China
Africa
Explore chapters and articles related to this topic
Temperature Regulation
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Cutaneous vasoconstriction is the primary response to a reduced environmental temperature and is mediated by increased sympathetic activity. Reduced cutaneous blood flow decreases heat loss from the skin. However, prolonged cooling can induce a paradoxical vasodilatation by a direct cold-induced paralysis of peripheral blood vessels that become unresponsive to catecholamines. Thereafter, vasoconstriction alternates with vasodilatation (‘hunting reaction’), which serves to prevent tissue damage such as frostbite. There is some evidence of vascular adaptation to cold. In people who are frequently exposed to cold, the vasoconstrictor effect is less severe, and the onset of vasodilatation is more rapid.
Basic Thermal Physiology: What Processes Lead to the Temperature Distribution on the Skin Surface
Published in Kurt Ammer, Francis Ring, The Thermal Human Body, 2019
Glabrous and non-glabrous skin differ slightly in their response to local cooling. Whilst in hairy skin vasoconstriction lasts if the stimulus continues, in skin without hairs, for example in the fingers, the initial vasoconstriction is reversed after a short time and skin blood flow start to fluctuate up and down. This phenomenon was called “hunting reaction” or “cold-induced vasodilation”, which was first described in 1930 by T. Lewis, who hypothesized an axon reflex as primary cause of cold vasodilation. The repeated alterations in skin perfusion are explained by active involvement of arterio-venous anastomoses (AVAs), which becomes more apparent when body core temperature is undisturbed, the skin is warm, the medium temperature for local cooling is very low, at low altitudes and absent mental stress. The hunting reaction may be modified by acclimatization to cold climate [105]. Cold-induced vasodilation was also observed in glabrous skin but without the typical fluctuations in blood flow [73].
Specialization in individual circulations
Published in Neil Herring, David J. Paterson, Levick's Introduction to Cardiovascular Physiology, 2018
Neil Herring, David J. Paterson
When a hand is placed in water at 10 °C or lower, the initial cold-induced vasoconstriction gives way to dilatation after 5-10 min (paradoxical cold vasodilatation), with flushing and pain relief (Figure 15.10c). This occurs in regions rich in AVAs, and contributes to the cold, red noses and hands seen in frosty weather. The phenomenon is attributed to the paralysis of noradrenergic neurotransmission by the cold and the release of vasodilators such as prostacyclin. Cold-induced vasodilatation is well developed in Arctic people (Inuit) and Norwegian fishermen, and helps prevent skin damage during prolonged cold exposure. If the exposure persists, vasoconstriction recurs after a while. During prolonged exposure, the skin oscillates between periods of vasoconstriction and vasodilatation at 15-20 min intervals. This is called the hunting reaction and is an adaptive response to cold that was discovered by Thomas Lewis in the 1930s. However, activating the hunting response with ice can be detrimental when treating sports injuries that involve muscle tears. Prolonged ice compressions (>10 min) will cause dilatation, exacerbate internal bleeding and promote haematoma.
Influences of ovarian hormones on physiological responses to cold in women
Published in Temperature, 2022
Andrew M. Greenfield, Nisha Charkoudian, Billie K. Alba
Following the initial sympathetically mediated vasoconstrictor response, acral skin also possesses the ability to increase blood flow through a phenomenon called cold-induced vasodilation or “the hunting reaction” [141]. Cold-induced vasodilation is characterized by oscillatory periods of vasodilation and subsequent fluctuations of local skin temperature. Though the mechanisms remain largely unknown, there is no clear evidence to suggest that sex modulates the onset or frequency of the cold-induced vasodilation response [141,153]. However, future studies examining the potential influence of the menstrual cycle and reproductive hormone status on cold-induced vasodilation are warranted.