Exam 7 CV Phsiology & Electrocardiogram
Exam 7 CV Phsiology & Electrocardiogram
Terms in this set (11)
How do you determine heart rate from an ECG strip?
1. Count the number of QRS complexes between ticks 2. Multiply that number by 20 = heart rate **If there are NO TICKS count the # QRS complexes between 15 large boxes = time between ticks... Multiply that number by 20 = Heart Rate
What are the cardiac depolarization/repolarization events (locations) that cause each ECG tracing deflection?
1. P Wave - Atrial Depolarization 2. P->R interval: Time between onset of ATRIAL REPOLARIZATION and onset of VENTRICULAR DEPOLARIZATION 3. QRS Complex: Ventricular depolarization 4. Q->T interval: Time between onset of ventricular depolarization and end of ventricular repolarization 5. S->T segment: completion of myocardial depolarization 6. T wave: Ventricular repolarization
Which cardiac conduction component has the fastest speed and which has the slowest speed?
1. Fastest = Purkinje Fibers 2m/sec
2. Slowest = AV node = .05-.1 m/sec
Which ions are going into and out of the myocardial cell during each phase of depolarization and repolarization?
1. Resting Phase
2. Phase 0: Rapid depolarization a)Influx of Na
3. Phase 1: Rapid initial repolarization a) K+ outward
4. Phase 2: Plateau/Prolonged depolarization a) Ca+ channels
5. Phase 3: Repolarization a) Ca channels gradually close b) K+ channels open (flow out)
6. Phase 4: Return to resting a)K+ flows inward (inward rectifying K channels)
What are the effects of epinephrine on the heart and how is this achieved (how the medication affects heart rate)?
a-adrenergic receptor agonist in vascular smooth muscle
B1 agonist in pace maker Effects on heart 1. Positive Chronotropic Effect:↑ HR by accelerating pacemaker potential 2. Positive Intropic Effect: ↑ Force of contraction as HR increases
What is the anatomic (histologic) arrangement of the myocardial cells and the structures which join them?
1. CM cells are not as large as skeletal muscle cells
a) Many are branched, attached to several neighboring cells
b) -Specialized intercellular connections: mechanically and chemically connected (gap junctions)
2. Heart as a pump a) No skeletal attachments
3. Form highly branched functional syncytium a)Branching, connected cells form an anatomical and functional synctium b) Cells in syncytium are joined at intercalated disk i)Areas of contact contain gap junctions = Low electrical resistance pathway -> efficient impulse conduction ii)Area of contact contain desmosomes: Promote firm mechanical connection -> efficient force transmission
What are the depolarization characteristics of a cardiac muscle cell compared to cell of the SA node?
Pacing cells have a faster rate of depolarization-repolarization-depolarization than ventricular cells
Define inotropic effect Positive inotropic effect has _______. Negative inotropic effect has ________.
1. Positive Inotropic Effect: increased contractility 2. Negative Inotropic Effect: decreased contractility
Define refractory period. What is the ionic movements during this phase of cardiac activity?
1. Absolute Refractory Period (ARP): a)Time from opening of Na channels in depolarization until closing of Ca channels at end of plateau b) During this time, no new AP can be generated
2. Relative Refractory Period (RRP): a) Time from end of closing of Ca and K channels until return to normal resting membrane potential. b)A new AP could be generated during this period if a strong enough stimulus is presented.
What is the conduction pathway from the SA node to the ventricular muscle cells?
SA node --> propagation in atrial muscle cells --> AV node --> Bundle of His --> Bundle Branches --> Purkinji fibers --> Ventricular muscle cells
Skeletal muscles are attached to ________/_______. Cardiac muscles are attached to __________.
2. Other cardiac muscle cells
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