sacral region. The prevertebral ganglia, which lie midline and anterior to the aorta and vertebral column, include the celiac, aorticorenal, and superior and inferior mesenteric ganglia. The third group of ganglia comprises the previsceral or terminal ganglia, which are located close to the target organs of the sympathetic nervous system. The previsceral ganglia have long preganglionic fibers and short postganglionic fibers. In contrast, the paravertebral and prevertebral ganglia give rise to long postganglionic fibers, which extend to the target organs of the sympathetic nervous system (e.g., heart, lungs, vascular smooth muscle, liver, kidneys, bladder, and reproductive organs; see Fig. 3-4). Of particular importance to the control of blood pressure are the sympathetic receptors located in the heart, vasculature, kidneys, and renal medulla.
Table 3-1 ▪ CARDIOVASCULAR EFFECTS OF AUTONOMIC NERVOUS SYSTEM INNERVATION
for 10% to 20% of vasodilation in response to hyperthermia.67,68,73 Cholinergic nerves, which innervate the sweat glands, release a yet to be described co-transmitter that may be functionally linked to the large and important active cutaneous vasodilation seen in heat stress.69,73,74 Additionally, under conditions of hyperthermia, nitric oxide is necessary for the vasodilatory response.69 Endothelial nitric oxide (eNOS) is responsible for vasodilation in response to local cutaneous heating,75 whereas neuronal nitric oxide (nNOS) is responsible for vasodilation in response to whole-body heating.76 The cutaneous veins constrict in response to local cold and are reflexly constricted in response a decrease in skin or core body temperature.77
effects.81 The direct effects are secondary to occupation of the β-adrenergic receptors and inhibition of norepinephrine release, and the indirect effects occur through inhibition of the adrenergic second messenger cAMP.82,83 There are also M1, M3, and M5 receptors in the heart, which may have pharmacologic implications.84 Of clinical importance, the negative chronotropic and inotropic effects associated with the M2 receptor are blocked by atropine.
(effect greater on the arteries than the veins) as well as positive inotropic (particularly in the right atria and ventricle) and chronotropic effects.96,97 VIP-induced peripheral vasodilation is caused by increased calcium-extrusion or sequestration induced by VIP or natriuretic protein-C receptor stimulation. This peripheral vasodilation enhances the VIP-mediated inotropic effects.98
levels of ANP may offset the detrimental effects of increased angiotensin-aldosterone and the sympathetic nervous system.111,119