Control of breathing
... valves (tricuspid and mitral) move toward the closed position as atrial diastole comes to an end. Atrial systole begins after the wave of depolarization passes over the atrial muscle forcing some additional blood into the ventricles. At the start of ventricular systole the AV valves close and the ventricular pressure increases. When the ventricular pressure exceeds that of the aorta (80 mm Hg) and pulmonary arteries (10 mm Hg) the aortic and pulmonary valves open and blood is ejected. Left and right ventricular pressure rises to a maximum of about 120 mm Hg and 25 mm Hg, respectively. The AV valves are pulled down into the ventricle by the contraction of the ventricular muscle. About 70-90 ml of blood is ejected with each stroke, but about 50 ml remains in each ventricle. Cardiac output, an important index of cardiac function, is the product of stroke volume and heart rate. Ventricular diastole begins with as the pressure drops and the aortic and pulmonary valves close. When the ventricular pressure falls below the atrial pressure the AV valves open and blood begins to quickly fill the ventricles. Roles and Responsibilities within the group of 5 people. Subject, Respiratory valve operator, (open and close the valve), Beathe counter, (counts each respiration of the subject), Timer, (Controls the stop clock and dictates to others start/stop their actions), Heart Rate monitor, (records all data). Equipment. A Douglas bag, Falconia tubing, A respiratory valve, A mouth piece, A stop clock, Tissues, Polor heart rate monitor, (watch and chest strap), Data sheets and a pen. Procedure. • Weigh the subject, Attach a 1.5kg mass load to the load carriage on the Ergometer, Evacuate TWO Douglas bags. Assemble the tubing, mouth and valve, Attach chest strap and watch receiver, The subject must be sat on the bike at complete rest. They must have the valve in their mouth and breathe through it for a couple of minutes which allows them to become used to having the mouth piece in and also clear the dead space in the tubing, Timer counts down 3…2…1… go and the clock begins, the valve is turned allowing air to be collected in the bag, the breath counter begins, Every 30 seconds the heart rate counter records the amount, This continues until the timer counts 3…2…1… now on 5 minutes. The valve is then closed, The subject can then remove the mouth piece, Then the subject cycled for 10 minutes at a resistance of 60rpm, Tubing was removed from bag one and attached to bag two, Heart rate monitor recorded values every 10 seconds for the 1st minute, then every 30seconds for the next 9 minutes, mouthpiece and nose clip were placed on in the 4th minute of exercise and the subject began to breathe for 1 minute to familiarise herself, air was collected and breaths were counted between 5 – 6 minutes, timer counted (3…2…. 1 go) and the valve was opened on 5 minutes and closed on 6min, subject still on the ergo meter was allowed to recover, heart rate monitor carried on recording heart rate every 10 seconds for 2 minutes, Douglas bags were evacuated and all the data was colleted to for form in the results. By examining results it can be seen that the subject heart rate is of relatively normal values, (69 BPM to 76 BPM) (appendix 1) during rest, which is within average rest heart rate, (the norm average heart rate being around 60 to 80 beats a minute). Before exercise began the subjects heart beat jumped from 69BPM to 74BPM in the last 30 seconds this was probably due to a anticipatory response which is shown at point a on the graph. This response is due to a release of adrenaline and emotional excitement acting on the medulla. However environmental surroundings may have contributed to the change the subjects heart rate and she may not have been at total resting heart rate. The best time to take the most accurate heart rate would be whilst you are in bed first thing in the morning. At the beginning of exercise, heart rate increases relatively compared with amount of exercise that she is doing, this initiates the increase supply of oxygen to working muscles and to remove waste products such as carbon dioxide and lactic acid. The increased heart rate is due to a nerve reflex response, initiated by the receptors, which stimulate the cardiac control centre. Also within the muscles Chemoreceptors respond to increase in lactic acid and other chemical changes by sending messages to the cardiac control centre to increase heart rate and Baroreceptors will detect the changes in blood pressure and inform the cardiac control centre thus also increasing heart rate. With the exercise heart muscle will begin increase in temperature, which leads to in venous return, placing increased stress on the heart than usual. This stimulates the SA node and increases heart rate and it also increase the force of concentration. The relationship between increase in stroke volume and an increase in venous return is known as Starlings Law. As the subject reaches a steady heart rate, this is when the rate of work is held constant at sub maximal levels of exercise; heart rate will increase rapidly until reaching a plateau (shown at point b on the graph as being 119BPM). This plateau is the steady state heart rate, and it is the optimal heart rate for meeting the circulatory demands at that specific rate of work. After the subject had finished exercise on the cycle ergometer, the heart was recorded for 2 minutes, this being the recovery period after exercise shown at point c. As you can see from the graph, there is a dramatic drop in heart rate in the first minute from 122 BPM to 78BPm. When exercise is finished the subjects heart rate will not instantly return to its resting heart rate, during this recovery period oxygen debt will occur which is the amount of oxygen consumed during recovery above that which normally would have been consumed at rest in the same period of time. This oxygen debt is used to compensate for the oxygen deficit. The deficit is the amount of extra oxygen required to complete the exercise if all the energy could have been supplied aerobically. As oxygen is not available for the first 3 minutes of exercise a deficit will always occur. The oxygen debt will not always equal the deficit, because during recovery the oxygen debt must also; Supply oxygen to provide energy for restoration of the oxy-myoglobin link, and supply energy for increased cardiac and respiratory rates that remain high during the recovery phase. Alactacid debt and Lactacid debtare the 2 components of O2 Debt. Alactacid debt – which is the first to be replenished, it is the volu...