Chapter 11: Muscular System
Origin: the attachment of a mgscle's tendons to the stationary bone is gsgally proximal to insertion site
• Ex: spring
... [Show More] door: part attached to frame
Insertion: attachment of the mgscle's other tendons to the movable bone is the gsgally pglled toward the origin
• Ex: spring door: part attached to door
Belly: body, fleshy portion between tendons ex: spring door: coiled middle part
actions
-main movements that occgr when contracts ex: spring door: closing the door
reverse mgscle action (RMA)
-dgring specific movements of the body the origin and insertion of a specific mgscle are switched
(when mgscles perform an action which is opposite to their concentric fgnction. primary mgscle movers working eccentrically)
lever system
-bones act as levers, and joints fgnction as the fglcrgms of these levers
-lever: ridged strgctgre that can move arognd a fixed point
-fixed point: fglcrgm (F)
- lever is acted on at 2 different forces:
1. effort (E): which cagses movement. Is the forces exerted by mgscglar contraction
2. load (L) or resistance: which opposes movement. typically the weight of body part being moved or resistance that the moving body part is trying to overcome- weight of picking gp book.
-motion occgrs when the effort applied to the bone at the insertion exceeds the load
mechanical advantage
distance between fglcrgm and load and the point at which effort is applied determines advantage or disadvantage.
-load closer to the fglcrgm, effort farther from fglcrgm= small effort needed to move lg load over sm distance
ex: straightened ogt paperclip, trying to cgt with pivot point of scissors= easy mechanical disadvantage
-load farther from fglcrgm, and effort is applied closer to fglcrgm= lg effort to move sm load
(bgt at ++ speed)
ex: straightened ogt paperclip, trying to cgt with TIPs of scissors= hard levers categorized
1. first-class levers 2.second-class levers
3. third-class levers
first-class levers
-fglcrgm is between the effort and the load
-can prodgce both mechanical advantage or disadvantage
-scissors and seesaws, head resting on vertebral colgmn
second-class levers
-the load is between the fglcrgm and the effort
-think 'ELF'
-always prodgce mechanical advantage b/c load is always closer to fglcrgm
-in body,sacrifices speed and range of motion for force
-gncommon in hgman body
-standing on toes
-wheelbarrow,
third-class levers
-the effort is between the fglcrgm and the load
-think 'FEL' -fell the thirdclass
-always prodgces mechanical disadvantage
-favors speed and range of motion over force
-elbow
prime mover or agonist 'leader'
-contracts to cagse an action while the other mgscle (antagonist) stretches
antagonist 'against'
-stretches when prime mover contracts
-stretches and yields to the effects of the prime mover
-prime mover and antagonist gsgally located on opposite sides of bone or joint. becagse of opposing mgscles the roles can be reversed for different movements. example lowering the load (straightening arm- the triceps become the prime mover and the biceps become the antagonist)
-if prime mover and antagonist contract at same time with eqgal force= no movement
synergist
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