Final answer:
Sodium ions will move from the inside of the cell to the outside by diffusion, due to a higher concentration inside the cell. If facilitated channels are present, this is specifically called facilitated diffusion. Osmosis, however, refers to the movement of water, not sodium ions.
Step-by-step explanation:
If there is a higher concentration of sodium inside the cell compared to the outside, sodium ions (Na+) will tend to move from the inside of the cell to the outside. This movement is due to diffusion, which is the process where particles move from an area of higher concentration to an area of lower concentration until equilibrium is reached.
Normally, sodium concentration is about 10 times higher outside the cell than inside. This gradient is maintained by the sodium-potassium pump, which actively transports sodium out of the cell and potassium into the cell against their respective concentration gradients, creating a negative charge inside the cell. However, if we consider a scenario where sodium ions are indeed higher inside, they would still move by diffusion, not osmosis, because osmosis specifically refers to the movement of water molecules through a semipermeable membrane.
When sodium moves across a cell membrane, it often passes through specific channels or 'pores' because it cannot move through the nonpolar lipid bilayer due to its charge. This type of diffusion through channels is known as facilitated diffusion, which is still a passive process and does not require energy from the cell.