Nursing Elites

1. 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.

2. A symbiotic relationship where one organism benefits and the other is not harmed is called:

• A. Mutualism
• B. Commensalism
• C. Parasitism
• D. Predation

Correct answer: B

Rationale: B) Commensalism: In commensalism, one organism benefits while the other is neither helped nor harmed. This is the relationship described in the question. The correct answer is Commensalism because it specifically fits the scenario where one organism benefits without affecting the other. A) Mutualism: In mutualism, both organisms involved benefit from the relationship. C) Parasitism: In parasitism, one organism benefits at the expense of the other organism, which is harmed. D) Predation: In predation, one organism (predator) kills and consumes another organism (prey) for food.

3. Which structure in the skin is responsible for producing hair?

• A. Sudoriferous gland
• B. Sebaceous gland
• C. Melanocyte
• D. Hair follicle

Correct answer: D

Rationale: The correct answer is D: Hair follicle. Hair follicles are structures in the skin responsible for producing hair. They are specialized structures that contain the hair root and the bulb, where hair growth originates. Sudoriferous glands produce sweat, sebaceous glands produce sebum, and melanocytes are responsible for producing melanin, the pigment that gives hair and skin their color. Choices A, B, and C are incorrect because sudoriferous glands produce sweat, sebaceous glands produce sebum, and melanocytes produce melanin, respectively, but they are not responsible for producing hair.

4. Melatonin is a hormone produced by the pineal gland. What is its primary function?

• A. Regulate blood pressure
• B. Stimulate the digestive system
• C. Control sleep-wake cycles
• D. Maintain bone density

Correct answer: C

Rationale: Melatonin is primarily known for its role in controlling sleep-wake cycles. It is produced by the pineal gland in response to darkness, helping signal the body that it is time to sleep. Melatonin levels typically rise in the evening and stay elevated throughout the night, promoting sleep. Choices A, B, and D are incorrect as melatonin's primary function is not to regulate blood pressure, stimulate the digestive system, or maintain bone density. While melatonin may have some indirect effects on these functions, its main role lies in regulating the circadian rhythm and promoting a restful sleep cycle.

5. How are sister chromatids distinguished from homologous chromosomes in meiosis I?

• A. Sister chromatids share the same centromere, while homologous chromosomes have different centromeres.
• B. Sister chromatids have identical DNA sequences, while homologous chromosomes have slightly different sequences due to crossing over.
• C. Sister chromatids repel each other, while homologous chromosomes attract each other during synapsis.
• D. Sister chromatids separate during anaphase I, while homologous chromosomes separate during anaphase II.

Correct answer: B

Rationale: In meiosis I, sister chromatids are exact copies of each other, containing identical DNA sequences. On the other hand, homologous chromosomes are pairs of chromosomes, with one inherited from each parent, and they can have different versions of genes due to genetic recombination during crossing over in prophase I. Choice A is incorrect because homologous chromosomes naturally have different centromeres. Choice C is incorrect as sister chromatids and homologous chromosomes do not exhibit repulsion or attraction during synapsis. Choice D is incorrect as sister chromatids separate during anaphase II, not anaphase I, while homologous chromosomes separate during anaphase I.

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