What tells a muscle when to contract?

What tells a muscle when to contract?

Explanation:

(1) A message travels from the nervous system to the muscular system, triggering chemical reactions.

(2) The chemical reactions lead to the muscle fibers reorganizing themselves in a way that shortens the muscle--that’s the contraction.

(3) When the nervous system signal is no longer present, the chemical process reverses, and the muscle fibers rearrange again and the muscle relaxes.

The nervous system generates a signal, which triggers a muscle to contract

Explanation:

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.