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
There are 10 groups which contain 2 participants in the
experiment. The participants are required to dip their face in to water where
their mouth and nose are covered this is done for 30 seconds. The participant is seated in a relaxed
position, where their elbows are also rested. Throughout the whole
investigations they should maintain this position. An informed consent is
handed out to know about the risks or benefits which is signed by all the
A blood pressure monitor is used to measure the systolic and
the diastolic blood pressure. The cuff
used is placed at the same level as the heart and throughout the experiment it
should be kept at this level, by doing this the best results can be achieved.
To start the participant is relaxed and a reading is taken
by using the blood pressure monitor, a note is made on the heart rate, systolic
and diastolic blood pressure. To make
sure a steady reading is made after 5 minutes another reading is taken of the
rest period. Another reading is now taken when the participant is holding their
breath, the breath is approximately held for 30 seconds until the reading has
The first water for facial immersion is warm, to start the
participant is given 5 minutes of rest time this is to ensure the
cardiovascular values are steady. In a plastic bowl warm water is added at a
temperature around 25®C, a thermometer is used to make sure the temperature is
right. The participants face is then
immerged in the water while the face is submerged there should be no exhaling
against the closed airways. The blood pressure monitor is then started and the
face is submerged until the monitor obtains a reading the face is submerged for
around 30 seconds and the participant is reassured and kept calm by giving them
a reminder on how long is left.
The participants are giving a 5-minute rest period again and
this allows the cardiovascular values to stay same. The plastic bowl is filled
again with cold water at approximately 10® C. The participant immerses their
face in the water and the blood pressure monitor gives a reading.
Three tests are done they are the shapiro wilk normality
test this is done to find out if the data is parametric or not, the second test
done was the paired T test and this test is able to compare the means between
two groups which are related on the same variable. The final test which is done
is known as the repeated ANOVA test. A two way repeated ANOVA is able to
compare the mean difference between the groups which have been split.
From the results the descriptive statistics has the highest
standard deviation in the systolic blood pressure in warm water and cold water.
Standard deviation is able to show the measurements for a group which have been
spread out from the mean. For cold water
the standard deviation is 24.161 while the standard deviation for warm water is
24.927. The lowest standard deviation is 6.124 this is for the warm water and
the heart rate. For cold water the heart rate the standard deviation is 7.533
which is higher than the standard deviation for warm water. The highest mean is
148.67 which is the cold water systolic blood pressure, the warm water systolic
blood pressure has the second highest mean showing 135.11. The lowest mean was
64.00 for the heart rate of the cold water.
After looking at the paired samples Test the third pair has
shown the highest mean at 13.389 and this it between the resting heart rate and
the cold water heart rate. But the standard deviation is not very high and this
means the data is not spread away far away from the mean. This means the
results are consistent. Pair 6 has the lowest mean at -29.500 but the highest
standard deviation of 16.432.
Paired sample statistics have shown the highest standard
error mean at 8.309. The lowest standard error mean is 2.041. The pairs which
show that there is a significant difference are pairs 2,3,5,6 and 9. The pairs
which had shown no significant difference are pairs 1,4,7 and 8.
The multivariate test shows that the Wilk’s lambda has a
value of 0.34 and this is smaller than the value of 0.05 and this is the alpha,
this therefore makes it significant. The
significant column of the chart is 0.389 and this is also smaller than the
alpha value so it significant. Even though the results are significant, the
significant P value is over 0.05 so it undermines the result.
The descriptive statistics have shown high standard
deviation for the systolic blood pressure while holding breath and systolic
blood pressure with warm water. The high standard deviation shows that the data
has been spread out over wider range of values. When the standard deviation is
low like the warm water and heart rate this means that the data is close to the
mean. The mean for the descriptive statistics. As you can see from the
descriptive statistics the systolic blood pressure in warm water is lower than
cold water this shows that there is a sig difference between the two. For
diastolic blood pressure in warm water and cold water, the diastolic blood
pressure is higher in cold water than in warm water. Overall the systolic blood
pressure has the highest mean when in cold water and overall higher than the
diastolic blood pressure.
Blood pressure and heart rate are regulated by rise and fall
effect. For example, blood pressure is low (64) when heart rate is high in cold
water (148). When blood pressure is high (67) the heart rate is low (135).
There are many limitations which may impact the results. The
participant makes have anxiety which can make a big impact on the results.
Another reason may be the participant may have a short breath which won’t allow
the monitor to take its reading as it takes approximately 30 seconds for a
reading. Changes to the results can also be if you are a smoker. Medical
conditions will also make a big difference such as heart disease, diabetes or a
type of respiratory condition.
When there is immersion of the face in water a diving reflex
is triggered, the best effect of the diving reflex can be seen if the face is
submerged in cold water. The initial stimuli are the receptors on the face,
this then inhibits trigeminal nerves which then inhibits the respiratory centre
to inhibit the respiratory muscles. The receptors on the face are not the only
stimuli arterial chemoreceptors stimulate the cardiovascular center, the heart
is inhibited to allow vasoconstriction balance which reduces the energy
consumption of the heart. Vasoconstriction
is stimulated this redirects the blood towards the vital organs such as the
brain and the heart.
To conclude the aim of the investigation was to see the
changes in heart rate when the face is submerged in cold and warm water. The
results have shown there are changes in the systolic and diastolic blood
pressure as well as the heart rate when the face is submerged. We can see the
diving reflex can be seen at its peak when the face is submerged in cold water.