Cardiovascular System I - L06 - 10/05

Function of:
1. Coronary circulation
2. Pericardium
3. Valves
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Terms in this set (22)
Function of:
1. Coronary circulation
2. Pericardium
3. Valves
1. Autoregulation to maintain coronary blood flow. Affected by blockage/ atherosclerosis

2. Anchords heart, prevents infection, and reduces friction

3. Prevents backflow
a. Atrioventricular Valves: Papillary muscles attached to valves via chordae tendineae
- Mitral (bicuspid) > left ventricle
- Tricuspid > right ventricle

b. Semilunar Valves (Cusps): Aortic and Pulmonary valves
Describe the flow of blood through the CV system
Image: Describe the flow of blood through the CV system
Cardiac Muscle Cell Characteristics
Involuntary
Striated
Single Nucleus
Branched
Intercalated Discs
Much smaller than skeletal
Numerous mitochondria
Cardiac Muscle Cell vs Skeletal Muscle SR. Purpose?
In skeletal muscle forms a triad
Cardiac forms a dyad (junction at t-tubule and terminal cisternae of SR)

Cardiac muscle adapted to the slower and more sustained single contraction
What holds the intercalated discs together? Allows ion flow?
Mechanical Junctions:
- Fascia Adherens - anchors actin to membrane
- Desmosomes - bind intermediate filaments of adjoining cells

Gap junction: propagate APs to neighboring cells
What are two ways that an AP is propagated in the muscle cell?
At the dyad and the gap junctions
Describe the phases of pacemaker APs and when each channel activates
- Phase 4, I (Potential): Funny Na+ channel opens (K+ channel closes)
- Phase 4, II (Potential): Transient (T-Type) Ca2+ channel opens
- Phase 0 (depolarization): L-Type Ca2+ channel (LTCC) opens
- Phase 3 (repolarization): K+ channel opens
Image: Describe the phases of pacemaker APs and when each channel activates
Describe the phases of ventricular myocytes and when each channel activates
- Phase 4 (Resting): Na+/ K+ pump, K+ channels
- Phase 0 (Depolarization): Na+ influx (fast)
- Phase 1 (Early repolarization): K+ efflux (transient)
- Phase 2 (Plateau): Ca2+ influx (LTCC) + K+ efflux
- Phase 3 (Rapid Repolarization): K+ efflux
Image: Describe the phases of ventricular myocytes and when each channel activates
Describe Na+ channel gating and its importance in regulating refractory periods in cardiac muscle

How does this prevent tetanus?
Inactivation gate prevents Na channels from refiring. Plateau caused by simultaneous Ca influx and K efflux prolongs refractory period in myocytes. Once rapid repolarization occurs the inactivation gate opens back up readying up the sodium channel for another AP

Action potential is longer than the contraction, therefore tetanus is not permitted
Cardiac conduction system pathway
SA > internodal > Bachmann's + AV > His > to L/ R branches > purkinje > ventricles
Image: Cardiac conduction system pathway
Why do we have differential conduction velocities?AV node has the slowest conduction velocity to allow for the complete contraction of the atria prior to ventricular contractionDescribe the intrinsic firing rates of each cell type.SA Node: 60-100 AV NODE: 40-60 Purkinje: 20-40 Bundle of His: 1-20What does the EKG Tell us? How does it work?- Electrical activity of the heart - Heart Rate - Conduction abnormalities - Presence of Myocardial ischemia, infarct, and cell death - Compares difference in voltage at two different electrodes on body surfaceDescribe EKG anatomy- P: Atrial Depolarization - QRS: Ventricular Depolarization - T: Ventricular Repolarization - PR Segment: Time delay b/w atrial and ventricular activation (AV Node) - PR Interval: Onset of atrial activation to onset of ventricular activation - ST segment/ interval: Time b/w ventricular depolarization and repolarization - QT Interval: Length of ventricular depolarization and repolarization - R-R Interval: Length of one cardiac cycle (heartbeat)Relate Ventricular AP phases to EKG- Phase 4 (Resting): Na+/ K+ pump, K+ channels - Phase 0 - QRS Complex (Depolarization): Na+ influx (fast) - Phase 1 (Early repolarization): K+ efflux (transient) - Phase 2 - ST (Plateau): Ca2+ influx (LTCC) + K+ efflux - Phase 3 - T Wave (Rapid Repolarization): K+ effluxWhat are systole and diastole?Diastole: Ventricular relaxation & filling w/ blood - Pressure greater in atria, opening AV valve Systole: Ventricular contraction & pumping blood out of heart - Pressure greater in ventricles > SL valves open > blood to aorta and pulmonary arteryWhat are the four phases of the cardiac cycle? Relate phases to wigger diagramFour Phases of the Cardiac Cycle Inflow Phase: a. Rapid Ventricular filling b. Reduced ventricular filling c. Atrial Contraction Isovolumetric Contraction Outflow Phase: a. Rapid Ejection b. Reduced Ejection Isovolumetric RelaxationWhat are the typical pressures in the heart?Just know Atria, Ventricles, Pulmonary Artery, and AortaHeart sounds- S1 (1st): Closing of the AV valves causes turbulent flow (lub) - S2 (2nd): Closing of the aortic, pulmonary valves (dub)What is stroke volume? How is it calculated?Amount of blood pumped by the LV in one systolic contraction SV = EDV - ESVWhat is cardiac output? Equation? Normal?Volume ejected per minute CO = SV * HR Normal CO: 5L/ minWhat is Ejection fraction (EF)? Equation?Fraction of EDV that is ejected during systole