The T-tubule is present in this area.

It is composed of a single t-tubule paired with a terminal cisterna of the sarcoplasmic reticulum.

It has been applied to measure the action potentials of a single t-tubule of cardiomyocytes by Guixue Bu et al.

In cardiac muscle, the T-tubule membrane is normally opposed to a single terminal cisterna, which may wrap around the T-tubule.

Conversely, the mechanical interaction between the T-tubule's L-type calcium channel and the calcium-release channel is critical to proper skeletal muscle contraction, whereas it contributes little to the contraction of cardiac muscle.

Using confocal microscopy in conjunction with ANNINE-6plus, single sweep action potentials with high peak signal-to-noise ratio (SNR) have been recorded from single transverse tubule (t-tubule) of a few micrometers in the ventricular cardiomyocyte.