Karius: Cardiac Cycle and Normal ECG ibook notes Flashcards
Fast action potentials are found where
atrial and ventricular
Slow action potentials are found
in the SA and AV nodes
Fast action potential phase 0:
rapid upsweep (depolarization)
voltage gated Na channels open and the cell is rapidly depolarizing
same as skeletal muscle
Fast action potential phase 1:
occurs around +20 mV
Initial repolarization
sodium channels inactivate so no more sodium enters; voltage gated potassium channels open
Fast action potential phase 2:
plateau
“slow voltage gated calcium channels opening” AND “special voltage gated K channels closing”
Fast action potential phase 3:
Repolarization, Slow Ca channels closing and special K channels opening
Fast action potential phase 4:
resting potential sustained by high potassium conductance
around -85 mV
SA node and AV node AP: phase 4
resting membrane potential is NOT isotonic, gradually increases (depolarizes) until threshold value achieved and SA first; this is due to the funny Na voltage gated channels. (Na channels open during repolarization)
this is an intrinsic spontaneous event
AV node has same thing but phase 4 is much slower, normally doesnt reach threshhold value before being stimulated by an action potential originating in the SA node
SA node and AV node AP: phase 0
due to opening of slow Ca gates and closing of special K gates
same for AV node
SA node and AV node AP: phase 3
remember: no 1 or 2 phase, goes from 0 to 3
Normal EKG: P wave
atrial contraction
Normal EKG: QRS wave
ventricular contraction
Normal EKG: T wave
ventricular repolarization
PR interval
starts at beginning of P wave and ends at beginning of QRS complex
AV nodal delay time.
represents time it takes to pass from atria to the ventricles via the AV node: this is incorrect I believe
ST wave
begins at end of QRS, ends at beginning of T
QR interval:
begins with beginning of the QRS complex and ends at the end of the T wave, so it includes two waves
QRS and T wave
represents total time any ventricular myocite is depolarized
beginning of P wave and the cardiac cycle
both atria and ventricles are in diastole
all voltage gated channels are closed except for leaky K and Na/K ATPase
SA and AV nodes in P4, with funny Na channels operating (pre-potential)
AV has fewer funny channels so its pre-potential is slower to develop
Tricuspid and Bicuspid are open
Aortic and pulmonic are closed
pressure of left and right atrium during diastole
diastolic mmHG is usually 4 mmHg
pressure in left and right ventricles during diastole
0 mmHg
pressure in ventricle must be less than in atria for blood to flow
Pulmonary artery pressure diastole
15 mmHg
Aorta pressure diastole
80 mmHg
how will diastole pressure be effected if resistance in the arteries is high?
diastolic pressure will be higher
how will diastole pressure be effected if resistance in the arteries is low?
diastolic pressure will be lower
Jugular Vein: why is this sensitive to blood flow changes?
there are no valves between the atria and the veins
changes in atria; pressure will effect venous return
Atrial contraction: wave, pressure direction, direction of blood, and ventricular pressure
P wave
from atria into ventricles
ventricular pressure increases as well
Why doesnt the ventricle contract before the atria?
the AV has a slow ventricular depolarization to allow for blood to fill
What is the normal pressure of the ventricles at their height of contraction?
around 120 mmHg, on the left side
During the ___ wave the left ventricular pressure begins to increase.
P wave
During the QR phase, the left ventricle pressure
decreases for a moment and then increases,
the mitral valves open at _____ wave
the pinnacle of the R wave
Left ventricular pressure goes _______ during RS phase
WAY up, very steep increase: the aortic valve is closed during this period, hence the pressure build up
the ST line corresponds roughly with the ventricular pressure diagram. What is the character of the pressure?
pressure increases in the left ventricle from the pinnacle of the R wave to the very beginning of the T wave. it increases just a bit more and then decreases mostly during the T wave
the aortic valves close near the ____ point on the EKG
right after the T wave (repolarization)
the mitral valve opens during what part of the EKG?
inbetween the T and P waves (during the isoelectrical period)
The first heart sound (S1) occurs immediately
after the AV valves close: blood suddenly hits the closed valve/cardiac structure (now closed) making the first “lub” sound
S1 is the loudest sound
What waves are you going to count to determine the net deflection in the limb leads?
QRS
What waves are you going to count to determine the net deflection in the limb leads?
QRS
What waves are you going to count to determine the net deflection in the limb leads?
QRS
Inferior leads =
II, III, AVF
What waves are you going to count to determine the net deflection in the limb leads?
QRS
Inferior leads =
II, III, AVF
What waves are you going to count to determine the net deflection in the limb leads?
QRS
Inferior leads =
II, III, AVF
What waves are you going to count to determine the net deflection in the limb leads?
QRS
Inferior leads =
II, III, AVF
What waves are you going to count to determine the net deflection in the limb leads?
QRS
Inferior leads =
II, III, AVF
what does the PR interval indicate?
no voltage difference between the atria
what direction does the SA node depolarize the atria?
Right to Left
segment refers to
a single event on an ECG
interval refers to
several events on an ECG
In what phase of an atrial or ventricular action potential do you find the voltage gated potassium channels, and what kind of voltage opens them?
phase 1: they open during depolarization
In what phase of an atrial or ventricular action potential do you find the timed gated potassium channels, and what kind of voltage opens them?
phase 3
stays closed during phase 2 and then helps open during phase 3.
the T wave represents depolarization of ventricular myocytes
the timed gated potassium channels are found during the 2nd phase and they are voltage gated, but they close during depolarization, and stay closed for a finite amount of time
what phase on the ECG is represented by phase 0?
P wave and QRS respectively
PR segment vs PR interval
PR interval represents the beginning of P wave until beginning of QRS: how long does the signal take to geth through the AV node
PR segment represents the end of atrial depolarization until beginning of QRS-
QT interval is largely controlled by what gates?
timed potassium gates
what is responsible for controllign plateau phase?
closing of potassium gates and opening of calcium gates
Inferior leads =
II, III, AVF, R. coronary artery
septal regions =
V2 and V3
anterior region of the heart region =
V2, V3, V4
Lateral heart
I, AVL, V4,V5, V6