In Figure 2 (above ), a control action potential (A) was first generated with a
ID: 60115 • Letter: I
Question
In Figure 2 (above), a control action potential (A) was first generated with a large, brief stimulus (initial potential -60 mV, stimulus 600 mA/cm2for 0.1 ms beginning at time 0). Next, two stimuli were given, the first one as in A and the second one (with same magnitude and duration) followed the first after a delay of 5 msec, giving rise to the signal B. Finally, the same protocol was repeated except that the second stimulus followed the first (A) after a delay of 7 msec, giving rise to signal C.
Questions:
How does the different stimulus magnitude in Fig. 1 and Fig. 2 (curve A) affect the action potential size and time course? Explain.
Provide two explanations that could account for trace B in Figure 2. How would you determine which explanation is correct?
What happens to the shape and size of the action potential in trace C and why?
Compare the values of the peak Na+ conductance in traces A and C and account for any differences.
Figure 2 Stimulus: 40 Magnitude-600 A/cm2 Duration- 0.1 msec V20 Vm (mV) mv) C. 20 40 60. 80 GK Stimulus 0 Time (msec)Explanation / Answer
1. The action potential has entered to positive side, that is more exited state from its resting state.
2. Before the cell returns to the resting state an another stimulus has occurred which had led to mild excitation of the cell where the action potential has increased to -20 suddenly.
The second explanation could be a third stimulus has exited both cells from ground state as well as in the exited state to another level.
3. In trace C, the first stimulus has again happened in the curve A where as in C the the impulse has started half the way.
4. The Na+ conductance in traces A and C accounts for a difference of 10 mV. In A it is -50 mV and in C it is -40 hence the difference is 10 mV.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.