Sports Science HL B.1.3 Sliding Filament Theory

Myofibrils

In muscle fiber, contain the contractile proteins that cause a muscle contraction. Made up of repeating units called sarcomeres.

Sarcomeres

Make up myofibrils, made of several proteins. These proteins are a thin actin filament, and a thick myosin filament.

SFT Step 1

Brain sends electrical impulse down motor neuron

SFT Step 2

Motor neuron releases acetylcholine at synapse

SFT Step 3

Muscle cells receives acetylcholine to cause action potential in muscle cell

SFT Step 4

Action potential causes release of calcium from sarcoplasmic reticulum

SFT Step 5

Calcium binds to troponin which moves contraction inhibitory protein tropomyosin so inhibition stops.

SFT Step 6

Tropomyosin no longer inhibiting muscle contraction, actin and myosin can interact and allow cross bridge

Control of Muscle Force

Central nervous system controls how much force is produced. Small units first followed by larger ones when necessary, coding of motor unit recruitment is the faster use of large motor units when very large forces are needed.