Explaining Fainting Goats

“Fainting Goat” By Joey Newton

Videos of goats fainting have had their internet fame over the past few years but I’ve never known the reason why goats would “faint”.  From an evolutionary standpoint, it makes next to no sense for a heard of goats to faint when a predator approaches, and if it were a trait that occurred in their natural environment,  it would be weeded out rather quickly.  This behavior, while amusing, hasn’t seem to emulate any other naturally occurring behaviors I’ve seen, so I decided to take a deeper look into the evolution and origin of the viral sensation.

“Fainting goat falls off swing” By The Peakill Farm

First of all, fainting goats don’t actually faint.  These goats have a skeletal muscle disease known as myotonia congenita which causes a prolonged response in their fight or flight response.  Fight or flight is a survival response when a threat is introduced which causes changes in the nervous and endocrine system.  These changes cause a physical change in the animal that prepare it to retreat or react depending on the situation.  When the threat is sensed, the hypothalamus activates the adrenal-cortical system by sending cortcotropin-releasing factor (CRF) to the pituitary gland.  The pituitary gland releases the hormone ACTH which finds its way to the adrenal cortex.  The arednal cortex releases corticosteriods hormones such as hydrocortisone, which regulates how the body produces energy from protein, fats, and carbohydrates, and cortisterone, which regulates immune response and surppresses inflammatory reactions.  The other system activated is the sympathetic nervous system which is activated when the hypothalamus tells the adrenal medulla to release epinephrine and norepinephrine (also known as, adrenaline and noradrenaline).  These hormones are released into the blood stream which causes the blood pressure and heart rate to increase which is why these are known as stress hormones.  When these hormones are released into the system a number of other bodily reactions also occur such as,  dilated pupils, constriction of veins to send blood to more important muscles, increase in blood-glucose levels, the brain is focused on only the response at hand making small tasks difficult to focus on, and systems that aren’t necessary shut down so as much energy as possible is in the emergency functions.

The Fight or Flight Response” By jvnkfood CC BY-SA 4.0

Myotonia congenita, also known as Thompsen disease, is a genetic disorder found in many mammals which causes a prolonged reaction to the fight or flight response.  The disorder is caused by the CLCN1 gene and can occur by several different mutations.  When these mutation occurs, the function or structure of chloride channels in smooth muscle cells are altered which cause the CLC-1 channels to not allow proper ion movement reducing the amount of chloride ions that can enter the cell.  Chloride is used as a counter to the accumulating K+ (potassium) ions located in the T tubules.  When chloride is reduced, the potassium ions depolarize the T-tubules lumen creating a self-sustaining action potential which causes the contraction of the muscle to prolong when the stimulus is introduced, the stimulus in this case is when threat or scare is introduced.

So you might still be wondering, how did so many goats that have myotonia congentia survive when others population wouldn’t tense up in the presence of a predator?  Sadly they wouldn’t.  Fainting goats can be traced back to 19th century on a farm owned by Dr.Mayberry where he had 4 goats that would tense up and faint.  He bred these goats and their offspring also fainted, so he suspected these were a different breed of goats all together and named them the Tennesee fainting goat.  Goat herders prefer these goats as the chances of them escaping from the herd are much less likely.  If they do happen to escape, the chances of survival are slim for these unnaturally selected goats which means they need to be protected much more than any other domesticated animal.

“Cat Fainting Gif” From Giphy.com

4 Replies to “Explaining Fainting Goats

  1. Nice post for neurobiology. Josh- you really should link your different class sites together and link, not copy posts for each class, and then have a landing or home page with your professional identity. I know I have been talking to you about this for quite a while now, it’s not hard to do.

    1. This post is only on my animal behavior site. I went into it thinking it’d be a little more behavior related but then I saw it was a muscle mutation so I tried to focus on the fight or flight a little bit more because it’s relevant in so many animals. If you want I could move it to my neuro site if you don’t think it belongs on this one?

  2. Very interesting post. The proximate causation for the fainting behavior was very well explained. One concern I had involved the discussion of the action potential created. I was under the impression that the action potential for skeletal muscles was created by concentrations of potassium and sodium, not potassium and chlorine. Could you explain?

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