Respiratory System Flashcards
(25 cards)
Cellular respiration
Aerobic muscle respiration:
- C6H12O6 + 6O2 = 6CO2 = 6H2O
- 36 ADP = 36 ATP
Anaerobic muscle respiration:
- C6H12O6 = 2C3H6O3 (lactic acid)
- oxygen debt.
Feed forward
Breathing rate increases before muscles need more oxygen
Deciding to exercise/run is enough to trigger this
Measuring HBO/Hb (oxygenated vs non oxygenated) ration blood oxygen level dependent in the brain centres controlled breathing: feed forward can be observed
Breathing
Inhalation requires energy - volume increases and opens up the lungs and pressure goes down so air comes in (as there is less pressure inside then outside the lungs).
Exhalation normally passive - rib cage and longs collapse, that puts pressure on the air inside and it exits the lungs
The pleura
Keeps the lungs open at all times so they don’t collapse
- visceral pleura (inner layer) stuck tightly to the lungs
- parietal pleura lines the inside of the chest cavity
- pleura cavity
- pleura fluid
Intrapleural pressure is always negative - the lungs stay inflated within the chest cavity:
- elasticity of the lungs inwards
- elasticity of the thoracic wall - outwards
- functional residual capacity: the volume at which the pull of the chest is equal and opposite to the inward pull of the lungs
Breathing route
- Nasal or oral cavity
- trachaea
- bronchi
- secondary bronchii
- tertiary bronchii
- smaller bronchii (20-30 orders of branching in total)
- bronchioles
- terminal bronchioles
- respiratory bronchioles
- alveoli
Surfactant and lung compliance
Surfactant keeps the lungs moist and stops the alveoli from sticking together
Surfactant increases polmonary compliance, the ability of the lungs to expand
Bigger alveoli expand more slowly due to surfactant more spread out
All alveoli in the lungs expand at eh same rate. Bigger: rise in surface tension = slower expansion
Surfactant reduces surface tension more readily when the alveoli are smaller because the surfactant is more concentrated
Airway conductance
Airway resistance = combined resistance of individual airways
Combined radii increases due to the large number of small tubes
Overall the resistance is decreased in the alveoli
Thin film of water lining the alveoli, useful for gas exchange, but hydrogen bonds between water molecules would pull the walls of the alveoli inwards - collapse
- So there is a increase in muscular work required to inflate the lungs
Would tend to collapse the alveoli, making them useless for gas exchange
- pulmonary surfactant and Laplace’s law
Laplace’s las: pulmonary surfactant
Pressure to collapse an alveolus is directly proportional to the surface tension and inversely proportional to the radius of the alveolus
Partial pressure
The tendency of a particular type of molecule to diffuse from one area to another is given by the difference in density
Gaseous mixture: pressure of one type of molecule depends on its density
Pressure exerted by each type of gas molecules adds up - density of a single type of gas is called partial pressure
Physical limitations to gas exchange
Exchange occurs when gas levels (diffusion potential) are not in equilibrium - there is a diffusion gradient
The rate at which the gradient decays, which is specified by the equation time
The amount of gas available in the high potential medium, and the amount that can be absorbed bey the low potential medium
What happens in alveolar air?
Alveolar air has a lot of water vapour
Diffusion across membrane into the haemoglobin
Difference in partial pressure: alveolar air - oxygen = 100mmHg and CO2 = 40mmHg (not the same as in atmospheric air)
In pulmonary capillaries (prior to gas exchange) - O = 40mmHg and CO2 = 45mmHg
Haemoglobin
Haemoglobin (Hb) is a tetra Eric protein of 2 alpha and 2 beta subunits, each with a haeme co-factor
Haeme group contains a ferrous ion (Fe2+) that allows the haeme group to reversible bind to O2
Each subunit associates with a haeme group - each haeme group can associates with one oxygen = so each haemoglobin can associate with 4 oxygens
Affinity of O2 is controlled by the chemical environment and by co-operative interactions between protein-globin subunits
Factors that can influence partial pressure of oxygen
- pH: changes the shape of proteins (haemoglobin is protein)
- CO2: liked to pH in water and competes with oxygen for haemoglobin
- temperature
- 2,3-BPG or 2,3-DPG: metabolic intermediate in the glycolysis pathway - in anaerobic respiration (lactic acid will influence the pH).
- Cl- ions
Control of breathing
- medulla oblong at and Pons coordinate breathing
- aortic and carotid pH sensors also relay information to the brain stem
Neural control of breathing: generation and control of rhythmic behaviour
- central areas
- central pattern generators (CPG)
- afferent pathways (central and peripheral chemoreceptors, mechanoreceptors and higher brain centres)
- effrontery pathways (muscle control)
Detection of CO2 in the brainstem
Consequences of departures of O2, CO2 and pH from their set point
- hypoxia: low levels of oxygen - reduced metabolism (sleepy)
- hyperopia: high levels of oxygen - can lead to tissue damage
- hypocapnia: low CO2 - suppression of gas exchange
- hypercapnia: excess CO2, panic and sensations of drowning
- acidosis: low pH - cramps and other metabolic disturbances
- alkalosis: high pH - insufficient oxygen to tissues, when low pH haemoglobin gives up oxygen more readily to tissues
Carbon dioxide
CO2 dissolves in water - forms carbonic acid - dissociates to give protons and bicarbonate ions
This process is catalysed by carbonic anhydrase
The haemoglobin hinds H+ to act as a proton buffer, and also binds CO2 in the carbamino reaction
Chloride shift: removal of bicarbonate ions from the red blood cell could change the electrical balance (negative charges being removed), so chloride ions come in to balance this. When there is enough CO2 to initiate O2 binding to haemoglobin there will be an increase in chloride ion concentration within the red blood cel. Chloride ion is another signal to the haemoglobin to release more oxygen
The Haldane effect
Describes the phenomenon by which binding of oxygen to haemoglobin promoters the release of carbon dioxide
How is CO2 transported in the blood?
- Bicarbonate (HCO3) - 60%
- Carbamino-haemoglobin - 30%
- Dissolved in the plasma - 10%
Myoglobin
Found in big muscles
Stores oxygen and has a higher affinity for oxygen
It’s only made of one subunit (however haemoglobin is co-operative).
Emphysema
Chronic long term disease.
Walls of the alveoli damaged.
Caused by the the release of the enzyme alpha-1-anti-trypsin due to irritants
Heart has to work harder to achieve gas exchange due to being full of mucus (increases diffusion distance) and destroyed alveoli - eventually heart failure
Destruction of alveoli means less surface area for gas exchange
Oedema
Fluid in interstitial space
Increases diffusion distance
Arterial pressure of CO2 may be normal due to high CO2 solubility
Caused: some forms of heart failure and pneumonia
HAPE: high altitude pulmonary oedema
Lower air pressure at high altitudes. Hypoxic. Can lead to pulmonary vasoconstriction (pulmonary hypertension). Increased permeability of vascular epithelium
Reduced ventilation - asthma
Increased airway resistance, decreases airway ventilation
Chronic Obstructive Pulmonary Disease (COPD)
Chronic bronchitis and emphysema usually both present (asthma)
Causes (irritants):
- cigarette smoke
- cystic fibrosis
- some pollutants can also cause it
Permanent damage to airway - chronic
Symptoms:
- cough - productive cough (comes and goes at first, a lot of sputum coughed up)
- breathlessness and wheezing
- chest infections much more common
