Nokea
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.
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What are the primary differences between systemic and pulmonary circulation?
- A. Systemic circulation is shorter and has lower blood pressure
- B. Pulmonary circulation is shorter and has higher blood pressure
- C. Systemic circulation is longer and has higher blood pressure
- D. Systemic circulation is shorter but has higher blood pressure
Correct Answer: C
Rationale: The correct answer is C. Systemic circulation is longer as it involves carrying oxygenated blood throughout the body, requiring higher blood pressure. Pulmonary circulation is shorter and involves the flow of blood only through the lungs, hence having lower blood pressure. Therefore, systemic circulation is longer and has higher blood pressure compared to pulmonary circulation. Choice A is incorrect as systemic circulation is longer, not shorter, and has higher blood pressure. Choice B is incorrect as pulmonary circulation has lower blood pressure, not higher. Choice D is incorrect as systemic circulation is longer, not shorter, despite having higher blood pressure.
What are the components of the male external genitalia and their functions?
- A. Prostate gland: produces seminal fluid
- B. Scrotum: protects and maintains the temperature of the testes
- C. Penis: delivers sperm to female reproductive tract
- D. Urethra: conducts urine out of the body
Correct Answer: C
Rationale: The correct answer is C. The penis is responsible for delivering sperm to the female reproductive tract during sexual intercourse. The scrotum is not involved in producing sperm but rather protects and regulates the temperature of the testes, which is essential for sperm production. The prostate gland is involved in producing seminal fluid, not sperm. The urethra serves the purpose of conducting urine out of the body and also acts as a passage for semen during ejaculation.
A pediatrician notes that an infant's cartilage is disappearing and being replaced by bone. What process has the doctor observed?
- A. Mineralization
- B. Ossification
- C. Osteoporosis
- D. Calcification
Correct Answer: B
Rationale: The doctor has observed the process of ossification. Ossification is the natural process where cartilage in the body is replaced by bone. This process takes place during fetal development, growth, and bone fracture healing. Ossification involves the formation of bone tissue by depositing minerals like calcium and phosphorus within the cartilage matrix, leading to the development of a bone structure. Choice A, mineralization, refers to the process of forming mineral deposits in tissues, but it does not involve the replacement of cartilage by bone. Choice C, osteoporosis, is a condition characterized by bone density loss and increased fragility, not the natural process of cartilage replacement by bone. Choice D, calcification, is the process of deposition of calcium salts in various tissues, but it does not specifically involve the replacement of cartilage by bone as in ossification.
Which molecules are soluble in nonpolar solvents but are hydrophobic?
- A. Carbohydrates
- B. Lipids
- C. Proteins
- D. Nucleic acids
Correct Answer: B
Rationale: Lipids are hydrophobic molecules that are soluble in nonpolar solvents like oils but insoluble in water. They consist of fats, oils, waxes, and steroids and play essential roles in energy storage, insulation, and cell membrane structure. Carbohydrates, proteins, and nucleic acids are not typically soluble in nonpolar solvents and do not exhibit the same hydrophobic characteristics as lipids. Carbohydrates are usually hydrophilic and soluble in water, proteins have both hydrophilic and hydrophobic regions but are not generally soluble in nonpolar solvents, and nucleic acids are polar molecules that are not known for their solubility in nonpolar solvents.
What is the approximate composition of blood?
- A. 45% plasma, 55% formed elements
- B. 55% plasma, 45% formed elements
- C. 55% water, 45% blood cells
- D. 45% water, 55% plasma
Correct Answer: B
Rationale: Blood is composed of approximately 55% plasma (mostly water with proteins, electrolytes, and nutrients) and 45% formed elements (red blood cells, white blood cells, and platelets). Choice B is the correct answer. Choice A is incorrect as it reverses the percentages. Choice C is incorrect because it incorrectly states that blood cells make up 45% of blood, while they are part of the formed elements along with platelets. Choice D is incorrect as it suggests that water makes up 45% of blood, which is not accurate.