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Diving reflex Save 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 reflexesand is found in all air-breathing vertebrates studied to date.
The diving reflex is exhibited Stimulated diving and heart rate in aquatic mammalssuch as seals , ottersdolphins , and muskrats , and exists as a lesser response in other animals, including humansbabies up to 6 months old see Infant swimmingand diving birdssuch as ducks and penguins.
The most noticeable effects are on the cardiovascular system, which displays peripheral vasoconstriction, slowed heart rate, redirection of blood to the vital organs to conserve oxygen, release of red blood cells stored in the spleenand, in humans, heart rhythm irregularities.
Mild bradycardia is caused by subjects holding their breath without submerging the face in water. The exact mechanism for this effect has been debated and may be a result of brain cooling similar to the protective effects seen in people treated with deep hypothermia.
The fluid shift is largely from the extravascular tissues and the increased atrial volume results in a compensatory diuresis.
Plasma volume, stroke volume, and cardiac output remain higher than normal during immersion. The increased respiratory and cardiac workload causes increased blood flow to the cardiac and respiratory muscles. Stroke volume is not greatly affected by immersion or variation in ambient pressurebut bradycardia reduces the overall cardiac output, particularly due to the diving reflex in breath-hold diving.
However, breath-hold time is reduced when the whole body is exposed to cold water as the metabolic rate increases to compensate for accelerated heat loss even when the heart rate is significantly slowed. Peripheral vasoconstriction occurs during submersion by resistance vessels limiting blood flow to muscles, skin, and visceraregions which are " hypoxia -tolerant", thereby preserving oxygenated blood for the heart, lungs, and brain.
Diuresis is reduced in dehydrated subjects, and in trained athletes in comparison with sedentary subjects. This may occur during higher intensity exercise while immersed or submersed.
Hypothermia is not the major problem in the early stages of exposure as other stresses are more immediately life-threatening. It generally starts with a gasp reflex in response to sudden and rapid chilling of the skin, and if the head is immersed there is a risk of inhaling water and drowning.
This is followed by a reflexive hyperventilationwith a risk of panic and fainting if not controlled. Cold induced vasoconstriction causes the heart to work harder and the additional work can overload a weak heart, with a possible consequence of cardiac arrest.
Cold incapacitation is the next stage, and generally occurs within 5 to 15 minutes in cold water. Blood flow to the extremities is reduced by vasoconstriction as the body attempts to reduce heat loss from the vital organs of the core.
This accelerates the cooling of the periphery, and reduces the functionality of the muscles and nerves.
The duration of exposure to produce hypothermia varies with health, body mass and water temperature. It generally takes in the order of 30 minutes for an unprotected person in water to become hypothermic. Diving mammals and birds have a considerably greater blood volume than terrestrial animals of similar size, and in addition have a far greater concentration of haemoglobin and myoglobin, and this haemoglobin and myoglobin is also capable of carrying a higher oxygen load.
During diving, the haematocrit and haemoglobin are temporarily increased by reflex splenic contraction, which discharges a large additional amount of red blood cells. The brain tissue of diving mammals also contains higher levels of neuroglobin and cytoglobin than terrestrial animals.
The muscle mass of aquatic mammals is relatively large, so the high myoglobin content of their skeletal muscles provides a large reserve. Myoglobin-bound oxygen is only released in relatively hypoxic muscle tissue, so the peripheral vasoconstriction due to the diving reflex makes the muscles ischaemic and promotes early use of myoglobin bound oxygen.Jan 21, · The diving response is a very powerful collection of reflexes that allow an organism to preserve intrinsic oxygen, contained especially within its blood, and thus prolong aerobic metabolism in its two most important organs, the heart and the brain.
The mammalian diving response consists of a respiratory apnea, a parasympathetically mediated. baroreceptor reflex the reflex responses to stimulation of baroreceptors of the carotid sinus and aortic arch, regulating blood pressure by controlling heart rate, strength of heart .
Oxygen use is minimised during the diving reflex by energy efficient swimming or gliding behaviour, and regulation of metabolism, heart rate, and peripheral vasoconstriction.  Aerobic diving capacity is limited by available oxygen and the rate at which it is consumed.
Heart rate, blood pressure, and ECG measurements were used to determine that only face immersion in water elicited the diving reflex, evident by the statistically significant (p-value= ) decrease in heart rate (mean= 14% reduction, mean= An involuntary response to breathing is called bradycardia, or slowing of the heart.
Apneaic bradycardia is triggered when by cold moisture on the face, which slows the heart rate. Breath Hold Diving. 1. During breath hold diving the circulatory system uses oxygen stored in the lungs, muscles and blood to supply tissues. Aug 25, · The first thing Ice Bucket challengers and those immersed in cold water experience is a sudden drop in skin temperature, which triggers a reflex called the cold shock response.