The human body comprises over 600 muscles, which play critical roles in movement, posture, and heat production. Muscle contractions occur through tension-generating sites within fibers, with types of contractions being concentric when muscles shorten and eccentric when they lengthen.
if the muscle length lengthens, the contraction is eccentric
If the muscle length shortens, the contraction is concentric
activation of tension-generating sites within muscle fibers.
length and tension
Fibers
600+ muscles in the body
Helps Body Movement
Help Posture
3 Main Types
Cardiac
Located in the walls of the heart. appear striated, and are under involuntary control.
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
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