|  | Conditions Treatments | Heart Disease

What Are the Four Properties of Cardiac Tissue?

In the body, there are three distinct types of muscle tissue. Skeletal muscle contracts to perform external body movements. Smooth muscle causes peristaltic waves in veins, arteries and the alimentary canal. Cardiac muscle causes the heart to beat. Characteristics of cardiac muscle include striation, i.e., alternating light and dark bands perpendicular to the fiber; centrally located nuclei; branched cells; and intercalated discs, which separate individual cells. Properties of cardiac muscle are slightly different. They include excitability, conductivity, contractility and rhythmicity.

  1. Excitability

    • Excitability is the ability of cardiac muscle to respond to an appropriate amount of stimuli and generate an action potential---an electrical pulse that spreads across the entire heart, causing a single beat. Heart beats are measured in two portions. Systole refers to the contraction portion of a heart beat. Diastole refers to the relaxation portion. Systole actually initiates a few milliseconds before the action potential travels across the heart.

    Conductivity

    • Conductivity is the cardiac muscle's ability to transfer the action potential from muscle cell to muscle cell originating at the sino-atrial (SA) node---the pacemaker of the heart. An action potential from the SA node travels through the heart at a rate of 0.8 to 1 meter per second. The action potential moves from cell to cell via the intercalated discs that bridge the gap between cells.

    Contractility

    • Contractility is the ability of cardiac muscle to convert an electrical signal into mechanical action. The strength with which the cardiac muscle contracts determines the heart's pumping ability. Cardiac muscle cells act as one unit, forming a "functional syncytium" and contracting harmoniously, according to a presentation by King Saud University.

    Rhythmicity

    • Rhythmicity is the cardiac muscle's ability to contract at regular intervals without innervation, i.e., nerve supply. Action potentials originate in the SA node, which is a collection of cardiac muscle cells, rather than by nervous activity. The action potential propagates through the cells without neural input.

Heart Disease - Related Articles