Question

Describe how the tissue responds to each of the following stimuli. Be sure to include the underlying mechanism—don’t just tell me a stimulus will result in contraction, tell me HOW the stimulus will result in contraction. I will focus on the mechanism on the exam!

Elevated extracellular K+

K+ inhibitor (Barium Chloride)

Answer 1

We know that the resting membrane potential is the potential difference between the charge inside the cell and outside the cell. In case of a skeletal muscle tissue it is -70 mV. This means the potential of the fibre is 70 less than outside. The posttasium is more inside the cell than outside making it more negative. If there are more K+ in extra cellular fluid the potential decreases as the charge outside the cell changes. If so when a stimulus came the influx of Na+ to reduce the potential will be less and less depolarization occurs and leads to a reduced contraction making it less forcefull.

If K+ inhibitor is applied then when a stimuli comes the depolarization occurs as the Na+ moves in. At that time the k+ channels are almost closed. Soon after the stimuli the K+ channel needs to open and to make the k+ moves in. But as it is blocked the repolarization is mostly affected and the muscle remains in the contracted state and the come back to the normal state is much affected and the refractory period is extended.