An isotope of an element contains different numbers of
The Correct Answer is {"dropdown-group-1":"C"}
A. Electrons: In a neutral atom, the number of electrons is equal to the number of protons to maintain electrical neutrality. While atoms can lose or gain electrons to become ions, changing the electron count does not define an isotope, as isotopes primarily differ in their nuclear composition and mass rather than their outer shell configurations or chemical charge.
B. Protons: The number of protons, also known as the atomic number, defines the identity of an element. If the number of protons were to change, the atom would become an entirely different element. All isotopes of a specific element must possess the exact same number of protons.
C. Neutrons: Isotopes are defined as atoms of the same element that possess the same number of protons but vary in their number of neutrons. This variation in the nucleus changes the atomic mass of the atom without significantly altering its chemical properties, which are determined by the electron configuration.
D. Both protons and neutrons: A change in both subatomic particles would result in both a different element and a different mass. Isotopes must remain the same element, which requires the proton count to remain constant. The defining characteristic of an isotope is specifically the fluctuation of the neutron count while the atomic number remains fixed.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Neutrophil fraction: The neutrophil fraction, which is the most abundant type of leukocyte, typically accounts for 50% to 70% of the total white blood cell count. These granulocytes are the primary responders to acute bacterial infections and utilize phagocytosis and degranulation as their main effector mechanisms, making them the largest component of the differential count.
B. Eosinophil fraction: This type of granulocyte that usually accounts for only 2% to 4% of the total white blood cell population. These cells are specialized for the defense against multicellular parasites and are significant mediators of allergic inflammatory responses, but they represent a much smaller percentage of the differential than lymphocytes.
C. Basophil fraction: The basophil fraction is the rarest leukocyte type, normally constituting less than 1% of the total white blood cell count. Basophils contain large granules filled with histamine and heparin and are primarily involved in systemic inflammatory and hypersensitivity reactions, making them the smallest identifiable segment in a standard leukocyte differential.
D. Lymphocyte fraction: The lymphocyte fraction accounts for approximately 20% to 40% of the total count. Lymphocytes, including B-cells, T-cells, and Natural Killer (NK) cells, are the central mediators of adaptive immunity and are responsible for antigen recognition, antibody production, and the destruction of virally infected cells.
E. Monocyte fraction: The monocyte fraction makes up about 3% to 8% of the circulating leukocytes and represents the largest individual cell type in the blood. Monocytes are agranulocytes that migrate into tissues to differentiate into macrophages and dendritic cells, serving as critical antigen-presenting cells that link the innate and adaptive immune responses.
Correct Answer is A
Explanation
A. Hypophysis (Pituitary Gland): Positioned within the sella turcica of the sphenoid bone, this "master gland" is connected to the hypothalamus via the infundibulum. It is divided into the anterior adenohypophysis and posterior neurohypophysis, serving as the primary endocrine hub for regulating growth, metabolism, and reproduction through various trophic hormones.
B. Corpus Callosum: This expansive white matter tract consists of hundreds of millions of axonal fibers that facilitate rapid interhemispheric communication between the left and right cerebral hemispheres. This C-shaped structure located superior to the diencephalon is essential for integrating cognitive, motor, and sensory information across the brain's midline.
C. Pineal Gland: Situated in the epithalamus posterior to the third ventricle, the pineal gland is a small, pinecone-shaped endocrine structure responsible for the synthesis and secretion of melatonin in response to light-dark cycles. This structure plays a fundamental role in regulating circadian rhythms and the sleep-wake cycle by interpreting information from the retina.
D. Hypothalamus: The hypothalamus is a small, but vital, region of the diencephalon located below the thalamus and above the brainstem. It plays a central role in maintaining homeostasis by regulating body temperature, hunger, thirst, sleep-wake cycles, and autonomic nervous system activity.
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