Skeleton, joints and antagonistic muscles – elbow lever and range of motion
BiologyHuman & Animal PhysiologyAges 13–14
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Sign in to playTap the bones of a human skeleton to see how they support the body, protect organs, allow movement and make blood cells in red bone marrow, and tap the joints to compare ball-and-socket, hinge, pivot, cartilaginous and fixed joints, their range of movement and the parts of a synovial joint. On the elbow lever, change the load, the biceps insertion distance and the elbow angle and use the principle of moments to find the muscle force while the biceps and triceps work as an antagonistic pair. Then measure range of motion with a virtual goniometer and record the results.
Lesson: The skeletal and muscular systems: functions of the skeleton, joints, antagonistic muscles and range of motion
What it shows
The skeleton supports the body, protects organs, allows movement and makes blood cells in red bone marrow. Bones meet at joints: fixed sutures, slightly movable cartilaginous joints and freely movable synovial joints such as hinge, pivot and ball-and-socket joints, where cartilage, synovial fluid, the capsule and ligaments reduce friction and keep the joint stable. Muscles pull on bones through tendons and work in antagonistic pairs, like the biceps and triceps. The forearm is a lever: by the principle of moments, the biceps force times its distance from the elbow equals the load times its distance. A goniometer measures a joint's range of motion.
How to use
On Skeleton, tap a bone or a joint ring and use the Show function buttons; for a synovial joint press Show joint structure. On Elbow lever, move the sliders, press Flex elbow or Extend elbow, then press Record. On Goniometer, drag the axis and both arms onto the limb, press Record reading at Start and End, then press Next volunteer.
Parameters you can change
- Starting screen Skeleton and joints, Elbow lever (moments), Goniometer (range of motion)
- Highlighted function None, Support, Protection, Movement, Making blood cells
- Load held in the hand 0–20 kg
- Distance from the elbow to the biceps insertion 2–8 cm
- Distance from the elbow to the load 20–40 cm
- Elbow angle 40–140 °
- Include the weight of the forearm
- Movement measured with the goniometer Elbow flexion, Knee flexion, Shoulder flexion (arm forwards), Hip flexion
Questions to explore
- Why must the biceps pull with a force many times the weight of a load held in the hand?
- Why is the hip joint more stable but less mobile than the shoulder joint?
- How could you make your goniometer measurements of range of motion more reliable?
