Name the heart valves and describe their location, function, and mechanism of operation.
Heart valves open and close in response to pressure changes as the chambers contract and relax. Two types of valves:
atrioventricular valves (tricuspid, bicuspid)
semilunar valves (pulmonary, aortic)
Atrioventricular valves are forced OPEN as pressure increases in the atria. Blood returning to atria forces heart places pressure on atrioventricular valves! As atria fills, A flaps hang loose into ventricles. Atria contract, forcing blood flow into ventricles. AV valves are then forced closed by ventrical pressure.
Semilunar Valves: (Pulmonary and aortic) Forced open as pressure grows in ventricles! Blood is pressing against them... so they open. Pressure from blood in the arteries makes it close.
Describe the normal heart sounds and the events in the heart they correspond to.
Auscultation: act of listening to sounds within the body
. Lub DUB!
Describe the events that occur during cardiac muscle contraction.
Three major phases during contraction:
Depolarization: Rapid depolarization due to Na+ inflow when voltage gated fast Na channels open.
Plateau : Maintained depolarization due to Ca2 inflow when voltage gated slow Ca2+ channels open and K+ outflow when some K+ channels emerge.
Repolarization: Dulse to close of Ca+ channels and K+ outflow when additional voltage gated K+ channels open.
Name the components of the cardiac conduction system.
Specialized cardiac muscle fibers called autorhythmic fibers make your heart beat!! Autorhythmic fibers act as:
Pacemaker: initiates the signal
Conduction system: propagates the signal throughout the heart
Trace the pathway of conduction in the heart.
Sinoatrial (SA) node (pacemaker): generates impulses.
Atrioventricular (AV) node: impulse pauses here
Atrioventricular (AV) bundle: Connects atria to ventricles
Right/left bundle branches: conducts impulses through interventricular septum
Purkinje fibers (in walls of ventricles): Depolarize!