What is that which spontaneously depolarise to trigger contraction of cardiac muscle and establishes the heart rate

Name the type of chemical that speeds up digestion

Granite rock is light in color. which feature directly contributes to this color? the process that forms granite the amount of silica minerals in granite the shape of the grains found in granite the unique pattern formed by grains in granite

How does this experiment explain why it is often milder in areas such as coastal maryland while areas such as kansas or iowa have more extremes in temperature