The carotid sinus baroreceptor reflex was studied in 11 normotensive subjects, using a variable pressure neck chamber and correcting for imperfect pressure transmission to the carotid sinus. Decreased carotid baroreceptor stimulation caused a sustaineded rise in arterial pressure, and increased carotid baroreceptor stimulation caused a sustain fall. The responses were in linear relation to the ...

To identify the brain areas involved in central command, four monkeys were trained to attenuate the tachycardia of exercise while different brain sites affecting heart rate (HR) were simultaneously stimulated electrically. Among 24 brain sites located mostly in the limbic structures, we have identified four types of control systems that mediate cardiovascular and motor behavior during exercise....

In response to changes in central venous volume, changes in vagal efferent cardiac outflow have been demonstrated in animals but not in humans. In this study, frequency domains analysis was used to quantify modulation of heart rate by respiration and blood pressure in normal human adults undergoing mild central hypovolemic stress induced by blood donation and postural change. In supine subjects...

The bronchial hyperreactivity characteristic of asthma may be related to enhanced parasympathetic nervous activity. We postulated that an abnormality in the autonomic control of airway caliber might be reflected by a parallel change in the reflex control of heart rate. We examined the heart-rate variations induced by deep breathing (respiratory sinus arrhythmia), the Valsalva maneuver, and stan...

OBJECTIVE To investigate whether the time rate of change in heart rate i.e. cardiac acceleration, during aerobic exercise in human subjects could be used to differentiate vagal withdrawal from sympathetic stimulation. METHODS Fifteen male subjects exercised on a bicycle ergometer at 50 Watts (Step 1), then 100 Watts (Step 2), for 2 minutes each. RESULTS Heart rate (HR) was monitored from a ...

Decreased baroreflex sensitivity is an early sign of autonomic dysfunction in patients with type-1 diabetes mellitus. We evaluated the repeatability of a mild baroreflex sensitivity decrease in diabetics with respect to their heart rate. Finger blood pressure was continuously recorded in 14 young diabetics without clinical signs of autonomic dysfunction and in 14 age-matched controls for 42 min...

Dynamic heart rate control by parasympathetic nervous input involves feedback mechanisms and reflex bursting of efferent cardiac vagal fibers. Periodic vagal bursting induces phasic changes in sinoatrial cycle length and can entrain the pacemaker to beat at periods that may be identical to those of the vagal burst. We investigated the electrophysiological basis of these phenomena in isolated si...

Atrial fibrillation (AF) is the most prevalent arrhythmia in hospital emergency departments and is a serious disease associated with a twofold increase in morbidity and a high mortality rate. However, the management of AF in this scenario is variable and frequently inadequate. This is probably a consequence of the diverse clinical aspects and therapeutic options to consider in the management of...

For a given cardiac function, the cyclic blood pressure (BP) curve results from 2 different phenotypes: the mean arterial pressure (MAP), a steady component reflecting the resistance of the microvascular network, and pulse pressure (PP), another component corresponding to large artery stiffness and wave reflections. Around birth, cardiovascular (CV) survival is critically influenced by the coup...

BACKGROUND The overall effect of vasoactive drugs on blood pressure is determined by a combination of the direct effect on vascular tone and an indirect baroreflex-mediated effect, a baroreflex buffering of blood pressure. Differences in baroreflex function affect the responsiveness to vasoactive medications, particularly baroreflex buffering of blood pressure; however, the magnitude is not kno...