piloerection reflex

The “piloerection reflex” is the involuntary response where tiny muscles at the base of hair follicles contract, causing hair to stand on end. This reflex, often triggered by cold or emotional stimuli like fear or excitement, helps trap a layer of air to insulate the body and can also serve as a defensive mechanism to make an animal appear larger. In humans, piloerection is commonly known as “goosebumps.”