Answer:
In general, it is possible to affirm that in areas where there is malnutrition there are high deficits in all the essential vitamins for humans. A characteristic poor diet in these countries occasionally lacks vitamins and with this malnutrition. However, the reports mainly focus on deficits of vitamin A and D because there are more investigations. Vitamins are essential substances for the body and its function and cannot be synthesized by the same body but must be ingested from food. Vitamin deficiency is considered serious because it causes blindness and even death.
It could be biased or misleading.
The main responsible for the delay among the atrial and
ventricular contractions is the action potential conduction velocity of the AV
node cells. If the atria and ventricles contract simultaneously, atria cannot
give any help in filling the ventricles, which is needed, especially in those
with stiff ventricles as in the elderly. Hence atria have to contract first and
then the ventricles.
