BIOM20002 Lecture Notes - Lecture 54: Bicarbonate, Carbonic Anhydrase, Anemia

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plumdeer622

15 Sep 2018

School

University of Melbourne

Department

Biomedicine

Course

BIOM20002

Professor

All

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Document Summary

O2 goes from higher pressure in lungs to lower in blood. Po2 in blood leaving lungs = po2 in lungs. Blood branches off so that each organ receives blood with po2=100. Solubility: indicates number of molecules that dissolve at a given partial pressure. If you leave a soft drink out in the open the co2 moves from higher pressure of co2 in drink to the lower pressure in the room. At tissues with low po2 o2 moves from hb to tissues. Hb allows blood to carry 197ml of o2 per l of blood. A small decrease in arterial po2 will have little effect on hb affinity for o2. A decrease in po2 to 70 mm hg only results in a reduction of ~5% in hb affinity for o2. During exercise the po2 of the tissues (systemic capillaries) decrease to approximately 25 mm. Hg dissociating large amounts of o2 from hb.

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Background

Almost all animal and plant cells require oxygen and give off carbon dioxide. This is called gas exchange and it occurs by passive diffusion. Some animals do all or most of their gas exchange across their skin (for example amphibians) but they have very low metabolisms and use very little oxygen and get rid of very little carbon dioxide.

On the other hand humans (and other mammals) have very high metabolic requirements and we canât rely on gas exchange over the limited 1.5 to 2.0 square meters of our skin to get enough oxygen in and carbon dioxide out fast enough. Our gas exchange takes place across a very thin membrane in the Alveoli of the lung and the gas exchange surface in humans is estimated to be between 50 and 100 square meters, or between 25 and 67 times our skin surface area.

Our lungs provide a huge surface for gas exchange but they are a dead-end system. Once the oxygen in the lungs is used up it needs to be replenished and carbon dioxide builds up in the air spaces in the lungs and needs to get out. This is where the diaphragm and a few of the skeletal muscles become important. In its relaxed state the diaphragm is at its longest and the space in the thoracic cavity (and the lungs) is small. When the diaphragm contracts it shortens, which increases the volume of the thoracic cavity (and the lungs). The increase in size means the pressure is lower in the lungs than outside so air comes into the lungs (inhalation). As the diaphragm relaxes, the lungs decrease in size enough that the pressure inside the lungs is higher than the external air pressure so air comes out (exhalation).

Introduction

In this lab you will be building a model of a lung and experimenting with different ways to breath.

Supplies:

In the Lab Kit

One round 9" balloon (one lung, we donât need two for this)
medium-sized plastic bag large enough to fit over bottom end of bottle (diaphragm)
medium-size, thin rubber band

You supply

plastic 2-liter soda bottle with bottom cut off (thoracic cavity)

Tape (optional)

Directions:

1. Insert the balloon through the open bottom of a modified 2-liter soda bottle and up over the neck of the bottle. Pull the end of the balloon over the edges of the neck of the bottle. The balloon is held open by the neck of the bottle.

2. Place the plastic bag over the bottom (open) end of the 2-liter bottle and use the rubber band to hold it in place. This will serve as the diaphragm. To inflate the lung, blow into the balloon just before you fasten the rubber band. You can also wrap tape over the edges of the plastic bag to minimize air leaks

3. Grasp the bottom of the plastic bag and pull it down and push it up. Watch as the "lungs" (the balloon) expand and contract as you do this. The balloon has to change size because the air space between the balloon and bottle must remain constant. (Well, it would if the seal around the plastic bag and bottle were perfect).

You may block the "trachea" (the neck of the bottle) so that the air supply is cut off and watch as nothing happens when the "diaphragm" is pushed in and out.

This model isnât perfect. None of the joints are air tight as they would be in a real thoracic cavity. Pull the âdiaphragm down and watch the lungs expand . If you hold it in place, the lungs will collapse again over time. This is because of leaks and is not how real lungs work. Pushing the diaphragm in and pulling it out over and over does give you an idea of how lungs work. As the diaphragm tightens, contracts (pull down on the plastic bag) the lungs fill with air. As the diaphragm relaxes (push up on the plastic bag) air is expelled from the lungs .

There are several different ways we breath, i.e. expand our thoracic cavity so that our lungs can expand. You have just made a demonstration model of the diaphragm at work. You can also use your rib cage to expand and contract so that you can inhale and exhale. There are muscles between and around your ribcage which you can use to change the size of your thoracic cavity.

This is approximately what your model of a lung will look like.

Answer the questions on the Report Page

Report Page Name

1. Put a hand on your lower ribcage and try moving your ribs out and in. Does air also move in and out?

2. Someone with an upper back or neck injury may not have the options of using diaphragm or ribs to breath. They can learn to use the clavicle and the muscles attached to expand their thoracic cavity a small amount and breathe independently for short periods of time. Put your hand on you clavicle and try to raise and lower just that bone without using your diaphragm or your ribs. It isnât easy but you should be able to get a little air into and out of your lungs this way. How effective do you think this way of breathing is?

3. When you take a really deep breath you use all these muscle groups to help. Take a really deep breath and notice that your ribs expand, your lower abdomen comes out (a sign that the diaphragm has contracted) and your shoulders lift a little (the upper chest and clavicle are working). Now take a relaxed breath. Only your abdomen should go in and out. The movement of your abdomen is a result of the contracting diaphragm pushing on the contents of your âgutâ which forces your abdomen to push out.

Do you breath in or out when your diaphragm contracts?\

4. If a hole were poked in your thoracic wall (the wall of the pop bottle â the hole should be at least the diameter of a pencil)

a. what would happen when you tried to breath? (This is a pneumothorax).

b. Is the space between the balloon and plastic bottle still required to remain constant?

5. Would it be possible to live with a paralyzed diaphragm? Explain your answer.

fuchsiamuskrat152

True of False: Freshwater environments have a higher concentration of oxygen than saltwater environments.

QUESTION 2 If the difference in partial pressure of gas on either side of the barrier to diffusion is 0, which of these events will occur?

The area for gas exchange will increase to accommodate this similarity.

The constant for diffusion will decrease.

The rate of diffusion will be 0.

The distance thickness of the barrier to diffusion will also be 0.

QUESTION 3 On the x-axis of the oxygenâhemoglobin equilibrium curve is the partial pressure of oxygen in tissues. Which type of blood is most likely to be represented by the right-hand side of the axis? (Hint: the oxygen-hemoglobin equilibrium curve is figure 45.14 in your book on pg 913)

blood found in the left ventricle

blood found in the right atrium

blood found in the superior vena cava

blood found in the inferior vena cava

QUESTION 4 Which of these is an example of pulmonary circulation?

Blood is pumped from the right ventricle to the lungs.

Blood is pumped from the left ventricle to the aorta.

Blood is pumped from the aorta to the cardiac vein.

Blood is pumped from the inferior vena cava to the right atrium.

QUESTION 5 O2 will diffuse from blood to tissue faster in response to which of the following conditions?

an increase in the PO2 of the tissue

a decrease in the PO2 of the tissue

an increase in the thickness of the capillary wall

a decrease in the surface area of the capillary

QUESTION 6 Which of the following promotes oxygen release from hemoglobin?

a decrease in temperature

a decrease in carbon dioxide levels

a decrease in pH

a decrease in carbonic anhydrase

QUESTION 7 How does the medulla oblongata sense the amount of carbon dioxide in the blood?

A. Carbonic anhydrase produced by cells performing cellular respiration is exported and travels though the blood, and binds to a receptor on the medullary respiratory center, which causes a signal amplification resulting in a change in gene expression which results in the production of proteins that will cause the diaphragm to contract

B. CO2 produced by cells performing cellular respiration reacts with blood plasma for form an acid, which increases the pH of the blood, which causes the medullary respiratory center to contract the diaphragm

C. CO2 produced by cells performing cellular respiration reacts with blood plasma for form an acid, which decreases the pH of the blood, which causes the medullary respiratory center to contract the diaphragm

D. A and B

E. A and C

QUESTION 8 Which of the following parts of the lung are considered "dead space"? A. The alveoli B. The trachea C. The bronchi D. B and C E. All of the above

QUESTION 9 Which of the following blood vessels have the thinnest walls?

arteries

arterioles

capillaries

venules

veins

QUESTION 10 How does the interstitial fluid return to the bloodstream?

A. Interstitial fluid flows into the capillary where the osmotic pressure driving fluid into the bloodstream is greater than the blood pressure driving fluid out of the blood

B. Interstitial fluid flows into the capillary where the blood pressure driving fluid into the bloodstream is greater than the osmotic pressure driving fluid out of the blood

C. Interstitial fluid leaves the tissue via lymphatic ducts and travels through the lymphatic system, which returns the fluid to the veins. D. A and C

E. B and C

QUESTION 11 True or False: When an electrocardiogram (EKG or ECG) shows a flat line (aka asystole), medical personnel will restart the heart using a defibrillator.

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fill the blanks with the terms given

Terms: 0.21, 21, 78, 760, altitude, blood, Boyle's, Dalton's,decimal, decreased, diaphragm, directly, external intercostal,Henry's, into, inverse, lowers, out of, oxygen, parasternal,partial, percent concentration, pressure, solubility, temperature,total, volume

_________ law states that there is a/an ________ relationshipbetween [listed alphabetically] the _________ of a gas and the___________ of the gas. That is, an increase in one of the factorsis associated with a decrease in the other factor and vice versa.Thoracic cavity size determines the volume of the air in the lungs.Thus, this law is fundamental to explaining why an increase in thethoracic cavity size due to expansion of the rib cage in thehorizontal [front-to-back and side-to-side] directions viacontraction of the ___________ and _________ muscles, (listedalphabetically) and vertical [up-and-down] direction viacontraction of the ___________ causes a resultant decrease inintrapulmonary pressure, creating a pressure gradient that drivesair _____________ the lungs. Conversely, it explains why when thesize of the thoracic cavity is _________ by relaxing the musclesused during inspiration, the pressure of the gas in the lungsincreases, exceeding atmospheric pressure, creating a pressuregradient that then forces air _________ the lungs ________ lawstates that the _______ pressure of a mixed gas is equal to the sumof the ___________ pressures exerted by each of the individualgasses in the mix, which are exerted independent of one another.This law is important to pulmonary physiology because theatmospheric air we breath is a mixed gas that contains roughly__________% nitrogen and _______% oxygen. Moreover, according toHenry's law, it is the partial pressure of the oxygen in the air webreath that is the main determinant of how much of the air's oxygenwe can drive into our blood and make available to the body. A gas'spartial pressure can be calculated by multiplying the totalpressure of the mixed gas by the gas's ____________ in the mixedgas. Thus, the partial pressure of oxygen, at sea level isdetermined by multiplying total atmospheric pressure at sea level -which equals ___________ millimeters of mercury (denoted mm Hg) by________ - oxygen's percent concentration in atmospheric air,expressed as a ____________. ________ law actually states that theamount of gas we can drive into solution is _________ dependentupon 3 factors. These 3 factors are 1) the solubility of theparticular liquid for the particular gas you are considering, 2)the temperature (more gas can be driven into liquids at lowertemperatures than at higher temperatures) and 3) the partialpressure of the gas under consideration. In the body, theparticular gas we are interested in driving into a fluid is__________ and the particular fluid we are interested in drivingthe gas into is our ___________. Because blood has a particularsolubility for oxygen - and this is constant, and because thehomeostatic mechanisms in the body keep body temperature relativelyconstant, this means the single most important factor thatdetermines how much oxygen can be driven in to our blood is thepartial pressure of the oxygen in the air we breath. At sea level -the partial pressure of oxygen in atmospheric air = 760 x 0.21 =159 mm Hg. However, if one climbs to the peak of Mt. Everest, wherethe air is still a mixed gas that contains only ~21% oxygen, butthe air there is 'thinner' i.e. there is just less of it up there,the total pressure of the gas drops to about 250 mm Hg, whichsignificantly __________ the the partial pressure of oxygen and theamount of air that can be forced into the blood at that altitude.Thus this gas law explains why many individuals initiallyexperience ____________ sickness when they vacation in the Rockiesor the Swiss Alps but normally live at much lower elevations.

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BIOM20002 Lecture Notes - Lecture 54: Bicarbonate, Carbonic Anhydrase, Anemia

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