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

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