Final answer:
The duration of the cardiac cycle can be influenced by exercise, medications, hormones, and emotions. These factors impact heart rate and stroke volume, thus affecting the phases of systole and diastole within the cycle. An ECG can measure the electrical impulses of the heart and show the influence of these factors.
Step-by-step explanation:
The duration of the cardiac cycle can be affected by several factors including exercise, medications, hormones, and emotions. During exercise, the heart rate increases to supply more oxygenated blood to meet the demands of the muscles, leading to a shorter cardiac cycle duration. Medications can alter heart rate and blood pressure, affecting the cardiac cycle.
Hormones like epinephrine and thyroid hormones accelerate heart rate, thus impacting the cycle duration. Emotions can trigger changes in heart rate through the autonomic nervous system, influencing the cardiac cycle as well. Together, these factors affect both heart rate (HR) and stroke volume (SV), which are critical components of the cardiac cycle.
Systole is the phase of the cardiac cycle where the heart contracts, pushing out blood to the body. The duration of systole can be influenced by these factors, alongside diastole, the period of relaxation and filling of the heart chambers. The balance between these phases determines the overall length of the cardiac cycle.
Additionally, electrocardiograms (ECGs) measure the electrical impulses in the heart and can indicate how these various factors have influenced the heart's function. Factors such as increased levels of calcium, temperature changes, or conditions like hypoxia can also affect heart rate and rhythm.