Which best describes the primary afferent pathway that conveys cold signals from peripheral thermoreceptors to the hypothalamus for thermoregulatory responses?

• A Aδ fibres → spinothalamic tract → ventroposteromedial thalamus → somatosensory cortex → hypothalamus
• B Aβ fibres → dorsal column → thalamus → anterior hypothalamus
• C Aδ (cold) and C (warm) fibres → spinothalamic tract → posterior hypothalamus → anterior hypothalamus ✓
• D C fibres only → spinoreticular tract → medullary thermoregulatory centre → hypothalamus

Explanation

Peripheral thermoreceptors use Aδ fibres (cold, sharp cooling) and C fibres (warm, slow burning warmth) which project via the spinothalamic tract to the posterior hypothalamus (integration of heat conservation) and anterior hypothalamus (heat dissipation). The anterior hypothalamus/preoptic area acts as the primary thermostat: warming this area triggers sweating and vasodilation; cooling it triggers shivering and vasoconstriction. Dorsal columns carry proprioception and fine touch, not temperature.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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