Mean arterial pressure parasympathetic nervous system

Figure 15.4 Effects of the autonomic nervous system on mean arterial pressure. The baroreceptors, chemoreceptors, and low-pressure receptors provide neural input to the vasomotor center in the brainstem. The vasomotor center integrates this input and determines the degree of discharge by the sympathetic and parasympathetic nervous systems to the cardiovascular system. Cardiac output and total peripheral resistance are adjusted so as to maintain mean arterial pressure within the normal range.

Figure 15.5 Effects of sympathetic and parasympathetic nervous activity on mean arterial pressure. The parasympathetic nervous system innervates the heart and therefore influences heart rate and cardiac output. The sympathetic nervous system innervates the heart and veins and thus influences cardiac output. This system also innervates the arterioles and therefore influences total peripheral resistance. The resulting changes in cardiac output and total peripheral resistance regulate mean arterial pressure.

Baroreceptors monitor the pressure in the carotid sinuses, the aortic arch, and other large systemic arteries and increase their firing rate when the pressure increases. Their response is nonlinear and depends on whether they are exposed to mean pressure only, pulsatile pressure only, or a combination of both. Katona et al. [1967] developed a model of baroreceptor feedback that has become the basis for many CV neural control models. The output of the baroreceptor model is often passed through a low pass filter representing the CNS and then mapped back to changes in heart rate, contractility, vascular resistances, and vascular unstressed volumes through the sympathetic and parasympathetic nervous systems (Figure 10.8), for example, see Yu et al. [1990]. 

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