Block 6 (Week 11&12) Cardiovascular Physiology Exercise (Lab Exercise Lab Report

Block 6 (Week 11&12) Cardiovascular Physiology Exercise ( Exercise 6) - Lab Report ExampleThe period of time surrounded by the operationive refractory period and phase 4 is the relative refractory period. The refractory period of cardiac muscle is about 250 millisecondsalmost as long as the contraction of the means.Summation does not occur in the philia muscle contraction. The refractory period of the heart muscles is longer than that in the raddled muscles, therefore heart twitches do not overlap and hence increased (summed) ventricular contraction is not seen.Summation would result in more tidy contraction of the ventricle causing irregular high cardiac output. Heart might find it diffult to recvoer from this double-twitch, i.e. repolarization might take a long time. This irregular pumping of heart would cause dysrhythmia.Vagus nerves are the part of para-sympathetic nervous system and act by decreasing the heart pass judgment by direct effect on the SA and AV nodes in the h eart atrium. Parasympathetic stimulation by the vagal nerve endings in the atrium results in slowing down of the heart govern and can bring the cardiac output to almost zero.Vagus nerves are parasympathetic and supply to AV and SA nodes. Parasympathetic stimulation result in decrease in the heart rate and cardiac output. Since the vagal fibers are primarily distributed in the atria, they result in a decrease in the heart rate. Decrease in the heart rate along with slight decrease in ventricular contraction can decrease the cardiac output by 50%.The cardiac muscle has inherent autorhythmicity, i.e. they can generate the contraction activity automatically. However, the un-stimulated heart beats at a much slower rate and needs continuous sypathetic stimulation to maintain the nornal heart rate, i.e. 70 pulses a minute. Also, sympathetic stimulation increases the power of the ventricular contraction to as much as double the normal, thereby increasing the volume of blood pumped and incr easing the ejection pressure. The vagal nerve endings