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3.1 Negative & Positive Feedback — Test 1
Q1. The most commonly applied principle for regulating hormone secretion is:✓ Negative feedback
Q2. Insulin secretion in response to a rise in blood glucose is an example of negative feedback because:✓ Insulin lowers blood glucose, which then reduces further insulin secretion
Q3. Parathyroid hormone secretion is controlled by negative feedback in which:✓ Low serum Ca²⁺ stimulates PTH, and the resulting rise in Ca²⁺ inhibits further PTH
Q4. Positive feedback in endocrinology is best described as:✓ Rare, explosive and self-reinforcing
Q5. The mid-cycle LH surge is an example of positive feedback because:✓ Rising estrogen stimulates more LH from the anterior pituitary
Q6. In a classic 'long-loop' negative feedback, the final target-gland hormone feeds back on the:✓ Hypothalamus and anterior pituitary
Q7. Cortisol restrains its own axis by inhibiting:✓ CRH (hypothalamus) and ACTH (pituitary)
Q8. Match each loop with an example and choose the correct option.✓ A-ii, B-i
Q9. Negative feedback makes hormone secretion:✓ Self-limiting
Q10. During labour, oxytocin and cervical stretch form a positive-feedback loop in which:✓ Cervical stretch raises oxytocin, which strengthens contractions and stretch further
Q11. In a feedback axis, the variable being held constant (e.g. serum Ca²⁺ or glucose) is the:✓ Regulated (controlled) variable
Q12. Loss of negative feedback (e.g. an autonomous hormone-secreting tumour) typically causes:✓ Hormone excess with suppressed tropic (stimulating) hormone
Q13. A short-loop feedback would be illustrated by:✓ An anterior-pituitary hormone inhibiting hypothalamic releasing-hormone secretion
Q14. Why is positive feedback comparatively uncommon in physiology?✓ It is inherently unstable and drives systems to an extreme
Q15. The LH surge differs from luteal-phase feedback in that estrogen at the surge acts by:✓ Positive feedback on the anterior pituitary
Q16. The dexamethasone suppression test relies on the principle that a synthetic glucocorticoid will:✓ Suppress ACTH by negative feedback in normal individuals
Q17. GHRH inhibiting its own secretion from the hypothalamus is an example of:✓ Ultra-short-loop feedback
Q18. In primary hypothyroidism, low thyroid hormone causes TSH to:✓ Rise (loss of negative feedback)
Q19. A feed-forward (anticipatory) element in endocrine control is exemplified by:✓ Incretins (GIP/GLP-1) boosting insulin before glucose peaks
Q20. The essential outcome of negative feedback is to:✓ Maintain the regulated variable near its set-point