Final answer:
A sinusoidal FHR tracing is influenced by the autonomic nervous system's parasympathetic and sympathetic divisions, which slow down and speed up the heart rate, respectively. The rhythm is controlled by the sinoatrial node, with cardiac reflexes adjusting to the body's demands, influenced by various types of receptors and the limbic system.
Step-by-step explanation:
Sinusoidal Fetal Heart Rate (FHR) tracing is influenced by parasympathetic and sympathetic stimulation impacting normal sinus rhythm. When parasympathetic stimulation occurs, the heart rate (HR) slows down. Conversely, sympathetic stimulation leads to an increase in HR. Normal sinus rhythm is the regular, rhythmic contraction of the heart, driven by the sinoatrial node, which serves as the heart's natural pacemaker.
Signals initiate at this node and travel through the heart's conduction pathways causing the atria and ventricles to contract in sequence. This process can be modulated by various inputs to the cardiovascular center, which adjusts the balance between parasympathetic and sympathetic stimulation in response to the body's needs, as seen during increased physical activity.