If the stimulus reaches the threshold an action potential will be generated. If the stimulus doesn't reach it no action potential will be generated. If the stimulus will be stronger the action potential will have the same amplitude. The refractory period makes it harder to generate an action potential so they decrease the frequency of action potential production.
Geologists in Egypt and Ethiopia are comparing rock samples from rocks found in the two countries. They are sharing information about the rocks to figure out whether they are the same or different types of rock. The information is as follows: Rock A formed from small pieces of rock.