What is meant by altered automaticity?

Altered automaticity refers to changes in the heart's ability to generate electrical impulses, specifically through the pacemaker cells in the sinoatrial (SA) node and other parts of the heart. When automaticity is described as increased, it indicates that the pacemaker cells are firing at an elevated rate, which can lead to conditions such as tachycardia.

Increased firing rate of pacemaker cells can occur due to various physiological stimuli or pathologies, resulting in a faster heart rate. This concept is central to understanding how the heart can respond to different demands, such as increased activity or stress, by adjusting its rhythm through alterations in automaticity.

The other choices do not accurately reflect the concept of altered automaticity. A decrease in heart rate would suggest diminished automaticity rather than an alteration that increases frequency. Failure of impulse generation indicates a total halt in automaticity, which is opposite to the definition of increased automaticity. Decreased contraction strength does not specifically relate to the rate at which pacemaker cells fire; it focuses more on the force of heart muscle contractions rather than the electrical activity controlling the heart's rhythm.