Systole heart beats—is cued by messages from the brain, reflecting the brain's responses to conditions of the body, such as pain, emotional stress, level of activity, and to ambient conditions including external temperature, time of day, etc. Electrical systole opens voltage-gated sodium, potassium and calcium channels in cells of myocardium tissue. Subsequently, a rise in intracellular calcium triggers the interaction of actin and myosin in the presence of ATP which generates mechanical force in the cells in the form of muscular contraction, or mechanical systole. The contractions generate intra-ventricular pressure, which is increased until it exceeds the external, residual pressures in
Cooperative Human Tissue Network given for 2008 through 2013, and the sixth for 2014-2019, with supplemental funding bridging the years in between grants. The name was changed in 2014 to the "Collaborative" Human Tissue Network. The CHTN obtains biospecimens from routine diagnostic or therapeutic surgical resections and autopsies, which otherwise would be discarded. Malignant, benign, diseased and normal biospecimens are collected and distributed to both national and international investigators. In addition, remnant body fluids are available on some patients and limited histological services can be obtained by special arrangement. Requests for large sample sizes, large numbers of biospecimens, rare biospecimens or biospecimens in high