The Respiratory System Flashcards
Describe the features of alveoli that adapt them to gas exchange
- alveoli increase surface area
- wall of alveoli/capillaries is one layer of flattened cells
- cells in wall secrete fluid (surfactant) to keep inner wall moist
- dense network of capillaries
Distinguish between ventilation, gas exchange, and cell respiration.
Ventilation (breathing) - surrounding to lungs (alveoli); fresh air enters alveoli, stale air exits; refreshes O2 concentration, lowers CO2
Gas Exchange - alveoli to blood capillaries; difference in concentration of gases between alveoli and blood cause diffusion in/out; O2 diffuses from alveoli into capillaries in exchange for CO2
Cell Respiration - cytoplasm/mitochondria; O2 used in mitochondria, CO2 produced; O2 used to release energy (from glucose) to form ATP
Location - Process - Function
Explain the necessity for a ventilation system.
- Needed to maintain concentration gradients in the alveoli
- O2 in/CO2 out only if there is gradient between air in alveoli and blood in pulmonary capillaries
- Diffusion equalizes CO2 and O2 concentration in alveoli and capillaries (stale air), gas exchange stops
- Air has higher O2 and lower CO2 concentration than capillaries
- O2-poor capillaries let O2 into blood from alveoli, CO2 vice versa
Draw and label diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles, and alveoli
• Draw alveoli in inset diagram at higher magnification
Explain the ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm, and abdominal muscles
- Inspiration (in)
- volume increase inside thoracic cavity, pressure decrease inside lungs
- external intercostal muscles contract
- diaphragm contracts downwards
- lungs expand, air in - Expiration (Out)
- volume decrease inside thoracic cavity
- pressure increase inside lungs
- external intercostal muscles and diaphragm relax (quiet breathing); elasticity forces air out
- internal intercostal and abdominal muscles contract (forced breathing)
- volume decrease in lungs, air out
Define partial pressure
Pressure exerted by gas in a mixture of gases
Explain the oxygen dissociation curves of adult hemoglobin, fetal hemoglobin and myoglobin
Adult: S-shape (sigmoidal) due to cooperative binding among subunits of Hb
• one O2 binds, remaining subunits have higher affinity
• one O2 released, remaining have lowered affinity
Fetal: Hb has higher affinity for O2
Myoglobin: greatest affinity for O2; stores O2 in muscles for long time
Describe how carbon dioxide is carried by the blood, including the action of carbonic anhydrase, the chloride shift, and buffering by plasma proteins
- blood plasma (7%), bound to Hb (23%), bicarbonate (70%)
- CO2 diffuse into RBCs through plasma
- CO2 + H2O = H2CO3 (carbonic anhydrase as catalyst)
- H2CO3 dissociates, forming HCO3- and H+
- HCO3- move out by facilitated diffusion, to capillaries via plasma
- Cl- replaces negative ions lost in RBCs (chloride shift)
- H2CO3 dissociates, decrease in pH, H+ reacts with Hb; buffers (plasma proteins) by binding to H+ in blood
• Oxyhemoglobin releases O2 - HCO3- diffuses back to RBCs, carbonic anhydrase reverses H2CO3 to H20+CO2
Explain the role of the Bohr shift in the supply of oxygen to respiring
- pH increases, more O2 binds; pH decreases, less O2 binds
- shift to right of dissociation curve
- H+ bind to Hb changing conformation so O2 binds less easily
Explain how and why ventilation rate varies with exercise
- change in CO2 concentration leads to low pH
- detected by chemosensors in aorta/carotid arteries that send impulses to breathing centre in brain
- impulses then sent to diaphragm/intercostal muscles to increase relax/contract rates
Outline the possible causes of asthma and its effects on the gas exchange system
Allergic reaction in the lungs: - occurs after initial sensitization of immune system - response to antigens (ie. dust mites, pollen, animal dander, mold spores, viral/bacterial infections) Symptoms: - coughing, wheezing, breathless, dizzy Result from: - inflammation of bronchioles - constriction of bronchioles - more mucus secreted in airways
Explain the problem of gas exchange at high altitudes and the way the body acclimatizes
- air at high altitudes has lower pressure, therefore pressure (amount) of oxygen decreases
- causes mountain sickness above 5000m (ie. headache, insomnia, poor appetite, nausea, vomiting, dizzy, tired, cough, breathless)
- ascending quickly could lead to fluid collecting in brain and lungs
Adjustments: - increased heart rate (mins)
- increased breathing (mins-days)
- increased concentration of oxygen in blood (days)
- increased RBC production (days-weeks)
- increased myoglobin concentration (days-weeks)
- increased capillary density (weeks)
