. The closing of the tricuspid and mitral valves
- C. The opening of the aortic and pulmonary valves
- D. The opening of the tricuspid and mitral valves
Correct Answer: B
Rationale: The correct answer is B. The first heart sound, known as the 'lub' sound, is produced by the closure of the tricuspid and mitral valves, which are the atrioventricular valves. This sound marks the beginning of systole in the cardiac cycle. Choice A, the closing of the aortic and pulmonary valves, is incorrect as these valves produce the second heart sound ('dub'). Choice C, the opening of the aortic and pulmonary valves, is incorrect because the first heart sound occurs during ventricular contraction (systole). Choice D, the opening of the tricuspid and mitral valves, is incorrect as the 'lub' sound is associated with the closure, not the opening, of these valves.
Which of the following blood proteins can destroy pathogens?
- A. Complement system
- B. Fibrinogen
- C. Major histocompatibility complex
- D. Platelets
Correct Answer: A
Rationale: The correct answer is A: Complement system. The complement system is a vital component of the immune system responsible for destroying pathogens through various mechanisms like promoting inflammation, enhancing phagocytosis, and directly lysing pathogens. Fibrinogen is crucial for blood clotting, the major histocompatibility complex is involved in immune responses, and platelets aid in blood clotting and wound healing. However, none of these directly destroy pathogens as the complement system does.
Which of the following substances has an acidic pH?
- A. Lemon juice
- B. Blood
- C. Urine
- D. Salt water
Correct Answer: A
Rationale: The correct answer is A, Lemon juice, which has an acidic pH typically around 2 due to its citric acid content. Blood, urine, and salt water are not typically acidic in nature. Blood has a slightly basic pH, urine can vary but is usually slightly acidic to neutral, and salt water is neutral to slightly alkaline. Lemon juice is a commonly known acidic substance, often used in cooking and cleaning due to its acidic properties.
Which of the following inventions likely had the greatest impact on combating nutrition deficiencies in developing countries?
- A. Food products fortified with dietary vitamins and minerals
- B. Integrated statistical models of fish populations
- C. Advances enabling microscopes to use thicker tissue samples
- D. Refrigerated train cars for transportation of food
Correct Answer: A
Rationale: Food products fortified with dietary vitamins and minerals have had the greatest impact on combating nutrition deficiencies in developing countries. By fortifying food products with essential nutrients such as vitamins and minerals, it becomes easier to address specific deficiencies in populations that may not have access to a diverse range of foods. This innovation has been particularly impactful in addressing common deficiencies like vitamin A, iron, zinc, and folic acid, improving overall health outcomes in populations with limited access to nutrient-rich foods. Choices B, C, and D are incorrect. Integrated statistical models of fish populations, advances in microscopy, and refrigerated train cars, while important in their own right, do not directly address combating nutrition deficiencies in developing countries as effectively as food fortification with essential nutrients.