Cvs Flashcards
Cardiac muscle types
Atrial ventricular and excitatory muscles
Cardian synctium, types and contraction
Group of cardiac muscle cells that are separated by intercalated disc
Types are atrial and ventricular synctium
Division of synctium is so that atria contract little time ahead of ventricles
Movement of electric potential and delay in contraction of atria and ventricles
Electric potential starts at SA node(superior lateral wall next to superior vena cava) then contracts atria —> av node —> ventricles
Delay of 0.1seconds occurs between atria and ventricles
What is mEq
The milliequivalent (mEq) is the unit of measure often used for electrolytes. It indicates the chemical activity, or combining power, of an element relative to the activity of 1 mg of hydrogen. Thus, 1 mEq is represented by 1 mg of hydrogen (1 mole) or 23 mg of Na+, 39 mg of K+, etc.
Difference in opening and closing of Fast sodium and sodium calcium channels
Fast-Na channels open n close in one thousandth of second while Na-Ca channels are slow to open and remain open for several tenths of a second
What causes action potenial of cardiac miscles and plateu
2 reasons
First is that 2 types of channels cause action potential in cardiac muscles fast Na channels and Na-Ca channels and na-ca channels are slower
Second is because action potential in cardiac muscles decrease the permeability for k channels about 5 folds
When and how repolarization occur in cardiac cells
The cause of low permeability of k channels is high influx of ca by na-ca channels. After 0.2-0.3sec na-ca channels influx ceases and k ions moves out and repolarization occur.
Cardiac work
Oxygen consumption depends on what and which part of cardiac work requires more oxygen
CW = CO * aortic pressure
CO shows volumic work
Oxygen consumption is directly proportional to Cardiac work i-e = CO *Aortic pressure
Pressure work requires more oxygen bcz more contraction it has to do
PW needs more oxygen
What is ficks principle and what it shows and how ? Give example
Ficks principle states that more the oxygen consumed more will be the CO , it shows CO
CO=O2 consumption/ venous O2 content -arterial O2 content
If 50 ml 02 is added each time when it passes lungs eg 50 ml were added to 1L then how many litres consumed 250ml 02 …….i-e 5L hence co is 5L
Sv
CO
EDV
EF and what is shows
Sv is volume of blood ejected per beat
CO=SV*HR -> volume of blood ejected per minute
EF=SV/EDV -> fraction of diastolic volume ejected per systole
EF shows efficiency of heart
What are phases of p-v graph(left ventricular pressure and volume)
What this area subtended shows
When some of phases increase and when decrease
4 phases 1-2period of filling (left to right). 2-3 of IVC (bottom to top). 3-4period of ejection(right to left). 4-1period of IVR(top to bottom)
The area subtended shows the cardiac work output OR END-SYSTOLIC VOLUME(edv-sv)
1-2 î when preload î or venous return î
3-4 î when contractility î or sv î
Half distance beyond 1 to 2 and î 2-3 and 3 to half distance beyond and then again the same shows î afterload
Laplaces law
Laplace law states that
P=2tensionthickness/radius
Decreasing radius(ventrodilators and diuretics) increase pressure
Contractility
dP/dt
Rate of pressure development during isovolumic contraction
Depends on EF and adrenaline
Contractility î when dp/dt î ,î peak of LF pressure, î V of relaxation
In ischemic heart disease or any other disease heart needs gets less oxygen so what can we do
We can reduce oxygen demand of heart by leplaces law
Relationship of SV with preload, contractility and Afterload
SV@ preload*contractility
Sv@1/afterload
@(propotional)
Effect of potassium ions on heart
K ions block the transmission of electrical impulse from SA node to AV node .actually decreases the resting membrane potential( depolarize it ). Therefore high K level from 8-12 mEq/L
Preload
Afterload
Load on ventricles after contraction means at relaxation
Can be called as EDV
Load on muscles during contraction or load against which ventricles has to work
Depends on MAP
Heart get its chemical energy from
70% fatty acid metabolism
30% other nutrients(specially glucose and lactate)
whats the relation of oxygen consumption and tension Whats the tension of heart muscle according to laplaces law
Oxygen consumption is directly proportional to tension which is itself proportional to pressure times radius of ventricles
Heart beat is regulated by ??
1) intrinsic regulation i-e described by frank starling mechanism which states the grtr the stretch of ventricles grtr will be the contraction (to lesser extent grt atrial p î heart rate bcz of stretch of SA node which itself has direct effect on heart beat)
2) control by sympathetic and parasympathetic nervous system
Nerve which transmit parasympathetic stimulation to heart and where it is attached
Vagus nerve are mainly distributed to SA and AV node less to atria and very less to ventricles
Effect of temperature on heart
Heat increases the permeability of ions therefore î heart beat
Effect of load on cardiac output
When load î cardiac output does not decrease upto a limit i-e 160mmhg because î arterial pressure î venous return ….co is Lowest on 250
Which channels open when myocardial cells depolarise
and what they cause and how this causes diminishes
Voltage gates k and ca channels open. K goes out while ca comes in . This causes plateau. As time passes by (in plateau) k permeability î and ca permeability decrease therefore plateau diminishes and repolarization occur