Heart Exam 2
impulse delayed at
AV node
dysrhythmia
Abnormal heart rhythm
Systole
Contraction of the heart
internodal pathways
Interconnect the SA Node with the AV Node, conducts impulses throught to the atrial working cells.
Depolarization
K+ rushes out of cell through slow potassium channels
Caleb's heart allows oxygenated and deoxygenated blood to mix. Based on your knowledge of the heart and the great vessels, describe other anatomical abnormalities that cause the mixing of oxygenated and deoxygenated blood. Would more or less blood circulate to the lungs?
Less blood would be circulated to the lungs because Caleb is breathing harder to try to get more O2 in his body. Less pressure to pump blood due to the hole.
3 main waves of ECG
P, QRS complex, T
Waves and complexes
P, QRS, T
Segments
PR, ST
Intervals
PR, ST, QT
In a normal ECG wave tracing, atrial depolarization is hidden by
QRS complex
diastole
Relaxation of the heart
1st step of the intrinsic conduction system
SA node activity and atrial activation begin (60-100 action potentials per minute at rest), time= 0
impulse pathway
SA node, internal pathway, AV node, AV bundle (bundle of His), right and left bundle branches, Purkinje fibers
One of the problems that worried Tiffany was that Caleb seemed to be breathing too hard all the time. Let's consider how this symptom is related to his heart defect. Describe what would happen to the blood volume and pressure entering the pulmonary circuit as a result of his VSD.
The total amount of blood would be more. The heart is working harder to pump because the hole causes less pressure.
right and left bundle branches
Two pathways in interventricular septum Carry impulses toward apex of heart
In Caleb's heart, what color would the blood be within the right and left ventricles?
a mix of red and blue due to the whole in between both ventricles
atrioventricular (AV) node
a node of specialized heart muscle located in the septal wall of the right atrium; receives impulses from the sinoatrial node and transmits them to the atrioventricular bundle
PR (segments)
atrial contraction
P wave
atrial depolarization
SA node generates impulse:
atrial excitation begins
1st step of heart mechanical movement
atrial systole begins: atrial contraction forces a small amount of additional blood into relaxed ventricles
2nd step of heart mechanical movement
atrial systole ends, atrial diastole begins
the p wave represents _____ depolarization, which leads to atrial _____
atrial, contraction
the intrinsic conduction system consists of
autorhythmic cardiac cells
Where do you think would be the best place to auscultate Caleb's abnormal heart sound?
between the left and right ventricles
P-Q interval much longer than normal indicates
blockage in the normal conduction pathway
Heart Block
blocked AV node, slows or prevents ventricular depolarization
Right ventricles have what color blood
blue (deoxygenated)
Based on the location of Caleb's defect, what part of the conductive system might be at risk for abnormalities?
bundle branches/bundle of his
"DUB"
closing of semilunar valves at end of systole/beginning of diastole
"LUB"
closing of the AV valves at the beginning of systole
ECG shows and measures
conductive system and electrical activity (not muscle contraction), used to detect if the electrical conduction pathway within the heart is normal and if any damage has been done to the heart
atrioventricular (AV) bundle
conducts the impulse to the ventricles
unlike skeletal muscle, cardiac muscle
contracts on its own
relies on _____ conduction to move blood
electrical
pacemaker cells are not part of the nervous system, it is its own
electrical system
Plateau
extracellular Ca2+ enters cytosol through slow calcium channels
Purkinje fibers
fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract
conducting cells
found in the internal pathways
pacemaker cells
found in the sinoatrial (SA) node and atrioventricular (AV) nodes
the intrinsic conduction system coordinates heart activity by determining the direction and speed of ______. This leads to a coordinated heart contraction.
heart depolarization
blood flows from
higher to lower pressure
autorhythmic cardiac cells
initiate and distribute electrical impulses throughout the heart
repolarization
initiated relaxation of muscle (diastole)
depolarization
initiates contraction of muscle (systole)
Rapid depolarization
massive influx of Na+ through fast sodium channels
Q-T segment much longer than normal may indicate
myocardial damage
specialized cardiac cells:
pacemaker cells (autorhythmic) and conducting cells
sinoatrial (SA) node
pacemaker of the heart
ventricular excitation completion involves
purkinje fibers
Tachycardia
rapid heart rhythm (>100bpm), normal when exercising, abnormal at rest
Left ventricles have what color blood
red (oxygenated)
PR (interval)
signal from SA to AV
Bradycardia
slow heart rhythm (<60bpm), can be caused from damaged SA node
What would it mean if one of the peaks was off, missing or looked abnormal?
something is wrong in the atrial, electrical impulses (the ventricles) after AV nodes
2nd step of the intrinsic conduction system
stimulates spreads across the atrial surfaces and reaches the AV nodes (P waves: atrial depolarization), elapsed time= 50msec
pacemaker cells are the reason why
the heart still beats on its own when removed from body
5th step of the intrinsic conduction system
the impulse is distributed by purkinje fibers and relayed throughout the ventricular myocardium. Atrial contraction is completed, and ventricular contraction begins. Purkinje fibers. (QRS complex: completion of ventricular depolarization), elapsed time= 225msec
4th step of the intrinsic conduction system
the impulse travels along the interventricular septum within the AV bundle and the bundle branches to the purkinje fibers and; by the moderator band, to the papillary muscles of the right ventricle. Moderator band. (G waves: beginning of ventricular depolarization), elapsed time= 175msec
Bachmann's bundle
the structure that relays the electrical impulse from the SA node to the left atrium in a normal heart
3rd step of the intrinsic conduction system
there is a 100-msec delay at the AV node. Atrial contraction begins. AV bundle and bundle branches. (P-R Intervals: conduction through AV node and AV bundle), elapsed time= 150msec
two types of ECG variations that might signal abnormalities
variation of wave height (elevated or depressed) and/or normal time intervals
ST (segments)
ventricular contraction
ST (interval)
ventricular contraction and recovery
T wave
ventricular depolarization
QRS complex
ventricular depolarization and atrial repolarization
QT interval
ventricular depolarization and repolarization
5th step of heart mechanical movement
ventricular diastole-early: as ventricles relax, pressure in ventricles drops; blood flows back against cusps of semilunar valves and forces them closed. Blood flows into the relaxed atria
6th step of heart mechanical movement
ventricular diastole-late: all chambers are relaxed. ventricles fill passively
impulse passes to heart apex:
ventricular excitation begins (bundle branches)
3rd step of heart mechanical movement
ventricular systole-1st phase: ventricular contraction exerts enough pressure on the blood to close AV valves but not enough to open semilunar valves
4th step of heart mechanical movement
ventricular systole-2nd phase: as ventricular pressure rises and exerts pressure in the arteries, the semilunar valves open and blood is ejected