12) Motor nervous system controls: a. Signals from the spinal cord to the brain
b. Signals from the spinal cord to the muscles
c. Signals from the brain t the spinal cord
d. Signals from the senses to the spinal cord
e. Signals from muscle to muscle

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.