Create an account
7 ways to name muscles:
location, shape, relative size, direction of muscle fibers, number of origins, location of attachments, action they perform
also known as agonists; a muscle that has the major responsibility for producing a specific movement; biceps brachii is prime mover for elbow flexion
muscles that oppose or reverse a particular movement; help regulate action of prime mover by contracting slightly to provide some resistance to prevent overshooting the mark; prime mover and antagonists are located on opposite sides of joint which they act; triceps brachii is antagonist for forearm flexion
help prime movers by adding a little extra force to their movement or reducing unnecessary movements that might occur as prime mover contracts; "joint stabilizers"
synergists that immobilize a bone or a muscle's origin so the prime mover has a stable base to act on; help maintain upright posture
broad origin and fascicles converge toward single tendon of insertion; triangular or fan shaped
fascicles run parallel to long axis of muscle; straplike or spindle shaped with expanded belly--which can also be called fusiform muscles
fascicles are short and attach obliquely to a central tendon that runs the length of the muscle
fascicles insert into only one side of the tendon, like extensor digitorum longus of the calf
fascicles insert into tendon from opposite sides; muscle looks like a feather; rectus femoris of the thigh
if the load is close to the fulcrum and the effort applied is far from the fulcrum, a small effort exerted over a relatively large distance can be used to move a large load over a small distance (person using a jack to lift a car); a lever that operates at mechanical advantage allows the muscle to exert less force than the load being moved
load is far from the fulcrum and effort is being applied near the fulcrum, the force exerted by the muscle must be greater than the load to be moved
levers with mechanical disadvantage; useful because they allow a load to be moved rapidly over a large distance
first class levers
effort is applied at one end of the lever and the load at the other, with the fulcrum somewhere between; seesaws; lifting your head from your chest
second class levers
effort is applied at one end of the lever and the fulcrum is located at the other, with the load between them; standing on your tip toes; all in the body work at mechanical advantage because muscle insertion is always further from the fulcrum than the load; levers of strength, but sacrifice speed and range of motion
third class levers
effort is applied between the load and the fulcrum; speedy and always mechanical disadvantage; tweezers; most skeletal muscles of the body are third class levers; biceps muscle lifting forearm and carrying anything in the hand; permit a muscle to be inserted very close to the joint, which allows for rapid extensive movements (like throwing); these muscles tend to be thicker and more powerful
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together