For 10 points, name this kind of tissue that is responsible for producing the contractions of a beating heart.
RyR-2 and JP-2 are proteins most prevalent in this type of tissue. Membrane-bound granules containing the precursor to an aldosterone antagonist are found at both poles of the nuclei in one type of this tissue.  This tissue's function is governed by the (*) Frank-Starling law, and it often appears as diads instead of the triads found in a similar type of tissue.  Intercalated disks hold together the cells of this tissue.  An extensive sarcoplasmic reticulum network is responsible for the long refractory period of cells of this tissue, some of which are autorhythmic and some of which must be depolarized through a signal from the SA node.  For 10 points, name this kind of tissue that is responsible for producing the contractions of a beating heart.
RyR-2 and JP-2 are proteins most prevalent in this type of tissue.
{cardiac muscle} [prompt on things like {muscle}, as RyR-2 and JP-2 are most abundant in the cardiac type] (1) [DW]