MadSci Network: Neuroscience

Re: Why my hair rises on one side of my body when I get a kiss in the ear?

Date: Wed Nov 3 04:25:27 1999
Posted By: Paulette Caswell, Grad student Education, etc., AMICUS, Inc. Ed. Svcs.
Area of science: Neuroscience
ID: 940506866.Ns

The reason you are getting this reaction is a natural protection mechanism of the 
body to stress.  The body releases adrenalin in response to stress, which causes 
several reactions in the body, including the contraction of the arrector pili 
muscles at the base of each hair, which is often called "goosebumps."  The 
reaction is caused by the sympathetic nervous system to the adrenalin.  In 
animals with a lot of hair, this reaction can result in more insulation from cold 
(which is why humans get "goosebumps" when they are shivering in cold 
environments), and it can also make animals look more menacing.  But, humans do 
not have a lot of hair, so the function of this reaction in humans is not clear, 
and may just simply be the result of evolution.

A person can get this reaction of "hair standing on end," or "goosebumps," in 
many types of situations.  It can be caused by any kind of stress, including fear 
and anxiety, or even from emotional reactions to pleasurable stimuli (such as 
being kissed on the ear).  What you are experiencing is a stress reaction, even 
though it is pleasurable.  

The smaller hairs on the ear are highly sensitive, since the ear is a very 
valuable sense organ.  Thus, whenever something brushes against those hairs on 
your ear, your body detects a "foreign invader" and you get the "fight or flight" 
reaction of adrenalin. 

Evidently, you are getting this reaction more strongly on the side of your body 
that is being "invaded" so the reaction will be stronger.  But adrenaline does 
circulate to stimulate the sympathetic nervous system all over your body.  
Therefore, you are probably also getting the reaction on the other side of your 
body, too. But you notice the reaction more on the side that is being "invaded," 
because you have the highest level of need to avoid the "invasion" and your body 
will put your brain on notice of the stimulus on the same side as your kissed 
ear, so you can direct your body away from the stressful stimulus.  (Remember, 
the bodily reaction, and the adrenaline, does not cause a physical sensation of 
pain or pleasure.  The pleasure of such a stimulus is a psychological reaction, 
not a physical reaction.)

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