Frog Lab Report
Effects of Electrical Stimuli and Injected Reagents on Frog Hearts
Melissa Higdon
Section 05, Group 01
November 19, 2013
Introduction: The heart is a very complex muscle for all species. It is responsible for sending oxygenated blood throughout the body as well as sending deoxygenated blood to the lungs, and continuously circulate this way for as long as we are alive. Many things can be effected, for example how fast the heart beats or how much force the heart chambers contract with. In this experiment, many different methods will be used to test the effects of both external electrical stimulus as well as injected reagents on the heart rate and force of contractions of a frog. When the heart “skips a beat”, it is actually just your heart’s normal cardiac rhythm being somehow interrupted and causing an extra beat or a skipped beat (compensatory pause). The atria are supposed to contract first, but in this case the ventricles contract first which is wrong and the heart has to then correct itself by pausing and waiting for the atria to contract again (1). This is what feels like a skipped beat, and it appears like one too on an ECG because there is a big pause between atrial contractions. To cause the ventricles to contract early, an electrical stimulus (or one of many other problems that could potentially affect the heart, in this case it is electrical shock) must be applied during atrial relaxation to cause the ventricles to contract before the atria. Different chemicals, or reagents, cause different things to happen to the heart. Some reagents, like norepinephrine, are released during stressful times and cause the heart rate to increase and contract with more force. This is an example of an excitatory neurotransmitter, which can be depleted in many ways, for example by a reagent that does the opposite of what it does, which would be to decrease heart rate (2). Some reagents, like
Melissa Higdon
Section 05, Group 01
November 19, 2013
Introduction: The heart is a very complex muscle for all species. It is responsible for sending oxygenated blood throughout the body as well as sending deoxygenated blood to the lungs, and continuously circulate this way for as long as we are alive. Many things can be effected, for example how fast the heart beats or how much force the heart chambers contract with. In this experiment, many different methods will be used to test the effects of both external electrical stimulus as well as injected reagents on the heart rate and force of contractions of a frog. When the heart “skips a beat”, it is actually just your heart’s normal cardiac rhythm being somehow interrupted and causing an extra beat or a skipped beat (compensatory pause). The atria are supposed to contract first, but in this case the ventricles contract first which is wrong and the heart has to then correct itself by pausing and waiting for the atria to contract again (1). This is what feels like a skipped beat, and it appears like one too on an ECG because there is a big pause between atrial contractions. To cause the ventricles to contract early, an electrical stimulus (or one of many other problems that could potentially affect the heart, in this case it is electrical shock) must be applied during atrial relaxation to cause the ventricles to contract before the atria. Different chemicals, or reagents, cause different things to happen to the heart. Some reagents, like norepinephrine, are released during stressful times and cause the heart rate to increase and contract with more force. This is an example of an excitatory neurotransmitter, which can be depleted in many ways, for example by a reagent that does the opposite of what it does, which would be to decrease heart rate (2). Some reagents, like
References: (1) "Skipped Beats." Heart Rhythm Society. N.p., n.d. Web. 20 Nov 2013.