The label arrow illustrate
coarse adjustment
Fine adjustment
The Correct Answer is A
Coarse adjustment: The arrow points to the coarse adjustment knob, a large focusing knob on the microscope used to move the stage up or down quickly to bring the specimen into general focus. It is typically used with low-power objective lenses to locate the specimen and obtain an initial image. Using it with high-power lenses can risk damaging the slide or lens because it moves the stage in large increments.
Fine adjustment: A smaller focusing knob that moves the stage very slightly to sharpen the image after the specimen has been brought into general focus. It is mainly used with high-power or oil immersion objectives to achieve precise, clear visualization of cellular details without risking damage to the specimen.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Hemolysins are bacterial exotoxins that specifically target and lyse red blood cells, releasing hemoglobin into the surrounding environment. They are produced by certain pathogenic bacteria, such as Streptococcus and Staphylococcus species, and contribute to nutrient acquisition by providing iron from hemoglobin. Hemolysins can cause varying degrees of red blood cell destruction, resulting in different patterns on blood agar: alpha hemolysis (partial lysis with greenish discoloration), beta hemolysis (complete lysis with clear zones), and gamma hemolysis (no lysis). Their activity is an important virulence factor in bacterial infections.
Correct Answer is B
Explanation
A. To stain the bacteria: Heat fixing does not apply stain to the bacteria; staining is a separate step performed after the smear is fixed. Heat fixing prepares the cells to better accept the stain by immobilizing them and preserving their structure.
B. To kill bacteria and adhere them to the slide: Heat fixing serves two main purposes: it kills the bacteria, making the slide safe to handle, and it causes the proteins in the cells to coagulate slightly, which adheres the cells firmly to the glass slide. This prevents them from washing off during the staining and rinsing and preserves their morphology for accurate examination.
C. To increase magnification: Heat fixing has no effect on the magnification of the microscope. Magnification is controlled by the objective lenses and ocular lenses, not by the preparation technique of the smear.
D. To remove excess stain: Heat fixing does not remove stain; rather, it prepares the cells so that stains can bind effectively. Removal of excess stain is achieved through rinsing with water or appropriate solvents after staining, not through heat fixation.
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