Comprehensive Physiology Wiley Online Library

Cardiovascular Adjustments to Heat Stress

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Cutaneous Vascular Responses to Heat Stress
1.1 Microvascular Anatomy
1.2 Efferent Neural Control of Skin Blood Flow
1.3 Local Thermal Control of Cutaneous Blood Vessels
2 Hemodynamic Responses to Heat Stress
2.1 Cardiac Output during Heat Stress
2.2 Cardiovascular Pressures
3 Regional Circulatory Responses to Heat Stress
3.1 Splanchnic Circulation
3.2 Renal Circulation
3.3 Skeletal Muscle Circulation
3.4 Circulation to Brain and Spinal Cord
3.5 Coronary Circulation
4 Modifiers of Control by Internal Temperature
4.1 Thermoregulatory Modifications
4.2 Nonthermoregulatory Modifications
5 Conclusion
Figure 1. Figure 1.

Effect of cutaneous nerve anesthesia on forearm blood flow response to indirect heating. Responses in anesthetized arm are denoted by A, those in control arm by C. Nerve block caused elevation in forearm blood flow prior to body heating (vasoconstrictor abolition in skin and muscle) but significantly reduced reflex vasodilator response to heating, indicating that active vasodilator system was blocked. After Edholm et al. .

Figure 2. Figure 2.

Cutaneous vascular responses to cold stress (upper panel) and heat stress (lower panel) from one area of skin iontophoretically treated with bretylium, which blocks release of norepinephrine from sympathetic vasoconstrictor nerve terminals (filled symbols) and from an adjacent untreated site (open symbols). Skin blood flow was measured by laser‐Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated as LDF/blood pressure. The antiadrenergic effects of bretylium pretreatment blocked vasoconstrictor responses to cold stress (upper panel) but did not block vasodilator responses to heat stress (lower panel), indicating the presence of a non‐adrenergic vasodilator system . From Johnson .

Figure 3. Figure 3.

Three models for the relationship of active cutaneous vasodilation to control of sweating. A: Cholinergic control of sweat glands liberates an enzyme, which causes formation of the vasodilator peptide bradykinin . B: Vasoactive intestinal polypeptide (VIP) is co‐released with acetylcholine (ACH) from sudomotor nerves with endings on both sweat glands and cutaneous arterioles . C: Separate sudomotor and vasodilator nerves share control by central thermoregulatory centers (TRC) but are acted on differentially by nonthermoregulatory reflexes .

Figure 4. Figure 4.

Overall hemodynamic and regional circulatory adjustments by humans to whole‐body direct heating. Skin temperature (Ts) was held at high temperatures with water‐perfused suits. Blood temperature rose to 39.1°C, while cardiac output rose by an average of 6.6 l/min. The increase in skin blood flow of about 7.8 l/min, indicated by the rise in forearm blood flow (FBF), is met by this increase in cardiac output plus redistribution from splanchnic, renal, and skeletal muscle vasculatures. Arterial blood pressure shows a small fall which tends to recover. Right atrial pressure shows a sustained reduction. Stroke volume and central blood volume are not consistently changed (see text). From Rowell , by permission.

Figure 5. Figure 5.

gChange in superior mesenteric (intestinal) vascular resistance with internal temperature (Tc) during whole‐body heating in a representative baboon in unblocked state and during α‐adrenergic receptor blockade. Blockade eliminated vasoconstrictor response to heat stress, indicating its adrenergic nature. Adapted from Proppe .

Figure 6. Figure 6.

Average fall in renal blood flow and increase in renal vascular resistance vs. internal temperature (Tc) during whole‐body heating of five baboons on normal‐to‐high salt intake (N‐HSI) and low salt intake (LSI). Arrows indicate preheating control levels. Salt diet played no apparent role in renal vasoconstriction with environmental heating. FU, flow units; RU, resistance units. Adapted from Proppe .

Figure 7. Figure 7.

Decrease in renal blood flow (RBF) and increase in renal vascular resistance (RVR) per °C increase in internal temperature (%/ °C) during whole‐body heating of a representative baboon in three states: control (C), angiotensin‐II receptor blockade produced by saralasin (S), and β‐adrenergic receptor blockade produced by propranolol (P). Height of bar graph is average response from individual experiments. Renal vasoconstrictor responses to heat stress were less following S or P, indicating a role for β‐adrenergic stimulation of the renin‐angiotensin system. Adapted from Eisman and Rowell .

Figure 8. Figure 8.

Interrelationship of control of skin blood flow (SKBF) by internal (Ti) and skin (Tsk) temperatures. Elevation of skin temperature at normal body temperatures (A to A') will have little effect, whereas elevation of skin temperature at elevated internal temperatures (B to B') will have a marked effect on SKBF. See Johnson and Park . From Johnson , by permission.

Figure 9. Figure 9.

Increase in forearm blood flow (B.F.) with increase in esophageal temperature in one subject during exercise in warm environment in three different states: euhydrated (control), dehydrated by fluid restriction and exercise in heat (thermal dehydration), and dehydrated plus saline infusion (infusion). Thermal dehydration shifts the B.F.–esophageal temperature relationship rightward, an effect not totally reversed by saline infusion following dehydration. From Fortney et al. , by permission.

Figure 10. Figure 10.

Mean iliac (leg) blood flow, arterial blood pressure, and iliac vascular conductance vs. Tc before (leftmost data point of each curve) and during whole‐body heating of six baboons in euhydrated, dehydrated (65–69 h of fluid deprivation), and diuretic [furosemide (Lasix)]‐treated states. *Indicates that values in dehydrated and Lasix‐treated states are not statistically different from each other. From Proppe , by permission.



Figure 1.

Effect of cutaneous nerve anesthesia on forearm blood flow response to indirect heating. Responses in anesthetized arm are denoted by A, those in control arm by C. Nerve block caused elevation in forearm blood flow prior to body heating (vasoconstrictor abolition in skin and muscle) but significantly reduced reflex vasodilator response to heating, indicating that active vasodilator system was blocked. After Edholm et al. .



Figure 2.

Cutaneous vascular responses to cold stress (upper panel) and heat stress (lower panel) from one area of skin iontophoretically treated with bretylium, which blocks release of norepinephrine from sympathetic vasoconstrictor nerve terminals (filled symbols) and from an adjacent untreated site (open symbols). Skin blood flow was measured by laser‐Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated as LDF/blood pressure. The antiadrenergic effects of bretylium pretreatment blocked vasoconstrictor responses to cold stress (upper panel) but did not block vasodilator responses to heat stress (lower panel), indicating the presence of a non‐adrenergic vasodilator system . From Johnson .



Figure 3.

Three models for the relationship of active cutaneous vasodilation to control of sweating. A: Cholinergic control of sweat glands liberates an enzyme, which causes formation of the vasodilator peptide bradykinin . B: Vasoactive intestinal polypeptide (VIP) is co‐released with acetylcholine (ACH) from sudomotor nerves with endings on both sweat glands and cutaneous arterioles . C: Separate sudomotor and vasodilator nerves share control by central thermoregulatory centers (TRC) but are acted on differentially by nonthermoregulatory reflexes .



Figure 4.

Overall hemodynamic and regional circulatory adjustments by humans to whole‐body direct heating. Skin temperature (Ts) was held at high temperatures with water‐perfused suits. Blood temperature rose to 39.1°C, while cardiac output rose by an average of 6.6 l/min. The increase in skin blood flow of about 7.8 l/min, indicated by the rise in forearm blood flow (FBF), is met by this increase in cardiac output plus redistribution from splanchnic, renal, and skeletal muscle vasculatures. Arterial blood pressure shows a small fall which tends to recover. Right atrial pressure shows a sustained reduction. Stroke volume and central blood volume are not consistently changed (see text). From Rowell , by permission.



Figure 5.

gChange in superior mesenteric (intestinal) vascular resistance with internal temperature (Tc) during whole‐body heating in a representative baboon in unblocked state and during α‐adrenergic receptor blockade. Blockade eliminated vasoconstrictor response to heat stress, indicating its adrenergic nature. Adapted from Proppe .



Figure 6.

Average fall in renal blood flow and increase in renal vascular resistance vs. internal temperature (Tc) during whole‐body heating of five baboons on normal‐to‐high salt intake (N‐HSI) and low salt intake (LSI). Arrows indicate preheating control levels. Salt diet played no apparent role in renal vasoconstriction with environmental heating. FU, flow units; RU, resistance units. Adapted from Proppe .



Figure 7.

Decrease in renal blood flow (RBF) and increase in renal vascular resistance (RVR) per °C increase in internal temperature (%/ °C) during whole‐body heating of a representative baboon in three states: control (C), angiotensin‐II receptor blockade produced by saralasin (S), and β‐adrenergic receptor blockade produced by propranolol (P). Height of bar graph is average response from individual experiments. Renal vasoconstrictor responses to heat stress were less following S or P, indicating a role for β‐adrenergic stimulation of the renin‐angiotensin system. Adapted from Eisman and Rowell .



Figure 8.

Interrelationship of control of skin blood flow (SKBF) by internal (Ti) and skin (Tsk) temperatures. Elevation of skin temperature at normal body temperatures (A to A') will have little effect, whereas elevation of skin temperature at elevated internal temperatures (B to B') will have a marked effect on SKBF. See Johnson and Park . From Johnson , by permission.



Figure 9.

Increase in forearm blood flow (B.F.) with increase in esophageal temperature in one subject during exercise in warm environment in three different states: euhydrated (control), dehydrated by fluid restriction and exercise in heat (thermal dehydration), and dehydrated plus saline infusion (infusion). Thermal dehydration shifts the B.F.–esophageal temperature relationship rightward, an effect not totally reversed by saline infusion following dehydration. From Fortney et al. , by permission.



Figure 10.

Mean iliac (leg) blood flow, arterial blood pressure, and iliac vascular conductance vs. Tc before (leftmost data point of each curve) and during whole‐body heating of six baboons in euhydrated, dehydrated (65–69 h of fluid deprivation), and diuretic [furosemide (Lasix)]‐treated states. *Indicates that values in dehydrated and Lasix‐treated states are not statistically different from each other. From Proppe , by permission.

References
 1. Abramson, N., T. W. Piemme, and W. C. Kaufman. Effect of heat stress upon human renal function. Aerospace Med. 38: 234–238, 1967.
 2. Adolph, E. F. Blood changes in dehydration. In: Physiology of Man in the Desert, edited by E. F. Adolph. New York: Interscience, 1947, p. 160–171.
 3. Ahmad, A. Response of the blood vessels of the upper extremity to prolonged local heat. Clin. Sci. (Colch.) 15: 609–616, 1956.
 4. Allwood, M. J., H. Barcroft, J. P. L. A. Hayes, and E. A. Hirsjärvi. The effect of mental arithmetic on the blood flow through normal, sympathectomized and hyperhidrotic hands. J. Physiol. (Land.) 148: 108–116, 1959.
 5. Arnott, W. M., and J. M. Macfie. Effect of ulnar nerve block on blood flow in the reflexly vasodilated digit. J. Physiol. (Lond.) 107: 233–238, 1948.
 6. Badeer, H. Influence of temperature on S‐A rate of dog's heart in denervated heart‐lung preparation. Am. J. Physiol. 167: 76–80, 1951.
 7. Bailey, R. E., D. Bartos, F. Bartos, A. Castro, R. L. Dobson, D. P. Grettie, R. Kramer, D. MacFarlane, and K. Sato. Activation of aldosterone and renin secretion by thermal stress. Experientia 28: 159–160, 1972.
 8. Barcroft, H., K. D. Bock, H. Hensel, and A. H. Kitchin. Die Muskeldurchblutung des Menschen bein Indirekter Erwärmung and Abkühlung. Pflügers Arch. Ges. Physiol. 261: 199–210, 1955.
 9. Barcroft, H., W. M. Bonnar, and O. G. Edholm. Reflex vasodilation in human skeletal muscle in response to heating the body. J. Physiol. (Lond.) 106: 271–278, 1947.
 10. Barcroft, H., and O. G. Edholm. The effect of temperature on blood flow and deep temperature in the human forearm. J. Physiol. (Lond.) 102: 5–20, 1943.
 11. Bartfai, T., K. Iverfeldt, and G. Fisone. Regulation of the release of coexisting neurotransmitters. Annu. Rev. Pharmacol. Toxicol. 28: 285–310, 1988.
 12. Baumgartl, P., E. Knapp, A. Aiger, and E. Raas. Saunawirkung auf Hämodynamik und myokardiale Leistungsfähigkeit. München. Med. Wochenchr. 114: 479–483, 1972.
 13. Beam, A. G., B. Billing, and S. Sherlock. The effect of adrenaline and noradrenaline on hepatic blood flow and splanchnic carbohydrate metabolism in man. J. Physiol. (Lond.) 115: 430–441, 1951.
 14. Beiser, G. D., R. Zelis, S. E. Epstein, D. T. Mason, and E. Braunwald. The role of skin and muscle resistance vessels in reflexes mediated by the baroreceptor system. J. Clin. Invest. 49: 225–231, 1970.
 15. Bell, A. W., J. R. S. Hales, R. B. King, and A. A. Fawcett. Influence of heat stress on exercise‐induced changes in regional blood flow in sheep. J. Appl. Physiol. 55: 1916–1923, 1983
 16. Bell, C., W. Jänig, H. Kümmel, and H. Xu. Differentiation of vasodilator and sudomotor responses in the cat paw pad to preganglionic stimulation. J. Physiol. (Lond.) 364: 93–104, 1985.
 17. Benzinger, T. H. On physical heat regulation and the sense of temperature in man. Proc. Natl. Acad. Sci. USA 45: 645–659, 1959.
 18. Berlyne, G. M., J. P. M. Finberg, and C. Yoran. The effect of β‐andrenoceptor blockade on body temperature and plasma renin activity in heat exposed man. Br. J. Clin Pharmacol. 1: 307–312, 1974.
 19. Bini, G., K.‐E. Hagbarth, P. Hynninen, and B. G. Wallin. Regional similarities and differences in thermoregulatory vaso‐and sudomotor tone. J. Physiol. (Lond.) 306: 553–565, 1980.
 20. Bini, G., K.‐E. Hagbarth, P. Hynninen, and B. G. Wallin. Thermoregulatory and rhythm‐generating mechanisms governing the sudomotor and vasoconstrictor outflow in human cutaneous nerves. J. Physiol. (Lond.) 306: 537–552, 1980.
 21. Bini, G., K.‐E. Hagbarth, and B. G. Wallin. Cardiac rhythmicity of skin sympathetic activity recorded from peripheral nerves in man. J. Auton. Nerve. Syst. 4: 17–24, 1981.
 22. Blair, D. A., W. E. Glover, B. S. L. Kidd, and I. C. Roddie. Peripheral vascular effects of bretylium tosylate in man. Br. J. Pharmacol. 15: 466–475, 1960.
 23. Blair, D. A., W. E. Glover, and I. C. Roddie. Vasomotor fibers to skin in the upper arm, calf and thigh. J. Physiol. (Lond.). 153: 232–238, 1960.
 24. Blair, D. A., W. E. Glover, and I. C. Roddie. Cutaneous vasomotor nerves to the head and trunk. J. Appl. Physiol. 16: 119–122, 1961.
 25. Blumberg, H., and B. G. Wallin. Direct evidence of neurally mediated vasodilatation in hairy skin of the human foot. J. Physiol. (Lond.) 382: 105–121, 1987.
 26. Borkowski, K. R., C. Y. Kwan, and E. E. Daniel. Epinephrine facilitates neurogenic responses in isolated segments of dog mesenteric arteries. J. Cardiovasc. Pharmacol. 13: 760–766, 1989.
 27. Braverman, I. M. Ultrastructure and organization of the cutaneous microvasculature in normal and pathologic states. J. Invest. Dermatol. 93: 2S–9S, 1989.
 28. Brengelmann, G. L. Circulatory adjustments to exercise and heat stress. Annu. Rev. Physiol. 45: 191–212, 1983.
 29. Brengelmann, G. L. Temperature regulation. In: Scientific Foundations of Sports Medicine, edited by C. C. Teitz. Philadelphia: Decker, 1989, p. 77–116.
 30. Brengelmann, G. L., P. R. Freund, L. B. Rowell, J. E. Olerud, and K. K. Kraning. Absence of active vasodilation associated with congenital absence of sweat glands in humans. Am. J. Physiol. 240 (Heart Circ. Physiol 9): H571–H575, 1981.
 31. Brengelmann, G. L., J. M. Johnson, L. Hermansen, and L. B. Rowell. Altered control of skin blood flow during exercise at high internal temperatures. J. Appl. Physiol. 43: 790–794, 1977.
 32. Blbring, E., and J. H. Burn. Sympathetic vaso‐dilatation in the skin and the intestine of the dog. J. Physiol. (Lond.) 87: 254–274, 1936.
 33. Carlsten, A., A. Gustafson, and L. Werkö. Hemodynamic influence of warm and dry environment in man with and without rheumatic heart disease. Acta Med. Scand. 169: 411–417, 1961.
 34. Clark, E. R. Arteriovenous anastomoses. Physiol. Rev. 18: 229–247, 1938.
 35. Colton, J. S., and H. M. Frankel. Cerebrovascular response to CO2 during hyperthermia. Am. J. Physiol. 223: 1041–1043, 1972
 36. Conrad, M. C. Functional Anatomy of the Circulation to the Lower Extremities. Chicago: Year Book, 1971.
 37. Conradt, M., R. Kullmann, T. Matsuzaki, and E. Simon. Arterial baroreceptor function in differential cardiovascular adjustments induced by central thermal stimulation. Basic Res. Cardiol. 70: 10–28, 1975.
 38. Cooke, J. P., J. T. Shepherd, and P. M. Vanhoutte. The effect of warming on adrenergic neurotransmission in canine cutaneous vein. Cir. Res. 54: 547–553, 1984.
 39. Cooper, T., V. L. Willman, and C. R. Hanlon. Cardiac and peripheral vascular responses to hyperthermia induced by blood stream heating. J. Thorac. Cardiovasc. Surg. 44: 667–673, 1962.
 40. Crandall, C. G., J. M. Johnson, V. A. Convertino, P. B. Raven, and K. A. Engelke. Altered thermoregulatory responses following 15 days of head‐down tilt. J. Appl. Physiol. 77: 1863–1867, 1994.
 41. Crossley, R. J., A. D. M. Greenfield, G. L. Plassaras, and D. Stephens. The interrelation of thermoregulatory and baroreceptor reflexes in the control of blood vessels in the human forearm. J. Physiol. (Lond.) 183: 628–636, 1966.
 42. Damato, A. N., S. H. Lau, E. Stein, J. I. Haft, B. Kosowsky, and S. I. Cohen. Cardiovascular response to acute thermal stress (hot dry environment) in unacclimatized normal subjects. Am. Heart J. 76: 769–774, 1968.
 43. Daniel, P. M., and M. M. L. Prichard. Arteriovenous anastomoses in the external ear. Q. J. Exp. Physiol. 41: 107–123, 1956.
 44. Deschamps, A., and S. Magder. Effects of heat stress on vascular capacitance. Am. J. Physiol. 266 (Heart Circ. Physiol. 35): H2122–2129, 1994.
 45. Detry, J.‐M. R., G. L. Brengelmann, L. B. Rowell, and C. Wyss. Skin and muscle components of forearm blood flow in directly heated resting man. J. Appl. Physiol. 32: 506–511, 1972.
 46. Dietz, N. M., J. M. Rivera, D. O. Warner, and M. J. Joyner. Is nitric oxide involved in cutaneous vasodilation during body heating. J. Appl. Physiol. 76: 2047–2053, 1994
 47. Edholm, O. G., R. H. Fox, and R. K. MacPherson. The effect of body heating on the circulation in skin and muscle. J. Physiol. (Lond.) 143: 612–619, 1956.
 48. Edholm, O. G., R. H. Fox, and R. K. MacPherson. Vasomotor control of the cutaneous blood vessels in the human forearm. J. Physiol. (Lond.) 139: 455–465, 1957.
 49. Eisman, M. M., and L. B. Rowell. Renal vascular response to heat stress in baboons—role of renin–angiotensin. J. Appl. Physiol. 43: 739–746, 1977.
 50. Ekenvall, L., L. E. Lindblad, O. Norbeck, and B.‐M. Etzell. α‐Adrenoceptors and cold‐induced vasoconstriction in human finger skin. Am. J. Physiol. 255 (Heart Circ. Physiol. 24): H1000–;H1003, 1988.
 51. El eSherif, N., L. Shahwan, and A. H. Sorour. The effect of acute thermal stress on general and pulmonary hemodynamics in the cardiac patient. Am. Heart J. 79: 305–317, 1970.
 52. Emmelin, N. Nervous control of salivary glands. In: Handbook of Physiology. Alimentary Canal, edited by C. F. Code. Washington, DC: Am. Physiol. Soc., 1967, sect. 6, vol. 2, chapt. 37, p. 595–632.
 53. Escourrou, R., P. R. Freund, L. B. Rowell, and D. G. Johnson. Splanchnic vasoconstriction in heat‐stressed men: role of renin‐angiotensin system. J. Appl. Physiol. 52: 1438–1443, 1982.
 54. Faithfull, N. S., H. S. Reinhold, A. P. van den Berg, G. C. van Rhoon, J. Van Der Zee, and J. L. Wike‐Hooley. Cardiovascular changes during whole body hyperthermia treatment of advanced malignancy. Eur. J. Appl. Physiol. 53: 274–281, 1984.
 55. Falckh, P. H., I. S. de la Lande, R. E. Stitzel, M. Mano, and R. J. Head. Failure of propranolol to inhibit the epinephrine‐induced enhancement of responses to sympathetic nerve stimulation in the rat mesenteric vascular bed. J. Pharmacol. Exp. Ther. 253: 432–436, 1990.
 56. Finberg, J. P. M., M. Katz, H. Gazit, and G. M. Berlyne. Plasma renin activity after acute heat exposure in nonacclimatized and naturally acclimatized man. J. Appl. Physiol. 36: 519–523, 1974.
 57. Flavahan, N. A. The role of vascular α2‐adrenoceptors as cutaneous thermosensors. News Physiol. Sci. 6: 251–255, 1991.
 58. Folkow, B., J. Frost, K. Haeger, and B. Uvnäs. The sympathetic vasomotor innervation of the skin of the dog. Acta Physiol. Scand 17: 195–200, 1949.
 59. Folkow, B., G. Ström, and B. Unväs. Cutaneous vasodilation elicited by local heating of the anterior hypothalamus in cats and dogs. Acta Physiol. Scand. 17: 317–316, 1949.
 60. Follenius, M., G. Brandenberger, B. Reinhardt, and M. Simeoni. Plasma aldosterone, renin activity, and Cortisol responses to heat exposure in sodium depleted and repleted subjects. Eur. J. Appl. Physiol. 41: 41–50, 1979.
 61. Fortney, S. M., C. B. Wenger, J. R. Bove, and E. R. Nadel. Effect of hyperosmolality on control of blood flow and sweating. J. Appl. Physiol 57: 1688–1695, 1984.
 62. Fox, R. H., and O. G. Edholm. Nervous control of the cutaneous circulation. Br. Med. Bull. 19: 110–114, 1963.
 63. Fox, R. H., R. Goldsmith, D. J. Kidd, and H. E. Lewis. Blood flow and other circulatory changes with acclimatization to heat. J. Physiol. (Lond.) 166: 548–562, 1966.
 64. Fox, R. H., and S. M. Hilton. Bradykinin formation in human skin as a factor in heat vasodilation. J. Physiol. (Lond.) 142: 219–232, 1958.
 65. Frayser, R., J. C. Ross, H. S. Levin, J. Messer, and J. Pines. Effect of increased environmental temperature on pulmonary diffusing capacity. J. Appl. Physiol. 21: 147–150, 1966.
 66. Freeman, N. E. The effect of temperature on the blood flow in the normal and in the sympathectomized hand. Am. J. Physiol. 113: 384–398, 1935.
 67. Frey, M. A. B., and R. A. Kenney. Cardiac response to whole‐body heating. Aviat. Space Environ. Med. 50: 387–389, 1979.
 68. Galletti, P. M., P. F. Salisbury, and A. Rieben. Influence of blood temperature on the pulmonary circulation. Circ. Res. 6: 275–282, 1958.
 69. Garrey, W. E., and S. E. Townsend. Neural responses and reactions of the heart of a human embryo. Am. J. Physiol. 152: 219–224, 1948.
 70. Gaskell, P. Are there sympathetic vasodilator nerves to the vessels of the hands? J. Physiol. (Lond.) 131: 647–656, 1956.
 71. Gemmell, R. T., and J. R. S. Hales. Cutaneous arteriovenous anastomoses present in the tail but absent from the ear of the rat. J. Anat. 124: 355–358, 1977.
 72. Gisolfi, C. V., R. D. Matthes, K. C. Kregel, and R. Oppliger. Splanchnic sympathetic nerve activity and circulating catecholamines in the hyperthermic rat. J. Appl. Physiol. 70: 1821–1826, 1991.
 73. Glaser, E. M. The effects of cooling and warming on the vital capacity, forearm and hand volume, and skin temperature of man. J. Physiol. (Lond.) 109: 421–429, 1949.
 74. Glaser, E. M., F. R. Berridge, and K. M. Prior. Effects of heat and cold on the distribution of blood within the human body. Clin. Sci. (Colch.) 9: 181–187, 1950.
 75. Goldstein, D. S., R. McCarty, R. J. Polinsky, and I. J. Kopin. Relationship between plasma norepinephrine and sympathetic neural activity. Hypertension 5: 552–559, 1983.
 76. Gonnering, R. S. Pharmacology of botulinum toxin. Int. Ophthalmol. Clin. 33: 203–226, 1993.
 77. Gorman, A. J., and D. W. Proppe. Influence of heat stress on arterial baroreflex control of heart rate in the baboon. Circ. Res. 51: 73–82, 1982.
 78. Gorman, A. J., and D. W. Proppe. Mechanisms producing tachycardia in concious baboons during environmental heat stress. J. Appl. Physiol. 56: 441–446, 1984.
 79. Grant, R. T. Vasodilatation and body warming in the rat. J. Physiol. (Lond.) 167: 311–317, 1963.
 80. Grant, R. T., and H. E. Holling. Further observations on the vascular responses of the human limb to body warming; evidence for sympathetic vasodilator nerves in the normal subject. Clin. Sci. (Colch.) 3: 273–285, 1938.
 81. Grayson, J. Vascular reactions in the human intestine. J. Physiol. (Lond.) 109: 439–447, 1949.
 82. Grayson, J. The measurement of intestinal blood flow in man. J. Physiol. (Lond.) 114: 419–434, 1951.
 83. Green, H. D., W. B. Howard, and L. F. Kenan. Autonomic control of blood flow in hind paw of the dog. Am. J. Physiol. 187: 469–472, 1956.
 84. Greenfield, A. D. M. The circulation through the skin. In: Handbook of Physiology. Circulation, edited by W. F. Hamilton Washington, DC: Am. Physiol. Soc., 1963, sect. 2, vol. II, chapt. 39, p. 1325–1351.
 85. Greenway, C. V., and R. D. Stark. Hepatic vascular bed. Physiol. Rev. 51: 23–65, 1971.
 86. Gregor, M., W. Jänig, and W. Riedel. Response pattern of cutaneous postganglionic neurones to the hindlimb on spinal cord heating and cooling in the cat. Pflügers Arch. 363: 135–140, 1976.
 87. Haeusler, G., W. Haefely, and A. Huerlimann. On the mechanism of the adrenergic nerve blocking action of bretylium. Naunyn Schmiedebergs Arch. Pharmacol. 265: 260–277, 1979.
 88. Hales, J. R. S. Effect of exposure to hot environments on the regional distribution of blood flow and on cardiorespiratory function in sheep. Pflügers Arch. 344: 133–148, 1973.
 89. Hales, J. R. S. Effects of exposure to hot environments on total and regional blood flow in the brain and spinal cord of the sheep. Pflügers Arch. 344: 327–337, 1973.
 90. Hales, J. R. S. Effects of heat stress on blood flow in respiratory and non‐respiratory muscle in sheep. Pflügers Arch. 345: 123–130, 1973.
 91. Hales, J. R. S. Adrenergic mechanisms in the circulatory responses to heat stress. In: The Sympathoadrenal System, Alfred Benzon Symposium 23, edited by N. J. Christensen, O. Henriksen, and N. A. Lassen. Copenhagen: Munksgaard, 1986, p. 203–220.
 92. Hales, J. R. S., J. W. Bennett, and A. A. Fawcett. Integrated changes in regional circulatory activity evoked by thermal stimulation of the hypothalamus. Pflügers Arch. 372: 157–164, 1977.
 93. Hales, J. R. S., and R. A. L. Dampney. The redistribution of cardiac output in the dog during heat stress. J. Therm. Biol. 1: 29–34, 1975.
 94. Hales, J. R. S., A. A. Fawcett, J. W. Bennett, and A. D. Needham. Thermal control of blood flow through capillaries and arteriovenous anastomoses in skin of sheep. Pflügers Arch. 378: 55–63, 1978.
 95. Hales, J. R. S., and M. Iriki. Integrated changes in regional circulatory activity evoked by spinal cord and peripheral thermoreceptor stimulation. Brain Res. 87: 267–279, 1975.
 96. Hales, J. R. S., M. Iriki, K. Tsuchiya, and E. Kozawa. Thermally‐induced cutaneous sympathetic activity related to blood flow through capillaries and arteriovenous anastomoses. Pflügers Arch. 375: 17–24, 1978.
 97. Hales, J. R. S., C. Jessen, A. A. Fawcett, and R. B. King. Skin AVA and capillary dilation and constriction induced by local skin heating. Pflügers Arch. 404: 203–207, 1985.
 98. Hales, J. R. S., L. B. Rowell, and R. B. King. Regional distribution of blood flow in awake heat‐stressed baboons. Am. J. Physiol. 237 (Heart Circ. Physiol. 6): H705–H712, 1979.
 99. Heinz‐Erian, P., R. D. Dey, M. Flux, and S. I. Said. Deficient vasoactive intestinal peptide innervation in the sweat glands of cystic fibrosis patients. Science 229: 1407–1408, 1985.
 100. Hilton, S. M., and P. G. Lewis. The relationship between glandular activity, bradykinin formation and functional vasodilatation in the submandibular salivary gland. J. Physiol. (Lond.) 134: 471–483, 1956.
 101. Hökfelt, T., O. Johansson, A. Ljungdahl, J. M. Lundberg, and M. Schultzberg. Peptidergic neurones. Nature 284: 515–521, 1980.
 102. Horstman, D. H., and S. M. Horvath. Cardiovascular and temperature regulatory changes during progressive dehydration and euhydration J. Appl. Physiol. 33: 446–450, 1972.
 103. Iriki, M., W. Riedel, and E. Simon. Regional differentiation of sympathetic activity during hypothalamic heating and cooling in anesthetized rabbits. Pflügers Arch. 328: 320–331, 1971.
 104. Janssens, W. J., and P. M. Vanhoutte. Instantaneous changes of alpha‐adrenoceptor affinity caused by moderate cooling in canine cutaneous veins. Am. J. Physiol. 234 (Heart Circ Physiol 3): H330–H337, 1978.
 105. Johansen, K. Heat exchange through the muskrat tail. Evidence for vasodilator nerves to skin. Acta Physiol. Scand. 55: 160–169, 1962.
 106. Johnson, J. M. Nonthermoregulatory control of human skin blood flow. J. Appl. Physiol. 61: 1613–1622, 1986.
 107. Johnson, J. M. The cutaneous circulation. In: Laser Doppler Blood Flowmetry, edited by A. P. Shepherd, and P. Å. Öberg. Boston: Kluwer, 1990, p. 121–140.
 108. Johnson, J. M. Exercise and the cutaneous circulation. Exercise Sports Sci. Rev. 20: 59–97, 1992.
 109. Johnson, J. M., G. L. Brengelmann, J. R. S. Hales, P. M. Vanhoutte, and C. B. Wenger. Regulation of the cutaneous circulation. Federation Proc. 45: 2841–2850, 1986.
 110. Johnson, J. M., G. L. Brengelmann, and L. B. Rowell. Interactions between local and reflex influences on human forearm skin blood flow. J. Appl. Physiol. 41: 826–831, 1976.
 111. Johnson, J. M., M. Niederberger, L. B. Rowell, M. M. Eisman, and G. L. Brengelmann. Competition between cutaneous vasodilator and vasoconstrictor reflexes in man. J. Appl. Physiol. 35: 798–803, 1973.
 112. Johnson, J. M., D. S. O'Leary, W. F. Taylor, and W. Kosiba. Effect of local warming on forearm reactive hyperaemia. Clin. Physiol. 6: 337–346, 1986.
 113. Johnson, J. M., and M. K. Park. Reflex control of skin blood flow by skin temperature: role of core temperature. J. Appl. Physiol. 47: 1188–1193, 1979.
 114. Johnson, J. M., and M. K. Park. Effect of upright exercise on threshold for cutaneous vasodilation and sweating. J. Appl. Physiol. 50: 814–818, 1981.
 115. Johnson, J. M., and M. K. Park. Effect of heat stress on cutaneous vascular responses to the initiation of exercise. J. Appl. Physiol. 53: 744–749, 1982.
 116. Johnson, J. M., P. E. Pergola, F. K. Liao, D. L. Kellogg, Jr., and C. G. Crandall. Skin of the dorsal aspect of human hands and fingers possesses an active vasodilator system. J. Appl. Physiol. in press, 1995.
 117. Johnson, J. M., and L. B. Rowell. Forearm skin and muscle vascular responses to prolonged leg exercise in man. J. Appl. Physiol. 39: 920–924, 1975.
 118. Johnson, J. M., L. B. Rowell, M. Niederberger, and M. M. Eisman. Human splanchnic and forearm vasoconstrictor responses to reductions in right atrial and aortic pressures. Circ. Res. 34: 515–524, 1974.
 119. Jose, A. D., F. Stitt, and D. Collison. The effects of exercise and changes in body temperature on the intrinsic heart rate in man. Am. Heart J. 79: 488–497, 1970.
 120. Kaada, B., and O. Eielsen. In search of mediators in skin vasodilation induced by transcutaneous nerve stimulation: I. Failure to block the response by antagonists of endogenous vasodilators. Gen. Pharmacol. 14: 623–633, 1983.
 121. Kanter, G. S. Glomerular filtration and renal plasma flow during hyperthermia. Am. J. Physiol. 198: 1044–1048, 1960
 122. Kaufmann, W., H. Nieth, and J. G. Schlitter. Wasser‐electrolyte‐elimination und renale Hämodynamik bei Erhöhung der Umgebungstemperatur. Pflügers Archiv Ges. Physiol. 272: 31–32, 1960.
 123. Keeton, T. K., and W. B. Campbell. The pharmacologic alteration of renin release. Pharmacol. Rev. 32: 81–227, 1980.
 124. Kellogg, D. L., Jr., J. M. Johnson, W. L. Kenney, P. E. Pérgola, and W. A. Kosiba. Mechanisms of control of skin blood flow during prolonged exercise in humans. Am. J. Physiol. 265 (Heart Circ. Physiol. 34): H562–H568, 1991.
 125. Kellogg, D. L., Jr, J. M. Johnson, and W. A. Kosiba. Selective abolition of adrenergic vasoconstrictor responses in skin by local iontophoresis of bretylium. Am. J. Physiol. 257 (Heart Circ. Physiol 26): H1599–1606, 1989.
 126. Kellogg, D. L., Jr., J. M. Johnson, and W. A. Kosiba. Baroreflex control of the cutaneous active vasodilator system in humans. Circ. Res. 66: 1420–1426, 1990.
 127. Kellogg, D. L., Jr., J. M. Johnson, and W. A. Kosiba. Competition between cutaneous active vasoconstriction and active vasodilation during exercise in man. Am. J. Physiol. 261 (Heart Circ. Physiol. 30): H1184–H1189, 1991.
 128. Kellogg, D. L., Jr., J. M. Johnson, and W. A. Kosiba. Control of internal temperature threshold for active cutaneous vasodilation by dynamic exercise. J. Appl. Physiol. 71: 2476–2482, 1991.
 129. Kellogg, D. L., Jr., P. E. Pergola, W. A. Kosiba, and J. M. Johnson. Effects of muscarinic receptor blockade on cutaneous active vasodilation in humans. FASEB J. 7: A556, 1993.
 130. Kellogg, D. L., Jr., P. E. Pergola, K. L. Piest, W. A. Kosiba, C. G. Crandall, and J. M. Johnson. Cutaneous active vasodilation in humans is mediated by cholinergic nerve co‐transmission. FASEB J. 8: A263, 1994.
 131. Kenney, R. A. The effect of hot, humid environments in the renal function of West Africans. J. Physiol. (Lond.) 118: 25P–26P, 1952.
 132. Kenney, W. L., and J. M. Johnson. Control of skin blood flow during exercise. Med. Sci. Sports Exercise 24: 303–312, 1992.
 133. Kenney, W. L., E. Kamon, and E. R. Buskirk. Effect of mild essential hypertension on control of forearm blood flow during exercise in the heat. J. Appl. Physiol. 56: 930–935, 1984.
 134. Kenney, W. L., C. G. Tankersley, D. L. Newswanger, and S. M. Puhl. Alphal‐adrenergic blockade does not alter control of skin blood flow during exercise. Am. J. Physiol. 260 (Heart Circ. Physiol. 29): H855–H861, 1991.
 135. Kenney, W. L., D. H. Zappe, C. G. Tankersley, and J. A. Derr. Effect of systemic yohimbine on the control of skin blood flow during local heating and dynamic exercise. Am. J. Physiol. 266 (Heart Circ. Physiol. 35): H371–H376, 1994.
 136. Kerr, J. C., D. G. Reynolds, and K. G. Swan. Adrenergic stimulation and blockade in mesenteric circulation of the baboon. Am. J. Physiol. 234 (Endocrinol. Metab. Gastrointest. Physiol. 3): E457–E462, 1978.
 137. Kim, Y. D., C. R. Lake, D. E. Lees, W. H. Schutte, J. M. Bull, V. Weise, and I. J. Kopin. Hemodynamic and plasma catecholamine responses to hyperthermic cancer therapy in humans. Am. J. Physiol. 237 (Heart Circ. Physiol. 6): H570–H574, 1979.
 138. Kolka, M. A., and L. A. Stephenson. Cutaneous blood flow and local sweating after systemic atropine administration. Pflügers Arch. 410: 524–529, 1987.
 139. Kolka, M. A., L. A. Stephenson, A. E. Allan, and P. B. Rock. Atropine‐induced cutaneous vasodilation decreases esophageal temperature during exercise. Am. J. Physiol. 257 (Regulatory Integrative Comp. Physiol. 26): R1089–R1095, 1989.
 140. Koroxenidis, G. T., J. T. Shepherd, and R. J. Marshall. Cardiovascular response to acute heat stress. J. Appl. Physiol. 16: 869–872, 1961.
 141. Kosunen, K. J., A. J. Pakarinen, K. Kuoppasalmi, and H. Aldercreutz. Plasma renin activity, angiotensin II, and aldosterone during intense heat stress. J. Appl. Physiol. 41: 323–327, 1976.
 142. Kraft, E., and B. G. Zimmerman. Influence of histamine H1 and H2 blockers on sympathetic vasodilator and vasoconstrictor responses in canine paw. Br. J. Pharmacol. 53: 51–58, 1975.
 143. Kregel, K. C., and C. V. Gisolfi. Circulatory responses to heat after celiac ganglionectomy or adrenal demedullation. J. Appl. Physiol. 66: 1359–1363, 1989.
 144. Kregel, K. C., and C. V. Gisolfi. Circulatory responses to vasoconstrictor agents during passive heating in the rat. J. Appl. Physiol. 68: 1220–1227, 1990.
 145. Kregel, K. C., D. G. Johnson, and D. R. Seals. Tissue‐specific noradrenergic activity during acute heat stress in rats. J. Appl. Physiol. 74: 1988–1993, 1993
 146. Kregel, K. C., D. G. Johnson, C. M. Tipton, and D. R. Seals. Arterial baroreceptor reflex modulation of sympathetic‐cardiovascular adjustments to heat stress. Hypertension 15: 497–504, 1990.
 147. Kregel, K. C., J. M. Overton, D. G. Johnson, C. M. Tipton, and D. R. Seals. Mechanism for pressor responses to nonexertional heating in the conscious rat. J. Appl. Physiol. 71: 192–196, 1991.
 148. Kregel, K. C., P. T. Wall, and C. V. Gisolfi. Peripheral vascular responses to hyperthermia in the rat. J. Appl. Physiol. 64: 2582–2588, 1988.
 149. Kullmann, R., W. Schönung, and E. Simon. Antagonistic changes of blood flow and sympathetic activity in different vascular beds following central thermal stimulation. I. Blood flow in skin, muscle and intestine during spinal cord heating and cooling in anesthetized dogs. Pflügers Arch. 319: 146–161, 1970.
 150. Kvietys, P. R., D. N. Granger, and S. L. Harper. Circulation of the pancreas and salivary glands. In: Handbook of Physiology. The Gastrointestinal System. edited by S. G. Schultz, J. D. Wood, and B. B. Rauner. Bethesda, MD: Am. Physiol. Soc., 1989, sect. 6, vol. 1, pt. 2, chapt. 42, p. 1565–1595.
 151. Lewis, T., and G. W. Pickering. Vasodilation in the limbs in response to warming the body; with evidence for sympathetic vasodilator nerves in man. Heart 16: 33–51, 1931.
 152. Lind, A. R., C. S. Leithead, and G. W. McNicol. Cardiovascular changes during syncope induced by tilting men in the heat. J. Appl. Physiol. 25: 268–276, 1968.
 153. Lindblad, L. E., L. Ekenvall, and C. Klingstedt. Neural regulation of vascular tone and cold induced vasoconstriction in human finger skin. J. Auton. Nerv. Syst. 30: 169–174, 1990.
 154. Love, A. H. G., and R. G. Shanks. The relationship between the onset of sweating and vasodilation in the forearm during body heating. J. Physiol. (Lond.) 162: 121–128, 1962.
 155. Low, A., and R. A. Westerman. Neurogenic vasodilation in the rat hairy skin measured using a laser Doppler flowmeter. Life Sci. 45: 49–57, 1989.
 156. Lundberg, J., L. Norgen, E. Ribbe, I. Rosen, S. Steen, J. Thörne, and G. Wallin. Direct evidence of active sympathetic vasodilatation in the skin of the human foot. J. Physiol. (Lond.) 417: 437–446, 1989.
 157. Lundberg, J. M., A. Rudehill, A. Sollevi, and B. Hamberger. Evidence for co‐transmitter role of neuropeptide Y in the pig spleen. Br. J. Pharmacol. 96: 675–687, 1989.
 158. Mack, G., H. Nose, and E. R. Nadel. Role of cardiopulmonary baroreflexes during dynamic exercise. J. Appl. Physiol. 65: 1827–1832, 1988.
 159. Mack, G., H. Nose, A. Takamata, and T. Morimoto. Thermoregulatory control of skin blood flow during exercise. Med. Sci. Sports Exerc. 23: S156, 1991.
 160. Mark, A. L., and G. Mancia. Cardiopulmonary baroreflexes in humans. In: Handbook of Physiology. Peripheral Circulation and Organ Blood Flow, edited by J. T. Shepherd, and F. M. Abboud. Bethesda, MD: Am. Physiol. Soc., 1983, sect. 2, vol. III, pt. 2, chapt. 21, p. 795–813.
 161. McGirr, E. M. The rate of removal of radioactive sodium following its injection into muscle and skin. Clin. Sci. (Colch.) 11: 91–99, 1952.
 162. McNamara, H. I., J. M. Sikorski, and H. Clavin. The effects of lower body negative pressure on hand blood flow. Cardiovasc. Res. 3: 284–291, 1969.
 163. Meiri, U., M. Shochina, and M. Horowitz. Heat acclimated hypohydrated rats: age dependent vasomotor and plasma volume responses to heat stress. J. Therm. Biol. 16: 241–247, 1991.
 164. Mescon, H., H. J. Hurley, Jr., and G. Moretti. The anatomy and histochemistry of the arteriovenous anastomosis in human digital skin. J. Invest. Dermatol. 217: 133–144, 1956.
 165. Miki, K., T. Morimoto, H. Nose, T. Itoh, and S. Yamada. Canine blood volume and cardiovascular function during hyperthermia. J. Appl. Physiol. 55: 300–306, 1983.
 166. Montain, S. J., and E. F. Coyle. Fluid ingestion during exercise increases skin blood flow independent of increases in blood volume. J. Appl. Physiol. 73: 903–910, 1992.
 167. Moore, F. T., S. A. Marable, and E. Ogden. Contractility of heart in abnormal temperatures. Ann. Thorac. Surg. 2: 446–450, 1966.
 168. Morimoto, T. Thermoregulation and body fluids: role of blood volume and central venous pressure. Jpn. J. Physiol. 40: 165–179, 1990.
 169. Mosley, J. G. A reduction in some vasodilator responses in freestanding man. Cardiovasc. Res. 3: 14–21, 1969.
 170. Murray, R. H. Cardiopulmonary effects of brief, intense thermal exposures. J. Appl. Physiol. 21: 1717–1724, 1966.
 171. Nadel, E. R., E. Cafarelli, M. F. Roberts, and C. B. Wenger. Circulatory regulation during exercise in different ambient temperatures. J. Appl. Physiol. 46: 430–437, 1979.
 172. Nadel, E. R., S. M. Fortney, and C. B. Wenger. Effect of hydration state on circulatory and thermal regulations. J. Appl. Physiol. 49: 715–721, 1980.
 173. Nemoto, E. M., and H. M. Frankel. Cerebrovascular response during progressive hyperthermia in dogs. Am. J. Physiol. 218: 1060–1064, 1970
 174. Nielsen, B., J. R. Hales, S. Strange, N. J. Christensen, J. Warberg, and B. Saltin. Human circulatory and thermoregulatory adaptations with heat acclimation and exercise in a hot, dry environment. J. Physiol. (Lond.) 460: 467–485, 1993.
 175. Nielsen, B., L. B. Rowell, and F. Bonde‐Petersen. Cardiovascular responses to heat stress and blood volume displacements during exercise in man. Eur. J. Appl. Physiol. 52: 370–374, 1984.
 176. Nielsen, B., G. Savard, E. A. Richter, M. Hargreaves, and B. Saltin. Muscle blood flow and muscle metabolism during exercise and heat stress. J. Appl. Physiol. 69: 1040–1046, 1990
 177. Ninomiya, I., and S. Fujita. Reflex effects of thermal stimulation on sympathetic nerve activity in skin and kidney. Am. J. Physiol. 230: 271–278, 1976.
 178. Nishiyasu, T., X. Shi, C. M. Gillen, G. W. Mack, and E. R. Nadel. Comparison of the forearm and calf blood flow response to thermal stress during dynamic exercise. Med. Sci. Sports Exerc. 24: 213–217, 1992.
 179. Nishiyasu, T., X. Shi, G. W. Mack, and E. R. Nadel. Effect of hypovolemia on forearm vascular resistance control during exercise in the heat. J. Appl. Physiol. 71: 1382–1386, 1991.
 180. Nishiyasu, T., X. Shi, G. W. Mack, and E. R. Nadel. Forearm vascular responses to baroreceptor unloading at the onset of exercise. J. Appl. Physiol. 75: 979–985, 1993.
 181. Nose, H., G. W. Mack, X. Shi, K. Morimoto, and E. R. Nadel. Effect of saline infusion during exercise on thermal and circulatory regulations. J. Appl. Physiol. 69: 609–616, 1990.
 182. O'Leary, D. S. Regional vascular resistance vs. conductance: which index for baroreflex responses? Am. J. Physiol. 260 (Heart Circ. Physiol. 29): H632–H637, 1991.
 183. O'Leary, D. S., and J. M. Johnson. Baroreflex control of the rat tail circulation in normothermia and hyperthermia. J. Appl. Physiol. 66: 1234–1241, 1989.
 184. O'Leary, D. S., J. M. Johnson, and W. F. Taylor. Mode of neural control mediating rat tail vasodilation during heating. J. Appl. Physiol. 59: 1533–1538, 1985.
 185. Öberg, P. Å. Laser‐Doppler flowmetry. Crit. Rev. Biomed. Eng. 18: 125–163, 1990.
 186. Pérgola, P. E., D. L. Kellogg, Jr., W. A. Kosiba, and J. M. Johnson. Reflex control of active cutaneous vasodilation by skin temperature in humans. Am. J. Physiol. 266 (Heart Circ. Physiol. 35): H1979–H1984, 1994.
 187. Pérgola, P. E., D. L. Kellogg, Jr., W. A. Kosiba, and J. M. Johnson. Role of sympathetic nerves in the vascular effects of local temperature in human forearm skin. Am. J. Physiol. 265 (Heart Circ. Physiol. 34): H785–H792, 1993.
 188. Pergola, P. E., D. L. Kellogg, Jr., W. A. Kosiba, and J. M. Johnson. Neural mechanisms for the control of skin blood flow in exercising humans by whole body and local skin cooling. FASEB J. 8: A864, 1994.
 189. Peter, W., and W. Riedel. Neurogenic non‐adrenergic cutaneous vasodilatation elicited by hypothalamic thermal stimulation in dogs. Pflügers Arch. 395: 115–120, 1982.
 190. Phillips, H. H., and D. B. Jennings. Cardiorespiratory effects of hypothalamic heating in concious dogs. Am. J. Physiol. 225: 700–705, 1973.
 191. Piiper, J. Durchblutung der arterio‐venösen Anastomosen und Wärmeaustausch an der Hundeextremität. Pflügers Arch. 268: 242–253, 1959.
 192. Pleschka, K. Control of tongue blood flow in regulation of heat loss in mammals. Rev. Physiol. Biochem. Pharmacol. 100: 75–120, 1984.
 193. Prichard, M. M. L., and P. M. Daniel. Arterio‐venous anastomoses in the human external ear. J. Anat. 90: 309–317, 1956.
 194. Proppe, D. W. α‐Adrenergic control of intestinal circulation in heat‐stressed baboons. J. Appl. Physiol. 48: 759–764, 1980.
 195. Proppe, D. W. Influence of skin temperature on central thermoregulatory control of leg blood flow. J. Appl. Physiol. 50: 974–978, 1981.
 196. Proppe, D. W. Adrenergic control of the renal vasoconstriction during heat stress. Federation Proc. 43: 1081, 1984.
 197. Proppe, D. W. Control of plasma renin activity in heat‐stressed baboons on varied salt intake. J. Appl. Physiol. 62: 1531–1537, 1987.
 198. Proppe, D. W. Effect of sodium depletion on peripheral vascular responses to heat stress in baboons. J. Appl. Physiol. 62: 1538–1543, 1987.
 199. Proppe, D. W. Effects of hyperosmolality and diuretics on baboon limb vasodilation during heating. Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol 27): R309–R317, 1990.
 200. Proppe, D. W., G. L. Brengelmann, and L. B. Rowell. Control of baboon limb blood flow and heart rate–role of skin vs. core temperature. Am. J. Physiol. 231: 1457–1465, 1976.
 201. Radigan, L. R., and S. Robinson. Effects of environmental heat stress and exercise on renal blood flow and filtration rate. J. Appl. Physiol. 2: 185–191, 1949.
 202. Riedel, W., M. Iriki, and E. Simon. Regional differentiation of sympathetic activity during peripheral heating and cooling in anesthetized rabbits. Pflügers Arch. 332: 239–247, 1972.
 203. Riedel, W., E. Kozawa, and M. Iriki. Renal and vasomotor and respiratory rate adjustments to peripheral cold and warm stimuli and to bacterial endotoxin in conscious rabbits. J. Auton. Nerv. Syst. 5: 177–194, 1982.
 204. Roberts, M. F., J. D. Chilgren, and A. C. Zygmunt. Effect of temperature on alpha‐adrenoceptor affinity and contractility of rabbit ear blood vessels. Blood Vessels 26: 185–196, 1989.
 205. Roberts, M. F., and C. B. Wenger. Control of skin blood flow during exercise by thermal reflexes and baroreflexes. J. Appl. Physiol. 48: 717–723, 1980.
 206. Roberts, M. F., C. B. Wenger, J. A. J. Stolwijk, and E. R. Nadel. Skin blood flow and sweating changes following exercise training and heat acclimation. J. Appl. Physiol. 43: 133–137, 1977.
 207. Rocchini, A. P., J. R. Cant, and A. C. Barger. Carotid sinus reflex in dogs with low‐ and high‐sodium intake. Am. J. Physiol. 233 (Heart Circ. Physiol. 2): H196–H202, 1977.
 208. Roddie, I. C. Circulation to skin and adipose tissue. In: Handbook of Physiology. Peripheral Circulation and Organ Blood Flow, edited by J. T. Shepherd, and F. M. Abboud. Bethesda, MD: Am. Physiol. Soc., 1983, sect. 2, vol. 3, pt. 1, chapt. 10, p. 285–317.
 209. Roddie, I. C., and J. T. Shepherd. Evidence from venous oxygen saturation measurements that the increase in forearm blood flow during body heating is confined to the skin. J. Physiol. (Lond.) 134: 444–450, 1956.
 210. Roddie, I. C., J. T. Shepherd, and R. F. Whelan. The contribution of constrictor and dilator nerves to the skin vasodilation during body heating. J. Physiol. (Lond.) 136: 489–497, 1957.
 211. Roddie, I. C., J. T. Shepherd, and R. F. Whelan. The vasomotor nerve supply of the human forearm. Clin. Sci. (Colch.) 16: 67–74, 1957.
 212. Rolewicz, T. F., and B. G. Zimmerman. Peripheral distribution of cutaneous sympathetic vasodilator system. Am. J. Physiol. 223: 939–943, 1972.
 213. Rolewicz, T. F., and B. G. Zimmerman. Activation of sustained sympathetic vasodilatation in dog by spinal cord stimulation. Experientia 32: 1447–1449, 1976.
 214. Rothe, C. F. Venous system: physiology of the capacitance vessels. In: Handbook of Physiology. Peripheral Circulation and Organ Blood Flow, edited by J. T. Shepherd, and F. M. Abboud. Bethesda, MD: Am. Physiol. Soc., 1983, sect. 2, vol. 3, pt. 1, chapt. 13, p. 397–452.
 215. Rowell, L. B. Human cardiovascular adjustments to exercise and thermal stress. Physiol. Rev. 54: 75–159, 1974.
 216. Rowell, L. B. Cardiovascular adjustments to thermal stress. In: Handbook of Physiology. Peripheral Circulation and Organ Blood Flow, edited by J. T. Shepherd, and F. M. Abboud. Bethesda, MD: Am. Physiol. Soc., 1983, sect. 2, vol. 3, pt. 2, chapt. 27, p. 967–1024.
 217. Rowell, L. B. Human Circulation: Regulation During Physical Stress. New York: Oxford University Press, 1986.
 218. Rowell, L. B. Human Cardiovascular Control. New York: Oxford University Press, 1993.
 219. Rowell, L. B., G. L. Brengelmann, J. R. Blackmon, and J. A. Murray. Redistribution of blood flow during sustained high skin temperature in resting man. J. Appl. Physiol. 28: 415–420, 1970.
 220. Rowell, L. B., J.‐M. R. Detry, G. R. Profant, and C. Wyss. Splanchnic vasoconstriction in hyperthermic man–role of falling blood pressure. J. Appl. Physiol. 31: 864–869, 1971.
 221. Rowell, L. B., C. R. Wyss, and G. L. Brengelmann. Sustained human skin and muscle vasoconstriction with reduced baroreceptor activity. J. Appl. Physiol. 34: 639–643, 1973.
 222. Ryan, K. L., and D. W. Proppe. Effect of water or saline intake on heat‐induced limb vasodilation in dehydrated baboons. Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol. 27): R318–R324, 1990.
 223. Ryan, K. L., and D. W. Proppe. Effects of compartmental fluid repletion on heat‐induced limb vasodilation in dehydrated baboons. Am. J. Physiol. 259 (Regulatory Integrative Comp. Physiol. 28): R1139–R1147, 1990.
 224. Sadowski, J., B. Kruk, and J. Chwalbiñska‐Moneta. Renal function changes during preoptic‐anterior hypothalamic heating in the rabbit. Pflügers Arch. 370: 51–57, 1977.
 225. Saller, R., and B. Lemmer. Increased cardiac noradrenaline turnover in the rat after acute exposure to environmental heat. Experientia 33: 652–653, 1977.
 226. Sancetta, S. M., J. Kramer, and E. Husni. The effects of “dry” heat on the circulation of man. I. General hemodynamics. Am. Heart J. 56: 212–221, 1958.
 227. Savage, M. V., G. L. Brengelmann, A. M. J. Buchan, and P. R. Freund. Cystic fibrosis, vasoactive intestinal polypeptide, and active cutaneous vasodilation. J. Appl. Physiol. 69: 2149–2154, 1990.
 228. Savard, G., B. Nielsen, J. Laszczynska, B. E. Larsen, and B. Saltin. Muscle blood flow is not reduced in humans during moderate exercise and heat stress. J. Appl. Physiol. 64: 649–657, 1988.
 229. Schönung, W., C. Jessen, H. Wagner, and E. Simon. Regional blood flow antagonisms induced by central thermal stimulation in the conscious dog. Experientia 27: 1291–1292, 1971.
 230. Schönung, W., H. Wagner, C. Jessen, and E. Simon. Differentiation of cutaneous and intestinal blood flow during hypothalamic heating and cooling in anesthetized dogs. Pflügers Arch. 328: 145–154, 1971.
 231. Schönung, W., H. Wagner, and E. Simon. Neurogenic vasodilatory component in the thermoregulatory skin blood flow response of the dog. Naunyn Schmiedebergs Arch. Pharmacol. 273: 230–241, 1972.
 232. Senay, L. C., L. D. Prokop, L. Cronau, and A. B. Hertzman. Relation of local skin temperature and local sweating to cutaneous blood flow. J. Appl. Physiol. 18: 781–785, 1963.
 233. Simon, E., and W. Reidel. Diversity of regional sympathetic outflow in integrative cardiovascular control. Brain Res. 87: 323–333, 1975.
 234. Smith, J. H., S. Robinson, and M. Pearcy. Renal responses to exercise, heat and dehydration. J. Appl. Physiol. 4: 659–665, 1952.
 235. Smolander, J., J. Saalo, and O. Korhonen. Effect of work load on cutaneous vascular response to exercise. J. Appl. Physiol. 71: 1614–1619, 1991.
 236. Söderberg, U. Changes in the muscle circulation elicited by local heating of the hypothalamus. Experientia 12: 299–300, 1956.
 237. Solack, S. D., G. L. Brengelmann, and P. R. Freund. Sweat rate vs. forearm blood flow during lower body negative pressure. J. Appl. Physiol. 58: 1546–1552, 1985.
 238. Spence, R. J., B. A. Rhodes, and H. W. Wagner, Jr. Regulation of arteriovenous anastomotic and capillary blood flow in the dog leg. Am. J. Physiol. 222: 326–332, 1972.
 239. Spurr, G. B., and N. J. Dwyer. Hepatic blood flow and indocyanine green disappearance in hyperthermia and endogenous fever. J. Appl. Physiol. 32: 362–368, 1972.
 240. Stephenson, L. A., and M. A. Kolka. Menstrual phase and time of day alter reference signal controlling arm blood flow and sweating. Am. J. Physiol. 249 (Regulatory Integrative Comp. Physiol. 18): R186–R191, 1985.
 241. Stephenson, L. A., C. B. Wenger, B. H. O'Donovan, and E. R. Nadel. Circadian rhythm in sweating and cutaneous blood flow. Am. J. Physiol. 246 (Regulatory Integrative Comp. Physiol. 15): R321–R324, 1984.
 242. Takeshita, S., and C. M. Ferrario. Altered neural control of cardiovascular function in sodium‐depleted dogs. Hypertension 4 (Suppl II): 175–182, 1982.
 243. Taylor, W. F., and V. S. Bishop. A role for nitric oxide in active thermoregulatory vasodilation. Am. J. Physiol. 264 (Heart Circ. Physiol. 33): H1355–H1359, 1993.
 244. Taylor, W. F., S. E. DiCarlo, and V. S. Bishop. Neurogenic control of rabbit ear blood flow. Am. J. Physiol. 262 (Regulatory Integrative Comp. Physiol. 31): R766–R770, 1992.
 245. Taylor, W. F., J. M. Johnson, W. A. Kosiba, and C. M. Kwan. Graded cutaneous vascular responses to dynamic leg exercise. J. Appl. Physiol. 64: 1803–1809, 1988.
 246. Taylor, W. F., J. M. Johnson, and W. A. Kosiba. Roles of absolute and relative load in skin vasoconstrictor responses to exercise. J. Appl. Physiol. 69: 1131–1136, 1990.
 247. Taylor, W. F., J. M. Johnson, D. O'Leary, and M. K. Park. Effect of high local temperature on reflex cutaneous vasodilation. J. Appl. Physiol. 57: 191–196, 1984.
 248. Thauer, R. Circulatory adjustments to climatic requirements. In: Handbook of Physiology. Circulation, edited by W. F. Hamilton. Washington, DC: Am. Physiol. Soc., 1965, sect. 2, vol. III, chapt. 55, p. 1921–1966.
 249. Thornton, R. M., and D. W. Proppe. Attenuation of hindlimb vasodilation in heat‐stressed baboons during dehydration. Am. J. Physiol. 250 (Regulatory Integrative Comp. Physiol. 19): R30–R35, 1986.
 250. Thornton, R. M., and D. W. Proppe. Influence of vasoconstrictor systems on leg vasodilation during heating of dehydrated baboons. Am. J. Physiol. 254 (Heart Circ. Physiol. 23): H11–H19, 1988.
 251. Thornton, R. M., and D. W. Proppe. Influence of dehydration on locally mediated hindlimb vasodilation in baboons. Am. J. Physiol. 255 (Heart Circ. Physiol. 24): H266–H271, 1988.
 252. Tonnesen, A. S., C. Marnock, J. M. C. Bull, C. J. Morgenweck, and K. D. Fallon. Sweating, hemodynamic responses, and thermoequilibration during hyperthermia in humans. J. Appl. Physiol. 62: 1596–1602, 1987.
 253. Traks, E., and S. M. Sancetta. The effects of “dry” heat on the circulation of man. II. Splanchnic hemodynamics. Am. Heart J. 57: 438–448, 1959.
 254. Traks, E., and S. M. Sancetta. The effects of “dry” heat on the circulation of man. Renal hemodynamics. Am. Heart J. 64: 235–242, 1962.
 255. Trautwein, W., and J. Dudel. Aktionspotential und Mechanogramm des Katzenpapillarmuskels als Funktion der Temperatur. Pflügers Arch. 260: 104–115, 1954.
 256. Tripathi, A., G. W. Mack, and E. R. Nadel. Cutaneous vascular reflexes during exercise in the heat. Med. Sci. Sports Exerc. 22: 796–803, 1990.
 257. Tripathi, A., and E. R. Nadel. Forearm skin and muscle vasoconstriction during lower body negative pressure. J. Appl. Physiol. 60: 1535–1541, 1986.
 258. Turlejska, E., and M. A. Baker. Elevated CSF osmolality inhibits thermoregulatory heat loss response. Am. J. Physiol. 251 (Regulatory Integrative Comp. Physiol. 20): R749–R754, 1986.
 259. Turlejska‐Stelmasiak, E. The influence of dehydration on heat dissipation mechanisms in the rabbit. J. Physiol. Paris 68: 5–15, 1974.
 260. Van Beaumont, W., and R. W. Bullard. Sweating: the rapid response to muscular work. Science 141: 643–646, 1963.
 261. Vanhoutte, P. M. Physical factors of regulation. In: Handbook of Physiology. Vascular Smooth Muscle, edited by D. F. Bohr, A. P. Somlyo, H. V. Sparks, Jr., and S. R. Geiger. Bethesda, MD: Am. Physiol. Soc., 1980, sec. 2, vol. II, chapt. 16, p. 443–474.
 262. Walther, O.‐E., M. Iriki, and E. Simon. Antagonistic changes of blood flow and sympathetic activity in different vascular beds following central thermal stimulation. II. Cutaneous and visceral sympathetic activity during spinal cord heating and cooling in anesthetized rabbits and cats. Pflügers Arch. 319: 162–184, 1970.
 263. Wenger, C. B., R. B. Bailey, M. F. Roberts, and E. R. Nadel. Interaction of local and reflex thermal effects in control of forearm blood flow. J. Appl. Physiol. 58: 251–257, 1985.
 264. Wenger, C. B., M. F. Roberts, J. A. J. Stolwijk, and E. R. Nadel. Forearm blood flow during body temperature transients produced by leg exercise. J. Appl. Physiol. 38: 58–63, 1975.
 265. Wenger, C. B., L. A. Stephenson, and M. A. Durken. Effect of nerve block on response of forearm blood flow to local temperature. J. Appl. Physiol. 61: 227–232, 1986.
 266. Wezler, K., and R. Thauer. Der Kreislauf im der Wämeregulation. Z. Ges. Exptl. Med. 112: 345–379, 1943.
 267. Whittow, G. C. The effect of hyperthermia on the systemic and pulmonary circulation of the ox. (Bos Taurus). Q. J. Exp. Physiol. 50: 300–311, 1965.
 268. Wurster, R. D., R. D. McCook, and W. C. Randall. Cutaneous vascular and sweating responses to tympanic and skin temperature. J. Appl. Physiol. 21: 617–622, 1966.
 269. Wyss, C. R., G. L. Brengelmann, J. M. Johnson, L. B. Rowell, and M. Niederberger. Control of skin blood flow, sweating and heart rate: role of skin vs. core temperature. J. Appl. Physiol. 36: 726–733, 1974.
 270. Wyss, C. R., G. L. Brengelmann, J. M. Johnson, L. B. Rowell, and D. Silverstein. Altered control of skin blood flow at high skin and core temperatures. J. Appl. Physiol. 38: 839–845, 1975.
 271. Wyss, C. R., and L. B. Rowell. Lack of humanlike active vasodilation in skin of heat‐stressed baboons. J. Appl. Physiol. 41: 528–531, 1976.
 272. Yen, A., and I. M. Braverman. Ultrastructure of the human dermal microcirculation: the horizontal plexus of the papillary dermis. J. Invest. Dermatol. 66: 131–142, 1976.
 273. Zelis, R., D. T. Mason, and E. Braunwald. Partition of blood flow to the cutaneous and muscular beds of the forearm at rest and during leg exercise in normal subjects and in patients with heart failure. Circ. Res. 24: 799–806, 1969.
 274. Zimmerman, B. G. Sympathetic vasodilatation in the dog's paw. J. Pharmacol. Exp. Ther. 152: 81–87, 1966.
 275. Zoller, R. P., A. L. Mark, F. M. Abboud, P. G. Schmid, and D. D. Heistad. The role of low pressure baroreceptors in reflex vasoconstrictor responses in man. J. Clin. Invest. 51: 2967–2972, 1972

Contact Editor

Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite

John M. Johnson, Duane W. Proppe. Cardiovascular Adjustments to Heat Stress. Compr Physiol 2011, Supplement 14: Handbook of Physiology, Environmental Physiology: 215-243. First published in print 1996. doi: 10.1002/cphy.cp040111