Muscles

Smooth

located in walls of hollow visceral organs. Appear spindle-shaped, under involuntary control. Present in the eyes. produce their own connective tissue. Smooth muscle contraction relies on the presence of Ca++ ions

Skeletal

made up of bundles of individual muscle fibers called myocytes. occur in muscles which are attached to the skeleton. They are striated in appearance and are under voluntary control. Contractions are neurogenic

Cardiac

Located in the walls of the heart. appear striated, and are under involuntary control.

length and tension

activation of tension-generating sites within muscle fibers.

If the muscle length shortens, the contraction is concentric

if the muscle length lengthens, the contraction is eccentric