Based on Figure 2, what is the range of stimulus frequencies that correspond to
ID: 95460 • Letter: B
Question
Based on Figure 2, what is the range of stimulus frequencies that correspond to the natural range of heart rates for yellowfin tuna at 18 degree C and 24 degree C? Based on this, is there evidence that the percent contribution of SR Ca^2+ to force development differs with temperature? Explain. How does water temperature change when fish or other aquatic animals dive? Based on this, do you think tuna increase or decrease their percent contribution of SR Ca^2+ to force development during their dive?Explanation / Answer
1. Based on figure 2, the range of stimulus frequencies that correspond to the natural heart rate for yellofin tuna for temperature 18°C is 0.6 Hz to 1.13 Hz. Based on figure 2, the range of stimulus frequencies that correspond to the natural heart rate for yellofin tuna for temperature 25°C is 1.25 Hz to 2 Hz.
The SR contribute up to 60 % of the activator Ca2+ during force development at maximal contraction frequencies in the cardiac muscle of yellowfin tuna. The highest level of SR Ca2+ involvement in force production is the first evidence directly linking the high heart rates of tuna with increased dependence on intracellular Ca2+ cycling.At low frequencies cardiac muscles, at 18 °C and 25 °C utilized more SR Ca2+ than those at 15 °C. However it is observed that percentage SR Ca2+ utilization is greater at colder temperatures.
2. Temperature fluctuations that tuna experiences when it dives in are acute temperature changes from the acclimation temperature of 20 °C to either 15 ° or 18 °C. The SR Ca2+ utilization for a frequency within the physiological range is greater at 15 or 18 °C than at 25 °C. This suggests that when yellowfin dive from 20 °C into water at 18 or 15 °C to forage, they must increase their dependence on SR Ca2+ cycling to maintain a level of cardiac output similar to that at 25 °C. This precise is the reason that the dive duration to cooler waters is usually short
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