Important for circulation (pulmonary & systematic) of fluids, nutrients and blood around the body to keep tissues alive. Heart’s action can change based on the situation change impacting circulation, volume and pressure.
The heart is one-way valved that operates systematically:
Contains Trabeculae (Ventricles) & Pectinate (Atria) ridges which allow continuous bloodflow without clots
Atrioventricular Valves (AV)
Semilunar Valve (SL)
Vary from person-to-person, heart has a large muscle mass and needs bloodflow to deliver oxygen and remove CO2
Right Coronary Artery (RAD): Inferior Region
Left Main Artery (LM / LCA): Anterior Region
Circumflex (Cx): Lateral Region
Sinoatrial Nodes (SA Node): 60-100bpm
Oval-shaped near superior vena cava – Generates automatic depolarisation impulses modified by the Autonomic Nervous System (ANS). Primary pacemaker has the most intrinsic rate of depolarisation
The impulse is sent to atria through the internodal pathways where atrial will send impulse to AV node.
Atrioventricular Nodes (AV Node): 40-60bpm
Serves as a bridge between atria & ventricles (located in atrial septum) – receives impulse and delays It before conducting the ventricles; this delay is so the atria can fill up adequately before ventricular contraction.
Additional structures (to the SA node) that can serve as pacemakers – Term ‘latent’ refer to its role when the SA node fails. These nodes can assume the role of pacemaker as (normal autonomy) to prevent cardiac arrest
Bundle of His (AV Bundle): 40-60bpm
From AV node impulse – Splits impulse into left & right bundle branches – Subsequently branching into smaller bundles into Purkinje fibres.
Purkinje Fibres (PKF): 20-40bpm
From AV Bundle – Fast impulse (4m/sec) which runs through endocardium where impulse is sent to myocardial contractile cells (some extend into myocardium). Ventricular contraction therefore begins in endocardium and spread to epicardium
Cardiac cycle begins at cell-level where particle movement between cell membrane creates action potential which is transmitted along the conduction pathway – Done in five (5) stages. Any changes in electrolyte values (Na+ / Ca+ / K+) can affect cell’s action potential.
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|Thanh Bui, AP60825|
Event Medic, Emergency Medical Technician &
Volunteer Development Officer
Andrew Moffat, AP16790