Nokea
Which cells myelinate neurons in the CNS?
- A. Schwann cells
- B. Astrocytes
- C. Microglia
- D. Oligodendrocytes
Correct Answer: D
Rationale: The correct answer is D, Oligodendrocytes. Oligodendrocytes are responsible for myelinating neurons in the central nervous system (CNS). Schwann cells, found in the peripheral nervous system, are responsible for myelinating neurons there. Astrocytes support and maintain the neuronal environment, while microglia function as immune cells in the CNS, participating in immune responses and cellular debris clearance. Therefore, choices A, B, and C are incorrect for myelination of CNS neurons.
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What is a gene, and what is the relationship between genes, genotype, and phenotype?
- A. A gene is a sequence of amino acids; genes make up proteins; genotype determines phenotype
- B. A gene is a portion of DNA; genes determine traits; genotype is the genetic makeup; phenotype is the physical manifestation
- C. A gene is a protein; proteins determine traits; genotype is the set of all genes
- D. A gene is a lipid; lipids determine traits; phenotype is the physical manifestation
Correct Answer: B
Rationale: A gene is a portion of DNA that contains the instructions for a specific trait. Genotype refers to the genetic makeup of an organism, encompassing all its genes. Phenotype, on the other hand, is the observable physical manifestation resulting from the interaction between an organism's genotype and environmental factors. Choice A is incorrect because genes do not consist of amino acids directly; they are sequences of nucleotides. Choice C is incorrect as genes do not determine traits directly but provide the instructions for proteins that may influence traits. Choice D is incorrect as genes are not lipids, and lipids do not determine traits; they are a type of biomolecule with different functions.
A student hypothesizes that higher sugar consumption negatively impacts test scores. To investigate this, the student recruits participants to consume varying amounts of sugar, wait for one hour, and then complete an aptitude test. The student will record both the amount of sugar consumed and the test scores to analyze the relationship. What is the best experimental approach?
- A. Conduct one round of testing where each participant consumes a different amount of sugar.
- B. Conduct two rounds of testing: In the first round, participants consume varying amounts of sugar; in the second round, they consume the same amount of sugar as they did in the first round.
- C. Conduct two rounds of testing: In the first round, participants consume varying amounts of sugar; in the second round, participants consume no sugar.
- D. Conduct one round of testing where all participants consume the same amount of sugar.
Correct Answer: C
Rationale: Option C provides the most thorough experimental design by including a control group. In the first round, varying sugar intake levels help explore the relationship between sugar consumption and test scores. In the second round, by having participants consume no sugar, the student can compare results to observe any changes due to sugar intake. This approach enhances the validity of the findings by accounting for potential confounding factors and better identifying causal relationships. Choice A is not ideal as it lacks a control group and does not compare the impact of sugar consumption. Choice B does not explore the effects of sugar consumption adequately as it does not include a group without sugar. Choice D does not allow for comparison between different sugar consumption levels, limiting the ability to draw meaningful conclusions.
What is the fatty substance that coats axons to insulate, protect, and speed up impulses?
- A. Myelin
- B. Dendrite
- C. Neuron
- D. Synapse
Correct Answer: A
Rationale: The correct answer is 'Myelin.' Myelin is a fatty substance that functions as an insulator for axons, providing protection and enhancing the speed of electrical impulses along neurons. This insulation is essential for ensuring efficient and rapid communication within the nervous system. Choices B, C, and D are incorrect. Dendrites are branched extensions of a neuron that receive signals, neurons are the basic building blocks of the nervous system that transmit information, and synapses are the junctions between neurons where communication occurs.
What is the bottom number in a blood pressure reading?
- A. Diastolic pressure
- B. Systolic pressure
- C. Pulse rate
- D. Mean arterial pressure
Correct Answer: A
Rationale: The correct answer is A: Diastolic pressure. The bottom number in a blood pressure reading represents the diastolic pressure, which indicates the lowest pressure in the arteries when the heart is resting between beats. This value is important in understanding the overall health of the cardiovascular system. Choice B, Systolic pressure, is the top number in a blood pressure reading and represents the pressure in the arteries when the heart is contracting. Choice C, Pulse rate, refers to the number of times the heart beats in a minute. Choice D, Mean arterial pressure, is a calculated value using both systolic and diastolic pressures to provide an average pressure in the arteries during a cardiac cycle, but it is not the bottom number in a blood pressure reading.
A rock has a mass of 3 grams (g) and a volume of 4 cm³. What is its density?
- A. 8.90 g/cm³
- B. 0.38 g/cm³
- C. 77.22 g/cm³
- D. 2.65 g/cm³
Correct Answer: D
Rationale: Density is determined by the formula Density = Mass / Volume. For this rock, the mass is 3g, and the volume is 4 cm³. Applying the formula: Density = 3g / 4cm³ = 0.75 g/cm³. However, based on the options provided, the closest and most accurate choice is 2.65 g/cm³, corresponding to option D. Choice A, 8.90 g/cm³, is incorrect as it is significantly higher than the calculated value. Choice B, 0.38 g/cm³, and Choice C, 77.22 g/cm³, are also incorrect and do not match the correct calculation.