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26 terms

Chapter 10

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4 function groups of muscles?
prime movers, antagonists, synergists, fixators
7 ways to name muscles:
location, shape, relative size, direction of muscle fibers, number of origins, location of attachments, action they perform
prime mover
also known as agonists; a muscle that has the major responsibility for producing a specific movement; biceps brachii is prime mover for elbow flexion
antagonists
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
synergists
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"
fixators
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
circular fascicles
arranged in concentric rings; close by contracting; called sphincters
convergent fascicles
broad origin and fascicles converge toward single tendon of insertion; triangular or fan shaped
parallel fascicles
fascicles run parallel to long axis of muscle; straplike or spindle shaped with expanded belly--which can also be called fusiform muscles
fusiform muscles
spindle shaped muscles that are an expanded belly, like biceps brachii of arm
pennate fascicles
fascicles are short and attach obliquely to a central tendon that runs the length of the muscle
unipennate muscle
fascicles insert into only one side of the tendon, like extensor digitorum longus of the calf
bipennate muscle
fascicles insert into tendon from opposite sides; muscle looks like a feather; rectus femoris of the thigh
multipennate muscles:
looks like lots of feathers; deltoid muscle of shoulder
lever systems
partnerships between the muscular and skeletal systems
lever
ridgid bar that moves on a fixed point called the fulcrum, when a force is applied to it
effort
applied force to move a resistance, or load
load
the resistance
mechanical advantage
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
power lever
levers with mechanical advantage
mechanical disadvantage
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
speed lever
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
factors that affect force/speed of contraction? 3
levers, fasciculi, increase number of fibers = increase strength