Term
| Mid to Late TP Interval: Ventricular Diastole |
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Definition
Atria & ventricles are relaxed
blood flows from veins into atria
Atrial pressure is higher than ventricular pressure, so AV valves open and blood flows passively from atria to ventricles |
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Term
| P wave & PQ interval : Late Ventricular Diastole |
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Definition
SA node reaches threshold & fires
Atrial depolarization occurs ---> Atria contract (atrial systole)
Atrial Pressure still greater than Ventricular pressure, AV valves are open
This time, blood SQUEEZED at atrial contraction into ventricles |
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Term
| QR Interval : END ventricular diastole |
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Definition
AV valves still open because Atrial pressure higher than ventricular pressure
ELECTRICAL IMPULSE enters VENTRICLES from AV NODE
Ventricles begin to depolarize
R peak = end of ventricular relaxation
start of ventricular contraction |
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Term
| What intervals is Atrial Pressure Greater Than Ventricular Pressure? |
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Definition
Mid TP Interval
PQ Interval
QR Interval
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Term
| RS Interval : Early Ventricular Systole |
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Definition
Ventricles begin to contract
Atrial Pressure LESS THAN Ventricular Pressure
so AV valves close (prevent backflow)
Atrial contraction complete
Ventricular filling complete
BUT ventricular pressure not high enough to open Aortic/Pulmonary Valve yet
Atria repolarize at this time |
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Term
| End Diastolic Volume (EDV) is what? |
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Definition
| the volume of blood in ventricles |
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Term
| ST segment : Mid Ventricular Systole |
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Definition
At THIS time
VENTRICULAR PRESSURE GREATER THAN AORTIC PRESSURE
so Aortic Valve/ Pulmonary Valve Opens
Blood ejected into aorta/pulmonary valve from ventricles
Atria are relaxed (diastole) and filling with blood |
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Term
| Start of T Wave : Late Ventricular Systole |
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Definition
Repolarization of Ventricles Begins
(start of ventricular relaxation/diastole) |
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Term
| T wave PEAK and Early TP Interval: Early Ventricular Diastole |
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Definition
Peak of T wave = end of systole, start of diastole
Ventricles Begin to RELAX
ventricular pressure is LESS THAN aortic/pulmonary pressure, so aortic/pulmonary valve closes
No more blood can leave ventricles
Atria in diastole filling with blood |
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Term
| What is End-Systolic Volume (ESV)? |
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Definition
The remaining volume of blood in ventricles
about 65ml/ventricle |
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Term
| What is stroke volume (SV)? |
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Definition
| Stroke Volume = End Diastolic Volume (EDV) - End Systolic Volume (ESV) |
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Term
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Definition
Lub - AV valves closing
Dub - Aortic/Pulmonary Valves closing |
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Term
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Definition
Amount of blood pumped by each ventricle per minute
Heart Rate (HR) X Stroke Volume (SV) = Cardiac Output
ex. HR 70bpm
SV 70ml/beat
CO = 70 bpm/ 70 ml/beat = 4900ml/min |
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Term
How does
Parasympathetic NS modify
baseline heart rate? |
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Definition
Vagus Nerve: primary parasympathetic nerve to heart
can decrease rate of depolarization of SA NODE
increase AV Nodal Delay |
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Term
How can
Sympathetic (Fight or Flight) NS
modify baseline rate? |
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Definition
Sympathetic Cardiac nerves supply ATRIA, SA & AV NODES, & VENTRICLES
increase depolarization of SA node
decrease AV nodal delay
increase speed of AP thru Bundles of His & Purkinje Fibers |
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Term
| How does Parasympathetic NS affect STROKE VOLUME? |
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Definition
| shorten action potentials in atrial contractile cells, results in WEAKER contractions |
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Term
| How does Sympathetic NS affect STROKE VOLUME? |
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Definition
| increases contractile strength of atrial and ventricular cells by increasing Ca++ permeability |
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Term
| How does length of heart muscle fibers affect STRKE VOLUME? |
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Definition
longer the fiber is at start of contraction (stretched), more volume blood in chamber,
the stronger the contraction |
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