these observations are consistent with a ca-release mechanism in cardiac excitation-contraction coupling in which 1 ) the ca-release process can be modulated by membrane potential or 2 ) the ca entering the cell via ca channels has a preferential access [ compared with ca from the sarcoplasmic reticulum ( sr ) ] to the site ( s ) that control sr ca release .
C0007634
the cell
C0036226
sr