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30 terms

Cardiac Contraction

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What is the electrical activity of myocardium?
1. atria begin to depolarize
2. atria depolarize
3.ventricles begin to depolarize at apex; atria repolarize
4. ventricles depolarize
5. ventricles begin to repolarize at apex
6. ventricles repolarize
What happens during repolarization during contraction of myocardium?
the membrane returns to resting potential
-Ca2+ channels close
-K+ channels open
-rapid K+ out returns membrane to resting potential
In an EKG/ECG, these are invaluable for diagnosing:
-MI
-heart enlargement
-abnormalities in conduction pathways
-electrolyte and hormone imbalances
What is an electrocardiogram (ECG/EKG)?
Composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs and chest (detects electrical currents in the heart)
What is the T wave? P wave? P-Q segment? and S-T segment?
-T wave: ventricular repolariztion
-P wave: SA node fires (signal spreads through atria; atrial depolarization)
-P-Q segment: atrial systole
-S-T segment: ventricular systole
On an ECG, this complex is atrial repolarization and diastole (signal obscured) and AV node fires, ventricular depolarization.
QRS complex
Myocytes have stable resting potentials of _____ mV
-90
What happens during plateau?
200 to 250 msec, sustains contraction
What is the name of the technique where one is listening to sounds made by the body?
auscultation
What heart sound (either S1 or S2) makes the noise "lubb" and which makes "dupp"?
S1 makes the "lubb" sound
S2 makes the "dupp" sound
The noise "lubb" occurs when what structure closes?
closure of AV valves
The closure of what valve causes the "dupp" sound?
semilunar valve
What is a heart murmur?
sound of blood flowing backward due to valvular insufficiency
What is the difference between valvular stenosis and mitralvalve prolapse?
-Valvular stenosis: cusps are stiffened
-mitralvalve prolapse: mitral valve cusps bulge into left atrium
What can defective valves be replaced with?
pig valve or artificial valve
An _______ valve can eventually lead to heart failure.
incompetent
What is the quiescent period in the phases of cardiac cycle?
-all chambers relaxed
-AV valves open
-blood flowing into ventricles
Which phase of the cardiac cycle deal with:
-SA node firing, atria depolarizing
-P wave appears on ECG
-atria contract, force additional blood into ventricles
-ventricles now contain end-diastolic volume (EDV) of about 130mL of blood
atrial systole
>End systolic volume (ESV)-----___ mL
>Passively added to ventricle during atrial diastole-----___mL
>Added by atrial systole-----___mL
>Total: end-diastolic volume (EDV)----___mL
>>Stroke volume (SV) ejected by ventricular systole----___mL
>End systolic volume (ESV)---__mL
-60mL
-30mL
-40mL
-130mL
--70mL
-60mL
During this phase of the Cardiac Cycle:
-atria repolarize and relax
-ventricles depolarize
-QRS complex appears in ECG
-ventricles contract
-rising pressures closes AV valves
-heart sound S1 occurs
-no ejection of blood yet (no change in volume)
isovolumetric contraction
What is the phase where:
-rising pressure opens semilunar valve
-rapid ejection of blood
-reduced ejection of bloow (less pressure)
-stroke volume (What is this?)
-SV/EDV=ejection fraction
-end systolic volume (ESV): amount left in heart
Ventricular ejection
-stroke volume is amount ejected (about 70mL)
During the isovolumetric relaxation of ventricles (the last phase of cardiac cycle)
-__ wave appears in ECG
-ventricles repolarize and relax (begin to expand)
-semilunar valves _____
-___ vavles remain closed
-ventricles expand but do not fill
-heart sound ___ occurs
-T wave appears in ECG
-semilunar valves close
-AV valves remain closed
-heart sound S2 occurs
Where is the heart rate taken?
measured from pulse
What are the HR of infants?
120 beats per minute or more
What are the HR of young adult females and young adult males?
-Females: avg 72-80bpm
-Males: avg 64 to 72 bpm
What is tachycardia?
What is it from?
-persistent, resting adult HR> 100
-from stress, anxiety, drugs, heart disease or increased body temperature
What is bradycardia?
What is it from?
-persistant, resting adult HR<60
-common in sleep and endurance trained athletes
Positive chronotropic agents raise ______ and negative _______ agents lower HR
-heart rate (HR)
-chronotropic
An autonomic control center with 2 neuronal pools: a cardioacceleratory center (sympathetic) and a cardioinhibitory center (parasympathetic)
cardiac center of medulla oblongata
What three factors governs the Stroke Volume?
1. preload (increased preload or contractility causes increased SV)
2. contractility
3. afterload (increased afterload causes decreased SV)