2 different reasons why two muscles that act across the same side of the same joint are not necessarily redundant? Explain your reasons in detail and give at one real example that illustrates each reason
Although this is not my area of expertise, what about a twisting motion of the limb?
I guess I need a detailed answer because its worth 50 marks
Two muscles that act across the same side of the same joint are not necessarily redundant due to the following reasons:
1. Functional differences: Even though two muscles may both contribute to the same joint movement, they may have slightly different functions and biomechanical roles. These differences can influence their specific roles during different movements or activities. For example, consider the biceps brachii and brachialis muscles in the upper arm, both of which flex the elbow joint. While the biceps brachii is responsible for overall elbow flexion and forearm supination (rotation of the forearm so that the palm faces up), the brachialis primarily contributes to pure elbow flexion. In this case, although both muscles contribute to the same joint movement, they have distinct roles and cannot fully substitute for one another.
2. Joint stabilization: Muscles not only generate movement at joints but also contribute to joint stability. While two muscles may act across the same joint to produce a movement, they may have different roles regarding joint stability. For example, consider the rotator cuff muscles in the shoulder joint. The supraspinatus and infraspinatus muscles both contribute to shoulder external rotation. However, the supraspinatus is primarily responsible for aligning the humeral head within the glenoid cavity, providing stability to the joint, while the infraspinatus helps to generate the external rotation force. In this scenario, both muscles are necessary to ensure both movement and stability of the joint.
Real-life examples:
1. Quadriceps and hamstrings in the knee joint: The quadriceps and hamstrings muscles act across the knee joint and are responsible for knee extension and flexion, respectively. Although they both influence knee movement, the quadriceps muscles are more involved in activities like walking, running, and jumping, while the hamstrings are primarily active during activities like bending down or kicking.
2. Tibialis anterior and tibialis posterior in the ankle joint: The tibialis anterior and tibialis posterior muscles both act across the ankle joint and contribute to ankle inversion (inward movement of the foot). However, the tibialis anterior plays a more significant role in ankle dorsiflexion (bringing the foot upward), while the tibialis posterior aids in maintaining the arch of the foot and providing stability during walking or running.
In conclusion, two muscles acting across the same side of the same joint may not be redundant due to functional differences and variations in their roles regarding joint stabilization. Understanding these distinctions is essential in recognizing the importance of each muscle for specific movements and activities.