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Results for “Cardiovascular Physiological Phenomena”

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At least 19 recordsLinked to original sources
PubMed1977

Non-uniformity of regional vasomotor activity indicating the existence of 2 different systems in the sympathetic cardiovascular outflow.

In rabbits, 2 populations of sympathetic postganglionic fibres innervating the skin, heart, muscle and kidney could be classified by their different spike heights and their different susceptibility to noradrenaline and angiotensin amide. The ability of the 2 populations to respond to physiological stimuli in a highly differentiated manner leads to the assumption that 2 different systems in the cardiovascular sympathetic outflow exist.

Angiotensin II↗
PubMed1979

The physiological consequences of wearing industrial respirators: a review.

The American Industrial Hygiene Association (AIHA) and American Conference of Govermental Industrial Hygienists (ACGIH) Respiratory Protective Devices Manual, published in 1963, has as its primary source of physiological background the work of Silverman and co-workers performed during World War II. The adoption of permanent OSHA standards governing work tasks requiring workers to use respirators has created a need for further evaluation of the physiological effects of wearing a respirator. This review was undertaken to meet the need of an in-depth evaluation of the currently available psychophysiological data. It was concluded that it was of the utmost importance to develop a physiological and psychological medical screening examination to determine the capability of the worker to use a respirator.

Body Temperature Regulation↗
PubMed1978

Central adrenoceptors and cholinoceptors in cardiovascular control.

1. In cats anaesthetized with chloralose, adrenoceptor and cholinoceptor agonists and antagonists were localized to the posterior hypothalamus (PH), lateral medullary pressor area (LMPA) and spinal autonomic loci to delineate the role of central cholinoceptors and adrenoceptors in cardiovascular control. 2 All along the neuroaxis, the alpha-adrenoceptors seem to subserve an inhibitory and the beta-adrenoceptors a facilitatory role in cardiovascular control. There appear to be a predominance of alpha-adrenoceptors at the medullary level and beta-adrenoceptors at the hypothalamic level. 3 The nicotinic cholinoceptors at the hypothalamic, medullary and spinal levels were facilitatory, whereas muscarinic cholinoceptors were inhibitory for cardiovascular control. However, muscarinic receptors were undetectable at the posterior hypothalamus. 4 The central cardiovascular effects of nicotine are attributed to nicotinic receptor activation and release of central catecholamines. 5 There appears to be a relationship between central cholinergic and adrenergic mechanisms in cardiovascular control.

Animals↗
PubMed1979

Changes in penile volume during some cardiovascular reflexes and reactions in rabbit.

The effect of various cardiovascular reflexes and reactions on the plethysmographically recorded penile volume in rabbit was investigated. Stimulation of the aortic nerve or direct stimulation of the carotid sinus produced increase in penile volume, while carotid occlusion produced decrease. Brief volume load or protoveratrine given into the right atrium produced increase in penile volume. Asphyxia, hypercapnia, hypoxia, cyanide and lobeline produced decrease in penile volume, while hypocapnia increased it. Moderate blood taps decreased penile volume, while hypocapnia increased it. Moderate blood taps decreased penile volume. With the exception of the response to asphyxia all these reactions required intact vasomotor nerves. Clonidine increased penile volume if vasomotor nerves were intact but decreased it if the penis was decentralized. Penile volume decreased in shivering animals but increased on warming. Carotid occlusion impaired erectile responses to hypogastric and pelvic nerve stimulation. In certain experiments this effect was more pronounced in the latter case. It is concluded that the medullary neuron pool responsible for penile vasomotor tone participates in general reflex cardiovascular homeostasis and that this may have implications for normal erectile responses.

Animals↗
PubMed1979

Effect of intraventricular injection of transmitter substances and temperature on autonomic functions of conscious sheep.

1. Changes in cardiovascular and renal functions following injection of noradrenaline, 5-hydroxytryptamine and carbachol into one lateral cerebral ventricle were investigated in conscious sheep at ambient air temperatures of 0 and 40 degrees C. The dose rates used were known to produce predictable changes in thermoregulation in sheep. 2. The changes in body temperature, respiratory frequency and shivering caused by the intracerebroventricular (I.C.V.) injections of noradrenaline, 5-hydroxytryptamine and carbachol were as reported previously. 3. The cardiovascular and renal responses of the sheep at both high and low ambient temperatures were consistent for each transmitter indicating that these activities had no major dependence on the type of thermoregulatory response. 4. I.C.V. injection of noradrenaline increased heart rate and decreased pulse pressure but caused no change in mean arterial blood pressure (B.P.). Urine flow rate, sodium clearance, potassium clearance and osmolal clearance were decreased whereas solute-free water reabsorption was unaltered. 5. I.C.V. injection of 5-hydroxytryptamine caused no significant alterations in either cardiovascular or renal function. 6. I.C.V. injection of carbachol increased systolic and diastolic B.P., heart rate and haematocrit. Sodium, potassium and osmolal clearances were increased after administration of carbachol. 7. The changes in renal function after noradrenaline and carbachol injection could be explained by the concurrent changes in cardiovascular function.

Animals↗
PubMedDate not supplied

Modification of cardiovascular function in dogs by acupuncture: a review.

Acupuncture at Jen Chung (Go-26) in dogs under halothane anesthesia produces sympathomimetic-like effects on the cardiovascular system. This response can be inhibited by pretreatment with propranolol and to a lesser extent with phentolamine. Severe hypotension and cardiac arrest produced by hypoxia in dogs under halothane anesthesia can be reversed by acupuncture at Jen Ying (St-9). This also was interpreted as a sympathomimetic-like effect. Acupuncture at Tsu San Li (St-36) results in a parasympathomimetic-like effect on the cardiovascular system which can be inhibited by atropine. A parasympatholytic-like effect resembling that produced by atropine can be obtained in dogs with sinus arrhythmia and pulsus alternans by acupuncture at Yang Hsi (LI-5).

Acupuncture Therapy↗
PubMed1977

Heart rate and oxygen uptake response to angiotensin in the squirrel monkey at 10 degrees C.

Unanesthetized squirrel monkeys exposed to an ambient temperature of 10 degrees C showed elevations in total body oxygen consumption (VO2), systemic arterial blood pressure (BP), and heart rate (hr) above values recorded at 28 degrees C. Further elevation of BP in the cold by intravenous infusion of phenylephrine (5-50 microgram/kg-min) was accompanied by reduction in both VO2 and HR, and the changes in VO2 were proportional to those in HR. When BP was raised by intravenous infusion of angiotensin (0.05-1.0 microgram/kg-min), large elevations in BP were again accompanied by reductions in HR and VO2. However, for equivalent elevations in BP, the depressions in both HR and VO2 were much smaller with angiotensin than they were with phenylephrine. Previous studies in this laboratory have demonstrated that in response to experimental elevation of BP, reflexes originating at the sinoaortic baroreceptors depress not only HR but also VO2. The present results suggest that angiotensin modulates baro-reflexive responses to elevation in BP. The reductions in HR and VO2 that ordinarily occur in response to baroreceptor stimulation may be modified by an action of angiotensin on the central nervous system.

Angiotensin II↗
PubMed1975

Development of autonomic control of fetal circulation.

Development of parasympathetic and sympathetic reflexes controlling heart rate, vascular pressures, and blood flows was investigated in fetal lambs weighing 300-5,800 g (65-165 days' gestation). Cardiovascular responses to veratridine injections, atrial stretching, bilateral cervical vagotomy, and cholinergic blockade with atropine were used to test parasympathetic activities. Responses to propranolol and phenoxybenzamine were used to test beta- and alpha-adrenergic activities. Autonomic ganglionic blockade and stimulation provided additional information on both cholinergic and adrenergic systems. Fetal responses to various tests were compared to those of the mother. Results show: a) little parasympathetic tone on resting heart rate and other circulatory functions exists prior to fetal maturity; b) despite the feeble resting tone, the parasympathetic system is capable of exerting significant control when stimulated in both premature and mature fetuses, the capability increases as fetus approaches term; c) alpha- and beta-adrenergic tone in control of resting heart rate and peripheral circulation exists in early fetal life and increases as the fetus reaches maturity, and both adrenergic receptors respond strongly to stimuli in immature, premature, and mature fetuses; d) in immature fetuses, veratridine does not elicit a vagally mediated reflex; instead, it produces a centrally mediated alpha- and beta-adrenergic stimulation; e) the fetal cardiovascular response to any given test is dampened by the existence of the various vascular shunts, the umbilicoplacental circulation and, possibly, by incomplete maturation of vasomotor tone.

Anesthetics↗
PubMed1977

Properties of the laryngeal chemoreflex in neonatal piglets.

Cardiorespiratory reflex responses to laryngeal chemoreceptor stimulation were studied in 62 piglets of both sexes varying in age from 1 to 79 days. The distal trachea was cannulated to provide a free airway and the proximal end used to introduce fluids into the laryngeal area. Introduction of either water or milk produced apnea, bradycardia, and hypertension. Swab application of test fluids to the laryngeal epithelium produced similar responses. The reflex could be interrupted by flushing the laryngeal region with saline, by cutting the superior laryngeal nerves (SLN) or by anesthetizing the laryngeal epithelium with lidocaine. Electrical stimulation of SLN elicited identical responses. Respiratory inhibition by the reflex was enhanced following central depression with chloralose and overridden by administration of the respiratory stimulant, aminophylline. The relative potency of the laryngeal reflex was estimated to be equivalent to about 40% of the dose of chloralose which produced permanent respiratory arrest. It is concluded that in circumstances where respiratory drive is reduced the laryngeal inhibitory reflex is capable of caused persistent apnea and asphyxial death in the young piglet.

Aminophylline↗
PubMed1978

Cardiovascular reactivity of neonatal and adult sheep to autonomic stimuli during adrenergic depletion.

The cardiovascular responses of the neonatal and adult sheep to autonomic agonists and antagonists were studied in the resting state and following adrenergic neuronal depletion with reserpine. Both the neonates and adults showed similar supersensitivity of the effector system of the peripheral circulation to alpha adrenergic stimulation with catecholamines. In addition, the neonates exhibited supersensitivity of the myocardial effector system to beta-adrenergic stimulation. Unusual finding was a marked supersensitivity of the heart and peripheral circulation to cholinergic receptor blockade with atropine, the mechanisms of which are as yet unclear.

Acetylcholine↗
PubMed1979

Comparison of cardiovascular reflexes of the newborn and adult opossum.

Neural control of the cardiovascular system was compared in the newborn and adult opossum by measuring changes in blood pressure and heart rate following carotid arterial occlusion and vagal stimulation. The percent change in blood pressure of the newborn was not significantly different from that of the adult following these procedures. This would indicate that even though the newborn opossum is incompletely developed for some time after birth, its neural development was adequate for control of the cardiovascular system.

Age Factors↗