How do cardiac cells sustain a membrane potential of around 0 mv during the long plateau phase?

They are actually assisted by the Na + / Ca 2+ exchanger. This specific exchanger produces an inward (or depolarizing) current which helps sustain the membrane potential near 0 mV. This is achieved by moving 3 Na + into the cell for every 1 Ca2+ out.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

c. live where it’s cold and icy