Question

Explain the concept of summation that occurs within excitable tissues. In your response, describe the methods of summation, the importance of summation and how responses from summation differ in the skeletal, smooth and cardiac muscles.

Answer 1

The concept of summation refers to the addition of multiple stimuli to produce a larger overall response in excitable tissues. Different methods of summation occur in skeletal, smooth, and cardiac muscles. Wave summation occurs in skeletal muscle, temporal summation occurs in smooth muscle, and spatial summation occurs in cardiac muscle.

Step-by-step explanation:

The concept of summation refers to the addition of multiple stimuli to produce a larger overall response in excitable tissues. In the case of muscles, there are different methods of summation that occur in skeletal, smooth, and cardiac muscles.

In skeletal muscle, summation occurs through wave summation. When a motor neuron fires action potentials rapidly, the tension produced in the muscle increases with each subsequent stimulus. This is because the second stimulus triggers the release of more calcium ions, which activate additional sarcomeres and result in a stronger contraction.

In smooth muscle, summation occurs through temporal summation. This involves multiple stimuli being delivered one after another in quick succession. The smooth muscle fibers respond by producing a sustained contraction.

In cardiac muscle, summation occurs through spatial summation. The heart is composed of individual cardiac muscle cells that are interconnected through intercalated discs. When one cell is stimulated, the electrical signal can spread to neighboring cells, leading to a coordinated contraction of the entire heart.