13.8 : Regulation of the Cardiovascular System

The regulation of the cardiovascular system allows the body to adapt to various demands and maintain homeostasis.

The regulation of the cardiovascular system involves the autonomic nervous system (ANS), baroreceptors, and chemoreceptors, ensuring that heart rate and blood pressure are appropriately modulated in response to varying physiological demands.

The ANS comprises two main divisions: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system enhances cardiovascular function by increasing heart rate, accelerating impulse conduction through the atrioventricular (AV) node, and strengthening atrial and ventricular contractions. Beta (β)-adrenergic receptors intervene in these effects, which respond to norepinephrine and epinephrine. Conversely, the parasympathetic nervous system, primarily through the vagus nerve, slows heart rate by reducing impulses from the sinoatrial (SA) node and decelerating conduction through the AV node. This balance between sympathetic and parasympathetic input is vital for the dynamic regulation of heart rate.

Baroreceptors in the aortic arch and carotid sinus are sensitive to changes in arterial pressure. When these receptors detect increased pressure, they relay signals to the brainstem's vasomotor center, reducing sympathetic activity and increasing parasympathetic influence. This results in decreased heart rate and vasodilation. Conversely, a drop in arterial pressure prompts the opposite response, enhancing sympathetic outflow to increase heart rate and induce vasoconstriction, stabilizing blood pressure.

Chemoreceptors are strategically positioned in the aortic, carotid, and medulla bodies. These receptors respond to fluctuations in blood chemistry, particularly elevated levels of carbon dioxide (hypercapnia), decreased pH (acidosis), and reduced oxygen levels (hypoxia). Activating chemoreceptors stimulates the vasomotor center to increase blood pressure, primarily by enhancing sympathetic stimulation. This increases heart rate and myocardial contractility, Ensuring sufficient oxygen delivery and removing carbon dioxide from tissues.