I'm new to this and have heard about thumps, but can anyone explain,
physiologically, what thumps is and the mechanism that causes it? Also,
are certain types of horses prone to it? Thanks,
In a nutshell, when the body becomes depleted of
electrolytes, the electrical transmission of neural signals between the brain
and muscles gets out of whack. At the same time, the muscles themselves
become hyperirritable---it takes alot less neural stimulation for them to want
to contract. So you have muscles that are getting tighter and crampier,
plus you don't have very well integrated signals frrm the brain telling the
muscles what to do.
OK, a bit of anatomy. Just underneath the
heart is the phrenic nerve which, among other things, ennervates the
diaphragm muscle---the big muscle that divides the chest cavity from the
abdomen and drives respiration.
When the electrolytes get out of
balance/depleted, the electrical impulses traveling along the neurons aren't
very good, right?. But because the phrenic nerve travels so close to the
heart, it starts to have a tendency to pick up the electrical signals
generated by the heart itself. That electrical signal travels back to
the diaphragm which is just looking for any little signal to contract, and it
doesn't much care whether those signals are originating from the brain or the
heart. The diaphragm contracts in time with the electrical input with
the heart---which is why you can basically check a thumping horse's heart rate
from fifty feet away.
So a diaphragm contracting in time with the heart
is an indication that the horse has some fairly significant electrolytes
imbalances---if he didn't, you wouldn't have the disruptions in neural
transmission, and you wouldn't have the hyperirritable muscle
tissue.
The thumping itself isn't a lethal
condition---probably uncomfortable and weird for the horse, but not
fatal. BUT, it is an indicator that all is not well with the horse,
because poor neural/muscle integration to the diaphragm also mean the same
thing going on in other parts of the body---you're just not seeing outward
signs of it. So that means poor neural stimulation to the hindgut, poor
muscle coordination and so on.
So let's not blow thumps off, right? It
needs to be paid attention to and needs to be fixed.
Susan G