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Narrow range of atmospheric pressure

Pressure is a force exerted by a substance that is in contact with another substance. Atmospheric pressure is pressure exerted by the mixture of gases (primarily nitrogen and oxygen) in the Earth’s atmosphere. Although you may not perceive it, atmospheric pressure is constantly pressing down on your body. This pressure keeps gases within your body, such as the gaseous nitrogen in body fluids, dissolved. If you were suddenly ejected from a space ship above Earth’s atmosphere, you would go from a situation of normal pressure to one of very low pressure. The pressure of the nitrogen gas in your blood would be much higher than the pressure of nitrogen in the space surrounding your body. As a result, the nitrogen gas in your blood would expand, forming bubbles that could block blood vessels and even cause cells to break apart.

Atmospheric pressure does more than just keep blood gases dissolved. Your ability to breathe—that is, to take in oxygen and release carbon dioxide—also depends upon a precise atmospheric pressure. Altitude sickness occurs in part because the atmosphere at high altitudes exerts less pressure, reducing the exchange of these gases, and causing shortness of breath, confusion, headache, lethargy, and nausea. Mountain climbers carry oxygen to reduce the effects of both low oxygen levels and low barometric pressure at higher altitudes ( [link] ).

Harsh conditions

This photo shows Mount Everest as seen from a distance. It is a large, pyramid-shaped, craggy peak with many smaller snow-covered peaks in the foreground. The peak of Mount Everest is partially occluded by clouds.
Climbers on Mount Everest must accommodate extreme cold, low oxygen levels, and low barometric pressure in an environment hostile to human life. (credit: Melanie Ko/flickr)

Homeostatic imbalances

Decompression sickness

Decompression sickness (DCS) is a condition in which gases dissolved in the blood or in other body tissues are no longer dissolved following a reduction in pressure on the body. This condition affects underwater divers who surface from a deep dive too quickly, and it can affect pilots flying at high altitudes in planes with unpressurized cabins. Divers often call this condition “the bends,” a reference to joint pain that is a symptom of DCS.

In all cases, DCS is brought about by a reduction in barometric pressure. At high altitude, barometric pressure is much less than on Earth’s surface because pressure is produced by the weight of the column of air above the body pressing down on the body. The very great pressures on divers in deep water are likewise from the weight of a column of water pressing down on the body. For divers, DCS occurs at normal barometric pressure (at sea level), but it is brought on by the relatively rapid decrease of pressure as divers rise from the high pressure conditions of deep water to the now low, by comparison, pressure at sea level. Not surprisingly, diving in deep mountain lakes, where barometric pressure at the surface of the lake is less than that at sea level is more likely to result in DCS than diving in water at sea level.

In DCS, gases dissolved in the blood (primarily nitrogen) come rapidly out of solution, forming bubbles in the blood and in other body tissues. This occurs because when pressure of a gas over a liquid is decreased, the amount of gas that can remain dissolved in the liquid also is decreased. It is air pressure that keeps your normal blood gases dissolved in the blood. When pressure is reduced, less gas remains dissolved. You have seen this in effect when you open a carbonated drink. Removing the seal of the bottle reduces the pressure of the gas over the liquid. This in turn causes bubbles as dissolved gases (in this case, carbon dioxide) come out of solution in the liquid.

The most common symptoms of DCS are pain in the joints, with headache and disturbances of vision occurring in 10 percent to 15 percent of cases. Left untreated, very severe DCS can result in death. Immediate treatment is with pure oxygen. The affected person is then moved into a hyperbaric chamber. A hyperbaric chamber is a reinforced, closed chamber that is pressurized to greater than atmospheric pressure. It treats DCS by repressurizing the body so that pressure can then be removed much more gradually. Because the hyperbaric chamber introduces oxygen to the body at high pressure, it increases the concentration of oxygen in the blood. This has the effect of replacing some of the nitrogen in the blood with oxygen, which is easier to tolerate out of solution.

The dynamic pressure of body fluids is also important to human survival. For example, blood pressure, which is the pressure exerted by blood as it flows within blood vessels, must be great enough to enable blood to reach all body tissues, and yet low enough to ensure that the delicate blood vessels can withstand the friction and force of the pulsating flow of pressurized blood.

Chapter review

Humans cannot survive for more than a few minutes without oxygen, for more than several days without water, and for more than several weeks without carbohydrates, lipids, proteins, vitamins, and minerals. Although the body can respond to high temperatures by sweating and to low temperatures by shivering and increased fuel consumption, long-term exposure to extreme heat and cold is not compatible with survival. The body requires a precise atmospheric pressure to maintain its gases in solution and to facilitate respiration—the intake of oxygen and the release of carbon dioxide. Humans also require blood pressure high enough to ensure that blood reaches all body tissues but low enough to avoid damage to blood vessels.

Questions & Answers

what is partial pressure?
Tariq Reply
it is the pressure exerted by mixture of gases...
Fatukasi
What is the Important of studying anatomy and philosophy
Michael Reply
because to know the mechanisms of our body
Tariq
how many region do we have in human body
nsofor Reply
head thorax abdomen and many kind of...
Shan
what is principal ponatine nucleas
Tariq
Human body can be divided into different regions on the basis of: 1. Systems: e.g. digestive system, respiratory system, excretory system etc.. 2. Parts: e.g. head, thorax, neck, upper limbs, lower limbs etc..
AMEL
we have 9 region in d human body
ZAINAB
what is systematic anatomy?
nsofor Reply
it is the anatomy or study of a certain body system for example the digestive system. or respiratory system.
Summer
It is a group of structure that work together to perform a unique function..
RAPHERA
describe the division of anatomy and physiology
Vissa Reply
the what and the how
Josh
anatomy is the structure. physiology is the function.
Gavin
what is homeostasis?
nsofor
the balance if everything in your body
Kare
is the tendency of the body to maintain the internal environment
Flora
It is the ability of systems and living organisms to adjust its internal environment
RAPHERA
how does a saggital plane look like and a frontal plane
susan Reply
saggital plane divides left and right.. frontal plane divides front and back.. I'm trying to upload a picture but idk how.
Pipiena
tnx sis
Angella
what is a neurones?
Angella Reply
how many systems are there in human
Angella
It is a cell that specialized to conduct nerve impulse
RAPHERA
What is ovulation
Joy Reply
Ovulation is release of mature ovum from ovary
AMEL
what is physiology
Firdaus Reply
The study of how e body systems or structures function and interrelate with each other
Prettygal
what is the composition of the ground substance?
Nana Reply
large carbohydrates and proteins which is known as acid mucopolysacchrides
adam
thanks👍
Nana
you guy welcome
adam
Hi guys am new here
Nji
how does the negative feedback helps in maintaining body temperature at its normal range
dzreke
I need good sites that I can test myself on chapters 1,3,4,5. I have an exam tomorrow
Ana
please can you kindly share your questions here after the exams please
dzreke
What causes the banding pattern seen in the muscle fibril under the electron microscope
Nji
what organelles controls protein synthesis?
Katie Reply
Ribosome
AMEL
hmm...the ribosomes?
Fatukasi
ribosome
adam
Ribosome
Opara
Ribosome
Saifkhan
ribosome
DR
ribosome
ELIZABETH
are ribisomes made in the rRNA?
Lola
nop they are produced by cells of Nucleolus
adam
Is there anything about nerve and muscle physiology?
AMEL Reply
how many types of epithelial tissues do we have
Benedicta Reply
Epithelial tissues are grouped in two ways.. ●Based on the number of layers.(Simple and stratified ) ●Based of their shapes(Squamous,Cuboidal and columnar) Also we can have a combination of the two,say,simple Squamous
Prince
awww thanks dearie😊😊😊💖
Benedicta
describe the function and structure of blood
Belindah Reply
It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including: transporting oxygen and nutrients to the lungs and tissues.
Arlena
well answered arlena.. #thumbs up#
Fatukasi
have u some prepared MCQs on CNS and Special senses physiology?
dr
Anyone got the human heart labelled diagram
Sawmtei
you can download from Google... I don't think it's possible to share docs or files here
Fatukasi
ok thanks
Sawmtei
you're welcome..
Fatukasi
thanks
dr
Thank you
Drs
what's an easy way of knowing the different structures of tissues what they do and where their found
Lola
are you know function of the blood?
Drs
to carry nutrients to parts of the body
Lola
well Lola the easiest way is to attributes the tissues based on their funcs(especially those with similar funcs)..you can create your own mnemonics that will help you rmba em..and the a random reading.. it helps you retain em better
Fatukasi
and try random reading*
Fatukasi
ok thanks
Lola
funtction of WBCs
DR
bone tissue
Waqar
Blood is a fluid connective tissue made up of blood cells suspended in plasma, which is the fluid part of blood. The cell include erthrocytes, leukocytes and thrombocytes. Blood is responsible for transportation of substances around e body eg hormones oxygen and substances
Prettygal
Blood is responsible for defence... As it acts as a defense mechanism against microbes through action of leukocytes which destroy any foreign substances
Prettygal
identy the vein and arteries of coronary circulation
abdifatah Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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