BIO325H5 Lecture 5: Hydrostatic Skeleton
Document Summary
Hydrostatic skeletons: polyps, gv cavity; nematode, pseudocoelom; coelom, metamerism, burrowing; haemocoel, cfhct of kier, worm curve. Muscles need to be returned to their pre- contracted state. Mostly a different muscle but sometimes an elastomer. The mandible of a locust, is anchored by two articulations to the insect"s head [condyles fit into sockets- green x= location] These two points define an axis of rotation. Mandible pivots about this axis, completing an arc of a circle, adducted in the direction of the midline by the force of an adductor muscle. Red arrow (f)= magnitude & direction of force vector. Action crushes food against the opposite mandible. The mechanical advantage equals the moment arm of the effort (the distance between effort & fulcrum) divided by the moment arm of the load (the distance between load & fulcrum). Most of the levers associated with muscles operate with mechanical advantages less than 1- literally. Force advantage: effort multiplied by lever (ratio)
