help with Frank Starling law of the heart question!!!

Im working on my homework and im just not sure if Im answering the second part of the question right or if im missing anything? HELP!!

The question is -->State the Frank  Starling Law of the Heart, and explain its relationship to cardiac output using the appropriate formula for determining cardiac output. (2.5 marks)

My answer-->
The Frank-Starling Law of the Heart is the intrinsic relationship between the amount of ventricular stretching (amount of venous return) and the contractile force. This means that with an increase in the end-diastolic volume (caused by an increase in ventricular filling) the more the heart is stretched. This increase in the stretch of the heart causes a longer initial cardiac length before the hearts contraction. A greater force on the following heart contraction is due to the increase in cardiac length; furthermore, this causes an increase in the stroke volume. In other words this law states “more in = more out.”


Cardiac output is the amount of blood pumped by each ventricle each minute, furthermore, cardiac output is a product of how much blood the left ventricle pumps with each contraction (stoke volume) and heart rate. Cardiac output is directly related to venous return, which is the factor that determines the preload. When the heart rate is constant, the cardiac output is directly proportional to the preload. Therefore, an increase in preload will increase the cardiac output until a certain point (very high end diastolic volume). Additionally, any increase or decrease in the contractility of the cardiac muscle will increase or decrease the cardiac output. The Frank-Starling Law of the Heart is related to cardiac output can be seen in the formula CO= HR x SV (cardiac output = heart rate times stroke volume). For example seen in exercise a larger cardiac output is needed, therefore, there is an increase in venous return that is stimulated by the sympathetic nervous system. As a result, this increases end diastolic volume which in turn increases stroke volume. Additionally, heart rate is also increased during exercise. With the combined effects of an increase in stoke volume and an increase in heart rate this causes an increase in cardiac output. The benefit of an increase in cardiac output during exercise is an increase in blood flow to the working muscles.