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Exercise Physiology.

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Exercise Physiology Task 1 With physical activity in sport, exercising can have effects on the cardiovascular system. Certain forms of these are the cardiac cycle, blood pressure, the rate of blood flow, transporting respiratory gases and oxygen dissociation. The cardiovascular system includes: * Heart * Blood vessels The heart is a pump, the purpose of which is to drive the blood into and through the arteries. The right side of the heart pumps blood into the pulmonary circulation, and the left side pumps blood into the systemic circulation. The blood in the right side of the heart does not mix with the blood in the left. The heart is myogenic which means it can contract without receiving nervous stimulation from the central nervous system. There are four main neural sites, which work together, in order to ensure that the four chambers of the heart beat regularly. These sites are: * The sino - atrial node - pacemaker, sets the pace at which the heart beats. Also sends a nervous impulse across the atria and makes them contract at same time. * The atrioventricular node - receives impulse from SAN. ...read more.


Blood pours into the right and left atria from the great veins; they then contract simultaneously, emptying their contents into the ventricles. Atrial contraction lasts about 0.1 seconds. The ventricles then begin to contract and the atrio - ventricular valves are closed by the rising pressure; the closure of these valves causes the first heart sound, which can be heard through a stethoscope placed over the apex of the heart. Ventricular contraction continues lasting about 0.3 seconds in all. When the pressure in the ventricles is greater than that in the arteries the pulmonary and aortic valves are forced open, and the blood flows into the aorta and pulmonary trunk. As the ventricles relax the pressure in them decreases, the pressure in the great vessels forces the aortic and pulmonary valves to close, causing the second heart sound. This can be heard over the near end of the second right rib. During ventricular contraction the atria are relaxed. Following ventricular contraction the whole heart is relaxed for approximately 0.4 seconds. During this time blood is flowing into both atria and through the open atrio - ventricular valves into the ventricles. ...read more.


Oxygen combines with haemoglobin in oxygen - rich situations, such as in the lungs. Oxygen is released by haemoglobin in places where there is little oxygen, such as in exercising muscle. Myoglobin is haemoglobin like pigment found in muscle fibres, which binds only less oxygen to it compared to haemoglobin. It takes up oxygen from the haemoglobin in the blood and stores oxygen within the muscle itself. Oxygen dissociation curve This is an S shaped curve that represents the ease with which haemoglobin will release oxygen when it is exposed to tissues of different concentrations of oxygen. The curve starts with a steep rise because haemoglobin has a high affinity for oxygen. This means that when there is a small rise in the partial pressure of oxygen, haemoglobin will pick up and bind oxygen to it easily. Thus, in the lungs the blood is rapidly saturated with oxygen. However, only a small drop in the % saturation of haemoglobin. Therefore in exercising muscles, where there is a low partial pressure of oxygen, the haemoglobin will readily unload the oxygen for use by the tissues. Changes in blood carbon dioxide level and hydrogen ion concentration causes shifts in the oxygen dissociation curve. These shifts enhance oxygen release in tissues and increase oxygen uptake in the lungs. This is known as the Bohr effect. ...read more.

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