Cardiac Output ( Co )

Calculate the stroke volume of Suzie’s heart, and compare it to that of a normal individual.

Exercise increases heart rate by a process of sympathetic autonomic stimulation. Sympathetic (adrenergic) nerves increase the excitability of the sino-atrial node and reduce the P-R interval .As exercise continues, the physiological changes in the body are continuously monitored by a number of physiological systems and the balance of activity of the sympathetic system (speeding up) and the parasympathetic system (slowing down) is constantly adjusted. When exercise is over, the heart rate does not drop immediately as the body has to undergo a period of re adaption to return to the resting state.

How does venous return increase stroke volume? increase venous return to heart leads increase filling of ventricle of heart this increased filling by starling law leads more forceful contraction so stroke volume ie amount of blood ejected by single heart beat increases

This causes the ventricles to dilate in order to maintain adequate stroke volume. Usually, this will improve over the next 7-10 days.

B. Part B. PowerPhys Experiment 4 – Effect of Exercise on Cardiac Output (13 points total)

Calculate the stroke volume of Suzie’s heart, and compare it to that of a normal individual. Her low calcium intake causes weaker heart contractions and that makes her stroke volume way lower than it should be.

Contractility is the pumping of the heart muscle. It is measured as the ejection fraction. Contractility directly influences stroke volume. Increased contractility will increase stroke volume with any amount of preload. Diseases that disrupt myocyte activity reduce contractility. Myocardial infarction is the most common. Others include, but are not limited to, cardiomyopathies, degenerative valve disease, and myocarditis (Francis & Tang, 2003). Secondary causes of decreased contractility, such as myocardial ischemia and increased myocardial workload, contribute to neurohumoral , immune, and inflammatory changes and can cause ventricular remodeling. Ventricular remodeling occurs when the size, shape, and function of the affected chamber is distorted. Ventricular remodeling causes hypertrophy and dilation of the heart muscle and causes progressive myocyte contractile dysfunction over a period of time. When contractility is decreased, stroke

Preload is the amount of stretch of cardiac muscle cells prior to contraction. It is controlled by the amount of venous return to the heart. The more venous return, the more the cardiac muscle cells are stretched, which causes a stronger contraction during systole, and this increases the stroke volume. Contractility is the strength of a ventricular muscle contraction. An increase in contractility results in an increase in stroke volume because more blood is ejected from the heart. Afterload is the resistance that the left ventricle must overcome before it can eject blood. An increase in afterload causes a decrease in stroke volume because less of the blood in the ventricle would be ejected.

Stroke volume is the amount of blood pumped out of the heart and into the body from the left ventricle during each contraction and is measured in millilitres per beat. When the heart is resting stroke volume is at a normal pace. When the heart rate starts to increase stroke volume has to become faster and pump more blood out of the heart

It’s no secret that physical activity can have a positive effect on your cardiovascular functioning and overall health. The heart is an organ that is mostly composed of muscle, and just like all the other muscles in your body, it needs to be worked in order to maximize its efficiency. The heart is designed to pump blood throughout the body, the weaker the heart, the faster it has to pump to compensate for the amount of work needed to distribute the blood. There have been studies that highlight the adaptations that occur within the athlete’s heart; cavity enlargement as well as wall thickness within the ventricles are two adaptations thought to play a major role in lower heart rate during rest and exercise (Kovacs and Baggish, 2016).

In a sweeping fashion, the right atrium contracts and forces the final volume of blood into the right ventricle. The left atrium contracts and contributes the final 20% of volume to the left ventricle.

The effects of exercise on blood pressure, heart rate, respiration rate and electrical activity of the heart were assessed. The measurements of respiration rate, pulse rate and blood pressures were noted as described in Harris-Haller (2016). Data was first taken from subjects in a relaxed position and then followed by sets of reading after exercising based on one minute intervals. The data also noted sitting ECG traces from Harris-Haller (2016). The respiratory rate, pulse, blood pressure, P wave, QRS complex and T wave were defined for each subject. The class average was calculated for males and females and graphed to illustrate the results by gender for each cardiopulmonary factor.

With the advance of ultrasound technology, image quality has become better, being comparable with those of CMR, giving echocardiography the ability to provide mechanistic insights on cardiac morphology. Routine calculation of LV mass should be an integral part of an echocardiographic examination 77. Echocardiography is not only of use in assessing LV mass but also of use in demonstrating reduction in LV mass after therapy 78. Motion-mode (M-mode), 2-dimensional echocardiography (2DE) and finally 3-dimensional echocardiography (3DE) constitute the basis for echocardiographic LV mass

wall thickening and wall motion throughout the cardiac cycle and so, LV volumes and EF obtained by cMRI are highly accurate, reproducible and well validated (14) (15).

As the intensity of exercise increased, so did the rates of the heart and breathing. After a small period of rest, the heart rate and breathing rate both decreased to a point close to their resting rate. This proved the stated hypothesis. First, the hearts average resting rate was recorded to be 76 bpm. The heart is therefore transporting oxygen and removing carbon dioxide at a reasonably steady rate via the blood. During the low intensity exercise (Slow 20) the heart rate increases to 107 bpm, which further increases to 130bpm at a higher intensity level (Fast 20). The heart therefore needs to beat faster to increase the speed at which oxygen is carried to the cells and the rate at which carbon dioxide is taken away by the blood.