NEET UG 2005 — Neural Control and Coordination

One of the examples of the action of the autonomous nervous system is:

Parkinson's disease (characterized by tremors and progressive rigidity of limbs) is caused by degeneration of brain neurons that are involved in movement control and make use of neurotransmitter:

Four healthy people in their twenties got involved in injuries resulting in damage and death of few cells of the following. Which of the cell, are least likely to be replaced by new cells?