Practice Pakistan questions with answers and explanations.
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Erythrocytes carry respiratory pigments such as hemoglobin for oxygen transport. A low count reduces oxygen delivery to tissues.
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Innate immunity responds quickly to general patterns of infection or injury. It is less specific than adaptive immunity but essential for immediate defense.
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Endocrine axes often involve hypothalamus, pituitary, and a target gland. The final hormone provides feedback to regulate further secretion.
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Adrenaline prepares the body for rapid action by increasing heart rate, blood flow to muscles, and energy availability.
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Platelets help form clots by adhering at injury sites and triggering coagulation. This prevents excessive blood loss.
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Vaccines expose the immune system to antigens safely, leading to memory cells. Future exposure produces faster and stronger responses.
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Because hormones circulate, they can reach multiple tissues. Only cells with matching receptors respond, allowing broad but selective coordination.
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Target-cell specificity is central to endocrine function. Hormone molecules can circulate widely, but only receptor-bearing cells respond.
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Phagocytosis is the engulfment and digestion of particles or microbes by immune cells. It is an important nonspecific defense mechanism.
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Water-soluble peptide hormones typically bind cell-surface receptors. Second messengers carry the signal inside the cell to produce a response.
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Endocrine hormones are commonly transported through blood, so blood levels provide useful information about endocrine function and feedback status.
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Fish generally have single circulation: heart to gills to body and back to heart. The heart contains one atrium and one ventricle.
