Heart Physiology

_____ generates impulse causing _____ _____

SA node, atrial excitation

Impulse is delayed at

AV node

Leaving the AV node, the impulse goes to the

heart apex

_____ _____ begins when the impulse is passed to the heart apex

ventricular excitation

Ventricular excitation is complete at the

purkinje fibers

P wave corresponds to

depolarization of SA node

QRS complex corresponds to

ventricular depolarization

T wave corresponds to

ventricular repolarization

_____ _____ record is masked by the large QRS complex

atrial repolarization

Sounds of aortic valve are heard in

2nd intercostal space at right sternal margin

Sounds of pulmonary valve are heard in

2nd intercostal space at left sternal margin

Sounds of mitral valve are heard over the apex in

5th intercostal space in line with middle of clavicle

Sounds of tricuspid valve are heard in

5th intercostal space in right sternal margin

Peak of atrial depolarization is represented on the _____ _____ of EKG

P wave

Peak of ventricular depolarization is represented on the _____ _____ of EKG

R wave

Peak of ventricular repolarization is represented on the ____ _____ of EKG

T wave

Lub-dup heart sounds are associated with

closing of heart valves

First heart sound (lub) occurs as the _____ _____ close and signifies beginning of _____

AV valves, systole

Second heart sound (dup) occurs as the _____ _____ close at the beginning of _____ _____

sl valves, ventricular diastole

Refers to all events associated with blood flow through the heart

cardiac cycle

Contraction of heart muscle

systole

Relaxation of heart muscle

diastole

Ventricular filling occurs

mid to late diastole

Heart blood pressure is low as blood enters _____ and flows into _____

atria, ventricles

As ventricular filling is occurring, _____ _____ are open, then _____ _____ occurs

av valves, atrial systole

Relaxes during ventricular systole

atria

Rising ventricular pressure results in

closing of av valves

The isovolumetric contraction phase

ventricular systole

Opens semilunar valves

ventricular ejection

Isovolumetric relaxation occurs in

early diastole

Closes semilunar valves

backflow of blood in aorta and pulmonary trunk

Brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves

dicrotic notch

Blood that comes back into left ventricle after closure of aortic valve

dicrotic notch

ESV=

end systole volume

Depolarization is followed by

contraction of the heart

Amount of blood pumped out of a ventricle in one minute

cardiac output

Drug given to reduce heart beats

calcium blockers

Formula for measuring cardiac output

bpm X mL per beat

Causes of congestive heart failure

coronary artherosclerosis, persisent HBP, multiple myocardial infarcts, dilated cardiomyopathy

Blockage of coronary artery

coronary artherosclerosis

Lost of elasticity of myocardium

dilated cardiomyopathy

Non functional or weakened mitral valve disease

mitral valve prolapse

Most important factor for stretching cardiac muscles

amount of blood returning to the heart and distending its ventricles (venous return)

The degree to which cardiac muscle cells are stretched just before systole

preload

Pressure that ventricles must overcome to force open aortic and pulmonary valves

afterload

Prevents pooling of blood in the venous system

bainbridge reflex

Bainbridge reflex is initiated by

increased venous return, atrial filling

Chemicals that regulate the heart

hormones, ca2, K+

Decreased Ca2 levels cause

hypocalcemia

Effects of hypocalcemia

depress heart

Increased levels of Ca2 cause

hypercalcemia

Effects of hypercalcemia

increased heart irritability

Excessive K+ levels cause

hyperkalemia

Effects of excessive K+

interferes w depolarization by lowering rest potential, possible heart block, cardiac arrest

Effects of hypokalemia

Weak or arrhythmic heart beat

Decreased levels of K+ cause

hypokalemia

Local decrease in blood supply is called

ischemia

Absolute refractory period of heart muscle

250 ms

Heart muscle is stimulated by _____ and contracts as a _____

nerves, unit

Cardiac muscle contraction is similar to _____ _____ contraction

skeletal muscle

Function of intrinsic conduction autorhythmic cells

initiate action potentials

Autorhythmic cells have unstable resting potentials called

pacemaker potentials

Autorhythmic cells use _____ _____ for rising phase of the action potential

calcium influx

Cardiac intrinsic conduction pathway

SA node, AV node, bundle of his, bundle branches, purkinje fibers

SA=

sinoatrial

SA node generates impulses about _____ / minute

75

AV=

atrioventricular

AV node delays the impulse from the SA node by approximately

0.1 seconds

Cardiac impulses pass from atria to ventricles via the

bundle of his

_____ _____ branches carry the cardiac impulses toward the _____

bundle branches, apex

Purkinje fibers carry cardiac impulses to the _____ _____ and ______ _____

heart apex, ventricular walls

AV Bundle of His splits into these 2 pathways

bundle branches, purkinje fibers