Piloerection

Piloerection is the physiological response where small muscles at the base of hair follicles contract, causing hairs to stand upright, often referred to as "goosebumps." This reflex is primarily triggered by cold temperatures or emotional stimuli, serving to increase warmth or create an appearance of greater size in response to threats. Clinically, piloerection can indicate autonomic nervous system activity and is associated with conditions like hyperthyroidism, where excessive sympathetic stimulation occurs.