IntroductionWhen our face is cooled or when mammals hold their breaththere are some reflexes which are activated known as the diving reflex. It isusually found in aquatic mammals such as the dolphins, seals and otters but itcan also be found in mammals such as humans .The diving reflex allows amechanism where the body is able to tolerate the body’s oxygen level. When theface is submerged in the cold water there is a quick trigger within thecardiovascular system and this helps the mammal make the oxygen in the lung andblood. To start there is a decrease in the heart rate, later blood is directedtowards all the vital organs and away from the body’s surface, capillaries andlimbs are also constricted. By the bodydoing this it does save more oxygen for the usage by the brain and heart, italso happens to preserve the body’s temperature in the cold water. Though thedownside is the muscles will need to use anaerobic energy and this will buildup the lactic acid leading to tiredness quickly. The 3 main changes in the body are known as Bradycardia,peripheral vasoconstriction and blood shift.
Bradycardia is when there is a 10%reduction in the heart rate. Peripheral vasoconstriction is when the bloodvessels are narrowed to reduce blood flow as there is less blood flow towardsthe limbs the blood is able to travel towards the vital organs such as thebrain and heart where oxygen can be received. Blood shift is the passing ofwater and blood plasma through organs and walls to the chest cavity.
This protectsthe organs from the difference in pressure. The lungs also reabsorb when thepressure drops. There is also splenciccontraction when there are lower levels of oxygen or a higher level of carbondioxide the spleen contracts and this releases red blood cells increasing theamount of oxygen of the blood, this may also start before the bradycardia. All these changes in the body allow themaximum time to be spent underwater.When there is facial contact with the cold water the heartrate decreases quickly when the water is colder the reaction takes placequicker. The information is transmitted to the brain by a nerve called thetrigeminal facial nerve, bradycardia and peripheral vasoconstriction then takesplace after then vagus nerve is innervated. When the oxygen levels are veryclose to critically low the reflex is takes place.
The blood which isaccumulated in large amounts in the blood vessel of lungs is acted asprotection as it prevents the lung from collapsing from the pressuredifference. All the blood in the bodybecomes concentrated towards the vital organs such as the brain and heart. Thevasoconstriction shunts the blood away from the arms and the legs andcirculates it towards the heart and the brain. As the heart is working at a lowintensity there is less oxygen needed to work the muscles so it is a cleversurvival mechanism.