Cells, tissues, and organs undertake a variety of self-maintenance behaviors without the direction of the brain. Although low-level behaviors like these are abundant, high-level examples also exist, like when an arm pulls away from a hot stove as soon as the signal reaches the spinal cord. The organism is a recursive system, with sub-systems behaving with varying degrees of autonomy while also depending on the larger system. The seat of consciousness possesses only a limited view.

That's not sentience. That's just life.

Neurons do not have a brain. They do not have emotions or feelings or thoughts. This conversation is so absurd that it's well into the realm of fantasy.

What causes a neuron to perform its functions if it isn't some brain? The answer would likely be physics, and I would say that first-person experience is fundamental in the physics if it exists at all.

Or somekind of electrical system, acting as a software layer on top of the hardware (neurons) layer. This electrical thing is what controls and orchestrates everything and also is our ego.

You can use this approach to make complex behavior from simple rules https://en.wikipedia.org/wiki/Subsumption_architecture