Question
The diagram shows a section through part of the leg of an insect and antagonistic muscles X and Y. The tibia moves in the direction shown by the arrow when the muscle is flexing.
(a) Outline a reason for the muscles being described as antagonistic.
(b) Describe the role of muscle Y.
(c) Outline how the muscle attachment of insects differs from humans.
(d) Explain the role of calcium ions in muscle contraction.
Answer/Explanation
Ans:
(a)
cause opposite movements / pull in opposite directions / when one contracts the other
relaxes;
(b)
a. flexor/flexion;
b. bends/flexes the leg/limb/joint;
(c)
insect muscle is attached inside (the skeleton) and human muscle outside (the skeleton);
insect muscle is attached to exoskeleton and human to endoskeleton/bones;
(d)
a. calcium released from sarcoplasmic reticulum;
b. calcium binds to troponin;
c. causes tropomyosin to move;
d. uncovers binding sites;
e. myosin heads bind to the actin forming cross bridges;