According to J. Stein Carter, Professor Emeritus at the University of Cincinnati, Clermont, skeletal, cardiac and smooth muscle tissues differ in terms of structure, function and location. Additionally, the way in which the muscles are excited varies from one type to the next.
Skeletal muscles have striated structure, similar to cardiac muscles. By contrast, the cells of smooth muscles are spindle shaped and feature no striations. MedlinePlus states that skeletal muscles attach to the various bones of the skeleton and are responsible for allowing people to walk, stand and lift things. Smooth muscles are found in the outer walls of all of the hollow organs lining the viscera, except the heart, which is where the cardiac muscles are located.
As the Carter asserts, skeletal muscles are controlled consciously, a characteristic scientists call voluntary control. By contrast, both smooth and cardiac muscles are called involuntary muscles because they function without conscious thought. There are exceptions though as the diaphragm, which is responsible for drawing air into and forcing air out of the lungs, normally operates automatically; but people can also exert conscious control over it.
According to J. Stein Carter, muscles always operate by contracting or relaxing. Muscles cannot move by pushing; instead, humans accomplish pushing movements through the use of antagonistic muscle pairs.