Muscle Physiology
Start with the big picture
In skeletal muscle, calcium binds troponin-C, shifting tropomyosin to expose actin’s myosin-binding sites. ATP-dependent cross-bridge cycling then shortens sarcomeres. Excitation–contraction coupling links T-tubule depolarization to calcium release from the sarcoplasmic reticulum, while SERCA supports calcium reuptake. Muscle mechanics include length–tension and force–velocity relationships, isometric and isotonic contractions, and the effects of summation and tetanus. Recruitment and fatigue add further context for how muscle output is regulated. Cardiac muscle uses calcium influx to trigger further calcium release and has a long refractory period that prevents tetanus. In smooth muscle, calcium–calmodulin activates myosin light-chain kinase; relaxation and the latch state provide additional contrasts with striated muscle.
What you'll learn
- Describe how calcium and troponin-tropomyosin regulate actin–myosin interaction.
- Outline skeletal muscle excitation–contraction coupling and calcium handling.
- Distinguish key muscle mechanics, including length–tension and force–velocity relationships.
- Compare contraction and relaxation mechanisms in skeletal, cardiac, and smooth muscle.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
