The cardiac muscle cells of the heart (called the myocardium) are tightly bound together in layers and encircle the blood filled chambers of the heart. When the heart contracts the myocardium encloses on the blood filled chambers and blood is propelled around the body. With greater filling of blood (i.e. increased end diastolic volume; EDV) the force of contraction of the heart is subsequently greater. Experiments in the late 19th century, using frog hearts, demonstrated this ability of the heart, known as the Frank-Starling Law of the heart, named after Otto Frank and Ernest Starling.
The heart requires a number of important resources to carry out its role. Calcium, oxygen and adrenaline are all required for normal functioning and any changes in their levels can affect the force of contraction.
This simulation examines factors that control the Contraction of Cardiac Muscle. The "data" you will collect is "real" data, taken from recordings made of the test conditions you will see in this simulation, done in previous years. This practical uses isolated strips of toad ventricular muscle that are electrically stimulated to contract. The force of cardiac muscle contraction is recorded (with grams of tension of the Y axis and time in seconds on the X axis of the recording).
Watch the video below before commencing with the simulation:
The effect of oxygen deprivation on the force of contraction
Oxygen is essential for the survival of the human body and the cardiac muscle is no exception. Without oxygen the tissues of the body die rapidly. For instance, when a coronary artery supplying the cardiac muscle is blocked, the cardiac muscle it supplies dies within minutes.
However, cardiac muscle will recover after a brief period of no oxygen, as you will see in the simulation.
- Click the Start button and record your observations.
- Next click the Deoxygenated solution button and observe the force of contraction (tension). What happens to your recording?
- Once the recording stabilizes, click the Normal solution button. What happens then to your recording?
Oxygen deprivation simulation
Mobile Support Warning
This simulation was designed with a desktop interface in mind, and may not function correctly on smaller screens or mobile devices.