Final answer:
Terminally differentiated cells, such as mature cardiac muscle cells and nerve cells, cease division and remain in the Go phase. These cells provide assistance to neighboring cells.
Step-by-step explanation:
Cells that cease division are called terminally differentiated cells. These cells have exited the cell cycle and have entered a phase called Go. Two examples of terminally differentiated cells are mature cardiac muscle cells and nerve cells. They have stopped producing the active G₁ checkpoint kinase and remain in the Go phase indefinitely, providing assistance to their neighboring cells.