Goosebumps?

​You will often see goosebumps when you are cold but do not be surprised if they appear at other times. They are a universal but poorly understood phenomenon, but our understanding is improving.  The recent discovery linking goosebumps with hair follicle regeneration could lead to more than just a better understanding of goosebumps.  It could lead to new ways of fighting baldness or improving tissue healing.

Goosebumps?
By Pierre Mouchette | Bits-n-Pieces

They go by goosebumps, goose pimples, and goose flesh.  But they all refer to the same condition.  The medical term is cutis anserine (cutis means skin, and anser means goose).  In this condition, the similarity in skin texture is just too close to goose skin to ignore.  Other medical terms for goosebumps are horripilation, piloerection, or the pilomotor reflex.  Each of these terms describes a temporary change in the skin from smooth to bumpy, most commonly arising after exposure to cold.
 
What Are Goosebumps?
They result from tiny muscles flexing in the skin, making the hair follicles rise.  Goosebumps are an involuntary reaction of nerves from the sympathetic nervous system.  The nerves that control the fight or flight response control these skin muscles.
In the animal kingdom, a threatened animal reacts similarly, causing fur to be puffed out a bit.  It makes the animal appear more significant and dangerous.  Perhaps the most dramatic example is the porcupine, which puffs out its quills when sensing danger, making a threatening adversary think twice before attacking.  It could also explain why the sympathetic nervous system controls goosebumps because the reflex is bound in the fight or flight response.
Note:  researchers studying mice have linked goosebumps to the regeneration of hair and hair follicles.  It spears that nerves connected to the tiny muscles responsible for goosebumps also connect to hair follicle stem cells, which are responsible for hair growth.  So, in response to cold, the nerves tell the muscles in the skin to contract (causing goosebumps), and the same nerve activates hair follicle stem cells for new hair growth.
 
So, What Purpose Do Goosebumps Serve?
Goosebumps may help you conserve heat when exposed to cold.  They may do this in several ways.

• As with larger muscles, contraction of the muscles in the skin (called arrectores pilorum) generates heat.
• Hairs standing up trap a layer of air near the skin, holding onto body heat.
• The raised hair follicles cause skin pores to close.

The above may be more critical for furry animals than for humans.  It is not clear how essential goosebumps are in humans.  For example, if you could not form goosebumps, it would not necessarily mean you have temperature control problems.  Goosebumps may be a leftover from our evolutionary ancestors (like the coccyx or tailbone) that serves no vital purpose.  The discovery linking goosebumps with hair follicle stem cells can be explained as a longer-term response to cold, at least for animals with fur.  They get goosebumps (or the animal equivalent) in the short term to conserve heat and thicker fur to keep warmer in the long term.
 
Goosebumps Are More Than Just Being Cold
Most people associate goosebumps with unpleasant situations, such as feeling particularly cold or feeling afraid.  Yet there is more to it than that.  The arrectores pilorum connects to the sympathetic nervous system, and the sympathetic nervous system has input from many parts of the brain, including those involved with motivation, arousal, and emotion.  So other stimuli may cause goosebumps, for instance:

• awe
• excitement
• fear
• pride
• hearing music or seeing art that is particularly moving or completely engrosses you.  Which is why you might say, "It gave me chills."

 
Goosebumps and Disease
Though rare, goosebumps can indicate a seizure disorder called temporal lobe epilepsy, a sympathetic nervous system disorder, or other brain disorders.  They are also common during heroin or opiate withdrawals.  One explanation for the origin of the expression quitting cold turkey is that goose bumps that develop during withdrawal from heroin mimic cold turkey flesh.