Physiology Flashcards
What’s meant by the syncytium when referencing the heart?
The cells interconnected via gap junctions.
What influence does inotropy have on the heart? What is pos and neg inotropy?
It influences myocardial contractility
pos=increased force of contraction
neg=decreased force of contraction
What influence does chromatropy have on the heart? Pos and neg chromatropy?
It affects HR
Pos increases the rate of impulse formation in the SA node
Neg decreases impulse formation
What influence does Dromotrophy have on the heart? Pos and neg dromotrophy?
Affects conduction velocity
Pos speeds conduction
Neg delays conduction
What are connexin proteins used for? Why is there role important and what are some implications of genetic disorders in genes that code for these proteins?
Forming gap junctions between adjacent cardiac cells; responsible for the syncytia of atria and ventricles
These gap junctions facilitate depolarization of cardiac cells and make proper contraction of the heart possible.
There are 21 connexin genes. Connexin 43 is the most studied. Mutations in these genes can neg affect heart conduction and contraction.
In a lab experiment gone wrong an electrically charged nanotube pierces the heart of one of your employees directly on the left ventricle. What do you think will happen next?
A) Nothing, because electrical stimulation must come from the SA node to depolarize myocardial cells
B) Depolarization of the myocardium beginning with the left ventricle
C) Positive chromatropy
D) Negative chromatropy
B) Depolarization of the myocardium can be initiated at ANY site and it will propagate due to intercalated disks that contain gap junctions. No neural input is required to depolarized these cells, or the SA node itself.
What is the effect of hypocalcemia on the heart? Hypokalemia?
Hypocalcemia-decreased contractility/flaccidity similar to a hyperkalemic state.
Hypokalemia- abnormal heart beat (arrhythmia) lead to death from cardiac arrest.
An increase in end diastolic blood volume/preload would have what effect on contractility of the heart? What effect would this have on stroke volume? How else can you influence contractility?
Increase in EDV would increase the length of the sarcomeres (stretching the myocardium) and increase contractility.
Stroke volume (blood ejected during systolic contraction) would increase
Positive inotropy: is the other way to influence contractility and involves increase the force of the contraction by increasing Ca2+ content.
Which form of troponin found in the blood is used to determine time from MI? What gene does this come from?
Troponin I - binds to actin
Gene- TNNT2
The positive inotropic effect will ______peak tension, ______rate of tension, and lead to _________relaxation.
A) Increased, Increased, Faster
B) Increased, decreased, Faster
C) Decreased, Decreased, Slower
D) Decreased, Increased, Faster
A
Negative dromotropy will have what effect on heart rate? What other way could you describe this effect?
Decrease HR, b/c decreased conduction velocity
Decreased chronotropy
