Cardiovascular System: Electrocardiography Lab Flashcards
What causes heart contractions?
results form a series of electrical potential changes (depolarization waves) that travel through the heart at the beginning of each beat .
Cardiac muscle cells are electrically connected via __________? ;therefore the entire myocardium behaves like a ________?
gap junctions, syncytium (coordinated unit)
T/F: cardiac muscle contacts/ beats intrinsically and does not depend on impulses from the nervous system to initiate contraction (cardiac heart will continue to contract rhythmically even if all nerve connections are severed)
TRUE
the autonomic nervous system can accelerate heart rate via?
sympathetic nervous system
the autonomic nervous system can decelerate heart rate via?
parasympathetic nervous system
another name for the intrinsic conduction system
nodal system
what kind of tissue does the intrinsic conduction system consist of and what does it ensure?
- specialized non contractile myocardial tissue.
- it ensures that heart muscle depolarizes in a special manner (from arteries to ventricles)
What are the components of the intrinsic conduction system?
- Sinoatrial (SA) node
- Atrioventricular (AV) node)
- AV bundle (bundle of His)
- Purkinje fibers
where is the Sinoatrial (SA) node located?
right atrium just inferior to the entrance to the superior vena cava
where is the Atrioventricular (AV) node located?
the lower atrial septum at the junction of the atria and ventricles
where are the AV bundles located?
located in the inter ventricular septum
what are purkinje fibers?
long strands of barrel shaped cells called purkinje myocytes
where are purkinje fibers located?
ramify within the muscle bundles of the ventricular walls
why are purkinje fibers more dense and elaborate in the left ventricle?
because the left ventricle is larger in size
what does the SA node do?
sets the rate of depolarization for the heart as a whole
what is the SA node referred to as?
pacemaker
From the SA node, where does the impulse spread to?
Spreads throughout the atria and to the AV node. The electrical signal is immediately followed by atrial contraction.
from the AV node, where does the impulse spread to?
the impulse is monetarily delayed (0.1 sec) allowing the atria to complete the contraction. the wave then passed through the AV bundle and the purkinje fibers and results in ventricular contraction.
what are the atria and ventricles are separated from one
another by? what does this do?
- electrically inert connective tissue.
- So the depolarization wave can be transmitted to the ventricles only via the tract between the AV node and AV bundle.
Impulses through the heart can be detected on the
body’s surface and recorded with an instrument called?
electrocardiograph
The recording of the electrical changes (depolarization followed by repolarization) occurring during the cardiac cycle is called an?
electrocardiogram (ECG or EKG)
what does an ECG record?
records the electrical events occurring in the bulk of the heart muscle (not the activity of nodal tissue).
what are the intervals in a ECG?
Time measurement that includes a wave and/or a complex
what are the segments in a ECG?
Time measurement that does not include a wave and/or a complex
The baseline of an ECG tracing is called?
isoelectric line
what does an isoelectric line suggest?
no electrical activity detected
An ECG is recorded as a pattern of a baseline and is broken by a?
P wave, a QRS complex, and a T wave
ECG summary of the SA node
- SA node initiates depolarization in the right and left atria causing contraction (corresponds to the P wave).
- SA node also sends the depolarization wave to the AV node (with a 0.1 sec delay to let the atria finish contracting), which in turn, causing contraction in both ventricles (corresponds to the QRS wave). At the same time, the atria repolarize and relax (hidden by the QRS complex).
Ventricles repolarize and relax
corresponding to the T wave
