Cardiac A&P Flashcards
What is the function of the valves of the heart?
To control the flow of blood between chambers and into the great vessels
When do the mitral and tricuspid valves close?
During Ventricular systole
What are the two branches of the Left Main Coronary artery?
The Left Anterior descending and the circumflex arteries
What are the three branches of the Left anterior Descending artery
Ramus, Diagonals, Septals
The circumflex artery ecentually becomes the ___
Obtuse Marginals
What is Automaticity?
The ability of the cardiac cells to initiate an electrical stimulus
What is Excitability
The ability of the myocardial cells to respond to a stimulus
What is conductivity
The ability to transmit the impulse from one cell to another
what is contractility?
The ability of myocardial cells to shorten (contract) in response to an electrical stimulus
What is refractoriness?
The inability of cells to respond to an electrical impulse if they have not recovered from the previous episode.
What are the two refractory periods?
The absolute and the relative
WHat is the absolute refractory period?
The period of time when the heart will not respond to stimuli of any magnitude
What is the relative refractory period?
The heart can still respond to a strong stimuli
What is stroke Volume?
The amount of blood ejected with each contraction of the LV
WHat is heart rate?
The number of times the ventricles contract in one minute
What is cardiac output?
The volume of blood pumped in one minute
What is the normal range for Cardiac output?
4-7 Liters per minute
How is Cardiac Output calculated?
Stroke volume X Heart rate
CO= SV X HR
WHat is the Cardiac index?
An asjustment made to the CO based on the body size in terms of BSA
What is the normal range for Cardiac INdex?
2.7-3.2 L/min/M sq
Why is Cardiac Index important?
Because it takes body size into account when calculating Cardiac Output Needs. An obese Person will need more CO to supply their tissues so a normal CO value may still be inadequate for them
How is Cardiac Index calculated?
CI= CO/BSA
What is preload?
The amount of myocardial stretch at the end of the diastole.
What determines the Pre-load?
The Left Ventricular End Diastolic Volume (LVEDV)
Preload is tied to what law
Starlings Law
How are LVEDV and SV/CO interrelated
When LVEDV increases, the strength of the contractions in the LV are increased causing an increase in SV and CO
What is the afterload?
The pressure that the LV must overcome to eject blood into the aorta.
What are the cardiac risk factors that can not be modified?
4
GAEF
- Gender
- Age
- Ethnic Background
- Family History of CV disease
What are the Cardiac risk factors that CAN be modified?
5
CPOTA
- Cigarette Smoking
- Physical Activity
- Obesity
- Type A
- Stress
What is the resting membrane potential of cardiac cells?
-90 millivolts
At what MV does an action potential occur in cardiac cells?
-60 MV
What is the threshold potential?
The point at which an action potential is triggered
Cardiac action potential has _ phases
5
What are the 5 phases of cardiac potential?
0-Depolarization 1-Early repolarization 2-Plateau 3-Rapid Repolarization 4-Resting Membrane potential
What occurs during the depolarization phase of cardiac potential?
- Shown as a vertical line moving away from the resting membrane potential
- Occurs when the membrane is stimulated
- When stimulated, sodium channels open up.
- Sodium is positively charged and thus causes a sharp positive spike in membrane potential from -90 to +20MV
What occurs during phase 1 (early Repolarization) of cardiac potential?
- Membrane potential charge goes from +20 to around 0
- Occurs when sodium channels are closing and some chloride (neg) enters the cell
What occurs during phase 2 (plateau) phase of cardiac potential?
- Charge stays around 0 mv
- Calcium channels open and calcium enters the cell
What occurs during phase 3 (rapid repolarization) of cardiac potential
- When action potential returns to resting membrane potential
- Occurs because potassium rushes out of the cell
What occurs during phase 4 (Resting potential) of cardiac potential?
- Cell is at resting membrane potential
- Absolute refractory due to cell charge being opposite
- Sodium potassium pump returns to restore proper balance to cell
What is the SA node?
The sino-atrial node
- The normal (primary) pacemaker of the heart
- Depolarized at 60-100 time per minute
- Located near where the Superior vena cava enters the right atrium
What is the function of the internodal pathway?
Delivers the impulse to the RA from the SA node
What is the finction of bachmann’s bundle?
Delivers impulse to the LA from the SA node
What is the AV node?
- Located at the junction between the Ventricles and the atria
- Slows the Impulse as it moves through the conduction system
- If the SA node fails, the AV node will take over at 40-60 BPM
What is the function of the bundle of his
- Slows the impulse in conjunction with the AV node
- Delivers impulse to the ventricles
What are the bundle Branches?
- Two main branches. Left bundle branch (LBB) and Right bundle branch (RBB)
- IMpulse moves through them to the purkinje fibers
What are the purkinje fibers?
- Deliver the impulse rapidly to the ventricular myocardium
- Impulse is delivered almost instantly throughout all cells to ensure a coordinated, effective contraction
- Can take over in both SA and AV nodes fail. Will impulse at 20-40 times per second
On EKG paper, the amount of time between two vertical lines is?
0.04 seconds
On EKG paper, the amount of time between two darker vertical lines is?
.2 seconds
What does the vertical axis on EKG paper measure?
Voltage
On EKG paper, What is the voltage between two horizontal lines?
.1 mv
On EKG paper, what is the voltage between two darker horizontal lines?
0.5 mv
What does the P way signify?
-Signifies Atrial Depolarization
What is the mechanical action associated with the P wave?
Atrial contraction
What is the general, normal appearance of the P wave?
Small, round positive deflections from the baseline
What does the PR interval (PRI) signify?
The period of time between the beginning of the P wave and the beginning of the QRS complex.
-Start of Atrial depolarization to the start of Ventricular depolarization
What is the normal range of the PRI?
0.14 to 0.2 seconds
What does the QRS complex represent?
Ventricular depolarization.
What is the mechanical action associated with the QRS complex?
Ventricular Contraction
What is the normal duration range for the QRS complex?
0.04 seconds to 0.1 second
What does the T wave represent?
Ventricular Re-polarization
-Generally upright
What are the five questions when assessing EKG strips?
- Are there P waves
- Is there a P wave in front of each QRS complex?
- What is the duration of the PRI
- What is the duration of the QRS complex
- What is the Ventricular Rate/Rhythm?
When asking “are there P waves?” What additional things need to be considered?
a. is the morphology consistant?
b. What is the rate/rhythm?
When asking “Is there a P wave in front of each QRS complex?” What is an additional/alternative question to ask?
Or, is every P wave followed by a QRS complex?