diving refex

Diving reflex

The diving reflex is a common and well developed adaptation in aquatic mammals. Completed by special anatomical and physiological properties
it makes diving for an extending period reaching greater depth possible.
Non-water bound mammals do have a diving reflex, but not as significant.
Man shows an intermediate form, but much stronger than their next of kin, the other great apes.
In this project, the main source is the publication of dr. E. Schagatay on the subject.

Link to publication of mrs Schagatay

In this part, four aspects will be considered:
The changing of the heart beat and pumping volume, the factors and senses triggering it, the changes in partial oxygen pressure in the lungs and the spleen as possible resource of extra blood.
It is the "trigger" for the diving reflex.

The "Snoepje hap" experiment.

In her paper, Erica Schagatay states that sensors in the facial skin are the trigger for the diving reflex.
Temperature differences between air and water are an important factor. In the original paper of mrs.
Schagatay you can find out what procedures the used in the research.

"Snoepje hap" method (D. Meijers)

A. Observing a diving reflex (slowing of the heartbeat rate) in a test personA. Using the "Snoepje hap" method (figure above).
Find out the heart rate of a test person sitting relaxed in front of the bucket. Repeat the measurement after the person has tucked his head in and did keep his breath
for about 30 seconds.
The heart rate can be measured with a watch with breast band as used in sports (figure) and with an earlobe or fingertip sensor connected to a computer (Pasco or Vernier software) or a wrist type of blood pressure measuring instrument.
You have to repeat the test a number of times to be sure of the results. Snoepjehappen is a Dutch game on birthday parties, children have to pick up a
sweet from the bottom with their mouth, as depicted.

B. Diving reflex-test in a swimming pool For this test you need a water resistant heart rate monitor as used in sports and diving goggles to check your
heartbeat rate whilst being emerged. You can prolong your stay under water if you hyperventilate vigorously four times before entering the water.
Hold your breath at first and than slowly release air (this helps to stop panic).The best option is to ask a local diving club to assist you for safety reasons.
They are usually very helpful, interested as they are in these phenomena.Information:

Every mammal living on land is capable of holding its breath. But humans share with water bound animals like seals, dolphins and otters the ability to do this
for considerable time and in a more controlled way.
It was one of the reasons for postulating the "Aquatic Ape Theory" by prof. Alistair Hardy (Oxford 1960), bringing forward the option of a more aquatic past of mankind.
One of the adaptations involved is the diving reflex, the slowing of the heartbeat when submerged in the water. After a few seconds, the beat rate slows down 10 - 40 %, something that does not happen if one just holds his breath. (Generally it amounts to 13 beats less per minute.)
To observe this under water in a swimming pool, you could use a water resistant heart rate monitor with breast belt

.
Timex water resistant heart rate monitor

The results an description in PPT (plus more)

Diving Reflex Test
We are making use of the procedure used by the Dutch Swimming and Diving Information Centre Duik en Zwem informatiecentrum

At first :

Every non aquatic mammal does hold its breath if submerged, but man is abel to do this for a prolonged time, the way diving mammals do like otter, beaver, seal, dolphin and whale.
It seems that we are also adapted to water during our evolutionary history, as is stated in the "Aquatic Ape Theory" of Prof. Hardy (Oxford 1960) .

One of these adaptations is the diving reflex. In diving, our heart beat slows down
10 - 40 %, something that is not happening when we hold our breath normally.
In general a slowing down with about 13 beats per minute is observed. Tests to show the diving reflex.

A.	Standing on the platform, take your heart beat for 20 seconds and multiply by 3. Repeat tree times.	=	____beats per minute (mean)
B.	The same, laying down on the platform	=	____ beats per minute
C.	The same, floating horizontally, wit your face under water .	=	____ beats per minute
D.	Repeat standing on the bottom at the deepest point with a lead girdle attached.	=	____ beats per minute

Note:
In C. and D. a partner gives the signal for the start and end of 20 the second time lap by tapping the swimming pool ladder or by slightly pulling a string, attached to the upper arm of the swimmer.

A divingclub can assist by using assistant breathing under water.

Question 1.
What is the difference between beats per minute in A. B. C. and D?
Fill in the table below.

Differences in beats/minute	A.	B.	C.	D.
A.
B.
C.
D.

Question 2.
Find out what the advantages of the diving reflex are in active diving.
Question 3.
If your own observations are compared to the ones mentioned in the illustration below, what are the conclusions about your achievement?

The results movie: diving reflex experiment (200MB mov)

Three measurements are taken for every test person, with an adequate period of recovery in between.Present the results of your measurements in a table. Draw your conclusion about the question; is there a noticeable diving reflex in humans?
You can compare the outcomes with the original figures presented by mrs. Schagatay and the dutch "Zwem Informatie en Documentatiecentrum".If you had the opportunity to get help from a local diving club, you can ask scuba divers to wear water resistant heart rate measurers while making dives to greater depths.
This could give an answer to the question if hydrostatic pressure does have an influence (as seems to be the case in the documentary A Deeper Blue).
It is also reported from sponge gathering divers in the Mediterranean and pearl divers in Japan, but this could be the result of adaptation by training.

Ama, woman of the Japanese pearl diver cast.

C. Deep Diving and relative oxygen pressure Read this first: Free dive girl: Watch the documentary film The Science of Diving (1 hrs)
Search on WWW for the latest record in this extreme sport of free deep diving.

The Science of Diving DVD

What physiological changes are described for these divers concerning heartbeat, blood circulation in the extremities and partial pressure of oxygen (=concentration) in the lungs compared to the values in blood.
As a result of the increasing hydrostatical pressure the lungs are compressed as does the volume of air contrapted.
This compressing of the air mass has an advantage for the diver, related to the oxygen saturation of blood in the lungs. Describe how this works.
Hint: it as to do with the relative amount of oxygen in the volume, total pressure increases by1000 hPa per 10m depth.
Calculate in % the effect on relative change in O2_pressure for a free diving Ama pearl diver, operating at a depth of 5m.
Do the same for Tanya Streeter, diving to a depth of 100m.

D. Is there a link between the diving reflex and the function of the spleen?Free divers do think, that the spleen can give an extra boost to them whilst descending to great depths.
Find out about it in an article by diving instructor Eric Seedhouse: Erik Seedhouse ; on the free dive site "Deeper Blue" .

Extra information: Spleen and Diving (pdf)