Homeostasis and response
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Which sequence shows negative feedback?
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A rise causes a response that lowers the condition towards its usual range.
The response opposes the rise, and should decrease as the deviation becomes smaller.
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Why can high humidity reduce cooling by sweating?
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Water evaporates less readily, so less heat is removed from the skin.
Evaporation requires heat; reduced evaporation reduces this route of heat loss.
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Body temperature falls below normal. Which response helps to bring it back up?
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Arterioles in the skin constrict, so less blood flows near the surface
Vasoconstriction reduces heat loss from blood near the skin surface.
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Which description identifies an endocrine function of the pancreas?
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Islet cells release insulin directly into the blood.
A hormone entering the blood from ductless endocrine tissue is an endocrine secretion.
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Which response directly helps correct low blood glucose?
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Glucagon promotes liver glycogen breakdown and glucose release.
The liver releases glucose, raising blood glucose towards its normal range.
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After a meal, a person's blood glucose rises from 5 to 8 mmol/dm3 and returns to 5 within two hours. Which hormone mainly brings it back down, and how?
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Insulin, by making liver cells convert glucose to glycogen
Insulin is released when glucose rises and causes the liver to store glucose as glycogen.
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Which statement about a sedentary lifestyle is accurate?
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It raises the risk but does not decide who develops it.
Risk describes likelihood rather than certainty. Regular activity is one broad approach used in prevention and management.
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What follows a decrease in ADH release, with other conditions comparable?
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Less collecting-duct water reabsorption and a larger volume of dilute urine.
Lower water permeability means more water remains in the filtrate and leaves as urine.
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Which route correctly describes a simple withdrawal reflex?
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Receptor -> sensory neurone -> relay neurone in spinal cord -> motor neurone -> muscle
The muscle is the effector, and its contraction produces the withdrawal response.
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Which pair correctly links a structure with its function?
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Retina: contains receptors that detect light
Receptors in the retina detect light, and the resulting signals are carried towards the brain.
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Which combination focuses a near object?
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Ciliary muscles contracted; ligaments slack; lens more convex
The rounder lens refracts the divergent rays from a near object more strongly.
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A person looks up from a book to a distant tree. Which change happens in the eye?
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Ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner
For a distant object the lens must be thinner, so the ciliary muscles relax and the ligaments pull on the lens.
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Which response follows an increase in light intensity?
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Circular iris muscles contract, radial muscles relax and the pupil narrows.
A smaller opening reduces the amount of light entering the eye.
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