SC 118 Respiration Online Exercise

(revised and printed with permission from Seeley, Stephens & Tate, 2003. Human Anatomy and Physiology. McGraw-Hill.)

PART 2 – INHALING (VENTILATION)

How do you inhale? Use the website http://learningat.ke7.org.uk/scienceweb/alevel/biology/AS%20Interactive/e-a-level/10/10.7.htm or http://health.howstuffworks.com/adam-200022.htm

to follow an inhalation cycle and see what the blood is doing as you inhale and exhale.

What muscle is mainly responsible for inhalation?

What gas is picked up by the blood as it passes through the lungs?

What gas is dropped off by the blood as it passes through the lungs?

If somebody stopped breathing, what would happen to the amount of O2 in their blood?

What would happen to the amount of CO2 in their blood?

What change do you see in the erythrocyte (red blood cell) when it picks up O2?

CASE STUDY:

Mrs. H was pregnant, and in her seventh month she began to have spotting. The doctors warned her that she was at risk for a premature delivery. In the hospital, they took a sample of the amniotic fluid surrounding her fetus and tested it for a compound called surfactant; the compound was not present, and the doctor told Mrs. H that she must stay off her feet to try and prevent giving birth until the compound appeared in the amniotic fluid. “If the baby is born before it is making surfactant, it will have to be put on a ventilator,” the doctor said.

Why does Mrs. H’s baby have to wait to produce surfactant? How will you explain it to her? Use the web site http://sprojects.mmi.mcgill.ca/resp/surfactant.htm to come up with a simple explanation.

Part 3 – OXYGEN AND HEMOGLOBIN

When you inhale, O2 diffuses from the air in your alveoli into your blood. It dissolves in your plasma, and can be measured; this measurement is recorded as pO2. Then some of the O2 diffuses into your erythrocytes and binds to the protein hemoglobin. Go to the site http://www.getbodysmart.com/ap/resp/gases/hemoglobin.html

and you can see what a molecule of hemoglobin is like.

What are the two subunits of a hemoglobin molecule?

What is each of these subunits made of?

What is a heme group? What is its role in the hemoglobin molecule?

What do you think would happen to somebody who could not make heme groups?

What happens to the shape of hemoglobin when it binds to O2?

A CLASSIC HEMOGLOBIN EXPERIMENT

If you bubble O2 through blood, the hemoglobin will pick up the O2. Go to the web site http://www.getbodysmart.com/ap/resp/gases/hbsatcurve.html and you can do this experiment.

The beaker of blood has a tube into it, which can deliver O2. You can control how much O2 is delivered by the buttons under ‘O2’ above the graph display. Click the up arrow and you’ll see the pO2 change from 0 to 10 – you’ll also see the O2 bubbling through the blood. Now click the ‘points’ button, and a dot will appear on the graph. This dot tells you how much O2 the erythrocytes are holding and what color they are.

Change the pO2 and click the point button until you have a graph showing what the hemoglobin is doing from a pO2 of 0 to a pO2 of 100. What change do you notice in the hemoglobin?

This experiment is the basis for the ‘pulse oximeter’ used in hospitals. It clips onto a patient’s finger and measures the amount of oxygen in their hemoglobin just by measuring the color of the erythrocytes!

Now look at the graph again. How high did the pO2 have to get before the hemoglobin was 100% full of O2?

CASE STUDY

Mr. T’s muffler started making a tremendous amount of noise, and he took his truck into the shop. “You have a hole in your exhaust manifold,” said the mechanic. “You better get that fixed right away, or you’ll have carbon monoxide getting into the cab.”

Mr. T didn’t have the money to waste on fixing his truck. “I’ll just drive with the windows open,” he thought. But one morning it was too cold, and he had to close the windows. By then, he had forgotten about the hole in his exhaust system.

Driving on the freeway, Mr. T began to feel awfully drowsy. He pulled over and put on his hazard lights; he left the engine on so the heater would work, but he couldn’t keep awake. A passing highway patrol car found Mr. T unconscious and flushed bright red. What was happening to him?

To find out, compare the results from your experiment of adding O2 to hemoglobin with what happens when you add CO (carbon monoxide) to the hemoglobin. Use this web site http://www.getbodysmart.com/ap/resp/gases/cosatcurve.html to see what happens to the erythrocytes when you add just a little CO. How much CO did it take to completely fill the erythrocytes up to 100%?

This case study involves the concept of ‘affinity’ which means ‘liking’. Which molecule does hemoglobin like better, O2 or CO? Which does it prefer to bind to? How does this explain what happened to Mr. T?

Hemoglobin’s job is to pick up O2 in the lungs, carry it to the tissues, and release it there so the cells can use it. If hemoglobin has high affinity for a compound, it will pick that compound up easily in the lungs, but it will not let go again to deliver that compound to the tissues.

CASE STUDY

Mrs. L has sugar diabetes. Her blood sugar is very high most of the time, because she doesn’t follow her doctor’s advice. She eats whatever she wants to! “I have a sweet tooth,” she says. “I always did and I always will.” So she ignores her diet, except when she has a doctor’s appointment. For the day before each doctor’s appointment, she eats very carefully, so her blood sugar levels will always be normal when she has her blood tested by the doctor.

The last time she went in to the doctor, they did a different test. They tested her hemoglobin to see if it had glucose attached. The doctor looked very serious when they discussed the results. “The high glucose in your blood attaches to your hemoglobin,” said the doctor. “Once it’s attached, the glucose will never come off the hemoglobin again – so I can tell that you have been letting your blood glucose get very high. This is a problem, because when glucose is attached to your hemoglobin the hemoglobin has an extra high oxygen affinity. Your tissues aren’t getting enough Oxygen! That’s why those sores on your feet aren’t healing properly.”

The doctor’s explanation doesn’t mean a thing to Mrs. L. “It’s all greek to me,” she says. How will you explain it to her, using a diagram or graph?