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
Human Tissue Authority and tissue from the living or the deceased for specified health-related purposes and public display. It also covers the removal of such material from the deceased. It lists the purposes for which consent is required (the "scheduled purposes"). The Act notably prohibited private individuals from covertly collecting biological samples, such as hair and fingernails, for DNA analysis, but excluded medical and criminal investigations from the offence. According to the Human Tissue Act, the HTA and its authority are governed by a code of conduct for the handling of human tissue, and the bodies of the deceased, but does not give