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41 Cards in this Set

  • Front
  • Back
What are the functions of the respiratory system?
Gas exchange
Regulation of humidity and pH - CO2 levels
Vocalisation
Olfaction
Protection against microorganisms
What are the 4 processes of respiration?
Ventilation - air into and out of lungs
External respiration - gas exchange between air-filled alveoli and blood
Gas transport - cardiovascular system
Internal respiration - gas exchange between blood and tissues
What is partial pressure?
Pressure exerted by each type of gas in a mixture and is proportional to its concentration in a mixture
What is Dalton's Law?
Total pressure exerted by mixture of gases is equal to the sum of partial pressures exerted by each gas
How do you calculate a gas's partial pressure
Multiply its concentration by total pressure
e.g. 21/100 x760 = 160 mm Hg
take away water vapour pressure at body temperature
What factors influence the diffusion of gases in the body?
Thickness and surface area of respiratory membrane
Partial pressure gradient, diffusion coefficient, solubility of gases
Alveolar ventilation and perfusion
How does oedema/pneumonia affect gas exchange in the alveoli?
Increases distance for gas diffusion between alveolus and blood
How does emphysema affect gas exchange in the lungs?
Destruction of alveolar walls, low PO2 due to loss of elasticity of lungs, can decrease surface area for gas exchange
How does asthma affect gas exchange in the lungs?
Increases airway resistance by decreasing radius/diameter of bronchioles, decreases airway ventilation
What does the composition of gases in alveolus affect?
Gives the same composition in pulmonary vein going to left side of heart
Oxygen cascade shows
Oxygen cascade shows
Partial pressure of O2 at different levels in respiration
Hypoventilation causes decrease in O2 levels in alveolus and tissue
What causes the decrease from 100mm Hg to 90mm Hg from pulmonary capillaries to systemic capillaries?
Shunting of blood
Deoxygenated blood returning to pulmonary vein from bronchial circulation
O2 dilution returning from coronary circulation (Thebesian veins)
Why is there a much smaller partial pressure difference with CO2 compared to O2?
Same volumes of gas move because CO2 is 20x more soluble and therefore moves quicker than O2
How does change in ventilation affect partial pressures of O2/CO2 in alveoli?
Increasing ventilation to alveoli increases PO2, decreases PCO2 in alveoli -> not enough O2 taken in and co2 put out
Makes gas exchange more inefficient
What happens to alveoli gas composition if they have a high V:Q ratio?
High ventilation:low perfusion
high PO2, low CO2, closer to inspired air than mixed venous blood
What happens to pulmonary capillaries if hypoxic?
Vasoconstriction, blood diverted away from poorly ventilated areas
(low v:q ratio = hypoxic = vasoconstriction)
Where are central and peripheral chemoreceptors found?
Central - medulla
Peripheral - coronary sinus and aortic arch
What do peripheral chemoreceptors respond to?
PO2 and [H ions] in arterial blood
What do central chemoreceptors respond to?
Arterial CO2 (indirectly) and [H ions] in cerebral spinal fluid
COS crosses bbb and dissociates into H ions
What increases respiratory rate during exercise?
Proprioceptors sense movement during exercise (increases h rate too)
What are the respiratory centres in the medulla and what do they control?
Dorsal respiratory group in nucleus tractus solitarius - inspiration
Ventral respiratory group - inspiration and expiration
Pneumotaxic and apneustic centre
How do impulses form the dorsal respiratory group in the medulla control inspiration and expiration?
Impulses from DRG activate motor neurones in diaphragm/intercostal externals to cause inspiration
Stop firing, expiration begins
What is eupnoea?
Normal quiet breathing
What is apnoea?
Cessation of breathing
How is the VRG involved in breathing?
Only forced breathing - neurones activated accessory muscles (abdominals and internal intercostals for forced expiration during exercise)
Which respiratory group in medulla is not involved in eupnoea?
VRG
What controls the firing from the DRG?
Neuronal input from pons
Central pattern generator - ability to produce action potentials and then stop
What is the effect of the pneumotaxic centre on the DRG?
Acts as an "off-switch" to DRG neurones that can cut short inspiration
and can affect respiratory rate (weak signal to DRG = slower rate)
How does the apneustic centre affect the DRG?
Can prevent or retard off-switch to DRG - prolong inspiration or breath hold during inspiration
What is the ongoing stimulus for ventilation?
Normal levels of CO2 - low levels would induce hypoventilation
CO2 - crosses BBB, dissociates to H ions which stimulate central chemoreceptors
H causes increased depth and rate of breathing -> initiates inspiration
How do peripheral chemoreceptors respond to PO2 and [H ions]?
Respond to decreased PO2 and increased [H ions] (low pH)
Which peripheral chemoreceptors are more sensitive?
Carotid bodies - higher blood flow
Describe how peripheral chemoreceptors respond to low PO2
Normal levels of O2 keep K channels open -> hyperpolarisation
Low O2 shuts K channels and opens Ca voltage-gated channels -> depolarisation -> neurotransmitter dopamine is released -> excitation of sensory nerves and increased impulses to medulla-> increased ventilation to return O2 to normal levels
What types of sensory receptors are in the lungs/airways?
Stretch and irritant receptors
Where are stretch receptors found?
Smooth muscle in bronchi/bronchioles
What is the Hering- Breuer reflex?
In response to large lung inflation during high tidal volume -> enhances off-switch to DRG -> inhibits inspiration and promotes expiration
protection against lung overstretch?
Where are irritant receptors located?
Epithelium of airways
What are irritant receptors stimulated by and what does their response depend on?
Irritants
Location of irritant (cough, sneeze, rapid breathing)
Describe cough reflex
Deep inspiration, epiglottis and vocal cords shut, forced expiration, lung pressure rises, epiglottis and v.cs open -> explosion of air
What makes you want to breathe again after holding your breath?
Levels of CO2 increase -> stimulates chemoreceptors
What stimuli can also affect breathing?
Temperature - increased temp = increased breathing, emotion - laughing, pain - apnoea, baroreceptor - fall in b.p. (e.g. haemorrhage) increased breathing