Cardiovascular & Respiratory system Flashcards
Function of the CV System
- Delivery of oxygen and other nutrients
- Removal of carbon dioxide and other metabolic waste
- Transportation of hormones
- Maintenance of acid base balance and overall fluid balance
- Prevention- immune function
Blood flow through the heart
- Right side pumping deoxygenated blood to the lungs
- left side pumping oxygenated blood to all other tissues
Right side of heart
Right atrium – tricuspid valve – right ventricle – pulmonary valve to the pulmonary artery – carries blood to lungs for reoxygenation (pulmonary side)
Left side of heart
Pulmonary veins (from the lungs) – left atrium – mitral value – left ventricle – aortic valve – to aeorta and distributed via systemic circulation
Cardiac muscle
Myocardium.
Myocardial thickness differs around the heart according to the stress put on it.
The left ventricle is the most powerful of the 4 heart chambers – overcome gravity
Ventricular Systole (3)
Both ventricles contract simultaneously
The AV valve closes
The semilunar valve opens and blood enters the pulmonary trunk and aorta
Atrial Systole (2)
The semilunar valves are closed and AV valves are open
Both atria contract, forcing blood into the ventricles
Atrial & ventricular diastole (1)
Atria and ventricles are relaxed
atria and ventricles fill passively
AV valves are open
Semilunar valves are closed
4 Main components of the cardiac conduction system
Sinoatrial (SA) node
Atrioventricular (AV) node
AV bundle (Bundle of hiss)
Purkinje Fibres
Conduction system Process
SA node generates impulse; atrial excitation begins- heart pace maker
Impulse delayed at AV node (0.13 sec), then passed to ventricles – delay allows blood from atria to completely empty into ventricles to maximise ventricular filling before they contract
Impulse passes to heart apex via AV bundle branches - Ventricular excitation begins
Purkinje Fibres spread throughout ventricle (speed x6) – ventricle contracts
Regulation of HR - Parasympathetic
Lowers HR
Branch of the autonomic nervous system
Stimulates the release of acetylcholine which causes hyperpolarisation of the conduction ceels
Acts through vagus nerve - affects atria
Slower spontaneous depolarisation and a decrease in heart rate
Regulation of HR - Sympathetic nervous system
Adrenaline / nonadrenaline
Accelerates SA depolarization (chronotropic) (Atria & Vent)
Vasoconstriction around the body
Increases rate of depolarisation and conduction speed and hence heart
rate
Increases force of contraction of the ventricles
Physical or emotional stress – heart rate greater than 100 b.min
Use of an Electrocardiogram
Electrical activity of the heart can be recorded using an ECG
Monitor cardiac changes or diagnoe cardiac problems
Electrocardiogram - P wave
atrial depolarisation
(electrical impulse from SA node to AV node with atrium contraction)
Electrocardiogram - QRS complex
ventricular depolarisation
(impulse spreads from AV bundle to Purkinje fibres and ventricular contraction)
