Test 5 Study Guide Flashcards
a graphic recording of voltage plotted against time during
myocardial depolarization and repolarization.
Electrocardiogram (ECG)
Traced on specialized graph paper, or displayed on a LED monitoring screen
Electrocardiogram (ECG)
Cardiac Tamponade Signs and
Symptoms
Distended neck veins,
tachycardia,
systolic BP of 90 mmHg.
* Chest pain,
dyspnea.
* Muffled distant heart sounds,
loss of carotid artery pulse during
inspiration.
- Time required for the SA node impulse to reach ventricles
PR interval
measured from the beginning of the P-wave to the next deflection, whether it is a Q or Rwave.
PR interval
The average adult PR interval
0.12 to 0.20 seconds
- A PR interval >___ shows an abnormally slow pulse conduction from the atria to the ventricles.
> 0.20
The PR interval is _____ in fast heart rates
Shorter
- All sinus nodal impulses are conducted to the ______
Ventricles
- All sinus nodal impulses are conducted to the ventricles, but the conductions
time is slowed trough the _____ _____ bundle complex
AV Node
This slowed conduction in the AV Node is marked by an increase in the P-R interval >____
seconds.
> 0.20
In a first degree AV block, All QRS complexes are ______
Normal
The spaces between waves and complexes are called ______ and _______
intervals and segments
The P-wave represents _____ ______
atrial depolarization
The QRS-complex represents ______ _______
ventricular depolarization
T-wave represents ______ ______
ventricular repolarization.
The atrial repolarization wave is obliterated by the _____ _____ and is therefore not seen on an ECG
waveform.
QRS Complex
A normal (ST-segment) is normally ___, lying on the (ECG) baseline.
Flat
ST segment may be elevated ____ mm
above the baseline or depressed ___ mm below the baseline and still be considered normal.
2 mm or 0.5 mm
An (ST-segment) depressed more than 0.5 mm indicates myocardial tissue _____
ischemia
An (ST-segment) elevated more than 2 mm
indicates myocardial tissue _____
Injury
The ST segment Extends from the ___-point to the beginning of the ___-wave and represents the early phase of
ventricular repolarization
J-point to the T-wave
At its end, the normal ST-segment curves slightly ____ into the beginning of the T-wave.
Upward
The ST-length varies according to ___ ____
Heart rate
Fast heart rates will result in ____ ST-segments
Shorter
complete absence of electrical and mechanical activity. Cardiac death
Cardiac standstill (asystole)
Cardiac output during asystole
0
During asystole, BP falls to BP falls to ___ - ___ mmHg
5 – 7 mmHg
During asystole, ECG tracing appears a ___ line and indicates severe damage to the hearts electrical conduction system.
Flat
“dying heart” have periods of disorganized electrical activity may be
generated during long periods of asystole.
Agonal rhythm
Initiated by an ectopic focus in the ventricles below the branching portion of the (bundle of
His).
Premature ventricular contraction (PVC)
An abnormally irritable focus in the ventricle discharges before the next normal (SA node) impulse arrives.
Premature ventricular contraction (PVC):
PVCs can occasionally occur in healthy people, but can also be caused by:
Alcohol, caffeine, or tobacco use.
* Emotional stress
receives deoxygenated blood from superior vena cave, inferior vena cave, and
coronary sinus.
Right heart
passively receives blood from the R atrium until the ventricles are almost full.
Right ventricle
The Right atrium contracts to complete filling of the ___ ____
Right ventricle
- RV contraction sends ____ blood through the pulmonary arteries to the lungs.
Deoxygenated
receives oxygenated pulmonary venous blood from the lungs via the pulmonary veins. (2 from each lung)
Left heart
The LV passively receives blood from the ___ ____ until the ventricles are almost full.
Left atrium
The Left atrium contracts to complete filling of the ___ ____.
Left ventricle
LV contraction sends _____ blood through the aorta, left common carotid artery, left
subclavian artery, and the brachiocephalic trunk to the brain and body.
Oxygenated
The contraction, or period of contraction, of the heart, especially
of the ventricles, during which blood is forced into the aorta and pulmonary
artery.
Systole
The phase of the cardiac cycle in which the heart relaxes
between contractions; specifically, the period when the two ventricles are
dilated by the blood flowing into them
Diastole
Pacemaker
* Initiates electrical impulses that produce sequential
atrial and ventricular contraction
Sinoatrial (SA) node:
Prevents impulses from causing ventricles to fire
prematurely.
Atrioventricular (AV) node
Hollow muscular pump about the size of a
human fist.
Heart
The heart lies in _____ behind the sternum.
mediastinum
Apex of the heart points to the ____
Left
Heart Lays on diaphragm at level of ___ intercostal space
at the midclavicular line.
5th
most common congenital
defect malformation of the heart in children
Ventral Septal Defect (VSD)
hole in the wall that separates the
right and left ventricles of the heart.
Ventral Septal Defect (VSD)
Normally left ventricular pressure exceeds right ventricular
pressure, causing a ___ to ___ shunt
Left to right shunt (Small, high resistance VSD.)
occurs in large VSDs, because of right-to-left shunting
Hypoxemia (Venous blood mixes with oxygen rich blood.)
Large symptomatic VSD requires ____ ____
Surgical correction
observed that the greater the preload volume of the heart the greater
the force of contraction.
- Frank and starling
This occurs even in hearts removed from the body, confirming independence from neural
mechanisms.
Sarcomere length-dependent activation
A precontraction sarcomere length of ____ microns has the greatest force of contraction
2.2 microns
An increase in sarcomere length causes ____ cross-bridge cycling.
Increased
Pre-contraction length of the cardiac muscle fiber
Heart’s preload
- Open during diastole;
- Ventricular relaxation
AV valves: tricuspid and mitral valve
- Closed during systole;
- Ventricular contraction
AV valves: tricuspid and mitral valve;
- Open during systole;
- Ventricular contraction.
Pulmonary and aortic semilunar valves:
Closed during diastole;
* Ventricular relaxation.
Pulmonary and aortic semilunar valves:
Heart muscle forming the bulk of
the heart wall.
* Wraps around heart chambers
Myocardium:
Contraction ejects blood with
great force.
Myocardium:
Responds to high BP and stretch of ventricular walls.
* Produced in ventricular walls.
* Promotes sodium loss (diuresis).
B-type Natriuretic Peptide (BNP) mechanism: Hormone
Water loss causes ____ in blood volume, resulting in decreased
BP
Decrease
- In CHF, the ventricles become distended, and their walls are
stretched, this causes a ____ in blood levels of BNP.
Increase
- Increased BNP blood levels are a diagnostic marker for ___ ____
Heart failure
Differentiates pulmonary and cardiac dyspnea.
Increased BNP blood levels
(increased K+) in the extracellular fluid surrounding cardiac fibers decreases the
heart rate and stroke volume.
Hyperkalemia
Severe hyperkalemia causes ___ ____, or the inability of cardiac fibers conduct action potential
through the heart.
Heart block
K+ is primarily responsible for generating ___, and high extracellular K+ diminishes the outward
diffusion gradient of K+.
RMP
The RMP across the cell membrane is less ____ (closer to 0)
Negative
The cell membrane is closer to ____ ____
Threshold Potential
Makes the cell more excitable (easier to depolarize).
RMP
At rest, when the heart muscle fibers are relaxed, and cell membranes impermeable to ions:
Cell interior is ______
* Cell exterior is _____
Cell interior is electronegative (negative pole).
- Cell exterior is electropositive (positive pole).
As the permeability of the cardiac fiber membrane increases, ions rush in and out of the cell
_____ the membrane.
Depolarizing
initiates a series of electrochemical events responsible for heart muscle
contraction.
Membrane Depolarization
Cardiac cell permeability changes _____, alternating from impermeable to completely permeable.
Cyclically
The axes of precordial leads are located on a ______ plane through the chest.
Horizontal
The precordial leads consist of six ____ unipolar electrodes placed on the anterior surface of
the chest
Positive
Name the six precordial leads
V1, V2, V3, V4, V5, and V6
Comprises three bipolar limb leads, three unipolar limb leads,
and six precordial leads.
12 lead ECG
The 12 lead ECG allows the hearts ____ -vector to be viewed from 12 different electrical vantage points.
QRS-vector
As soon as the ventricles ___, the pressure that accumulated in the atria during
ventricular contraction pushes the AV valves open, filling the ventricles with
blood.
Relax
merely priming pumps for the ventricles, completing the
“preloading” process.
Atria
Rapid filling vs. slow filling phase
80% passive filling (0.7 seconds).
* 20% “atrial kick”, or atrial contraction (0.1 seconds).
The electrical charge difference between two sides of a polarized
myocardial cell membrane
“resting membrane potential
(RMP)
Myocardial cell RMP
-85 to -90 millivolts
The outside of the cell has ___ ground potential.
0
the difference between the cell’s inside potential and zero.
RMP
indicates the polarity
of the cells interior.
Negative sign in from the cell RMP (-90mV)
RMP generation inside the cell:
K+ and large protein anions (negatively charged ions).
- Intracellular (K+) (151 mEq/L) and extracellular (K+) (4 mEq/L).
- RMP generation outside the cell:
(Na+) and (Ca++);
* Extracellular (Na+) (144 mEq/L), (Ca++) (5 mEq/L).
* Intracellular (Na+) (7 mEq/L), (Ca++) (less than 1 mEq/L).
occurs when the fiber RMP of -90 mV abruptly changes to 0 MV
- Cardiac muscle fiber depolarization
occurs when the RMP is reestablished at -90 mV.
Repolarization
a real-time recording of the moment-to-moment changes in membrane
potential (voltage) as the cardiac fiber depolarizes and repolarizes.
Action potential
All cells in the cardiac conduction system are potential _____
Pacemakers
The takeover of pacemaker activity by lower order pacemakers
downward displacement of the pacemaker
Atrioventricular (AV) nodal fibers fire at a rate of ___ to ___ times/min
40 to 60
Purkinje fibers fire at a rate of ___ to ___times/min (30 second delay).
15 to 40
Delayed ventricular takeover of the heartbeat and fainting caused by periodic blocks of atrial
impulses
Stokes-Adams syndrome
control the permeability of the myocardial cell membrane to Na+
and K+
Voltage-gated ion channels
Sodium and potassium channels are Formed by large _____ molecules and are specific for each ion.
Protein
Voltage sensitive gating proteins open and close in response to changes in _____ _____
Membrane potential
K+ and Na+
channel activation gates are closed at a RMP of ______
-90mV
Some K+ and Na+ continue to diffuse through leak channels due to high ____ ____
Diffusion gradients
Phase 2: Plateau, lasts how many seconds?
0.2 - 0.3 seconds
During phase 2, Slow calcium channel activation gates open, allowing ____ and ____ to enter
the cell
Ca++ and a small amount of Na+
Ca++ entering the myocardial fiber during the plateau phase participates in the _____ contraction coupling between actin and myosin fibers.
Excitation
At the same time there is an equal outflow of K+ bringing membrane potential to near ___ mV, creating the action potentials plateau (phase 2).
0 mV
a drug that increases Ca++ influx, has an inotropic effect (increased contraction force).
Digitalis
When does the plateau phase end?
when Ca++ inactivation gates close, stopping Ca++
inflow.
Phase 3 and 4 is _____
Repolarization
During repolarization, The membrane is now highly permeable to only ____
ions, and K+ rushes out of
the cell restoring intracellular negativity.
K+
During repolarization, Na+ is pumped ___ and K+ is pumped ___
Na+ out
K+ in
During repolarization, The muscle fiber is ready to accept another ____ stimulus
depolarizing
