Introduction does save more oxygen for the usage

Introduction

When our face is cooled or when mammals hold their breath
there are some reflexes which are activated known as the diving reflex. It is
usually found in aquatic mammals such as the dolphins, seals and otters but it
can also be found in mammals such as humans .The diving reflex allows a
mechanism where the body is able to tolerate the body’s oxygen level. When the
face is submerged in the cold water there is a quick trigger within the
cardiovascular system and this helps the mammal make the oxygen in the lung and
blood. To start there is a decrease in the heart rate, later blood is directed
towards all the vital organs and away from the body’s surface, capillaries and
limbs are also constricted.  By the body
doing this it does save more oxygen for the usage by the brain and heart, it
also happens to preserve the body’s temperature in the cold water. Though the
downside is the muscles will need to use anaerobic energy and this will build
up 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 blood
vessels are narrowed to reduce blood flow as there is less blood flow towards
the limbs the blood is able to travel towards the vital organs such as the
brain and heart where oxygen can be received. Blood shift is the passing of
water and blood plasma through organs and walls to the chest cavity. This protects
the organs from the difference in pressure. The lungs also reabsorb when the
pressure drops.  There is also splencic
contraction when there are lower levels of oxygen or a higher level of carbon
dioxide the spleen contracts and this releases red blood cells increasing the
amount of oxygen of the blood, this may also start before the bradycardia.  All these changes in the body allow the
maximum time to be spent underwater.

When there is facial contact with the cold water the heart
rate decreases quickly when the water is colder the reaction takes place
quicker. The information is transmitted to the brain by a nerve called the
trigeminal facial nerve, bradycardia and peripheral vasoconstriction then takes
place after then vagus nerve is innervated. When the oxygen levels are very
close to critically low the reflex is takes place. The blood which is
accumulated in large amounts in the blood vessel of lungs is acted as
protection as it prevents the lung from collapsing from the pressure
difference.  All the blood in the body
becomes concentrated towards the vital organs such as the brain and heart. The
vasoconstriction shunts the blood away from the arms and the legs and
circulates it towards the heart and the brain. As the heart is working at a low
intensity there is less oxygen needed to work the muscles so it is a clever
survival mechanism.