Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, cardiovascular and thoracic biology (CTB) module.
Lecture 5 on some of the techniques that we can use to evaluate the way the heart and lungs are working. These techniques are routinely used in the clinical evaluation...
Performance of cardiopulmonary system
How is hea.rt and lung function controlled ?
⑪
- heart produces its rhythm generated by specialised cells in the RA: sinoatrial nodes
=> depolarise => heart contraction
- intrinsic depolarisation rate = 110 beats per min
=> limited by the parasympathetic ‘brake’ (=frein)
- autonomic nervous system:
=> balance bw sympathetic & parasympathetic
=> controlled by cardiovascular control centre (in medulla oblongata)
=> at rest: PNS predominates => 72 bpm
Control of breathing
- voluntary control of our breathing (unlike heart): talking, coughing, holding our breathe...
=> controlled by motor cortex in pre-frontal gyrus
=> involve the phrenic nerves: send impulses from medulla to diaphragm
- involuntary control: respiratory control centre (in medulla oblongata) alters rate/ depth of breathing
=> afferent (sensory) signals affect rhythm via chemoreceptors (arterial CO2 conc)
, - diaphragm contraction: negative pressure in thorax => inspiration
- relaxation of diaphragm: positive pressure in thorax => exhalation
Interaction between control of hea.rt & lung function a
- activation of inspiration muscles inhibits vagus nerve (PNS) innervation of the heart
=> interbeat interval (= time bw triggered heart beats) is shorter during inspiration
How does exercise affect the cardiopulmonary system
- physical activity = biochemical movement produced by muscoskeletal system requiring metabolic E
- exercise = physical activity with a purposeful increase in E exprenditure
- anaerobic exercise (“power”) = high intensity + short duration
=> rely on E stored within muscles
- aerobic exercise (“endurance”) = low intensity + long duration
=> rely on steady supply of O2 & nutrients to muscles
Upregulating cardiopulmonary system during exercise
- skeletal muscles shorten & lengthen
=> activate afferents nerves (attached to mechanoreceptors)
=> immediate increase in ventilation (VE): breathing frequency increase + deepen
=> plateau phase = steady state: peripheral chemoreceptors balance supply & demand
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