Transcript Cardiac Cycle and Heart Sound

 a.
Sinoatrial node (SA node)
 b. Atrioventricular node (AV node)
 c. Atrioventricular bundle (AV bundle)
 d. Right and left atrioventricular bundle
branches
 e. Purkinje fibers
 Located
Junction of Superior Vena Cava
 Specialized Pacemaker Cells

Intrinsic Rhythm- without stimulation by nerve
impulses from brain and spinal cord
 Initiates
impulses at regular intervals
 From
SA node to Contraction of both Atriums
 Internodal Bundles- Right Atrium
 Interartial Bundle- Left Atrium
 Internodal Bundles to Atrioventricular node
 Av
Node to Bundle of His (AV Bundle)
 Left and Right Bundle Branches
 Branches to Purkinje Fibers
 Simultaneously Contract Ventricles
 SA
node Intrinsic Rhythmical rate 70-75 beats
 What
happens when SA node loses ability to
initiate impulse?


Another Excitable Component takes over
Abnormal/ ectopic pacemakers



AV Node or Purkinje Fibers
Slower rate than SA Node
AV Node- 40-60 beats per min
 Heart
Conduction Animation
 McGraw Hill
 ECG

a recording of the electrical activity (changes)
during a cardiac cycle
 How


(EKG)
it works
Two Electrodes of Voltmeter
Passing of Action Potential between two
electrodes
Wave – depolarization(+) of the atria
(atrial contraction – systole)
P

SA Node Atria
Complex – depolarization of the
ventricles (ventricular contraction, systole)
 QRS

AV  Purkinje Fibers
Wave – Repolarization(-) of the
ventricles
T
 Cardiac
Cycle is all the events associated
with the blood flow through the heart during
one complete heartbeat

Systole – contraction period of a chamber –
ejection of blood.

Diastole – relaxation period of a chamber –
filling of blood
 Contraction (Eject) and Relaxation (Filling)
ALWAYS follows electrical events seen in an
ECG
 SA
Node initiates action potential.
 Atrial
systole (1) causes Atrial
pressure to increase, blood sent to
ventricles through AV valve. (P Wave)
 Ventricular
Systole caused by impulse
traveling down Bundle of His to Purkinje
Fibers (QRS Wave)

Isovolumetric Ventricular Contraction (2)

AV valves snap close causing the “Lubb”
sound at the pressure rises in the ventricles
 Ejection
(3) of blood into pulmonary circuit
pressure in ventricle is greater than in the
arteries so semilunar valves are forced open.
 As pressure drops the Semilunar Valves snap
close causing “Dubb” sound

 Isovolumetric

Ventricular Relaxation (4)
Diastole begins, all valves closed. Once
pressure has dropped low enough, the AV
valves open and…..
 Passive
Ventricular Filling (5) because
atrial pressure is higher than ventricle
pressure. Toward the end of this period,
atrial systole begins.
 Closing
of the heart valves
 Described as “Lubb – Dubb”
Basic rhythm is lubb-dubb, pause, lubb-dubb,
pause, lubb-dubb, pause.
 First sound “Lubb” is the longest and loudest
occurring when AV valves close.
 Second sound “Dubb” is short, sharp sound
occurring when Semilunar valves close.
 Sound
is due to turbulence
 Generally, heart murmurs indicate heart
valve problem
 “Swishing” sound indicates an incompetent
valve - partially open valve after it should
be closed so the blood backflows through the
valve
 High-pitched or click sound indicates a
stenotic valve – the valve should be wide
open, but it is not.