![qarc whole ventricle qarc whole ventricle](https://heart.bmj.com/content/heartjnl/94/10/1357/F1.large.jpg)
All of these hypothalamic nuclei are located on both sides of the third ventricle ( Siegel and Sapru, 2011).Īmong other vital functions, the hypothalamus plays a critical role in the regulation of cardiovascular function ( Coote, 2004). The lateral nucleus extends from the tuberal to the posterior regions. The posterior nucleus and mammillary body are present in the posterior region. The periventricular, paraventricular (PVN), anterior, supraoptic, dorsomedial (DMN), ventromedial (VMN) and arcuate (Arc) nuclei are located in the tuberal region. The preoptic and suprachiasmatic nuclei are located in the anterior region.
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It is a complex structure and contains several groups of neurons. In the anterio-posterior direction, the hypothalamus can be arbitrarily divided into three regions: anterior, tuberal and posterior regions. The hypothalamus lies below the thalamus on both sides of the third ventricle and extends from the optic chiasm rostrally to the midbrain tegmentum caudally. Cardiovascular responses elicited by acupuncture have been reported to be mediated by direct and indirect projections of the Arc to the RVLM. Although the Arc is involved in mediating the cardiovascular responses to intravenously injected angiotensin II and angiotensin-(1-12), these effects may not be due to leakage of these peptides across the blood-brain barrier in the Arc instead, circulating angiotensins may act on neurons in the SFO and mediate cardiovascular actions via the projections of SFO neurons to the Arc. Some circulating hormones (e.g., leptin and insulin) may reach the Arc via the leaky blood-brain barrier and elicit their cardiovascular effects. Gamma aminobutyric acid type A receptors, neuropeptide Y1 receptors, and opiate receptors in the PVN mediate the depressor responses elicited from the Arc. The depressor responses to the Arc-stimulation are mediated via the hypothalamic paraventricular nucleus (PVN). The pathways within the brain mediating the pressor and tachycardic responses elicited from the Arc have not been delineated. Arc-stimulation elicits tachycardic responses which are mediated via inhibition of vagal input and excitation of sympathetic input to the heart. The pressor responses are mediated via increase in sympathetic nerve activity and involve activation of the spinal ionotropic glutamate receptors. The direction of cardiovascular responses (increase or decrease) elicited from the Arc depends on the baseline blood pressure. Both pressor and depressor responses can be elicited by the chemical stimulation of the Arc. Recently the hypothalamic arcuate nucleus (Arc) has been implicated in cardiovascular regulation.