ascending signals in the spinal cord travel via gray matter, while descending signals travel via white matter.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

what are the options? add them, then i will be glad to .

answer biotechnology;

answerhomologous structures;