What is the Pilomotor Reflex?

When you experience fear, excitement, or any intense emotion goosebumps may appear.

When your hair stands on end, it is commonly referred to as “goosebumps” or “piloerection.” This phenomenon is primarily caused by a physiological response known as the pilomotor reflex. Several factors can trigger this reflex, including emotions, temperature changes, and certain medical conditions.

The primary cause of hair standing on end is the activation of the sympathetic nervous system, which is responsible for the body’s “fight or flight” response. When you experience fear, excitement, or any intense emotion, your sympathetic nervous system is triggered, leading to the release of adrenaline[1].

Adrenaline causes the muscles at the base of each hair follicle, known as the arrector pili muscles, to contract. These contractions elevate the hair follicles, resulting in the appearance of raised hair or goosebumps.

Have you ever seen your cat’s hair stand on end when something startles it? Or noticed that your dog’s coat looks fluffier when it’s outside in the cold? Animals also have erector muscles that raise up their hair, but you’re not going to see goosebumps on something that furry! Having fluffier hair can make a threatened animal look bigger and maybe help it ward off an attacker, while a coat that’s puffed up in cold weather is better for insulating the animal and helping it to stay warm.

Hair standing on end can also occur due to temperature changes. When you feel cold, your body tries to retain heat by contracting the arrector pili muscles. This action raises the hair follicles, creating an insulating layer of trapped air around the skin. Additionally, certain medical conditions can cause hair to stand on end. For example, pilomotor seizures, a type of seizure disorder, can trigger the pilomotor reflex and result in goosebumps.

Goosebumps — sometimes called goose flesh or goose pimples. They’re called goosebumps because, when you have them, your skin looks like the skin of a goose or a chicken whose feathers have been plucked out. So, if you want, you could call them chicken bumps, too!

Other conditions, such as anxiety disorders or drug withdrawal, may also lead to hair standing on end as a physiological response to stress or emotional distress.

  1. Adrenaline, also known as epinephrine, is a hormone and neurotransmitter produced by the adrenal glands that plays a vital role in the body’s stress response. When faced with a threat or intense situation, the brain signals the release of adrenaline into the bloodstream. Adrenaline acts on various organs and tissues, triggering rapid physiological changes to prepare the body for “fight or flight.” It increases heart rate and blood pressure, dilates airways, releases glucose for energy, enhances mental alertness, and promotes sweating. These effects enable the body to respond effectively to stressors. However, prolonged or excessive activation of the stress response can have adverse health consequences. Adrenaline’s role in the stress response highlights its significance in regulating physiological reactions to challenging situations. [Back]

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Author: Doyle

I was born in Atlanta, moved to Alpharetta at 4, lived there for 53 years and moved to Decatur in 2016. I've worked at such places as Richway, North Fulton Medical Center, Management Science America (Computer Tech/Project Manager) and Stacy's Compounding Pharmacy (Pharmacy Tech).

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