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