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
Face and neck development of the human embryo tendon, dermis, pia mater and arachnoid mater, sensory neurons, and glandular stroma. Pharyngeal arches are formed during the fourth week. Each arch consists of a mesenchymal tissue covered on the outside by ectoderm and on the inside by epithelium of endodermal origin. In human embryology, there are six arches which are separated by pharyngeal grooves externally and pharyngeal pouches internally. These arches contribute to the physical appearance of the embryo because they are the main components that build the face and neck. In addition, the muscular components of each arch have their own cranial nerve, and wherever the muscle cells