Final answer:
The nervous system is typically free of microorganisms, with any presence indicating potential infection and a deviation from a healthy state.
Step-by-step explanation:
The nervous system is normally free from microorganisms, which includes bacteria, viruses, fungi, and parasites. Under healthy conditions, the presence of such microorganisms within nervous tissue suggests a deviation from a normal healthy state. This indicates that the body's defenses, such as the blood-brain barrier which typically prevents microorganisms from entering the central nervous system (CNS), have been compromised.
Infections like encephalitis or meningitis can occur if pathogens breach these defenses and include symptoms like inflammation of the brain or meninges, potentially leading to severe consequences such as blindness, deafness, coma, and even death.