physiology notes:

Notes: Respiratory System

1. Conducting Zone: brings oxygen to alveoli; includes nose, pharynx, larynx, bronchi, and bronchioles.
2. Respiratory zone: alveoli; may include alveolar sacs (clusters); air in the alveolar

spaces separated from blood by just two cell diameters.

3. Boyle’s Law: behavior of gasses when volume and pressure change.

P= 1/v. As the volume increases, pressure decreases; as volume decreases, the pressure increases.

4. Inspiration:
   1. diaphragm contracts (drops) increasing volume of thoracic cavity
   2. contraction of external intercostals muscle helps increase volume of

rib cage

4. 3. pressure in thoracic cavity↓.
   4. Lower pressure in thoracic cavity pulls on lungs causing inflation
   5. Inflation of lungs increases internal volume, decreasing their

internal pressure.

4. 6. air flows into lungs due to lower pressure inside

5. Expiration:
   1. Diaphragm relaxes and rises up; volume in thoracic cavity↓
   2. Contraction of internal intercostals muscles helps decrease volume of

rib cage.

5. 3. ↓ volume in thoracic cavity increases pressure
   4. ↑ thoracic pressure pushes lungs deflating them somewhat
   5. Deflated lungs have a lower internal volume and thus a higher internal

pressure forces air out of lungs.

6. Compliance: lungs being stretchable; can expand during inspiration
7. Elasticity: return of lungs back to original shape; this allows lungs to expel air during expiration.

8. Surface tension: water in the alveoli will stick to itself causing surface tension; lungs must overcome this force or lungs will collapse.

9. Surfactant: produced by the alveolar cells; reduces surface tension of water in the alveoli making it easier to overcome surface tension; not made until 8^th month of fetal life.

10. a. Tidal volume: amount of air inspired under normal quiet breathing

b. Inspiratory reserve: volume of air above tidal volume that can be inhaled during a maximal forceful inspiration

c. Expiratory reserve volume: volume of air above tidal volume that can beexhaled during a maximal forceful expiration.

d. vital capacity: total amount of exchangeable air (TV + IRV + ERV)

e. Anatomical dead space: trapped air that does not reach the alveolar spaces

(150 ml) within the conducting system; does not participate in gas exchange;

If tidal volume is not above the volume of anatomical dead space, no air will reach the alveoli and no gas exchange will occur.

f. Residual volume: air remaining in alveoli after forced exhalation

11. Medulla: contains a rhythmicity center with two types of interacting neurons that will regulate breathing patterns.

12. I neurons: cause inspiration by sending impulses to motor neurons that cause contraction of the diaphragm.

E neurons: cause expiration by inhibiting the I neurons, causing the relaxation of the diaphragm.

13. Pons: influences breathing by interfacing with the medulla oblongata.
14. Pneumotaxic center: area of the pons that inhibits inspiration; antagonizes the apneustic center that causes inspiration by stimulating I neurons

15. Cerebral cortex: exerts voluntary control over internal and external intercostal muscles .

16. Chemoreceptors: detect chemicals in blood; sites are in the medulla oblongata and peripheral areas

17. Aortic bodies: chemoreceptors in the aortic arch

Carotid bodies: chemoreceptors in carotid sinus

18. Carbon dioxide effect: CO2 combines with water→ carbonic acid; the chemoreceptors detect H+; high levels of CO2 cause more rapid deeper breathing; ↓ levels of CO2 cause breathing to become slower and more shallow

19. Oxygen: concentration changes very little because most oxygen is attached to hemoglobin (Hb); at low O2 pressure, chemoreceptors become more sensitive to CO2; at high oxygen pressure chemoreceptors become less sensitive to CO2.

20. Pulmonary stretch reflex: found in lungs; inhibit inspiration when lungs are stretched; helps to prevent damage to lungs due to excessive expansion during ventilation.

21. Oxygen exchange in tissues: partial pressure of oxygen in blood is 100mmHg;

In tissues, it is 40mmHg; blood diffuses out of blood into tissues.

22. Hemoglobin: Hb structure consists of globin with 4 polypeptide chains, each polypeptide holding one heme.

Heme: organic molecule with an iron atom at its center; iron atom can bind with one oxygen molecule

23. Oxyhemoglobin dissociation curve: at high PO2 large pressure changes are needed to unload oxygen, but at low PO2, little change in pressure is needed to unload oxygen .

24. Effect of pH on oxyhemoglobin: low pH causes Hb to give up Oxygen at lower PO2; curve shifts to the left; muscles that are being exercised→ lactic acid and CO2 which lower the pH; exercising muscle need extra O2 and the lower pH causes Hb to release O2 more easily.

25. Effect of temperature on oxyhemoblogin: ↑ temperature causes release of O2 at a lower PO2; exercising muscles generate heat causing Hb to release O2 more easily.

26. Myoglobin: red pigment in muscle similar to globin in Hb; it can hold one O2 molecule; used as a storage mechanism for O2 reserve.

27. Carbon dioxide transport:
    1. CO2 dissolved in the blood (plasma) 10% of blood CO2.
    2. Carbaminohemoglobin: CO2 attaches to an amino acid of Hb; 20%;

CO2 does not bind to the iron atom and thus does not block O2 binding.

27. 3. bicarbonate: 70% of the CO2 in the blood combines with water to form

carbonic acid; this breaks down into HCO3- + H+.

28. Removal of CO2: reversal of the bicarbonate formation to form carbonic acid, then CO2 and H2O; carbon dioxide diffuses out of the blood into the alveolar sacs for removal during expiration.