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. heart rate.
The data presented in this lab report was measured via ECG software for human and Crayfish cardiac activity, while the Daphnia’s heart rate was observed manually. In all experiments, cardiac activity is being determined via measurement of heart rate. 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 onditions.
The mild exercise condition was produced by having the subject do repetitive movements with 10-pound weight. The high exercise condition was produced by having the subject do a lap of ascending and descending stairs. This experiment explores whether physical activity has an increased or decreased effect on heart rate on the subjects. For the Crayfish ECG experiment, a crayfish was observed at rest and then subjected to varying stimuli. Each subsequent stimulus was subjected with intermittent rest; to see what kind of effect the stimuli had on the heart rate. The aforementioned stimuli include cold ringer solution, serotonin and GABA.
The intermittent rest was achieved by applying the warm ringer solution to the heart of the crayfish. It is hypothesized that varying stimuli results can result in varied cardiac activity, whilst stimulants increase heart rate, depressants decrease heart rate of any organism, and strenuous activity increases heart rate. The data for the Daphnia heart rate experiment was recorded in Table 1. The Daphnia was subjected, via submersion for two minutes, to different stimuli. In the time of 10 seconds and over hree trails, the number of heart beats under the varying stimuli were recorded.
The BPM (Beats Per Minute) values were calculated by average heart beats, in 10 seconds, being multiplied by 6. The “Water” stimulus serves as a control; it represents the resting heart rate of the Daphnia. The Daphnia, was stimulated by caffeine, ethanol, unknown solution A, and unknown solution B. In between the fore-mentioned stimuli, the Daphnia was submerged in water for a time of 120 seconds, for the Daphnia to return to resting heart rate. Discussion: Daphnia Heart Rate Experiment The data in Table 1 gives answers to the question whether unknowns A and B are stimulant or depressant.
For each stimulus, the daphnia was submerged for two minutes to allow the chemicals to take effect; since, Daphnia are ectotherms and their body adapts to the surrounding environment. The water stimulus is used to collect data about the Daphnia’s resting heart rate. This resting heart rate is compared against the various stimulus to determine whether each chemical is having a stimulant or depressive effect. With the caffeine stimulus, average BPM increased, hence, the heart rate increased. Therefore, caffeine has a stimulant effect on the Daphnia’s heart rate.
With the ethanol stimulus, average BPM decreased almost three fold. Therefore, ethanol is a depressant. Unknown A has an increased heart rate when compared against the water stimulus, i. e. the resting heart rate. However, unknown B has a larger increase of average BPM than unknown A. Therefore, Unknown A is a depressant and unknown B is a stimulant chemical. As hypothesized, the experiment successfully showed that stimulants increase heart rate and depressants decrease heart rate. This Table shows the measured ECG and pulse times of subject A at rest and then under different stresses.
The data was observed for each of the following variables: “rest,” “mild exercise” and “laps,” with three trails for each variable. The R-R was measured by the recording timeframe between the R points of adjacent QRS waves. The Pulse was measured by recording the timeframe between R point of QRS wave and the peak of the T-wave. This Table shows the measured ECG and pulse times of subject B at rest and then under different stresses. The data was observed for each of the following variables: “rest,” “mild xercise” and “laps,” with three trails for each variable.
The R-R was measured by the recording timeframe between the R points of adjacent QRS waves. The Pulse was measured by recording the timeframe between the R point of a QRS wave and the peak of the subsequent T-wave. Discussion: Human ECG Circulation Experiment Each subject’s cardiac activity is measured via ECG software. The ECG allows determination of the timeframe between subsequent atrial repolarizations, that is the “R-R. ” As well as the timeframe between atrial and ventricular repolarization, that is the “Pulse. A smaller “R-R” time frame is representative of quickened subsequent atrial repolarization occurring.
A smaller “Pulse” time frame is representative of atrial and ventricular repolarization occurring faster. Hence, lowered times suggest increased heart rate. Subject A and B’s “Pulse” timeframe decreases, as the stresses progress from rest to exercise to lap. Both Subject A and B’s “R-R” timeframe decreases, as the stresses progress from rest to exercise to lap. Therefore, as hypothesized, heart rate increases as the subject’s stress becomes more strenuous. This Table shows the measured ECG ctivity of a crayfish at rest and varying stimuli.
Resting 1 pertains to measurements taken before any stimulus was subject to the crayfish. The table also includes the observed ECG times for cold Ringer solution, serotonin, and GABA. The intermittent resting stimulus, namely 2 and 3, were done by subjecting the crayfish to warm Ringer solution. The time frame data was observed for the length of five ECG signal events. The Amplitude (V2-V1) represents the voltage difference between R and S points of the QRS wave. It is measured in mV. The average BPM were calculated using the following formula:
Discussion: Crayfish ECG Experiment In this experiment, average BPM is used to determine the effects of temperature, and drugs on Crayfish heart rate. “Resting 1” was measured before any stimulus is applied, and hence, tell us the resting heart “Resting 1” cannot truly be the resting heart rate of the Crayfish, because prior to the measuring “Resting 1,” all the limbs of the of the Crayfish. However, 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 imilar 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 rate. Summary The experiments explored in this lab report were performed on Daphnia, Humans and Crayfish to demonstrate the effects of various stimuli on cardiac activity. The cardiac activity changes by observing heart rate, and measuring ECG values, i. e. the time between atrial repolarizations or the time between atrial and ventricular repolarization. The Daphnia experiment explores the ffect of stimulants and depressants.
The results are evidence proving the hypothesis. The Daphnia experiment shows stimulants increase heart rate, while depressants decrease heart rate. The Human ECG circulation experiment tells of how heart rate increases as the subject’s stress becomes more strenuous. The Crayfish ECG experiment, although it doesn’t tell us the exact effect of the various drugs or solutions on heart rate, it does tell us about cardiac activity. Specifically, how cardiac activity is subject to change when the organism, that is the Crayfish, is stimulated.
