The effect of age and the influence of the relative size of the heart, brain, and blood oxygen store on the responses to submersion in mallard ducklings

1981 ◽  
Vol 59 (6) ◽  
pp. 986-993 ◽  
Author(s):  
Nigel H. West
Keyword(s):  
Heart Rate ◽  
Relative Size ◽  
The Self ◽  
Blood Oxygen ◽  
Allometric Relationships ◽  
Heart Rates ◽  
Oxygen Store ◽  
Arterial Blood ◽  
The Brain ◽  
Effect Of Age

Three newly hatched mallard ducklings showed profound bradycardia on head submersion. Heart rate fell from 485 beats∙min−1 predive to 75 beats∙min−1 after 30 s. Resting heart rates in a group of eight ducklings retested at weekly intervals fell from 430 ± 13 beats∙min−1 at one week after hatching to 183 ± 27 beats∙min−1 at 12 weeks. In spite of the wide difference in resting heart rates, the proportional fall in heart rate by 30 s after head submersion was very consistent, to some 20% of the predive rate. The absolute fall in heart rate during early submergence was much greater at 1 week than at 4 weeks. Previous experience with voluntary head submersion during feeding did not affect the heart-rate response.Predive mean arterial blood pressure, which rose from 77.1 mmHg at 1 week to 180.2 mmHg at 12 weeks was maintained constant, or rose slightly, during submersion in all the animals tested. The tolerance to prolonged submersion was markedly poorer in younger ducklings; birds at 1 week only tolerated some 67 s of apnoeic asphyxia before a breakdown of the circulatory adjustments, while at 12 weeks the same birds tolerated submersion for 240 s with no ill effects. This is partially due to the changing allometric relationships during development between the mass of the brain and the heart, major components of the oxygen sink during submergence, and the blood volume, a major component of the self-contained oxygen store.

scholarly journals Electrocardiographic Scaling Reveals Differences in Electrocardiogram Interval Durations Between Marine and Terrestrial Mammals

2021 ◽  
Vol 12 ◽  
Author(s):  
Rhea L. Storlund ◽  
David A. S. Rosen ◽  
Andrew W. Trites
Keyword(s):  
Heart Rate ◽  
Body Mass ◽  
Marine Mammals ◽  
Physiological State ◽  
P Wave ◽  
Breath Hold ◽  
Allometric Relationships ◽  
Heart Rates ◽  
Terrestrial Mammals ◽  
Qt Intervals

Although the ability of marine mammals to lower heart rates for extended periods when diving is well documented, it is unclear whether marine mammals have electrophysiological adaptations that extend beyond overall bradycardia. We analyzed electrocardiographic data from 50 species of terrestrial mammals and 19 species of marine mammals to determine whether the electrical activity of the heart differs between these two groups of mammals. We also tested whether physiological state (i.e., anesthetized or conscious) affects electrocardiogram (ECG) parameters. Analyses of ECG waveform morphology (heart rate, P-wave duration, and PQ, PR, QRS, and QT intervals) revealed allometric relationships between body mass and all ECG intervals (as well as heart rate) for both groups of mammals and specific differences in ECG parameters between marine mammals and their terrestrial counterparts. Model outputs indicated that marine mammals had 19% longer P-waves, 24% longer QRS intervals, and 21% shorter QT intervals. In other words, marine mammals had slower atrial and ventricular depolarization, and faster ventricular repolarization than terrestrial mammals. Heart rates and PR intervals were not significantly different between marine and terrestrial mammals, and physiological state did not significantly affect any ECG parameter. On average, ECG interval durations of marine and terrestrial mammals scaled with body mass to the power of 0.21 (range: 0.19–0.23) rather than the expected 0.25—while heart rate scaled with body mass to the power of –0.22 and was greater than the widely accepted –0.25 derived from fractal geometry. Our findings show clear differences between the hearts of terrestrial and marine mammals in terms of cardiac timing that extend beyond diving bradycardia. They also highlight the importance of considering special adaptations (such as breath-hold diving) when analyzing allometric relationships.

Effect of carotid sinus nerve stimulation pattern on cardiorespiratory responses

1976 ◽  
Vol 230 (4) ◽  
pp. 951-958 ◽  
Author(s):  
MN Levy ◽  
H Zieske
Keyword(s):  
Heart Rate ◽  
Carotid Sinus ◽  
Carotid Sinus Nerve ◽  
Intermittent Stimulation ◽  
Arterial Blood ◽  
Anesthetized Dogs ◽  
Carotid Sinus Nerve Stimulation ◽  
The Brain ◽  
Stimulation Pattern ◽  
Frequency Limitation

The reflex responses to steady and intermittent stimulation of the carotid sinus nerve (CSN) were compared in anesthetized dogs. Intermittent stimulation was less effective than steady stimulation in reducing the arterial blood pressure, and the disparity was exaggerated after acute sinoaortic denervation. With the sinoaortic nerves intact, at low mean stimulation frequencies the heart rate responses were greater during intermittent than during steady CSN stimulation. At higher mean stimulation frequencies, however, steady CSN stimuli were more effective than were the intermittent type. After sinoaortic denervation, steady stimuli evoked greater heart rate responses than did intermittent stimuli over the entire mean frequency range studied. Reflex changes in respiratory depth and frequency were also greater during steady than during intermittent CSN stimulation. The greater efficacy of steady than of intermittent stimulation in evoking.the observed reflex cardiovascular and respiratory changes is probably ascribable to the pronounced frequency limitation at the first synapse of the baroreceptor reflex in the brain.

Atrial natriuretic factor-induced vasodepression occurs through central nervous system

1988 ◽  
Vol 255 (3) ◽  
pp. H616-H622 ◽  
Author(s):  
E. R. Levin ◽  
M. A. Weber ◽  
S. Mills
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Nervous System ◽  
Fourth Ventricle ◽  
Saline Control ◽  
Arterial Blood ◽  
Adrenergic Antagonist ◽  
Adrenergic Nervous System ◽  
The Brain ◽  
Atrial Natriuretic

To characterize the blood pressure and heart rate effects of atrial natriuretic peptide (ANP) in the brain, we administered 20 micrograms/kg of atriopeptin III in 5 microliters of 0.9 normal saline into the fourth ventricle of awake, freely moving, spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. ANP produced a 13 +/- 1 mmHg decrease in mean arterial blood pressure (MAP) in the SHR (P less than 0.001 vs. base line or saline control, n = 10) and a 9 +/- 2 mmHg decrease in the WKY (P less than 0.02). Heart rate did not change significantly in response to ANP. To determine whether an interaction with the adrenergic nervous system played a role in the effects of ANP, we administered 100 ng yohimbine HCL, an alpha 2-antagonist, by intracerebroventricular injection, 45 min before ANP and completely prevented the ANP-induced decrease in MAP. In contrast, 100 ng intracerebroventricular prazosin, an alpha 1-adrenergic antagonist, had no significant influence on the MAP effect induced by ANP. A third group of SHR was pretreated with intracerebroventricular 6-OH dopamine to deplete central catecholamines or with saline. The rats pretreated with 6-OH dopamine (n = 6) had no significant response to ANP, which was administered 9 days later. This was significantly different from the saline-pretreated control group (n = 6), which responded with a 19 +/- 3 mmHg decrease in MAP (P less than 0.025). These studies indicate that the administration of ANP into the fourth ventricle of the brain decreases the MAP of rats through an interaction with the central alpha 2-adrenergic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Central inhibition of the aortic baroreceptors-heart rate reflex at the onset of spontaneous muscle contraction

2004 ◽  
Vol 97 (4) ◽  
pp. 1371-1378 ◽  
Author(s):  
Jun Murata ◽  
Kanji Matsukawa ◽  
Hidehiko Komine ◽  
Hirotsugu Tsuchimochi ◽  
Tomoko Nakamoto
Keyword(s):  
Heart Rate ◽  
Muscle Contraction ◽  
Brain Stem ◽  
Spontaneous Contraction ◽  
Adrenergic Blockade ◽  
Central Command ◽  
Decerebrate Cat ◽  
Arterial Blood ◽  
Passive Stretch ◽  
The Brain

Animals decerebrated at the precollicular-premammillary body level exhibit spontaneous locomotion without any artificial stimulation. Our laboratory reported that the cardiovascular and autonomic responses at the onset of spontaneous locomotor events are evoked by central command, generated from the caudal diencephalon and the brain stem (Matsukawa K, Murata J, and Wada T. Am J Physiol Heart Circ Physiol 275: H1115–H1121, 1998). In this study, we examined whether central command and/or a reflex resulting from muscle afferents modulates arterial baroreflex function using a decerebrate cat model. The baroreflex was evoked by stimulating the aortic depressor nerve (ADN) at the onset of spontaneous muscle contraction (to test the possible influence of central command) and during electrically evoked contraction or passive stretch (to test the possible influence of the muscle reflex). When the ADN was stimulated at rest, heart rate and arterial blood pressure decreased by 40 ± 2 beats/min and 11 ± 1 mmHg, respectively. The baroreflex bradycardia was attenuated to 55 ± 4% at the onset of spontaneous contraction. The attenuating effect on the baroreflex bradycardia was not observed at the onset and middle of electrically evoked contraction or passive stretch. The depressor response to ADN stimulation was identical among resting and any muscle interventions. The inhibition of the baroreflex bradycardia during spontaneous contraction was seen after β-adrenergic blockade but abolished by muscarinic blockade, suggesting that the bradycardia is mainly evoked through cardiac vagal outflow. We conclude that central command, produced within the caudal diencephalon and the brain stem, selectively inhibits the cardiac component, but not the vasomotor component, of the aortic baroreflex at the onset of spontaneous exercise.

Some effects of apneic underwater diving on blood gases, lactate, and pressure in man

1962 ◽  
Vol 17 (6) ◽  
pp. 938-942 ◽  
Author(s):  
C. Robert Olsen ◽  
Darrell D. Fanestil ◽  
Per F. Scholander
Keyword(s):  
Carbon Dioxide ◽  
Blood Pressure ◽  
Heart Rate ◽  
Pressure Rise ◽  
Blood Gases ◽  
Breath Holding ◽  
Blood Oxygen ◽  
Arterial Blood ◽  
Blood Pressure Rise ◽  
Arterial Blood Oxygen

Five men of outstanding diving ability performed apneic underwater dives in a specially fitted tank. The divers hyperventilated to extreme degrees of hypocapnia before submerging, and their arterial blood carbon dioxide tensions rarely rose above normal levels during a dive. Arterial blood oxygen content was 15.5 vol % or above at the end of two 3-min resting dives and of three 1.5-min exercise dives. Blood lactate concentrations increased during the latter half of exercise dives and reached peak values after surfacing. A rise in arterial blood pressure began by 10 sec in each dive and persisted, coincident with a falling heart rate, to the end of the dive. The rate of blood pressure rise was greater during a dive in water of 26 C than with breath holding by the same subject out of water. Some differences between the adaptations of diving men and of other diving mammals are briefly discussed. Submitted on April 2, 196

scholarly journals Respiratory and circulatory control during sleep.

1982 ◽  
Vol 100 (1) ◽  
pp. 223-244
Author(s):  
J H Coote
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Partial Pressure ◽  
Arterial Blood ◽  
Circulatory Control ◽  
Differential Pattern ◽  
Vascular Beds ◽  
The Brain

A survey of the literature on a large number of vertebrate animals shows that sleep is associated with profound cardiovascular and respiratory adjustments which are very similar in each species. A hypothesis is advanced that these adjustments are 'goal directed' by neural structures in the brainstem, to ensure an adequate O2 and CO2 transport to and from the brain whilst at the same time reducing energy cost. During synchronised sleep there is a vagal bradycardia leading to reduced cardiac output and a fall in blood pressure; despite this cerebral blood flow increases. During desynchronized sleep there is a tonic fall in blood pressure and heart rate resulting from a unique repatterning of sympathetic discharge, that to heart, kidney, splanchnic and pelvic vascular beds decreasing whilst that to skeletal muscle increasing; cerebral blood flow shows a further increase. This differential pattern is probably initiated by neurones located in the caudal raphe nucleus obscurus. Phasic increases in blood pressure and heart rate also occur during desynchronized sleep mainly as a consequence of increases in sympathetic activity. Ventilation decreases during synchronized sleep accompanied by an increase in partial pressure of arterial CO2, which vasodilates cerebral blood vessels, indicating that the influence of CO2 on the level of ventilation has changed. During desynchronized sleep ventilation increases and becomes very irregular but the partial pressure of O2 and CO2 in arterial blood is little changed from wakefulness. Control of respiration is shifted to a central generator which apparently is different to the automatic/metabolic one which is normally dominant during wakefulness. Reflex control of the circulation and respiration is mainly governed by peripheral chemoreceptors, the threshold of most other afferent inputs being significantly raised during sleep.

scholarly journals Anesthetic management of precise radiotherapy under apnea-like condition

2021 ◽  
Vol 49 (3) ◽  
pp. 030006052199026
Author(s):  
Shilong Zhang ◽  
Bin Zhao ◽  
Dongji Chen ◽  
Ying Qi ◽  
Youguo Ma ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oxygen Saturation ◽  
Anesthetic Management ◽  
Lung Tumors ◽  
Blood Oxygen ◽  
Blood Oxygen Saturation ◽  
Pharyngeal Wall ◽  
Oxygen Saturation Level ◽  
Arterial Blood

Objective To study the safety and feasibility of implementation of precise radiotherapy with inducement of an apnea-like condition. Methods Two patients with lung tumors underwent precise radiotherapy under an apnea-like condition. The apnea-like condition was induced 11 times between the two patients for tumor localization and treatment. The changes in the blood oxygen saturation, blood pressure, heart rate, and end-tidal carbon dioxide during the apnea-like periods were observed, and the incidence of adverse reactions was recorded. Results The average apnea-like time was 6.2 minutes (range, 3–9 minutes), and the average radiotherapy time was 4.6 minutes (range, 1–7 minutes). The lowest blood oxygen saturation level was 97%, with a change of <1%. The heart rate and average arterial blood pressure increased during the apnea-like periods. Contact sores appeared on the patients’ posterior pharyngeal wall after the first apnea-like period; no other adverse events occurred. Conclusion Precise radiotherapy under an apnea-like condition is safe and feasible for patients with lung tumors.

scholarly journals Focal acidosis in the pre-Bötzinger complex area of awake goats induces a mild tachypnea

2009 ◽  
Vol 106 (1) ◽  
pp. 241-250 ◽  
Author(s):  
K. L. Krause ◽  
H. V. Forster ◽  
S. E. Davis ◽  
T. Kiner ◽  
J. M. Bonis ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Pulmonary Ventilation ◽  
Respiratory Rhythm ◽  
Physiological Conditions ◽  
Arterial Blood ◽  
Bötzinger Complex ◽  
Chemosensitive Areas ◽  
The Brain ◽  
Insight Into

There are widespread chemosensitive areas in the brain with varying effects on breathing. In the awake goat, microdialyzing (MD) 50% CO2 at multiple sites within the medullary raphe increases pulmonary ventilation (V̇i), blood pressure, heart rate, and metabolic rate (V̇o2) ( 11 ), while MD in the rostral and caudal cerebellar fastigial nucleus has a stimulating and depressant effect, respectively, on these variables ( 17 ). In the anesthetized cat, the pre-Bötzinger complex (preBötzC), a hypothesized respiratory rhythm generator, increases phrenic nerve activity after an acetazolamide-induced acidosis ( 31 , 32 ). To gain insight into the effects of focal acidosis (FA) within the preBötzC during physiological conditions, we tested the hypothesis that FA in the preBötzC during wakefulness would stimulate breathing, by increasing respiratory frequency (f). Microtubules were bilaterally implanted into the preBötzC of 10 goats. Unilateral MD of mock cerebral spinal fluid equilibrated with 6.4% CO2 did not affect V̇i, tidal volume (Vt), or f. Unilateral MD of 25 and 50% CO2 significantly increased V̇i and f by 10% ( P < 0.05, n = 10, 17 trials), but Vt was unaffected. Bilateral MD of 6.4, 25, or 50% CO2 did not significantly affect V̇i, Vt, or f ( P > 0.05, n = 6, 6 trials). MD of 80% CO2 caused a 180% increase in f and severe disruptions in airflow ( n = 2). MD of any level of CO2 did not result in any significant changes in mean arterial blood pressure, heart rate, or V̇o2. Thus the data suggest that the preBötzC area is chemosensitive, but the responses to FA at this site are unique compared with other chemosensitive sites.

Effect of acetazolamide on cerebral blood flow and capillary patency

1992 ◽  
Vol 73 (5) ◽  
pp. 1756-1761 ◽  
Author(s):  
H. M. Frankel ◽  
E. Garcia ◽  
F. Malik ◽  
J. K. Weiss ◽  
H. R. Weiss
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Gases ◽  
Capillary Perfusion ◽  
Arterial Pco2 ◽  
Arterial Blood ◽  
Cerebral Capillary ◽  
The Brain

This study investigated the effects 2 h after administration of acetazolamide on cerebral blood flow and the pattern of cerebral capillary perfusion. Arterial blood pressure, heart rate, arterial blood gases, and pH were recorded in two groups of rats along with either regional cerebral blood flow or the percentage of capillary volume per cubic millimeter and number per square millimeter perfused as determined in cortical, thalamic, pontine, and medullary regions of the brain. Blood pressure, heart rate, and arterial PCO2 were not significantly different between the rats receiving acetazolamide (100 mg/kg) and the controls. Arterial blood pH was significantly lower in the acetazolamide rats. Blood flow increased significantly in the cortical (+ 102%), thalamic (+ 89%), and pontine (+ 88%) regions receiving acetazolamide. In control rats, approximately 60% of the capillaries were perfused in all of the examined regions. The percentage of capillaries per square millimeter perfused was significantly greater in the cortical (+ 52%), thalamic (+ 49%), and pontine (+ 47%) regions of acetazolamide rats compared with controls. In the medulla the increases in blood flow and percentage of capillaries perfused were not significant. Thus in the regions that acetazolamide increased cerebral blood flow, it also increased the percentage of capillaries perfused.

Effects of peripherally and centrally applied ghrelin on the oxidative stress induced by renin angiotensin system in a rat model of renovascular hypertension

2017 ◽  
Vol 28 (4) ◽  
Author(s):  
Vivian Boshra ◽  
Amr M. Abbas
Keyword(s):  
Oxidative Stress ◽  
Heart Rate ◽  
Renovascular Hypertension ◽  
Rat Model ◽  
Renin Angiotensin System ◽  
Angiotensin Ii Receptor ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Arterial Blood ◽  
The Brain

AbstractBackground:Renovascular hypertension (RVH) is a result of renal artery stenosis, which is commonly due to astherosclerosis. In this study, we aimed to clarify the central and peripheral effects of ghrelin on the renin-angiotensin system (RAS) in a rat model of RVH.Methods:RVH was induced in rats by partial subdiaphragmatic aortic constriction. Experiment A was designed to assess the central effect of ghrelin via the intracerebroventricular (ICV) injection of ghrelin (5 μg/kg) or losartan (0.01 mg/kg) in RVH rats. Experiment B was designed to assess the peripheral effect of ghrelin via the subcutaneous (SC) injection of ghrelin (150 μg/kg) or losartan (10 mg/kg) for 7 consecutive days. Mean arterial blood pressure (MAP), heart rate, plasma renin activity (PRA), and oxidative stress markers were measured in all rats. In addition, angiotensin II receptor type 1 (AT1R) concentration was measured in the hypothalamus of rats in Experiment B.Results:RVH significantly increased brain AT1R, PRA, as well as the brain and plasma oxidative stress. Either SC or ICV ghrelin or losartan caused a significant decrease in MAP with no change in the heart rate. Central ghrelin or losartan caused a significant decrease in brain AT1R with significant alleviation of the brain oxidative stress. Central ghrelin caused a significant decrease in PRA, whereas central losartan caused a significant increase in PRA. SC ghrelin significantly decreased PRA and plasma oxidative stress, whereas SC losartan significantly increased PRA and decreased plasma oxidative stress.Conclusions:The hypotensive effect of ghrelin is mediated through the amelioration of oxidative stress, which is induced by RAS centrally and peripherally.

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