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Flashcards in Heart Quiz 2 Deck (20)
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Operation of Semilunar Valves

Open when pressure generated in ventricle is greater than circulation
Close when pressure generated in ventricle is less than circulation


Coronary Circulation

Blood vessels of the heart will carry blood to the cardiac muscle


1st Branches of the Aorta

Left Coronary Artery and Right Coronary Artery


Left Coronary Artery

1. Anterior Interventricular Artery: supplies interventricular septum and anterior walls of ventricles
2. Circumflex Artery: passes around the left side of the heart, supplies left atrium and posterior wall of the left ventricle


Right Coronary Artery

Supplies right atrium
1. Marginal Artery: supplies lateral right atrium and ventricle
2. Posterior Interventricular Artery: supplies posterior walls of the ventricles


Structure of Cardiac Muscle

Made up of cardiocytes
Interconnected by intercalated disks
Larger T-Tubules than skeletal tissue that release Ca2+
Not prone to fatigue
Uses fatty acids as a fuel source, glucose at rest


Intercalated Disks

Join all cardiac cells


3 Features of Intercalated Disks

1. Interdigitating Folds: cells interlock with each other and increase surface area
2. Mechanical Junctions: fascia adherens and desmosomes
3. Electrical Junctions: gap junctions that allow ions to flow from cytoplasm to cardiocytes


Fascia Adherens

Most abundant



Prevent cardiocytes from pulling apart


Similarities Between Myocardial Cells and Skeletal Muscle Fibers

Use tropomyosin and troponin to contract


Differences Between Myocardial Cells and Skeletal Muscle Fibers

Skeletal: voluntary contraction, excitation coupling
Cardiac: involuntary contraction, SA node and gap junctions


Pacemaker Physiology

1. Slow leak Na2+ enters the cell
2. Voltage gated Ca2+ channels open (at -40mV)
3. K+ channels open (at 0mV)
4. Repeat once polarization is complete


Action Potential of Ventricular Cardiocyte

1. Voltage-gated Na+ channels open
2. Na+ depolarizes the membrane and opens more Na+ channels, creating a positive feedback cycle and rising membrane voltage
3. Na+ channels close when cell depolarizes, voltage peaks at +30mV
4. Ca2+ slowly enters and prolongs depolarization, causing a plateau
5. Ca2+ channels close and Ca2+ is transported out of the cell; K+ channels open, and outflow returns membrane to resting potential


Conduction System of the Heart

1. SA node fires
2. Excitation spreads through atrial myocardium
3. AV node fires
4. Excitation spreads down AV bundle
5. Purkinje fibers distribute excitation through ventricular myocardium


Electrical Activity of Myocardium

1. Atria begin to depolarize (P wave)
2. Depolarization is complete
3. Ventricular depolarization begins at apex and moves superiorly while atrial repolarization occurs (QR waves)
4. Ventricular depolarization is complete (S wave)
5. Ventricular repolarization occurs at apex (T wave)
6. Ventricular repolarization complete, heart ready for next cycle


Ventricular Fibrillation

Most serious disturbance
Heart cannot pump blood
Irregular waves of depolarization
Chambers contract in rapid, unsynchronized ways


Atrial Fibrillation

Atria quiver and prevents blood from entering ventricles
Most common in elderly


Heart Block

Conduction passes weakly from the atria through AV bundle
Damage to AV node causes total heart block
Ventricles beat at intrinsic rates


Premature Ventricular Contraction

Ectopic focus firing and setting off an extra beat before the normal signal
QRS is inverted
Common in college students
Caused by stress, sleep deprivation, caffeine