The horse's cardiovascular system is designed to transport oxygen from the lungs to body tissues through the blood. “Blood is the primary transporter through the body of essential water, oxygen, nutrients, chemical regulators and waste products. The blood is pushed along the blood vessels by the pumping action of the heart” (Hastie, 2012) Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Blood vessels are composed of arteries, veins, and capillaries. Arteries are the largest vessels; their purpose is to transport oxygenated blood away from the heart, the blood in these vessels is at high pressure. Artery walls are made up of smooth muscles and elastic fibers, which contract and relax to push blood through the cardiovascular system. Veins are responsible for transporting deoxygenated blood to the heart; the layers of the veins are much thinner and less elastic than those of the arteries. Veins contain valves that prevent blood from flowing backwards, arteries do not have this function; the blood in the veins is transported at a much lower pressure than in the arteries. Capillaries are the smallest of blood vessels; their cells are one cell thick. Their function is to allow easy exchange of components such as nutrients, oxygen, carbon dioxide and salts and to allow the removal of waste from cells between body tissues and the blood. The equine heart consists of two chambers made up of atria and ventricles. The atria are the chambers that collect blood returning to the heart while the ventricles are the chambers that pump blood from the heart to the entire body. The right atrium receives deoxygenated blood from the network of veins that returns to the heart; the atrium pushes blood past the tricuspid valve into the right ventricle. From the right ventricle, blood is pushed through the pulmonary arteries to the lungs where it is oxygenated with oxygen inhaled through breathing. The oxygenated blood is sent back to the left atrium through the pulmonary veins and then supplies the left ventricle through the mitral valve. To complete the cycle, the left ventricle pumps oxygenated blood past the aortic valve and throughout the body through the aorta. The purpose of this study is to determine whether the horse's heart rate is influenced by the pace at which it moves. Previous studies of heart rate variability have been used to evaluate the stress response in horses with laminitis after short- and long-term treatments; the results showed that heart rate decreased after the treatments (Gehrke et al., 2011). Another looked at heart rate variability in relation to stress and well-being; the results concluded that “HRV analysis in horses appears to be a sensitive measure of both physical and emotional stress responses” (von Borell et al., 2007). Studies have also been conducted on heart rate monitors to test their accuracy in recording heart rate data. The results of (Evans et al., 1986) showed that all four heart rate monitors (PEH 100, PU10, HR14 and HRM-7) used in their experiment showed significant correlations with heart rate recordings made by an electrocardiography simultaneous telemetry (ECG) which might suggest they are accurate, however there are still areas of error in the recordings. More recent experiments using Polar Equine Monitors, used in this experiment, are believed to be able to obtain accurate heart rate variability in horses (Gehrke et al., 2011). The Polar Equine Monitors.