NCC Certified Electronic Fetal Monitoring (C-EFM) Practice Exam

Marked variability in fetal heart rate is mediated by what activity?

1. Cholinergic activity

2. Adrenergic activity

3. Neural activity

4. Parasympathetic activity

The correct answer is: Adrenergic activity

Marked variability in fetal heart rate is primarily influenced by neural activity, which reflects the complex interplay of multiple systems that regulate heart rate fluctuations in the fetus. The autonomic nervous system, encompassing both sympathetic and parasympathetic branches, plays a significant role in this regulation. Neural activity affects the heart by integrating inputs from various sources, including baroreceptors, chemoreceptors, and higher brain centers. This integration allows for a dynamic response to changes in the fetus's environment and physiological state, resulting in variability in heart rate patterns. Sympathetic nervous system activity, often linked to adrenergic inputs, can enhance heart rate and overall cardiovascular dynamics. However, it is the balance and interplay of all these neural influences, particularly the dominant role of parasympathetic modulation through the vagus nerve, that lead to the characteristic variability seen in fetal heart rate. In this context, while adrenergic activity is involved, it is not solely responsible for the marked variability. The question focuses on the modulation of heart rate variability, which is more accurately attributed to overall neural activity, encompassing both the sympathetic and parasympathetic influences.