Pulmonary Physiology

Front 1

Define:

Tidal volume

Back 1

Volume of air moved into and out of the lungs during a a normal quiet respiratory cycle. (Average is 500mL)

Front 2

Define:

Inspiratory reserve volume

Back 2

Amount of air one can take in over and above tidal volume

(Males 3300 mL; Females 1900 mL)

Front 3

Define:

Expiratory reserve volume

Back 3

Amount of air that one can voluntarily expel after you have completed a normal, quiet respiratory cycle

(Males 1000mL; Females 700mL)

Front 4

Define:

Residual volume

Back 4

Amount of air that remains in your lungs even after maximal exhalation

(Male 1200mL; Females 1100mL)

Front 5

Define:

Inspiratory capacity

Back 5

Amount of air that you can draw into your lungs after you have completed a quiet respiratory cycle.

(Sum of Tidal Volume + Inspiratory Reserve Volume)

Front 6

Define:

Functional residual capacity

Back 6

Amount of air remaining in your lungs after you have completed a quiet respiratory cycle

(Sum of Expiratory Reserve Volume + Residual Volume)

Front 7

Define:

Vital capacity

Back 7

Maximum amount of air that you move into or out of your lungs in a single respiratory cycle.

(Sum of ERV + TV + IRV)

Front 8

Define:

Total lung capacity

Back 8

Total volume of your lungs.

(Males 6000 mL; Females 4200 mL)

Front 9

Define:

"Dead space"

Back 9

Volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfused.

Front 10

Define:

Bohr Effect

Back 10

Effect of pH on the hemoglobin saturation curve. When pH drops, saturation declines.

Front 11

Describe anatomy of respiratory system including vascular component

Back 11

Upper Respiratory System: Nose, nasal cavity, paranasal sinuses, and pharynx.

Lower Respiratory System: Larynx, trachea, bronchi, bronchioles, and alveoli.

Vascular component: Two circuits nourish lung tissue. One supplies respiratory portion and other perfuses the conducting portion.

Respiratory exchange surfaces receive blood from arteries of pulmonary circuit. Pulmonary arteries --> Lungs @ hilum and branch with bronchi as they approach lobule--> Each lobule receives an arteriole, venule, and capillaries surround each alveolus --> oxygen-rich blood from alveolar capillaries passes through pulmonary venules and then enters pulmonary veins, which deliver blood to left atrium.

Front 12

Explain the mechanics ofpulmonary ventilation and list the structures involved in this process.

Back 12

Physical movement of air into and out of the respiratory tract. Primary function is to maintain adequate alveolar ventilation.

When thoracic cavity enlarges, lungs expand to fill additional space. This increase in volume decreases the pressure inside the lungs. Air then enters the respiratory passageways because pressure inside lungs is lower than atmosphere and continues to enter the lungs until their volume stops increasing and the internal pressure is the same as that outside. When thoracic cavity decreases in volume, pressures increase inside the lungs, forcing air out of the respiratory tract.

Front 13

Explain the mechanics of pulmonary ventilation and list the structures involved in this process. (Part II)

Back 13

Muscles used in inhalation: Contraction of the diaphragm flattens the floor of thoracic cavity, increasing its volume and drawing air into the lungs. Contraction of external intercostal muscles assists in inhalation by raising the ribs.

Contraction of accessory muscles including sternocleidomastoid, serratus anterior, pectoralis minor, and scalene muscles can assist the external intercostal muscles in elevating the ribs.

Muscles used in exhalation: Internal intercostal and trasversus thoracic muscles depress ribs. Abdominal muscles including external and internal oblique, transversus abdominis, and rectus abdominis muscles, can assist the internal intercostal muscles in exhalation by compressing the abdomen.

Front 14

Define alveolar pressure

Back 14

Pressure inside respiratory tract at the alveoli. Direction of airflow is determined by the relationship between atmospheric pressure and intra-alveolar pressure.

Front 15

Define pleural pressure

Back 15

Pressure in the pleural cavity between parietal and visceral pleura. Pleural pressure remains below atmospheric pressure and thus creates respiratory pump that assists the venous return to the heart.

Front 16

Explain how the mechanicalact of inspiration affects pleural and alveolar pressures and its importance for the movement of air into the lungs.

Back 16

On inhalation, lungs expand and alveolar pressure drops to 759 mm Hg below atm (-1 mm Hg) and on exhalation, lungs recoil and pressure rises to 761 mm Hg (+1 mm Hg).

Intrapleural pressure averages at -4 mm Hg and during powerful inhalation, it can reach -18 mm Hg. Elastic fibers are not strong enough to recoil so much thus they are not strong enough to overcome the fluid bond between the parietal and visceral pleurae.

Front 17

Explain how surface tensionaffects alveolar collapse pressures and apply the role of surfactant to thisprocess

Back 17

Surfactant is on alveolar surfaces where it forms a superficial coating over a thin layer of water. Plays a key role in keeping alveoli open and reduces surface tension in the liquid coating the alveolar surfaces. Also, surface tension creates a barrier that keeps small objects from entering water but also tends to collapse small air bubbles.

Front 18

Describe how gas diffuses acrossthe respiratory membrane.

Back 18

Gases diffuse across the respiratory membrane between alveolar air spaces and alveolar capillaries, and across capillary walls between blood and other tissues.

Front 19

Identify the areas of thecentral and autonomic nervous system that regulate respiration rate, rhythm, and pattern.

Back 19

Thecerebral cortex can indirectly affect the respiratory centers:

1. Strong emotions can stimulate respiratory centers in the hypothalamus.

2. Emotional stress can activate sympathetic orparasympathetic division of the ANS, causing bronchodilation orbronchoconstriction.

3. Anticipation of strenuous exercise canincrease respiratory rate and cardiac output by sympathetic stimulation.

The respiratory centers are 3 pairsof nuclei in the reticular formation of the medullaoblongata and pons.

The respiratory rhythmicitycenters of the medulla oblongata set thepace of respiration. Each center can be divided into:

1. a dorsal respiratory group (DRG):- inspiratory center

- functions in quiet and forced breathing

2. a ventralrespiratory group (VRG):- inspiratory and expiratory center

- functions only in forced breathing

The activities of the respiratory centers are modifiedby sensory information from:

1. Chemoreceptors sensitive to the PCO2, PO2, or pH of blood orcerebrospinalfluid.

2. Baroreceptors in the aortic or carotic sinuses sensitive to changes inbloodpressure. 3. Stretch receptors that respond to changes in the volume of the lungs.

4. Irritating physical or chemical stimuli inthe nasal cavity, larynx or bronchial tree.

5. Other sensations including pain, changes inbody temperature, and abnormal visceral sensations.

Stimulationof chemoreceptors leads to increased depth and rate of respiration.

There are 2 baroreceptor reflexes involved only inforced breathing (the Hering- Breuer reflexes):1. The inflation reflex prevents overexpansion of the lungs duringforcedbreathing2. The deflation reflex inhibits theexpiratory centers and stimulates theinspiratorycenters when the lungs are deflating.

Front 20

Explain the effect ofcarbon dioxide levels on respiratory regulation by nervous system.

Back 20

Carbondioxide (CO2) is generated as abyproduct of aerobic metabolism (cellular respiration) in peripheral tissues.After entering the bloodstream, a CO2 molecule is either:

1. converted to carbonic acid

2. bound to the protein portion of hemoglobin, or

3. dissolved in plasma

• Most (70%) of the carbondioxide in blood is transported as carbonic acid (H2CO3) which dissociates intoH+ and bicarbonate (HCO3-). The bicarbonate ions are moved into the plasma byan exchange mechanism (called the chloride shift) that takes in Cl- ions without usingATP.

• 23% of the carbon dioxide inblood is bound to the amino groups of globular proteins of the Hb molecule,forming carbaminohemoglobin.

• The remainder of the carbon dioxide (about7%) is transported as CO2 dissolved in plasma.

Front 21

Understand how oxygen istransported in the blood

Back 21

Oxygen molecules bind to the iron ions in hemoglobin(Hb) molecules, in a reversible reaction. Each RBC has about 280 millionhemoglobin molecules, each of which can bind 4 oxygen molecules. The percentageof heme units containing bound oxygen is called hemoglobinsaturation.

• The most important environmental factors affectinghemoglobin are:

1. the PO2 of blood

2. blood pH

3. temperature

4. metabolic activity within RBCs

Front 22

Define “nitrogen washout”(aka absorption atelectasis), what causes it, and what the effect is on thelungs.

Back 22

Absorption atelectasis refers to the tendency for airways to collapse if proximally obstructed. Alveolar gases are reabsorbed; this process is accelerated by nitrogen washout techniques.

Oxygen shares alveolar space with other gases, principally Nitrogen. Nitrogen is poorly soluble in plasma, and thus remains in high concentration in alveolar gas. If the proximal airways are obstructed, for example by mucus plugs, the gases in the alveoli gradually empty into the blood along the concentration gradient, and are not replenished: the alveoli collapse, a process known as atelectasis. This is limited by the sluggish diffusion of Nitrogen. If nitrogen is replaced by another gas, that is if it is actively “washed out” of the lung by either breathing high concentrations of oxygen, or combining oxygen with more soluble nitrous oxide in anesthesia, the process of absorption atelectasis is accelerated. It is important to realize that alveoli in dependent regions, with low V/Q ratios, are particularly vulnerable to collapse.