PHYSIOLOGY OF THE HEART NOTES

Cardiac Conduction System

• SA node - (pacemaker) sinoatrial

• AV node – atrioventricular

• AV bundle

SA node - (pacemaker) sinoatrial

• Initiates impulses that contract the heart without brain or nerve signals.

• Located at the right atrium

• Impulse travels to left atrium and contracts it.

AV node - atrioventricular

• Impulse slowly moves through this node in right atrium.

AV bundle

• Located in septum

• End in purkinje fibers - in both ventricles

• Ventricles are stimulated to contract.

Contractions

• Normal average 70-75 beats/min.

• Emotions, exercise, hormones, pain, anxiety, fear, and anger can affect this.

Electrocardiogram (ECG)

• Graphic record of the heart’s action currents.

Electrocardiogram (ECG)

• An ECG is printed on paper covered with a grid of squares. Notice that five small squares on the paper form a larger square. The width of a single small square on ECG paper represents 0.04 seconds. To successfully interpret ECGs, you must have this value committed to memory.

Electrocardiogram (ECG)

• If each small square represents 0.04 seconds, then a second will be 25 small squares across. If you print out a minute's worth of your heart's electrical activity, the paper would be 1500 small squares wide. If something on an ECG is, let's say, 12 small squares in width, that means that it lasted 12 x 0.04, or almost half a second. A common length of an ECG printout is 6 seconds; this is known as a "six second strip."

Electrocardiogram Waves

• P-wave– Depolarization

(contraction) of atria.• QRS-wave

– Depolarization (contraction) of ventricle

• T-wave– Repolarization

(relaxation) of ventricles

Cardiac cycle

• Atrial systole - contracting atria forces blood into ventricle. P-wave of ECG

• Isovolumetric contraction - blood volume in ventricles remains constant. QRS-wave of ECG (1st heart sound)

• Ejection - blood ejected into pulmonary artery and aorta. T-wave

Cardiac cycle continued

• Isovolumetric relaxation - relaxation of ventricles (second heart sound)

• Rapid ventricular filling - return of venous blood

– Increases atrial pressure until av valves (tricuspid and bicuspid) open and blood rushes into ventricles.

• Reduced ventricular filling - increase in ventricular pressure and volume will slow blood filling.

Blood Pressure

• Sphygmomanometer - measures air pressure = to blood pressure

Blood Pressure

• Systolic pressure - 1st sound– blood pushing against artery

walls when ventricles contract.

• Diastolic pressure - 2nd sound– closing of valves, short sharp

sound

Directions for Taking Blood Pressure

• Pump pressure until no pulse is heard

• Release air until a spurt of blood is heard coming through. (systolic)

• Continue until sound stops (diastolic)

Video Clip

http://www.nlm.nih.gov/medlineplus/ency/anatomyvideos/000021.htmCardiac Conduction System

http://www.healthination.com/Conditions/Videos/Congestive-Heart-Failure/The-Failing-Hearthttp://www.healthination.com/topics.php?page=congestive_heart_failureCongestive Heart Failure

Heart AttackECG

http://www.sciencelearn.org.nz/Contexts/See-through-Body/Sci-Media/Animations-and-Interactives/Label-the-heartDrag and drop Tutorial