A. Pacemaker cells located in the atria fire before the pacemaker cells in the ventricles. B. It takes time for hormones to diffuse from the atria to the ventricles to trigger contraction. C.The electrical signal generated in the right atrium is delayed at the AV node before passing to the ventricles. D.The ventricular muscle cells contract more slowly than the atrial muscle cells.
Drugs that break down a psychological barrier against doing other drugs are known as gateways drugs.
A very known gateway drug (or at least one that has been considered as such) is marijuana or weed. A drug that is being widely consumed in various countries and is also being sold as a legal drug in some countries.
I believe the answer is Phenotype.
Calcium and phosphorus build strong and flexible bones. A diet lacking these nutrients can lead to osteoporosis.
