Final answer:
The staircase effect, known as treppe, is a warm-up phenomenon in skeletal muscles, which leads to stronger contractions due to increasing Ca2+ concentrations and efficient cross-bridge formation.
Step-by-step explanation:
The staircase effect, or treppe, represents a warm-up effect due to increasing intracellular calcium concentrations. This phenomenon occurs in skeletal muscles that have been at rest and are then stimulated to contract. The initial contractions are weaker, but as the muscle continues to contract, the force of contraction increases, much like ascending a staircase. This effect is believed to result from a higher concentration of Ca2+ ions in the sarcoplasm. When the skeletal muscle contracts, calcium ions released from the sarcoplasmic reticulum bind to the regulatory protein troponin within the muscle fibers, allowing myosin to form cross-bridges with actin, leading to muscle contraction.
Treppe is observed when a skeletal muscle experiences a series of stimuli at a frequency that allows complete relaxation between contractions. The increase in tension and contraction efficiency during treppe is due to the successive availability of calcium in the muscle, enhancing the formation of cross-bridges. The continued release of calcium ions, coupled with steady signals from the motor neuron, and a sufficient supply of ATP, are necessary to sustain this effect.