Extracellular Solution Lab Report

During this experiment, when the pipette was measuring just the extracellular solution, this was deemed the baseline. When we punctured each of the DEM, DEL1, and DEL2 crayfish muscles, we observed a large drop in voltage (refer to Figure 1), therefore indicating that inside the muscle was more negative in relation to the outside solution. The time when the pipette was intramuscular, the recording showed a steady reading of the intramuscular voltage potential (Figure 1). When the pipette was removed from the crayfish muscle and was back in the extracellular solution, the voltage measurement returned to baseline (Figure 1). The intramuscular recordings showed that all three crayfish muscles were depolarized compared to the K+ Nernst predicted value when the extracellular concentration of K+ was 5.4mM, and DEL1 and DEL2 were also significantly depolarized in 10mM and 20mM solutions (refer to Figure 2 and Table 1). Around 40mM of extracellular potassium concentration, the
With increasing external potassium concentration, the chemical gradient between the highly concentrated inside and the usually not very concentrated outside diminishes. In turn, this causes internal potassium to remain inside the cell, thus depolarizing it, which was confirmed by our results (refer to Figure 2 and Table 1). These findings are in line with Hodgkin’s (1951) who claimed that the internal potassium concentration of excitable cells, such as the crayfish muscle, is twenty to fifty times larger than the external, and appears to move freely in nervous and muscle cells. Proteins and other bodies in the cell produce large negative charges which, in conjunction with the outward flow of positive potassium ions gives a polarized resting membrane