Wilson central terminal

Because this is an unsolvable problem, the ideal unipolar lead does not exist. Nonideal solutions are to use one electrode at some remote point (e.g., at a limb or an earlobe). Another solution is to add the voltages picked up by more than one electrode, such as two limb electrodes (augmented leads) or three limb electrodes (Wilson central terminal). 

Other Lead systems are also possible and have been standardized into what is known as the 12-lead system that constitutes the clinical ECG. In addition to leads I, II, and m, there are three others known as the augmented leads aVR, aVL, and aVF. These leads use an electric addition process of the limb-electrode signals to create a virtual signal reference point in the center of the chest known as the Wilson central terminal (WCT). From the WCT reference point, the augmented lead vectors point to the right arm, left arm, and left leg, respectively. 

Neutral PU electrodes are also called indifferent or reference electrodes. A PU electrode may be more or less indifferent depending on its area and position with respect to signal sources. The ideal unipolar models presuppose an enormous spherical neutral electrode, infinitely far away and at zero potential. In a limited tissue volume such as the human body, the ideal indifferent electrode is not feasible, and we use flie concept of quality of an indifferent electrode. A practical approach is to take the average potential of several electrodes (e.g., Wilson s central terminal in ECG). It is not ideal to connect electrodes of different potentials resulting in exchange current flow between them, but each electrode may first be connected to a buffer amplifier. 

Copper is absorbed from food in the upper small intestine. The absorption is primarily dependent on the quantity of the copper present in the diet. High intake of zinc diminishes copper absorption by inducing metallothionein formation in the mucosal cells. Metallothioneins, due to their high affinity for copper, bind it preferentially and the bound copper is lost during the sloughing of cells from the villi. Copper accumulation in patients with Wilson s disease can be reduced by giving oral zinc acetate, which decreases absorption (discussed later). Absorbed copper is transported to the portal blood where it is bound to albumin (and probably transcuprein), amino acids, and small peptides. Copper binds to albumin at the N-terminal tripeptide (Asp-Ala-His) site. The recently absorbed copper is taken up by the liver, which plays a central role in copper homeostasis. 

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