Where Are the Body's Heat Sensors Located?

Thermoreceptors (temperature sensors) are distributed throughout the body, not just under the epidermis:

• Skin: Free nerve endings in epidermis and dermis detect surface temperature changes (cold receptors: Krause end bulbs; warm receptors: Ruffini endings).
• Deep tissues: Muscle, joint capsules, viscera have thermoreceptors monitoring core temperature.
• Hypothalamus: Central thermostat; contains neurons sensitive to blood temperature (preoptic area).
• Spinal cord/brainstem: Additional central sensors.

This distributed system allows precise thermoregulation: skin receptors trigger behavioral responses (seeking shade/clothing); core receptors drive autonomic responses (shivering, sweating, vasodilation/constriction).