Heart Quiz 2 Flashcards
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
- Anterior Interventricular Artery: supplies interventricular septum and anterior walls of ventricles
- 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
- Marginal Artery: supplies lateral right atrium and ventricle
- 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
- Interdigitating Folds: cells interlock with each other and increase surface area
- Mechanical Junctions: fascia adherens and desmosomes
- Electrical Junctions: gap junctions that allow ions to flow from cytoplasm to cardiocytes
Fascia Adherens
Most abundant
Desmosomes
Prevent cardiocytes from pulling apart
Similarities Between Myocardial Cells and Skeletal Muscle Fibers
Striated
Z-Discs
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
- Slow leak Na2+ enters the cell
- Voltage gated Ca2+ channels open (at -40mV)
- K+ channels open (at 0mV)
- Repeat once polarization is complete
Action Potential of Ventricular Cardiocyte
- Voltage-gated Na+ channels open
- Na+ depolarizes the membrane and opens more Na+ channels, creating a positive feedback cycle and rising membrane voltage
- Na+ channels close when cell depolarizes, voltage peaks at +30mV
- Ca2+ slowly enters and prolongs depolarization, causing a plateau
- 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
- SA node fires
- Excitation spreads through atrial myocardium
- AV node fires
- Excitation spreads down AV bundle
- Purkinje fibers distribute excitation through ventricular myocardium
Electrical Activity of Myocardium
- Atria begin to depolarize (P wave)
- Depolarization is complete
- Ventricular depolarization begins at apex and moves superiorly while atrial repolarization occurs (QR waves)
- Ventricular depolarization is complete (S wave)
- Ventricular repolarization occurs at apex (T wave)
- 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
