Vygotsky's social account of psychology is comprehensible when viewed in relation to his political views and his early work experience. A brief discussion of this context is therefore in order before explaining the details of his psychological stand- point.
1 Central cyanosis and its causes are all associated with peripheral cyanosis. 2  Decreased pumping of blood by the heart or reduced cardiac output. 3  This is seen in heart failure or circulatory shock. 4  Diseases of circulation like thrombosis or embolism. 5  Constriction of blood vessels of the limbs, fingers and toes.
1 If the plasma Ca2+ decreases to less than 50% of the normal value of 9.4 mg/dl, action potentials may be spontaneously generated, causing contraction of peripheral skeletal muscles. Hypocalcemia is not a term for tetany but is rather a cause of tetany.  The usual cause of tetany is lack of calcium.