1. Respiratory System II Gas Exchange in the Lungs Control of Breathing
Defense and Interesting Stuff

2. Blood and Respiratory System
each blood cell contains 280 million hemoglobin molecules  each of those can carry four oxygen molecules
a single cell can carry ~ one billion molecules of oxygen
the chemical combination of oxygen and hemoglobin is loose and reversible

3. Alveoli
a network of capillaries surrounds each alveolus – capillary and alveolus each is only one cell thick
alveoli are small but very numerous (several hundred million)
surface area is 100 m2 – the size of a tennis court
gases dissolve in warm, moist, mucus lining
(In contrast, the surface area of the body is 2 m2.)

4. DIFFUSION – the movement of molecules from an area of high concentration to one of lower concentration
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5. AIR air is nearly 80% nitrogen – we can’t use this and it is exhaled
~20% is oxygen – much higher concentration in air than in blood
carbon dioxide is at a higher concentration in blood than in air (due to cellular respiration)
differences in concentration cause diffusion across alveoli in both cases
Normal blood oxygen levels in humans are considered %
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6. Image from: http://3. bp. blogspot

7. CO2 and O2
recall: CO2 is mostly transported as carbonic acid, which dissociates into bicarbonate ions and hydrogen ions
in the capillaries of the lungs, the bicarbonate and hydrogen ions combine to reform carbon dioxide, which diffuses into the alveoli  EXHALE
O2 from air diffuses into alveoli  INHALE where it is picked up by RBCs (hemoglobin)

8. Image from: http://4. bp. blogspot

9. Overview of diffusion
oxygen diffuses across the membrane of the alveolus from air ____________into the RBC ___________
carbon dioxide diffuses from the plasma ____________to the alveolus ____________

10. HEALTHY
SMOKER
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11. Consequences? Above: bacteria allowed to colonize alveoli
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Image from:
Above: bacteria allowed to colonize
alveoli
Right: emphysema
Consequences?
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12. and Control of Breathing
Homeostasis
and Control of Breathing
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13. Homeostasis
Recall: homeostasis is the maintenance of a balanced internal environment
ability of the body to maintain levels of CO2 and O2
breathing movements are controlled by muscles, not by lungs
muscles are stimulated by nerve impulses from the brain
nervous feedback from the muscles to the brain tells it that inspiration or expiration has occurred

14. Negative feedback mechanism
the muscles contract because of the nerve impulses, and stop contracting when the nervous system detects the contraction
motor neurons of the respiratory centre of the brain (medulla oblongata) carry impulses to the respiratory muscles (diaphragm and intercostals), causing contractions
sensory neurons carry impulses from the respiratory muscles to the medulla, shutting off motor impulses, and stopping the contractions
 is a repeating cycle
[Positive feedback is more rare – in those cases, the phenomena will build as the signal loops (e.g. ovulation – the signal builds until the follicle bursts).]

17. chemoreceptors in the aorta and carotid arteries
medulla oblongata
chemoreceptors in the aorta and carotid arteries
diaphragm and intercostal muscles contract
blood pH decreases
breathing rate increases
and CO2 released
blood pH returns to normal
EXERCISE

18. Control of Breathing Rate
usually, breathing movements supply enough O2 as rapidly as required, and remove enough CO2 at the same time
occasionally, CO2 can accumulate and O2 may be needed in greater supply (often these events are simultaneous)
either condition can increase the rate and/or depth of breathing

19. the body is more sensitive to increased CO2
breathing rate is controlled by medulla oblongata, which monitors blood CO2
O2 is monitored by sensory cells in the aorta and common carotid arteries
change in breathing hastens the removal of CO2 and brings in more O2
CO2 causes the formation of carbonic acid in the blood
increased H+ ions cause pH to decrease.
the change in pH is detected, not the actual CO2 levels
CO2 +H2O  H2CO3
H2CO3  H+ + CO3–

20. Defense Mechanisms
AND OTHER COOL STUFF

21. Effects of Elevation on Breathing
higher elevations have less oxygen in the air
you must breathe faster and deeper in the mountains
people who live there have more alveoli and blood vessels in the lungs, as well as a higher red blood cell count (70% vs %)
 acclimatization

22. Image from: http://shelledy. mesa. k12. co

23. Coughing
a reflex action in response to irritation of the throat, trachea, lungs, or pleural membrane
rapid contraction of the chest, causing rapid intake of air
epiglottis closes as the chest relaxes – a build up of pressure occurs
epiglottis suddenly opens and the air blows out, taking harmful particles with it

24. Sneezing sudden expulsion of air through the nose
air is taken in normally
the soft palate closes off the mouth
air is forced out the nose carrying particles
during a sneeze, the heart stops momentarily

25. Hiccoughing result of stimulation of the vagus nerve
impulse is relayed from the spinal cord to the diaphragm
causes an involuntary spasm of all or a part of the diaphragm
sudden closing of the epiglottis makes the sound

26. Yawning and Snoring Yawning:
combination of psychological and physical reactions, resulting in an involuntary stretching of the mouth and a large intake of air
air is exhaled as the mouth closes
result of decrease in breathing rate (oxygen) due to tiredness, boredom, or drug action
Snoring
vibrations of the soft palate during sleep