Sliding filament theory
Length-tension relationship
Skeletal Muscle | Cardiac Muscle | |
---|---|---|
Structure | Fibres are 10-100um diameter. Each fibre is the length of the muscle | Network of branching fibres connected by intercalated discs (low resistance gap junctions), allowing for synchronised depolarisation. Called a functional syncytium |
AP Duration | Short | Long |
Summation / Tetanus Possible? | Yes | No |
AP Spread | Fibres stimulated independently | AP spreads between muscle fibres via the gap junctions |
Excitation-Contraction Coupling | Ca2+ released into cytoplasm from sarcoplasmic reticulum | Ca2+ enters cytoplasm from from SR and extracellular fluid |
Pacemaker Activity | None. Cannot contract without nerve stimulation | Action potentials originate from pacemaker cells in heart |