CV3 Flashcards
what conducts action potentials into the left atrium
Bachmanns bundle
what is the speed of atrial conduction
it is relatively slow (80ms-100ms)
where is the important delay during conduction in the heart
conduction slows down during the AV node to allow blood from atria to empty into the ventricles
what does slow conduction through the AV node allow
allows for completion of ventricle filling
how does ventricular contraction occur (direction)
from the bottom to the top
what is the speed of ventricle contraction
more rapid than atria contraction (60ms-100ms)
what is the hearts muscle arrangement to ensure blood is squeezed upwards
spiral arrangement
what is a complete conduction block
its caused by damage in conduction pathway
what does the electrocardiogram represent
the summed electrical activity of all cells recorded from the surface of the body
what does electrocardiogram record
electrical changes in the extracellular fluid
is the extracellular fluid a good conductor of electrical energy
yes
what is einthovens triangle
three leads (pair of electrodes). 3 separate recordings that give their own readings
what happens if the electrical activity of the heart is moving towards the positive electrode
an upward reflection would be recorded
if electrical energy is moving away from the positive electrode
a downward deflection is recorded
if the electrical energy is moving perpendicularly to the axis of the electrodes, what is the deflection
there is no deflection
what do leads measure (3)
current
how much its moving
and what direction its moving in
what are ECG’s
combination of waves and segments
what is the P wave
atrial depolarization
what is the P-R segment
conduction through AV node and AV bundle
what is the QRS complex
ventricular depolarization
what is the T wave
ventricular repolarization (Ca channels close)
what happens at the ST segment
ventricle contract and pump blood
what does the Q wave represent
the depolarization of the intraventicular septum
what does the R section represent
the depolarization of most of the ventricular walls
whats considered the plateau phase in cardiac cycle
S-T segment
(ventricular contraction)
what does the S phase represent
last phase of ventricular depolarization at the base of the heart
what is the heart rate on an ECG
P wave - P wave
which wave is often very small and not seen
Q
what is arrhythmia
abnormal rhythm
what are premature ventricular contractions? what is it perceived as?
purkinje fibres randomly kicking in as a pacemaker
perceived as a skipped beat or palpitation
what are the 2 arrhythmia examples he lists
premature ventricular contractions
Long QT syndrome
what is long QT syndrome
delayed repolarization of the ventricles due to a mutation
what is the cardia cycle
one complete contraction and relaxation
what are the 2 primary phases of cardiac cycle
systole
diastole
what is systole
the time when the cardiac muscle contracts
what is diastole
the time in which cardiac muscle relaxes
why are diastole and systole discussed separately ?
the atria and ventral do not contract and relax at the same time
whats the order of the cardiac cycle
late diastole
atrial systole
EDV
isovolumetric ventricular contraction
ventricular ejection
ESV
isovolumetric ventricular relaxation
what happens in late diastole
ventricles are filling passively
what happens in atrial systole
atrial contraction (just a little more blood goes into the ventricle)
what is EDV
the maximum amount of blood in the ventricles after ventricular diastole
what happens during isovolumetric ventricular contraction
ventrial starts contracting but no change in volume yet
AV valve close
first heart sound
what happens during ventricular ejection
blood flows into major artery
what is ESV
the amount of blood left in the ventricle after ventricular systole
what happens during isovolumetric ventricular relaxation
ventricles are relaxing
semilunar valve close
second heart sound
what causes the heart sounds
first is vibrations of the ventricular walls
second is the vibrations of the large arteries
what does the a-a’ segment represent
late diastole
what does the a’-b segment represent
atrial systole
what does the b-c segment represent
isovolumetric contraction
what does the c-d segment represent
ventricular ejection
what does the d-a segment represent
isovolumetric relaxation
whats on the x axis of the pressure loop for cardiac cycle
left ventricular volume
whats on the y axis of the pressure loop for cardiac cycle
left ventricular pressure
