Crayfish Lab

Lab Report 3: Daphnia, Human and Crayfish Cardiac Activity
Introduction
An electrocardiogram, abbreviated as ECG in this report, is a visual representation of an organism’s atrial and ventricular depolarization and repolarization. Previous research has shown that although there is variability in the amplitude and shape of the waves of ECG, dependent on the subject’s health, it follows a universal pattern that can be used effectively for biometrics. The experiments discussed in this lab report were performed on Daphnia, humans and crayfish to demonstrate the effects of various stimulus on cardiac activity, i.e. heart rate. The data presented in this lab report was measured via ECG software for human and Crayfish cardiac activity, while the
For the Daphnia heart rate experiment, the Daphnia was subjected to different chemicals via submersion. These chemicals were used as stimuli to prompt altered cardiac activity. The altered cardiac activity, measured through heart rate, would clue to whether a chemical is having a stimulant or depressant effect, or if any effect at all. Marley et. al discusses the effects of stimulants and depressants on the CNS (central nervous system). Research by Marley suggests that depressants tend to slow down activity of the CNS, while stimulants enhance over-activity of the CNS. Past literature shows that cardiac activity is autonomous and controlled by the CNS. In the Daphnia heart rate experiment, these two principles are tested together, and used to determine if unknowns A and B are stimulant or depressant. For the Human ECG circulation experiment, two human subjects were observed under resting, mild exercise and high exercise conditions. The mild exercise condition was produced by having the subject do repetitive
“Resting 1” was measured before any stimulus is applied, and hence, tell us the resting heart rate of the Crayfish. However, “Resting 1” cannot truly be the resting heart rate of the Crayfish, because prior to the measuring “Resting 1,” all the limbs of the Crayfish were cut off. Consequently, as Brotman et. al demonstrates, stress would cause dysrhythmia and the Crayfish’s heart rate to increase dramatically. Applying cold Ringer solution to the Crayfish causes a decrease in average BMP, if compared against “Resting 1.” The “Resting 2” stimulus shows no data because of the lack of detectable ECG activity of the Crayfish, after warm ringer solution was applied. The activity was once again detected after serotonin was applied. Zornik et. al suggests that serotonin increases heart rate. “Resting 3” stimulus, similar to “Resting 2,” was the addition of warm ringer solution. The observed average BPM, and amplitude is similar to Serotonin and GABA. GABA was the last stimulus, and it had a similar BPM value as Serotonin and “Resting 3.” Since there is no benchmark to compare the average BPM of these varying stimuli, we cannot say whether a stimulus is having a stimulant or depressant effect on the heart