...: The dive response is autonomically regulated, but many vertebrates can cognitively control cardiac function depending on the anticipated next dive. Here, we review the cognitive component of the diving response. Diving Breath holding Reflex Cognition Bradycardia Tachycardia Apnoea Ventilation...

... to a stepwise decrease in water oxygen level (100% to 30% air saturation) to determine the oxygen level at which bradycardia occurred. Resting f H was much lower in free-swimming fish than in those in respirometers (∼49 versus 69 beats min −1 ) and this was reflected in their scope for f H (∼104 versus 71 beats...

...-conserving mechanisms that support diving are underdeveloped at birth in pinnipeds and cetaceans. This Review explores how underdeveloped physiology makes immature marine mammals vulnerable to disturbance. Acidosis Blood Bradycardia Cetacean Dive response Heart rate Hypercarbia Hypoxia...

...Siri L. Elmegaard; Birgitte I. McDonald; Peter T. Madsen ABSTRACT Pronounced dive responses through peripheral vasoconstriction and bradycardia enable prolonged apnoea in marine mammals. For most vertebrates, the dive response is initiated upon face immersion, but little is known about the physical...

... of these factors on diving heart rate are poorly understood because of the difficulty of parsing their relative contributions in diving pinnipeds. Here, we examined the effects of apnea and external sensory inputs as autonomic drivers of bradycardia. Specifically, we hypothesized that (1) water stimulation...

..., this cannot be done without a certain degree of bradycardia to compensate for the ensuing increase in peripheral vascular resistance, and that is what is observed in most voluntary dives (e.g. Kooyman and Campbell, 1972 ; Hill et al., 1987 ). Thus, without knowing how the animal is managing its muscle...

... of bradycardia would be influenced by dive duration and activity, i.e. the dive f H response would be exercise modulated. In all dives, f H decreased compared with surface rates by at least 50% (mean maximum surface f H =173 beats min −1 , mean minimum dive f H =50 beats min −1 ); however, dive f H...

... depression at elevated temperatures. Here, we investigated how water temperature (both acute and chronic exposures) affected the physiology of juvenile estuarine crocodiles ( Crocodylus porosus ) performing predator avoidance dives (i.e. fright-dives). Diving oxygen consumption, ‘fright’ bradycardia...

...–contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 beats min −1 to 4.1±0.29 beats min −1 ( P <0.05) after 5 weeks, and heart...

...% in reference fish) and reduced intrinsic cardiac pacemaker rate. A barostatic response was evident in both groups, as pharmacologically induced increases and decreases in blood pressure resulted in atropine-sensitive bradycardia and tachycardia, respectively. Yet, the tachycardia in Biotest fish...

...Shawn R. Noren; Traci Kendall; Veronica Cuccurullo; Terrie M. Williams SUMMARY A hallmark of the dive response, bradycardia, promotes the conservation of onboard oxygen stores and enables marine mammals to submerge for prolonged periods. A paradox exists when marine mammals are foraging underwater...

... caused significant bradycardia (53.0±3.1). Conversely, pre-branchial occlusion caused a significant tachycardia(69.1±1.7). Prazosin treatment attenuated the bradycardia(57.8±2.9) but not the tachycardia (68.8±2.3). Atropine treatment completely abolished both responses( Fig. 2A ). Fig. 2. Heart...

... ). Atropine was able to inhibit the branchial vascular responses to ACh but not the hypoxic bradycardia, suggesting the presence of muscarinic receptors on the heart and gill vasculature, and that the hypoxia induced bradycardia is of non-cholinergic origin. The results suggest that adenosine mediates...

...-mail: [email protected] ) * Present address: Center for Sleep Research, UCLA/VA-GLAHS, Neurobiology Research 151-A3, 16111 Plummer Street, North Hills, CA 91343, USA 29 7 2004 © The Company of Biologists Limited 2004 2004 apnoea eupnoea respiration heart rate bradycardia sleep...

.... Injection (0.1-0.3 mm deep) in different rostrocaudal, medial-lateral positions induced a bradycardia, either increased or decreased blood pressure, ventilation frequency and amplitude and, sometimes, an initial apnea. Often these responses occurred simultaneously in various different combinations...

...Nicole M. Elliott; Russel D. Andrews; David R. Jones SUMMARY While diving, harbour seals ( Phoca vitulina ) manage their oxygen stores through cardiovascular adjustments, including bradycardia, a concurrent reduction in cardiac output, and peripheral vasoconstriction. At the surface,post-dive...

.... This was accomplished by measuring cardiorespiratory variables during acute hypercarbia (20 min at P CO 2 =8 mmHg; 1 mmHg=0.133 kPa) in fish subjected to selective bilateral extirpation of the first gill arch. The cardiovascular responses to hypercarbia in the intact fish included a significant bradycardia (from 75.0...

... the hypercarbia-induced ventilatory responses and virtually eliminated all CO 2 -elicited cardiovascular adjustments. Although the atropinized dogfish displayed a hypercarbic bradycardia, the magnitude of the response was significantly attenuated (36±6 % decrease in f H in controls versus 9±2 % decrease...

... ) 20 06 2000 22 08 2000 © 2000 by Company of Biologists 2000 Somateria mollissima Branta leucopsis Aythya fuligula heart rate bradycardia tachycardia oxygen consumption doubly labelled water telemetry exercise energy expenditure Accurate methods...

... Limited 1998 voluntary diving cerebral blood flow rCBF bradycardia cardiac output rat The ability of mammals to dive under water and extend underwater dive duration is dependent upon the utilization of internal oxygen stores. Maximal oxygen utilization is achieved by a cardiovascular...