Muscle Contraction Cycle In the presence of calcium, myosin binds to the actin filaments. The myosin head flexes inward and backward, causing the actin filament to shorten. In the presence of ATP, the myosin head detaches and then reattaches at a new position on the actin filament. This cycle repeats to continue the shortening of the muscle (contraction).
Relaxation Calcium is pumped into sarcoplasmic reticulum. Crossbridges are detached from the thin filaments. Troponin-tropomyosin regulated inhibition of actin and myosin interaction is restored. Active tension disappears and the rest length is restored.
Muscle can only contract (pull on bone) can’t push bone in opposite direction Another muscle is required to pull bone in opposite direction Skeletal muscles act in antagonistic pairs You have two sets of muscles attached to many of your bones which allow them to move. Skeletal Muscle and Bones:
Attached to bones by tendons Moves bones Origin: Bone that does not move when muscle contracts Insertion: Bone that moves when muscle contracts The skeleton and muscles function together as the musculoskeletal system Skeletal Muscle and Bones:
Skeletal Muscle Biceps – Origin is scapula (2 places), Insertion is radius Triceps are antagonistic to the biceps
Joint Movement Terms ABDUCT vs. ADDUCT Away from the sagittal planeTowards the sagittal plane
Joint Movement Terms FLEXION vs. EXTENSION flexion extension hyperextend flexion neutral extend Flexion: decrease in joint angle