Slide 1
Movement begins with a pull
Skeletal muscles transmit force to bones through tendons. Their coordinated pulls move joints and also help hold the body in position.
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Skeletal muscle is only one muscle type. Smooth muscle works in structures such as the digestive tract, while cardiac muscle forms the heart’s pumping tissue.
Slide 2
Smaller parts slide
Inside a muscle fibre, proteins called actin and myosin slide past one another. Many tiny interactions combine to produce tension.
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The repeating contractile unit is the sarcomere. Its boundaries move closer during shortening even though the main protein filaments do not need to become shorter themselves.
Slide 3
A signal opens access
A nerve signal triggers calcium release inside the muscle fibre. Calcium helps expose the sites where myosin can interact with actin.
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When the signal ends, pumps return calcium to storage. Relaxation therefore involves active cellular work rather than merely waiting for the muscle to run out of fuel.
Slide 4
The cycle requires energy
Myosin repeatedly attaches, pulls and detaches. ATP, a molecule used in cellular energy transfer, is required for this cycle to continue.
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ATP binding helps release myosin from actin before the next cycle. Energy is also needed to restore ion distributions, so muscular work includes maintaining the machinery as well as moving a load.
Slide 5
Movement is coordinated
A controlled movement depends on the timing and strength of several muscles. A muscle can also generate tension while holding a position.
More to Read
Tendons carry the force onward, while joints determine the possible movement. Studying muscle alone cannot explain every movement limit, because connective tissues and joint geometry contribute too.
Sources
- Health Lesson: Learning About Muscles
NIAMS, NIH
- Muscle Fiber Contraction and Relaxation
OpenStax, Rice University