Joints and levers within the human physique
Bones, ligaments, and muscular tissues are the constructions that kind levers within the physique to create human motion. In easy phrases, a joint (the place two or extra bones be a part of collectively) varieties the axis (or fulcrum), and the muscular tissues crossing the joint apply the pressure to maneuver a weight or resistance. Levers are sometimes labeled as top notch, second class, or third class. All three varieties are discovered within the physique, however most levers within the human physique are third class.
A primary-class lever has the axis (fulcrum) situated between the load (resistance) and the pressure (determine 1.21a). An instance of a first-class lever is a pair of pliers or scissors. First-class levers within the human physique are uncommon. One instance is the joint between the top and the primary vertebra (the atlantooccipital joint) (determine 1.21b). The load (resistance) is the top, the axis is the joint, and the muscular motion (pressure) come from any of the posterior muscular tissues attaching to the cranium, such because the trapezius.
Muscle mass and bones act collectively to kind levers. A lever is a inflexible rod (often a size of bone) that turns a couple of pivot (often a joint). Levers can be utilized so {that a} small pressure can transfer a a lot greater pressure. That is known as mechanical benefit.
There are 4 elements to a lever – lever arm, pivot, effort and cargo. In our our bodies:
bones act as lever arms
joints act as pivots
muscular tissues present the hassle forces to maneuver masses
load forces are sometimes the weights of the physique elements which can be moved or forces wanted to elevate, push or pull issues exterior our our bodies.
Levers may also be used to amplify motion, for instance, when kicking a ball, small contractions of leg muscular tissues produce a a lot bigger motion on the finish of the leg.
Levers are in a position to give us a energy benefit or a motion benefit however not each collectively.
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