This system provides oxygen to the brain, but in terms of nutrients to brain cells, then I would say the circulatory system since this carries nutrients to all parts of the body.
The subarachnoid space surrounds the brain and spinal cord and provides buoyancy for the brain. It also provides some nourishment for the brain. There are several subarachnoid collections of CSF called cisterns.
Your experiment tests whether your prediction is accurate and thus your hypothesis is supported or not. It is important for your experiment to be a fair test.
Rigor mortis first appears approximately 1-2 hours after death. Progressive stiffening occurs for approximately 12 hours, persists for approximately 12 hours, then diminishes over the next 12 hours as tissues break down as a result of autolysis and putrefaction.
