Respiratory System Flashcards

1
Q

What is the conducting zone

A
  • Consists of everything from the trachea to the terminal bronchioles, transfer air from the outside environment to the alveoli for gas exchange
  • Warms and humidifies air (facilitates gas exchange), filters air (mucus cilia, macrophages in alveoli)
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2
Q

What is the respiratory zone

A
  • Gaseous exchange, occurs in alveoli, 300 million alveoli
  • Large surface area for diffusion total area ~60-80m2, thing wall allowing for rapid diffusion of O2 and CO2
  • Secrete surfactant to prevent collapsing / sticking together
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3
Q

What is airway resistance

A
  • Airflow = (PI - P2) / resistance, where P1 - P2 is the pressure difference at the two ends of the airway
  • Change in pressure to facilitate flow from high pressure to low pressure
  • Determined by airway diameter
  • COPD, smoking asthma, flu, colds etc result in decreased flow, if the airway is reduced by half, flow decreases by 16x
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4
Q

What is pulmonary vs cellular ventilation

A

Pulmonary
- Movement of gas into and out of lungs due to pressure differences between the two ends of the passageway
- Refers to ventilation (breathing) and exchange of gases (O2 and CO2) in lungs
Cellular
- Relates to O2 utilisation and CO2 production by the cellular tissues

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5
Q

What are subscripts of V

A
  • V: Volume per unit time (one minute), Va + Vd
  • Vt: Tidal volume, volume inspired or expired
  • Vd: Dead-space, space occupied by the volume of air not participating in gaseous exchange
  • Vi: Volume inspired
  • Ve: Volume expired
  • Va: Air that reaches the respiratory zone, involved in gas exchange
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6
Q

What is partial pressure

A
  • Tension, the pressure of a specific gas in mixture of gasses
  • pO2: In the lungs is greater than in the blood so O2 moves from the lungs into the blood
  • pCO2: In the blood is greater than pCO2 in the lungs so CO2 moves from blood to lungs for exhalation
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7
Q

What is diffusion

A
  • Random movement of molecules from a high to low area of concentration
  • Dependant upon the partial pressure gradient, inversely proportional to the membrane thickness and the solubility of gases
  • Occurs rapidly in the lungs due to large SA, short diffusion distance
  • O2 and CO2 tensions in blood leaving the lung is almost in complete equilibrium with O2 and CO2 tension in the lung
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8
Q

What occurs in the respiratory cycle

A

Inspiration
- Inspiratory muscles contract (diaphragm descends; external intercostals rise rib cage)
- Thoracic cavity V increases
- Lungs are stretched
- Intrapulmonary V increases, intrapulmonary P drops
- Air flows into lungs down its pressure gradient until intrapulmonary is equal to atmospheric pressure
Expiration:
- Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages)
- Thoracic cavity V decreases
- Lungs recoil passively
- Intrapulmonary V decreases
- Intrapulmonary pressure rises, air flows out of lungs down pressure gradient

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9
Q

What are factors that affect pulmonary ventilation

A
  • Surface Tension: Of alveolar fluid, must be overcome to expand lungs during inhalation, surfactant reduces surface tension so lungs don’t collapse
  • Compliance: How much effort is required to stretch the lungs and chest wall, high compliance = easy, due to elastic fibres in lung tissue and surfactant
  • Airway Resistance: Diameter of airway, smooth muscle regulates airway diameter, walls of bronchioles expand and contract like the lungs
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10
Q

What is partial pressure and daltons law

A
  • The pressure of each gas in a mixture, the pressure that each gas exerts can be calculated by multiplying the percentage by the absolute pressure
  • PP of O2 at sea level (159 mmHg)
  • PP of N2 at sea level (600.7 mmHg)
  • The total pressure of a gas mixture is equal to the sum of the partial pressures
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11
Q

What are the partial pressures of blood throughout respiratory cycle

A
  • Blood Entering Lungs: pCO2 ~46 mmHg and pO2 ~40 mmHg
  • Alveolar Gas: pCO2 ~40 mmHg and pO2 ~105 mmHg
  • Blood Leaving Lungs: PO2 ~100mmHg and pCO2 ~40 mmHg
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12
Q

What is internal respiration

A
  • Exchange of gases between blood and tissue (not lungs), aerobic and anaerobic metabolism and provision of O2 (energy production in muscle) and removal of CO2, H and H2O
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13
Q

What is oxygen transport and blood O2 capacity

A
  • At alveolar PO2 of 100mmHg, 98% O2 is bound to Hb
  • Each heme group can combine chemically with one O2 molecule (Hb4O2)4)
  • Oxyhaemoglobin (oxygen bound) deoxyhaemoglobin (no oxygen bound)
  • SpO2is the % saturation of Hb, = (O2 actually combined with Hb) / (O2 capacity of Hb)
  • Fully saturated Hb carries 1.34ml O2
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14
Q

What is the arteriovenous oxygen difference

A
  • The difference between concentration of O2 in arterial and venous blood
  • Represents amount of O2 that is extracted or consumed by tissues per 100ml of blood
  • Fick
  • VO2 = Q x a-vO2
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15
Q

What are the mechanisms of CO2 transport

A
  • Plasma: 9-10% of CO2 is transported dissolved
  • Haemoglobin: 20% combines with Hb (carbamino-haemoglobin), unloading O2 to tissues facilitates loading of CO2, CO2 has a higher affinity for Hb than O2
  • Ions: 70% of CO2 as H ion and HCO3 ion
  • Carbonic Anhydrase: Facilitates combination of water and H to form carbonic acid (H2CO3)
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16
Q

What is blood buffering

A
  • H+ ions formed when H2CO3 dissociates will increase acidity of venous blood, free H+ ions buffered by Hb
  • As O2 is released from Hb and diffuses into the tissues buffering of H+ ions is facilitated (Root effect)
  • In turn, more HCO3- can be formed and more CO2 transported without change in blood acidity
17
Q

What is the ventilation perfusion ratio

A
  • Normal gas exchange requires a matching of ventilation to blood flow (perfusion)
  • An alveolus can be well ventilated, if blood flow to alveolus doesn’t match ventilation, normal gas exchange does not occur
  • At rest V/Q (ratio of ventilation / cardiac output) is around 0.82, during exercise V/Q may exceed 5
  • Athletic population doesn’t have a larger lung however changes in heart cause the differences
18
Q

What is the oxygen-haemoglobin dissociation curve

A
  • Flat Portion: Provides protection against low atmospheric pO2, large decrease in pO2 only results in a small desaturation of the Hb, resting state (100%), arteries / lungs
  • Steep Portion: Provides protection at tissue level for unloading of O2, small decrease in tissue O2 results in large unloading of O2 from Hb, venous blood, easily provided to tissues
  • Relationship: Loading (combination of O2 with H) and unloading (release of O2 with Hb)
  • Deoxyhaemoglobin + O2 ↔ Oxyhaemoglobin
19
Q

What causes changes in the dissociation curve

A
  • pH / Temperature: Increase in temp / acidity (H+ / exercise) results in a downward and rightward shift, increased availability / unloading of oxygen to tissues (warm up essential)
  • Bohr Effect: Effect of acidity, CO2 and increased temperature on the oxyhemoglobin dissociation curve
  • 2-3 DPG: By-product of RBC metabolism, rightward shift of curve, assists with unloading of O2, at altitude (hypoxia), not a major cause of rightward shift during exercise
20
Q

What is the myoglobin / haemoglobin dissociation curve

A
  • The higher affinity of myoglobin for O2 compared with haemoglobin assists in the exchange (off-loading) of O2 bound to haemoglobin and transported to muscle tissue
  • Myoglobin: Flat portion is large, high affinity to load oxygen, mitochondria, loosely bound
  • Haemoglobin: Affinity to unload oxygen, blood
21
Q

What is the acid base balance and how does it affect ventilation

A
  • Acid-Base Balance: Pulmonary ventilation removes H+ from blood by the HCO3– reaction
  • Equation: Muscles CO2 + H2O ← carbonic anhydrase → H2CO3 ←→ H+ + HCO3- Lungs
  • Increase Ventilation: CO2 exhalation, reduces pCO2 and H+ concentration (pH increase)
  • Decrease Ventilation: Buildup of CO2, increases pCO2 and H+ concentration (pH decrease)
22
Q

What is / the function of the respiratory control centre

A
  • Brain stem (medulla oblongata and pons)
  • Controls rhythm of ventilation, inspiratory area nerves innervate diaphragm and external intercostals via the phrenic nerves, impulses last ~2sec = contraction, relaxation lasts ~3sec \ 5sec cycle
23
Q

What are the 3 different inputs to respiratory control centre

A
  • Neural: Higher brain centres, voluntary regulation of breathing and emotional response via hypothalamus and limbic system
  • Sensory: Skeletal muscle / right ventricle mechanoreceptors, chemoreceptors in muscle
  • Humoral: Central chemoreceptors (medulla, changes in pCO2 and H+) and peripheral chemoreceptors (aortic and carotid bodies, increase in pCO2 / H+ and decrease in pO2 / K+
24
Q

Describe ventilatory effects of sub maximal vs maximal

A
  • Sub-Maximal: Primary drive, higher brain centres (central command), “fine tuned” by humoral chemoreceptors and neural feedback from muscle
  • Maximal: Non-linear rise in VE, increasing blood H+ stimulates carotid bodies, concentration of K+, body temperature, and blood catecholamines may contribute