Final answer:
The presence of gap junctions in the heart prevents summation from occurring in cardiac muscle.
Step-by-step explanation:
The presence of gap junctions in the heart prevents summation from occurring in cardiac muscle. Hence the correct answer is option B
Summation is a phenomenon in skeletal muscle where repeated stimulation results in an additive effect on the force of contraction. However, in cardiac muscle, gap junctions allow the quick transmission of action potentials from one cardiac muscle cell to the next, resulting in a coordinated contraction of the entire heart. This prevents the occurrence of summation and ensures that the heart contracts as a single unit.
Hence the correct answer is option B