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
The Human Body (TV series) The Human Body (TV series) The Human Body is a seven-part documentary series, first shown on 20 May 1998 on BBC One and presented by medical scientist Robert Winston. A co-production between the BBC and The Learning Channel, the series looks at the mechanics and emotions of the human body from birth to death. The series was nominated for numerous awards, winning several, including three BAFTA awards, four RTS awards and a Peabody Award. Described as the BBC's "first major TV series on human biology", it took over two years to make and aimed to be the definitive set of