Equine Exercise Physiology Flashcards
splenic contractions do what for the horse during exercise?
increase hematocrit from 35 to as high as 65
the relationship between heart rate and speed is _____. If the line is steeper it means ____, and if the line is not as steep it means____
linear
the horse is less fit
the horse is more fit
what does a normal ECG of a horse during exercise look like?
it is all QRS complexes with no P waves because the heart is going so fast
is an arrhythmia in horses common?
yes, especially when recovering from the race
what is AV block?
there is not a QRS complex for every P wave so the SA and AV nodes are not communicating properly
what is ventricular premature contraction?
an early heart beat originating from the ventricle and you get a wide or abnormal looking QRS complex. the ventricle goes rouge and doesn’t listen to the pacemaker. this is the one where if it happens several times in a row it can be super bad
what is atrial fibrillation?
irregularly regular so you can’t predict when the next heartbeat is
how do you test for damaged cells in the heart?
measure troponin levels in the blood and if there is more than normal in the blood it probably means there is something wrong with the cells of the myocardium
when do you want to use the cardiac troponin test? (hscTnT)
2-6 hours after the race, peaking at around 4 hours
______ are released during exercise which dilates the nasal cavity
catecholamines
why does the head extend when galloping?
so there are fewer bends in airways between external nares and lungs
where does most of the resistance come from in the airways? what is the greatest point of resistance?
from the nasal cavity
inside the nares at the nasal valve
what is the guttural pouch used for?
it cools the blood going to the brain
what cranial nerves are passing through the guttural pouch?
9, 10, 11, and 12
horses experience ____ and _____ during intense exercise especially in thoroughbreds
hypercapnia, hypoxemia
horses can’t increase ventilation after a certain point because
there is a coupling of ventilation and stride frequency
what are the 3 forces associated with exercise helping to generate airflow?
visceral piston
concussive limb impact transmitted to the thorax
lumbosacral flexion pressurizing abdominal cavity
the oxygen pressure in thoroughbreds is around what?
68mmHg
what is the main cause of exercise hypoxemia?
diffusion limitation! the blood doesn’t have time to become fully oxygenated because the blood is moving so quickly
how do horses deal with high CO2 levels in the blood?
they have a good buffering system to manage the high CO2 levels
why doesn’t training help with hypoxemia?
Because the heart is now bigger and can pump more volumes of blood more efficiently, and if the blood is pumping faster it has no time to become saturated with oxygen in pulmonary capillaries
what is exercise-induced pulmonary hemorrhage?
when there is bleeding from the lungs during exercise usually paired with poor athletic performance
what causes the lungs to bleed during exercise?
There is a rupture in the alveolar capillary membranes and there is a leakage of blood into the alveolar spaces. In the pulmonary artery, there is such a high pressure, and in the alveoli there is a lot of negative pressure (vacuum), creating a huge pressure difference so the capillary wall breaks and blood can then get into the lungs