Question

As humans grow from babies to adults, our brains become less and less able to repair themselves after brain injury. Though our brains retain an amazing capacity for change, they no longer are able to repair injuries caused by a stroke, head trauma, or neurological disease. Why do you think is? Provide an explanation for why this occurs. Your explanation can be either evolutionary (that is why hasn’t evolution led to humans whose adult brain can repair itself?) or physiological (what important changes might cause this transition from babies to adults?)

Answer 1

• The neurons of the CNS are incapable of regeneration due to lack of neurolemma in their neurons because their neurons are myelinated by oligodendrocytes not by Schwann cells. As the neurolemma cells will remain intact even if neurons undergo damage so that from its growing axon can reform.
• In the case of diseases such as brain injury, stroke, and other related disease axon connections get damaged. But in the PNS any damage to the axon connection can be repaired due to the presence of neurolemma in the myelin sheath form by Schwann cells even in adult mammals.
• The regeneration success depends on extracellular molecules and the intrinsic growth capability of the neurons. Thus the CNS has growth inhibitory factors while PNS has growth-promoting factors.
• The adult CNS has myelin-associated inhibitors and chondroitin sulfate proteoglycans inhibiting factors that prevent axon degeneration in the adult brain.
• The babies are born at their brain development acquires 30% of adult brain size because when the size is larger it is difficult to pass through the birth canal. And growth-promoting factors are present in babies while absent when the brain development completed that is in adults because of the inhibitory effect by astroglial cells.
• Also the brain development to 30% during birth is due to the evolutionary significant to enable bipideal motion and upright posture.
• Also, the brain is an organ associated with limited movement compared to others and are the most vulnerable organ so that it is preserved in a cranial box with some hole openings only. It is because of this lack o regeneration of its neurons.