Practice Pakistan questions with answers and explanations.
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Antidiuretic hormone increases water reabsorption in kidney collecting ducts, helping maintain body water balance and osmotic homeostasis.
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Steroid hormone-receptor complexes often bind DNA or influence transcription. This can lead to slower but longer-lasting physiological changes.
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Exocrine glands release secretions through ducts to surfaces or cavities. Endocrine glands release hormones directly into internal fluids without ducts.
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Amphibians have two atria and one ventricle, allowing partial separation of blood streams. It is an intermediate condition between fish and birds/mammals.
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The hypothalamus links nervous and endocrine systems. It releases factors that regulate the pituitary and receives feedback from circulating hormones.
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Exocrine glands use ducts to deliver secretions to body surfaces or cavities. Endocrine glands are ductless and release hormones internally.
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High thyroid hormone feeds back to reduce hypothalamic and pituitary stimulation, including TSH. This prevents excessive thyroid activity.
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Four-chambered hearts fully separate oxygenated and deoxygenated blood. This supports efficient oxygen delivery and high metabolism.
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Photoreceptors in the retina detect light and initiate neural pathways that control pupil size. This protects the retina and improves visual focus.
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Effectors are organs or cells that carry out responses, including muscles and glands. They respond to neural or hormonal commands.
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Rods are retinal photoreceptors specialized for low-light vision. Cones support color and high-acuity vision in many vertebrates.
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The thyroid produces thyroxine, which influences metabolic rate, growth, and development. Low thyroxine commonly slows metabolism.
