MCAT Question A Day - 9/1/14 - Answer!
Muscles cause movement at joints by:
A. inciting neurons to initiate an electrical "twitch" in tendons.
B. increasing in length, thereby pushing the muscle's origin and insertion farther apart.
C. filling with blood, thereby expanding and increasing the distance between the ends of a muscle.
D. decreasing in length, thereby bringing the muscle's origin and insertion closer together.
D is correct. Muscles cause movement by contracting (eliminating B and C), bringing origin and insertion closer together, usually by moving the insertion. Neurons cause contractions in muscles, not tendons, and the neural signals are not initiated by the muscle. This eliminates A.
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D is correct. Muscles cause movement by contracting (eliminating B and C), bringing origin and insertion closer together, usually by moving the insertion. Neurons cause contractions in muscles, not tendons, and the neural signals are not initiated by the muscle. This eliminates A.
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