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At least 415 records · Page 23Linked to original sources
PubMed1980

Cardiovascular effects of hot water immersion (suicide soup).

Deaths from thermal stress have been reported in saunas, diving environments, and now hot spa baths. While investigating the physiological effects of hyperthermic immersion and its application to the therapy of hypothermia, some disturbing physiological anomalies were noted in normal subjects. The effects of standing, cold water immersion and of exercise, each following hyperthermic immersion, were examined. This was a pilot study only but it now seems possible that the ectopic beats may be an effect of the hyperthermic environment rather than the return of cold blood to the extremities, as previously assumed.

Adult↗
PubMed2002

Ultimate divers.

An extraordinary variety of mammals, birds, amphibians and reptiles are adapted to life in the oceans. Many of them spend their entire lives there without being able to breathe underwater. But just how do they exploit this hostile environment?

Adaptation, Physiological↗
PubMed2006

[Survival in cold water. Physiological consequences of accidental immersion in cold water].

This survey addresses the immediate physiological reactions to immersion in cold water: cold shock response, diving reflex, cardiac arrhythmias and hypothermia. Cold shock response is the initial sympathetic reaction to immersion in cold water. The diving reflex is elicited by submersion of the face. Afferent and efferent nerves are the trigeminal and vagal nerves. Cardiac arrhythmias occur immediately after immersion. If the immersion persists, hypothermia becomes an issue. Hypothermia is delayed by habituation to immersion in cold water as well as insulating garments, subcutaneous fat and a large lean body mass.

Accidents↗
PubMed1966

The medical and human performance problems of living under the sea.

Recent undersea experiments in the United States and France showed that divers can live and work effectively for many days from dwellings placed on the continental shelf to depths down to 432 feet. If prolonged exposure to the hostile underwater environment is to be tolerated successfully, existing physical, biological and equipment hazards must be recognized, prepared for and, when possible, circumvented.

Adaptation, Physiological↗
PubMed1975

A gross and microscopic study of the respiratory anatomy of the Antarctic Weddell seal, Leptonychotes weddelli.

Four species of Phocidae, or true seals, inhabit the waters surrounding the Antarctic continent. These animals are thought to have different diving capabilities. The Weddell seal, Leptonychotes weddelli, is known to be capable of attaining depths up to 600 meters. The respiratiory system of the Weddell seal shows the usual adaptations to an aquatic environment characteristic of other marine. These include lungs that undergo compression acollapse at depths greater than 70 meters; hyaline cartilage in the tracheo-bronchial tree as far as the terminal bronchioles; and large amounts of smooth muscle surrounding the distal-most bronchioles. The collapsible lungs provide a mechanism by which air is forced from the alveoli adjacent to the pulmonary capillary beds thereby preventing the absorption of nitrogen gas into the bloodsteam. The presence of hyaline cartilage throughout most of the tracheo-bronchial tree increases the effective dead air space that accommodates most of the air forced from the collapsed lungs. The smooth muscle surrounding the respiratory bronchioles prevents their collapse while under the pressures of a deep dive. Collapse of the respiratory bronchioles not supported by cartilage would trap air in the lung alveoli during a dive. In addition, large- sac-like "diverticulae" are found in the submucosa throughout the tracheo-bronchial tree. These diverticulae, which open directly into the lumen of the tree, appear to be modified glands whose cells, in most cases, do not appear to be specialized for secretory function. They are most numerous in the more distal bronchi and terminal bronchioles where they are situated on both the luminal and adventitial sides of the hyaline cartilage supporting the walls of the air passages. Diverticulae are not found in the respiratory bronchioles or in the respiratory portion of the lungs.

Acclimatization↗
PubMed1997

Heart rates and abdominal temperatures of free-ranging South Georgian shags, Phalacrocorax georgianus

The South Georgian shag (Phalacrocorax georgianus) shows a remarkable diving ability comparable to that of penguins, yet nothing is known of the physiology of these birds. In this study, heart rates and abdominal temperatures were recorded continuously in four free-ranging South Georgian shags using an implanted data-logger. A time­depth recorder was also attached to the back of the implanted birds to record their diving behaviour. The diving behaviour of the birds was essentially similar to that reported in other studies, with maximum dive durations for individual birds ranging between 140 and 287 s, and maximum depths between 35 and 101 m. The birds, while at the nest, had a heart rate of 104.0±13.1 beats min-1 (mean ± s.e.m.) and an abdominal temperature of 39.1±0.2 °C. During flights of 221±29 s, heart rate and abdominal temperature rose to 309.5±18.0 beats min-1 and 40.1±0.3 °C, respectively. The mean heart rate during diving, at 103.7±13.7 beats min-1, was not significantly different from the resting values, but the minimum heart rate during a dive was significantly lower at 64.8±5.8 beats min-1. The minimum heart rate during a dive was negatively correlated with both dive duration and dive depth. Abdominal temperature fell progressively during a diving bout, with a mean temperature at the end of a bout of 35.1±1.7 °C. The minimum heart rate during diving is at a sub-resting level, which suggests that the South Georgian shag responds to submersion with the 'classic' dive response of bradycardia and the associated peripheral vasoconstriction and utilisation of anaerobic metabolism. However, the reduction in abdominal temperature may reflect a reduction in the overall metabolic rate of the animal such that the bird can remain aerobic while submerged.

Journal Article↗
PubMedDate not supplied

Body oxygen stores, aerobic dive limits, and the diving abilities of juvenile and adult muskrats (Ondatra zibethicus).

Intraspecific variability in body oxygen reserves, muscle buffering capacity, diving metabolic rate, and diving behavior were examined in recently captured juvenile and adult muskrats. Allometric scaling exponents for lung (b=1.04), blood (b=0.91), and total body oxygen storage capacity (b=1.09) did not differ from unity. The concentration of skeletal muscle myoglobin scaled positively with mass in 254-600-g juveniles (b=1.63) but was mass-independent in larger individuals. Scaling exponents for diving metabolic rate and calculated aerobic dive limit (ADL) were 0.74 and 0.37, respectively. Contrary to allometric predictions, we found no evidence that the diving abilities of muskrats increased with age or body size. Juveniles aged 1-2 mo exhibited similar dive times but dove more frequently than summer-caught adults. Average and cumulative dive times and dive&rcolon;surface ratios were highest for fall- and winter-caught muskrats. Total body oxygen reserves were greatest in winter, mainly due to an increase in blood oxygen storage capacity. The buffering capacity of the hind limb swimming muscles also was highest in winter-caught animals. Several behavioral indicators of dive performance, including average and maximum duration of voluntary dives, varied positively with blood hemoglobin and muscle myoglobin concentration of muskrats. However, none of the behavioral measures were strongly correlated with the total body oxygen reserves or ADLs derived for these same individuals.

Adaptation, Physiological↗
PubMed1975

An implantable transmitter for monitoring heart rate and respiratory frequency in diving ducks.

An implantable telemetry transmitter is described for monitoring respiratory frequency and heart rate in animal physiological studies. The ECG is transmitted directly while the respiratory signal, derived from the temperature variation of the air in the respiratory tract, modulates the frequency of a subcarrier oscillator. A magnetic switch allows the implanted device to be switched on and off remotely. Details are given of the high packing density achieved by a modified cordwood method of construction. This system is being used to investigate the changes in heart rate and respiratory frequency associated with spontaneous diving in ducks, and typical results are presented.

Animals↗
PubMed1986

The physiology of the nose.

The nose, as an organ initiating reflexes affecting itself and the rest of the body, and as a target organ of control, is highly complex. Its innervation includes parasympathetic, sympathetic, sensory/afferent, and somatic motor nerves, which combine in a variety of morphologic pathways. The vasculature of the nose contains capacitance vessels such as sinusoids and distensible venules, as well as arteriovenous anastomoses, arterioles, capillaries, and venules. The secretory tissue of the nose includes epithelial cells, submucosal glands, and relatively large anterior or lateral serous glands; in addition, some species have specialized secretory glands. The nose is the source of many powerful reflexes, including the diving response, sneeze and sniff reflexes, and reflexes affecting autonomic nervous function to the cardiovascular system, airways in the lungs, the larynx, and other organs. Axon reflex control of the nasal vasculature is also important. The nasal vasculature can be shown to be under parasympathetic and sympathetic control, but there is little precise information concerning the effect of nerves on different types of blood vessels. Pharmacologic experiments show that vascular resistance and vascular volume can be separately influenced by nerves and mediators, and that vascular resistance and airway resistance are not necessarily inversely related. Nasal secretion is also under the influence of both parasympathetic and sympathetic nerves, and can be induced by a wide range of neurotransmitters and mediators. In general, the concentrations needed to promote secretion are considerably higher than those that affect vascular resistance, at least with regard to the lateral nasal gland of the dog. In humans, nasal patency is affected by several nervous inputs, presumably acting via vascular beds. The nasal cycle is the alternation of resistances between the two sides of the nose, on which other changes are superimposed. In exercise and hyperpnea, nasal airflow resistance decreases, presumably with vascular decongestion. Recent studies of the crutch reflex (the ipsilateral nasal congestion caused by stimulation of the axilla) show that some of the reflex inputs to the nose can be unilateral.

Airway Resistance↗