Nucleic acids Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are made up of nucleic acids found in the nuclei of living cells.They are the vehicles of genetic inheritance. Nucleic acids are condensation polymers of nucleotides.ucleic acids Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are made up of nucleic acids found in the nuclei of living cells.
After the ventricles complete their contraction phase, they relax and the SA node initiates another impulse to start another cardiac cycle. The Heart: Conduction System The heart pumps blood through the body This is accomplished by contraction and relaxation of the cardiac muscle tissue in the myocardium layer.
The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump. The SA node sends another signal to the atria to contract, which starts the cycle over again.