Functions of the skeleton: support, protection, movement (levers), blood cell production, mineral storage.
The full notes, worked example and check questions for this subtopic are in the app.
Exam tip: For movement analysis give: joint, joint type, movement, plane, agonist and type of contraction.
B.1.2Muscles and contraction
Key terms
Sliding filament theory
Myosin heads bind to actin and pull it towards the centre of the sarcomere, shortening the muscle.
Agonist / antagonist
The muscle causing a movement / the muscle that relaxes or opposes it.
Concentric / eccentric
Muscle shortens under tension / lengthens under tension.
Isometric
Muscle produces tension without changing length.
Steps: action potential → calcium ions released from the sarcoplasmic reticulum → calcium binds troponin, moving tropomyosin → myosin binds actin (cross-bridge) → power stroke → ATP breaks the cross-bridge and resets the head.
The full notes, worked example and check questions for this subtopic are in the app.
Exam tip: When lowering a weight under control, the agonist is usually working eccentrically: a common trap.
B.1.3Levers
Key terms
Fulcrum
The pivot point of a lever (usually a joint).
Effort
The force applied (by muscles).
Load
The resistance to be moved.
Mechanical advantage
Effort arm ÷ load arm; above 1 means the lever can move a large load with less effort.
First class: fulcrum in the middle (neck nodding the head).
The full notes, worked example, interactive diagram and check questions for this subtopic are in the app.
Exam tip: Draw a quick lever sketch with F, L and E labelled: it makes the class obvious.