Fig. 1 shows a sports clinic image of the elbow joint of a person whose arm is bent to catch a ball. The labelled muscles work as an antagonistic pair. The ...
Question 1 Report
Fig. 1 shows a sports clinic image of the elbow joint of a person whose arm is bent to catch a ball. The labelled muscles work as an antagonistic pair. The humerus is the upper arm bone and the radius is one bone of the forearm.
(a) Name the muscles labelled X and Y. [2]
(b) Describe the movement of the forearm at the elbow when the person straightens their arm. [2]
(c) Explain how the muscles labelled X and Y cause the arm to bend at the elbow. [3]
(d) Complete the statements about this movement.
A muscle is attached to a bone by a __________. Muscles can only __________, so a second muscle is needed to pull the bone in the opposite direction. [2]
(e) Use Fig. 1 to name the type of joint at the elbow. [1]
Answer Details
(a) X is the biceps [1] and Y is the triceps [1].
(b) When the arm straightens, the forearm moves away from the upper arm and the angle at the elbow increases [1]. This movement is called extension [1].
(c) To bend the arm, the biceps contracts and shortens [1]. Its tendon pulls the radius, and therefore the forearm, upwards [1]. At the same time, the triceps relaxes and lengthens [1]. Antagonistic muscles work in opposite ways because muscles can pull but cannot push.
(d) A muscle is attached to a bone by a tendon [1]. Muscles can only contract or shorten [1].
(e) The elbow is a hinge joint [1], allowing movement mainly in one plane.
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