Sympathetic nervous system mean arterial pressure effects

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.

They examined the adrenaline-like effect of a large number of compounds, and they found, on the whole, that approximation to adrenaline in the chemical structure is linked with an increase and a sharper specificity of the action. Barger and Dale introduced the term sympathomimetic, which means that the effects produced resemble those obtained by stimulation of the so-called sympathetic system of nerves. The study of the sympathomimetic amines represents one of the earliest and most successful attempts to correlate pharmacological action with chemical structure. The sympathomimetic action includes rise of arterial blood pressure, stimulation of the heart muscle, constriction of the arterioles and either stimulation or inhibition of smooth muscle. Some of the drugs also stimulate the central nervous system. 

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