Orthostatic Intolerance of Viperid Snakes

@article{Lillywhite1993OrthostaticIO,
  title={Orthostatic Intolerance of Viperid Snakes},
  author={Harvey B. Lillywhite},
  journal={Physiological Zoology},
  year={1993},
  volume={66},
  pages={1000 - 1014}
}
  • H. Lillywhite
  • Published 1 November 1993
  • Environmental Science, Biology
  • Physiological Zoology
Whereas many terrestrial vertebrates can assume upright postures for long periods, some terrestrial snakes are unable to do so because blood circulation fails. Measurements of carotid arterial blood flow during head-up tilt in four viperid species demonstrate that blood flow to the head diminishes markedly when the body deviates from horizontal posture and ceases entirely at tilt angles greater than or equal to 30°. In this respect, large ground-dwelling vipers are similar to aquatic snakes… 
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References

SHOWING 1-10 OF 18 REFERENCES
Control of arterial pressure in aquatic sea snakes.
TLDR
In marine snakes major fluid shifts between nonvascular and vascular compartments significantly compensate hypovolemia but, because of minor autonomic adjustments, do not result in a well-regulated arterial pressure.
Postural Edema and Blood Pooling in Snakes
  • H. Lillywhite
  • Environmental Science, Biology
    Physiological Zoology
  • 1985
TLDR
The data indicate that cardiovascular adaptation for arboreal habits in snakes involves both effective control of arterial pressure and mechanisms that impede pooling of blood and edema in tissues.
Hemodynamic adjustments to head-up posture in the partly arboreal snake, Elaphe obsoleta.
TLDR
Radioactively-labeled microspheres were used to quantify adjustments of regional blood flows in 15 snakes subjected to 45 degrees head-up tilt and patterns of intraventricular shunting of blood acted to maintain pulmonary flow during tilt.
Regulation of arterial blood pressure in Australian tiger snakes.
TLDR
The results suggest that sympathetically mediated reflexes assist central blood pressure regulation in the tiger snake, with vasomotor adjustments having greater importance than changes in heart rate.
Blood pressure in snakes from different habitats
TLDR
This study indicates that adaptive evolutionary changes in arterial blood pressure regulation occurred during the transitions from terrestrial to aquatic or arboreal life in snakes.
Lability of blood volume in snakes and its relation to activity and hypertension.
TLDR
The lability of blood volume and its relationship to locomotor activity was investigated in two species of snakes Elaphe obsoleta, Say and Crotalus viridis, Rafinesque, demonstrating that blood volume varies substantially in relation to activity or the hypertensive state of these reptiles.
Specializations of the Body Form and Food Habits of Snakes
TLDR
Ancillary effects of the morphological features of vipers, plus the ability to ingest a very large quantity of food in one meal, should produce quantitative and qualitative differences in the ecology and behavior of viperid snakes.
Adrenergic innervation of the large arteries and veins of the semiarboreal rat snake Elaphe obsoleta
TLDR
The innervation pattern is consistent with known physiological adjustments to gravity and suggests a mechanism for regulating dependent blood flow via sympathetic nerves, which can be correlated with less gravitational disturbance in the pulmonary artery, which is relatively short in this and in other arboreal snakes.
...
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