How is most smooth muscle stimulated?

Most smooth muscle is predominantly stimulated by chemical stimuli. This type of muscle tissue is generally involuntary and responsive to various biochemical signals. These signals can come from neurotransmitters released by autonomic nerve fibers or hormones circulating in the bloodstream. For instance, chemical substances like acetylcholine and norepinephrine can bind to receptors on smooth muscle cells and induce contraction or relaxation. Additionally, local factors such as changes in pH, oxygen levels, and other metabolites can also influence smooth muscle activity, allowing it to respond to the changing needs of the body.

In contrast, smooth muscle is not primarily controlled by voluntary nervous input or external electrical stimulation, which are more characteristic of skeletal muscles. Auditory cues do not play a role in stimulating smooth muscle, as its action is largely governed by internal biochemical processes rather than sensory external inputs.