L37 - Respiration Regulation Flashcards
What does the respiratory system include?
Series of conducting airways which carry air from the mouth and nose to the lungs
What do the muscles enable in the respiratory system?
- breathing (diaphragm + intercostal muscles
What are the trachea and bronchi lined with?
Ciliated columnar epithelial cells
What are within the epithelium of the trachea and bronchi?
- gel phase, sol phase (mucus)
- cilia (in sol phase)
- goblet cells
- basement membrane
- submucosal gland
What is the epithelium like in bronchioles?
- simple cuboidal form
- goblet cells replaced by club cells
- club cells secrete protective and defensive mediators
What is the primary purpose of the respiratory system?
Gas exchange - provision of O2 and removal of CO2 from tissues
What are the other purposes of the respiratory system?
- regulation of acid-base (CO2 control)
- activation (angiotensin 1 to 2) deactivation (bradykinin, serotonin, noradrenaline) of cicrulation mediators
- filtering microthrombi
- speech
What is PO2?
partial pressure of oxygen
What is PCO2?
Partial pressure of CO2
What is PaO2?
- Partial pressure of arterial oxygen
- 80-100mm Hg
What is PaCO2?
- Partial pressure of arterial CO2
- 40mm Hg
What are the 3 inputs for neuronal control of breathing?
- cerebral cortex
- mechanoreceptors
- chemoreceptors
What are the types of control of respiration?
- neural
- chemical
What is the neutral control of respiration?
- central rhythm generator in medulla
- receptors cause sneexing, coughing and hypernoea
- nociceptors
What is the chemical control of respiration?
Central and peripheral chemoreceptors sense O2, CO2 and pH levels
What are the respiratory centres in brainstem that control automatic control?
- medulla
- pons
How does the medulla control automatic control of breathing?
- ventral and dorsal respiratory group
- discharge rhythmically
- efferent neurons to motor neurons
- receives afferent input from periphery and pons
- little activity in expiratory centre at rest
What are the different parts of pons?
- apneustic centre
- pneumotaxic centre
What does the apneustic centre do?
- prolongs medullary centre firing
- = depth of breathing increased
What does the pneumotaxic centre do?
- inhibits apneustic centre
- controls rate of breathing
What would happen if there was a transection above pons, above medulla and of the spinal cord?
- loss of voluntary control
- loss of feedback regulation, breathing continues
- breathing abolised
What is voluntary control of breathing via cereblar cortex like?
- sends signals direct to respiratory motor neurones
- sensitive to temp and emotion
What is ondine’s curse?
Loss of automatic control
What are the 2 chemoreceptors that control respiration chemically?
- central chemoreceptors
- peripheral chemoreceptors (carotid and aortic bodies)
What is CO2 and H+ likes in central control of respiration?
- HCO3- and H+ dont easily cross the BBB
- CO2 uncharged - crosses BBB and dissociates in CSF
What happens when O2 falls in peripheral control respiration?
- O2 sens K+channels close
- depolarisation
- DA release
- stimualates afferent fibres
- signals to medulla
What happens when PaO2 falls (regulation of afferent fibre activity from the carotid body)?
- nerve firing increases
- ventilation increases
- arterial CO2 levels kept stable
What is haemoglobin like?
- tetramer
- 4 oxygen-binding haem groups
- O2 binding to Hb increases affinity for next
- loss of )2 from saturated Hb gets easier as O2 is lost
- cooperative
What is oxygen transport like?
- 97% O2 transported in RBC to Hb
- Hb fully saturate at normal O2
- 90% saturated at 60mmHg
What is the total amount of oxygen in arterial blood calc?
O2 bound to Hb + O2 dissolved in blood
What does oxygen transport depend on?
- saturation of haemoglobin
- PO2
Why is the amount pressure required to cause CO2 diffusion much less than the pressure required to cause O2 diffusion?
CO2 can diffuse about 20 times as rapidly as oxygen
What is oxygen release in tissues like?
- oxygenated arterial blood reaches capillaries = O2 released
- consumed by cells
- arterial PO2 95mmHg
- venous PO2 40mmHg
What causes the pH of the blood to decrease? What happens as a result?
- tissue’s metabolic rate increases, CO2 waste production increases
- promotes dissociation of O2 from Hb
- surrounding tissues obtain enough oxygen to meet demands
What does myoglobin have a role in?
- O2 storage and transport in metabolically active cells
What is Mb like?
- skeletal anc cardiac mucle dont bind cooperatively
- single O2 binding site
- high affinity
- not affected by pH or CO2
- captures O2 released by Hb
What is the transport of CO2 like?
- from tissues diffuses into plasma
- enteres RBC, converted to bicarbonate by carbonic anhydrase
What is CO2 transport like statistically?
- 70% as HCO3-
- 7% as dissolved CO2
- 23% as carbamino haemoglobin (HbCO2)
What happens when CO2 production is increased?
- fraction of CO2 increases relative to HCO3-
- CO2 in CSF increases
- dissociates in CSF and H= detection by central chemoreceptors
What is the epithelium like in the alveoli?
- thin walls
- unciliated
- squamous epithelial cells
- close approximation to capillary endothelium
- fusion of their basement membrane = gas exchange
What is gas pressures like in alveoli and blood?
- PO2 same in alveolus and pulmonary vein - higher than in systemic veins
- PCO2 higher in veins than alveolus and systemic arterial blood
What causes the blood to release CO2?
- high PO2 in lungs
- O2 binds to Hb = acidic
- less formation of Hb.CO2
- H+ binds to bicarbonate = carbonic acid
What are the physiological responses to low inspired O2?
- increased ventilation
- pulmonary vasoconstriction
- increased haematocrit
What is the increased ventilation like?
- immediate
- driven by peripheral chemosensors
- not sustained
What is pulmonary vasoconstriction like?
- rapid and sustained
- homeostatic mech shunts blodd away from poorly ventilated aras
- not useful if lung is hypoxic
What is increased haematocrit like?
- activation of tf HIF (hypoxia inducible factors)
- HIF regulates transcription - erythropoetin production by kindeys, stimulates bone marrow to make RBC
What are the types of altityde sickness?
- acute mountain sickness
- chronic mountain sickness
What is acute mountain sickness like?
- flu like symptoms
- breathlessness
- hypoxic pulmonary vasoconstriction
- pulmonary and cerebral oedoma
What is chronic mountain sickness?
- low PO2 cannot be matched by ventilation
- inc EPO production in kidney
- too high haematocrit
- in load on right heart
- acetazolamide inhibits kidney EPO production - inc ventilation discussed earleir
What are genetic adaptation of high altitude populations?
- compensation by increased O2 uptake by tissues
- inc muscle capillaries
- high Mb levels
- Mb gene polymorphism
