Assessing Cardiopulmonary System Performance Flashcards
How does the heart beat?
Specialised cells in RA in sinoatrial node spontaneously depolarise, triggering a wave of excitation which is transmitted through the heart,resulting in the contraction of atria, followed by ventricles, after a delay. This rate is about 110bpm
How does the autonomic NS influence heart rate?
Both branches of the ANS are controlled by the cardiovascular control centre in the medulla. The PSNS is dominant at rest, and vagus innervation reduces HR to about 72bpm. To increase HR, the vagus brake is removed, and B-1 adrenoreceptors (in SAN) are activated by the SNS via release of noradr from nerves and adrenaline from adrenal medulla.
How is breathing controlled?
Mainly in the respiratory centres of the medulla. At rest phrenic nerves carry impulses to diaphragm. However, there is voluntary control for talking coughing etc (motor cortex). There are also sensory signals that affect breathing rhythm, such as arterial CO2 conc (from pH of CSF) which are detected by chemoreceptors, as well as stretch receptors in lungs.
How do heart and lung function control interact with eachother?
When inspiratory muscles are activated, the vagus nerve slowing down of HR is inhibited, so the interbeat interval is shorter during inspiration.
What is exercise and what are the differences between aerobic and anaerobic?
Exercise is a a purposeful increase in energy expenditure via physical activity - any biomechanical movement produced by musculoskeletal system that required metabolic energy. Aerobic exercise is low intensity, long duration, relies on steady O2 and nutrients. Anaerobic is high intensity, short duration, all about power, relies on stored energy in the muscle.
How does ventilation change during exercise?
There’s an immediate increase in volume expired which is mediated by nerves attached to mechanoreceptors that are activated when muscles shorten and lengthen. Demonstrated by moving an unconscious persons legs, which results in increased ventilation. After this, there’s a steady increase in ventilation due to increasing central stimulation. Peripheral chemoreceptors fine tune breathing in the plateau stage - steady state, balanced supply and demand. When exercise stops, ventilation has a sharp decreased (muscles no longer providing stim) which steadily decreases until O2 debt is repaid.
What is the pattern for increasing ventilation during exercise?
First phase involves the respiratory rate increasing to about 20 breaths/min (from 12-15) at light/moderate exercise. Ventilation increases by deepening each breath. At moderate-high intensity this becomes inefficient due to the energy required to fill and empty the lungs each time, so we increase the rate of ventilation.
What is the cardiovascular response to increased exercise?
Increased cardiac output (blood ejected from LV per min). In adults, exercise can 4X CO and also redistribute blood flow towards muscles and away from non-essential organs. CO = HR x SV.
Why is a super high HR (ventricular tachychardia) bad?
Because ventricles contract before full, greatly decreasing cardiac output
Why does long term training increase cardiac output?
Ventricles become stronger and bigger, increasing the volume of blood pumped per beat (stroke volume). Increased venous return in trained indiviudals and increased left ventricular end-diastolic volume (blood in ventricles before contraction) means that the heart walls stretch more, giving them more elastic energy and greater recoil force, allowing the ejection of more blood.
Explain chronic adaptations to sustained activity
Ventricular remodelling - Thickening of heart muscle via hypertrophy and hyperplasia
Increased vascularisation of alveoli - To make better use of ventilated air
Increased vascularisation of myocardium - Heart also needs alot of O2
Increased oxidative enzyme density - More enzymes that allow aerobic respiration to happen
No meaningful lung volume change - Usually fixed determined by genetics
Describe an electrocardiogram
Measures electrical activity of the heart including the frequency of beats (HR), timing between beats (rhythm), and the conduction of the signal through the myocardium. P is the depolarisation wave from SAN (contraction), QRS complex is wave moving fast through large amount of muscle at apex (causing ventricular systole), and T wave is ventricular diastole (repolarisation).
Describe an echocardiogram
Ultrasound imaging which looks at different cross sections of the heart and allows examination of valves and estimation of the volume of blood left in the heart before and after contraction
How does traditional spirometry allow us to assess lung function?
Maximal exhalation from TLC as forcefully as possible measures forced vital capacity and forced expiratory vol in 1 sec. FEV1:FVC is used to diagnose obstructive and restrictive diseases.
What does peak expiratory flow tell us about health?
PEF is maximum lung emptying rate and has long been associated with disease development. Measured by Wright peak flow meter. Performed 3 times and highest value compared to charts. COPD has stable PEF, asthma has variable
