Heart autonomic regulation

In an attempt to clarify further the cardiotoxicity of paclitaxel, its effect on cardiovascular autonomic regulation has been investigated in 14 women (21). The authors concluded that autonomic modulation of heart rate is impaired by paclitaxel, but they were unable to say whether it would return to normal on withdrawal. They also investigated the effect of docetaxel on neural... 

Because ACTH synthesis originates from the POMC precursor peptide, its production by the pituitary is closely tied to the secretion of endogenous opiate peptides, such as P-endorphin. The physiological effects of endogenous opiates include (1) sedation, (2) an increased threshold of pain, and (3) autonomic regulation of respiration, blood pressure, and heart rate. These peptides are also involved in modifying endocrine responses to stress and water balance... 

Equally as important, and potentially more clinically relevant, are the indirect mechanisms responsible for the antiarrhythmic activity of calcium inhibitory agents, including coronary vasodilation and subsequent increases in coronary artery blood flow (47, 114, 124, 157) decreased cardiac contractility, metabolism, and arterial vasodilation resulting in decreases in myocardial oxygen consumption and wall tension (92) and reflex alterations in autonomic regulation of heart rateToverdrive supression) and AV conduction (114) ... 

This study demonstrates that in situ somatic reprogramming can stimulate proper chronotropic heart function in a large-animal model of complete heart block. The gene delivery techniques were consistent with routine clinical practice in which venous access is considered the safest route for electronic pacemaker implantation [44]. The TBX18 biological pacemaker was superior to an electronic pacemaker in its responsiveness to the circadian rhythm and autonomic regulation, showing features of the native SAN. 

Nearing BD, Verrier RL. Simultaneous assessment of autonomic regulation and cardiac vulnerability during coronary occlusion and reperfusion by complex demodulation of heart rate variability and T-wave alternans. Circulation 1992 86(suppl I) I639. 

Vasomotor center. Autonomic nervous activity to the cardiovascular system is regulated by the vasomotor center (see Figure 15.4). Located in the lower pons and the medulla of the brainstem, the vasomotor center is an integrating center for blood pressure regulation. It receives several sources of input, processes this information, and then adjusts sympathetic and parasympathetic discharge to the heart and blood vessels accordingly. 

Physiologically, in both normal and hypertensive individuals, blood pressure is maintained by moment-to-moment regulation of cardiac output and peripheral vascular resistance, exerted at three anatomic sites (Figure 11-1) arterioles, postcapillary venules (capacitance vessels), and heart. A fourth anatomic control site, the kidney, contributes to maintenance of blood pressure by regulating the volume of intravascular fluid. Baroreflexes, mediated by autonomic nerves, act in combination with humoral mechanisms, including the renin-angiotensin-aldosterone system, to coordinate function at these four control sites and to maintain normal blood pressure. Finally, local release of vasoactive substances from vascular endothelium may also be involved in the regulation of vascular resistance. For example, endothelin-1 (see Chapter 17) constricts and nitric oxide (see Chapter 19) dilates blood vessels. 

Note The autonomic nervous system (ANS) regulates the functions of internal viscera such as the heart, blood vessels, digestive organs, and reproductive organs. 

The catecholamines (named for the catechol moiety that is part of their structure, Figure 10.1) are important in both the peripheral autonomic system and the central nervous system. Key functions in the periphery are regulation of heart rate and blood pressure. In the brain, they are involved in the regulation of posture and movement, and of psychical functions such as mood and alertness. 

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