Hunting reaction

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The hunting reaction or hunting response is a process of alternating vasoconstriction and vasodilation in extremities exposed to cold. The term Lewis reaction is used too, named after Thomas Lewis, who first described the effect in 1930. [1]

Vasoconstriction A decrease in the diameter of blood vessels, especially arteries, due to constriction of smooth muscle cells that line the vessels, and usually causing an increase in blood pressure.

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in staunching hemorrhage and acute blood loss. When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains mean arterial pressure.

Vasodilation An increase in the internal diameter of blood vessels, especially arterioles or capillaries, due to relaxation of smooth muscle cells that line the vessels, and usually resulting in a decrease in blood pressure.

Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, which is the narrowing of blood vessels.

A limb, or extremity, is a jointed, or prehensile, appendage of the human or other animal body. In the human body, the upper and lower limbs are commonly called the arms and the legs, respectively. Arms and legs are connected to torso or trunk.

Vasoconstriction occurs first to reduce heat loss, but also results in strong cooling of the extremities. Approximately five to ten minutes after the start of cold exposure, the blood vessels in the extremities will suddenly vasodilate. This is probably caused by a sudden decrease in the release of neurotransmitters from the sympathetic nerves to the muscular coat of the arteriovenous anastomoses due to local cold. This cold-induced vasodilation increases blood flow and subsequently the temperature of the fingers. A new phase of vasoconstriction follows the vasodilation, after which the process repeats itself. [1]

Neurotransmitter endogenous chemicals that transmit signals across a synapse from one neuron to another

Neurotransmitters are endogenous chemicals that enable neurotransmission. It is a type of chemical messenger which transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron to another "target" neuron, muscle cell, or gland cell. Neurotransmitters are released from synaptic vesicles in synapses into the synaptic cleft, where they are received by neurotransmitter receptors on the target cells. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available from the diet and only require a small number of biosynthetic steps for conversion. Neurotransmitters play a major role in shaping everyday life and functions. Their exact numbers are unknown, but more than 200 chemical messengers have been uniquely identified.

Sympathetic nervous system

The sympathetic nervous system (SNS) is one of the two main divisions of the autonomic nervous system, the other being the parasympathetic nervous system.

A circulatory anastomosis is a connection between two blood vessels, such as between arteries, between veins or between an artery and a vein. Anastomoses between arteries and between veins result in a multitude of arteries and veins, respectively, serving the same volume of tissue. Such anastomoses occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised, but may also occur pathologically.

The hunting reaction is one out of four possible responses to immersion of the finger in cold water. The other responses observed in the fingers after immersion in cold water are a continuous state of vasoconstriction, slow steady and continuous rewarming and a proportional control form in which the blood vessel diameter remains constant after an initial phase of vasoconstriction. However, the vast majority of the vascular responses to immersion of the finger in cold water can be classified as the hunting reaction. [1]

There are many factors which influence the strength of the response. People who live or regularly work in cold environments show an increased response. Through acclimatization tropical residents can develop an increased response which is indistinguishable from arctic residents. The role of genetic factors is not clear because it is difficult to differentiate between adaptation and acclimatization. [1]

Acclimatization or acclimatisation is the process in which an individual organism adjusts to a change in its environment, allowing it to maintain performance across a range of environmental conditions. Acclimatization occurs in a short period of time, and within the organism's lifetime. This may be a discrete occurrence or may instead represent part of a periodic cycle, such as a mammal shedding heavy winter fur in favor of a lighter summer coat. Organisms can adjust their morphological, behavioral, physical, and/or biochemical traits in response to changes in their environment. While the capacity to acclimate to novel environments has been well documented in thousands of species, researchers still know very little about how and why organisms acclimate the way that they do.

Adaptation Trait with a current functional role in the life history of an organism maintained and evolved by natural selection

In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection.

It was thought that the hunting reaction protected the fingers against cold injury and improved muscle function in the fingers. An experiment has shown cold acclimation minimizes the hunting reaction (reduced mean temperature of the digits and a prolonged time of cold exposure prior to initial vasodilation), thus putting the hand at a greater risk of cold injury when it is exposed to cold. [2]

Frostbite medical condition where localized damage is caused to skin and other tissues due to freezing

Frostbite occurs when exposure to low temperatures causes freezing of the skin or other tissues. The initial symptom is typically numbness. This may be followed by clumsiness with a white or bluish color to the skin. Swelling or blistering may occur following treatment. The hands, feet, and face are most commonly affected. Complications may include hypothermia or compartment syndrome.

See also

Hypothermia A human body core temperature below 35.0°C

Hypothermia is defined as a body core temperature below 35.0 °C (95.0 °F) in humans. Symptoms depend on the temperature. In mild hypothermia there is shivering and mental confusion. In moderate hypothermia shivering stops and confusion increases. In severe hypothermia, there may be paradoxical undressing, in which a person removes their clothing, as well as an increased risk of the heart stopping.

Thermoregulation ability of an organism to keep its body temperature within certain boundaries

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. For humans, this occurs when the body is exposed to constant temperatures of approximately 55 °C (131 °F), and with prolonged exposure at this temperature and up to around 75 °C (167 °F) death is almost inevitable. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours. The opposite condition, when body temperature decreases below normal levels, is known as hypothermia. It results when the homeostatic control mechanisms of heat within the body malfunction, causing the body to lose heat faster than producing it. Normal body temperature is around 37 °C (99 °F), and hypothermia sets in when the core body temperature gets lower than 35 °C (95 °F). Usually caused by prolonged exposure to cold temperatures, hypothermia is usually treated by methods that attempt to raise the body temperature back to a normal range.

Axon reflex

The axon reflex is the response stimulated by peripheral nerves of the body that travels away from the nerve cell body and branches to stimulate target organs. Reflexes are single reactions that respond to a stimulus making up the building blocks of the overall signaling in the body's nervous system. Neurons are the excitable cells that process and transmit these reflex signals through their axons, dendrites, and cell bodies. Axons directly facilitate intercellular communication projecting from the neuronal cell body to other neurons, local muscle tissue, glands and arterioles. In the axon reflex, signaling starts in the middle of the axon at the stimulation site and transmits signals directly to the effector organ skipping both an integration center and a chemical synapse present in the spinal cord reflex. The impulse is limited to a single bifurcated axon, or a neuron whose axon branches into two divisions and does not cause a general response to surrounding tissue.

Related Research Articles

Diuresis is increased urination and the physiologic process that produces such an increase. It involves extra urine production in the kidneys as part of the body's homeostatic maintenance of fluid balance.

The diving reflex, also known as the diving response and mammalian diving reflex, is a set of physiological responses to immersion that overrides the basic homeostatic reflexes, and is found in all air-breathing vertebrates studied to date. It optimizes respiration by preferentially distributing oxygen stores to the heart and brain, enabling submersion for an extended time.

Wrinkle fold, ridge, or crease in the skin

A wrinkle, also known as a rhytide, is a fold, ridge or crease in otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of aging processes such as glycation, habitual sleeping positions, loss of body mass, sun damage, or temporarily, as the result of prolonged immersion in water. Age wrinkling in the skin is promoted by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors. In humans, it can also be prevented to some degree by avoiding excessive solar exposure and through diet (in particular through consumption of carotenoids, tocophenols and flavonoids, vitamins, essential omega-3-fatty acids, certain proteins and lactobacilli.

Cold-stimulus headache brief pain or headache commonly associated with consumption of cold beverages or foods

A cold-stimulus headache, colloquially known as an ice-cream headache or brain freeze, is a form of brief pain or headache commonly associated with consumption of cold beverages or foods such as ice cream and ice pops. It is caused by having something cold touch the roof of the mouth, and is believed to result from a nerve response causing rapid constriction and swelling of blood vessels or a "referring" of pain from the roof of the mouth to the head. The rate of intake for cold foods has been studied as a contributing factor. A cold-stimulus headache is distinct from dentin hypersensitivity, a type of dental pain that can occur under similar circumstances.

Cold hardening is the physiological and biochemical process by which an organism prepares for cold weather.

Vibration white finger (VWF), also known as hand-arm vibration syndrome (HAVS) or dead finger, is a secondary form of Raynaud's syndrome, an industrial injury triggered by continuous use of vibrating hand-held machinery. Use of the term vibration white finger has generally been superseded in professional usage by broader concept of HAVS, although it is still used by the general public. The symptoms of vibration white finger are the vascular component of HAVS.

Diving disorders, or diving related medical conditions, are conditions associated with underwater diving, and include both conditions unique to underwater diving, and those that also occur during other activities. This second group further divides into conditions caused by exposure to ambient pressures significantly different from surface atmospheric pressure, and a range of conditions caused by general environment and equipment associated with diving activities.

Cold compression therapy, also known as hilotherapy, combines two of the principles of rest, ice, compression, elevation to reduce pain and swelling from a sports or activity injury to soft tissues and recommended by orthopedic surgeons following surgery. The therapy is especially useful for sprains, strains, pulled muscles and pulled ligaments.

Contrast bath therapy, is a form of treatment where a limb or the entire body is immersed in hot water followed by the immediate immersion of the limb or body in ice water. This procedure is repeated several times, alternating hot and cold. There does not yet appear to be any significant medical benefit from doing this, however.

Cold shock response is the physiological response of organisms to sudden cold, especially cold water.

Triple response of Lewis

The triple response of Lewis is a cutaneous response that occurs from firm stroking of the skin, which produces an initial red line, followed by a flare around that line, and then finally a wheal.

Swimming induced pulmonary edema (SIPE), also known as immersion pulmonary edema, occurs when fluids from the blood leak abnormally from the small vessels of the lung into the airspaces (alveoli).

Umbellulone chemical compound

Umbellulone is a headache-inducing monoterpene ketone found in the leaves of the tree Umbellularia californica, sometimes known as the "headache tree".

Microvasculature is defined as the microvessels – venules and capillaries of the microcirculation, with a maximum average diameter of 0.3 millimeters. As the vessels decrease in size, they increase their surface-area-to-volume ratio. This allows surface properties to play a significant role in the function of the vessel.

References

  1. 1 2 3 4 Daanen, H.A.M. (2003). "Finger cold-induced vasodilation: a review". European Journal of Applied Physiology. 89 (5): 411–426. doi:10.1007/s00421-003-0818-2. PMID   12712346.
  2. ↑ Geurts, C. L. M.; Sievert, G. G.; Cheung, S. S. (2005). "Local cold acclimation of the hand impairs thermal responses of the finger without improving hand neuromuscular function". Acta Physiologica Scandinavica. 183 (1): 117–124. doi:10.1111/j.1365-201X.2004.01374.x.
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