25 pts. Describe in detail the electrical and contractile activity of the heart

Question

25 pts. Describe in detail the electrical and contractile activity of the heart which accounts for the cardiac cycle. How can your discussion explain the following EKG results:

5 pts.Apply the length-tension relationship of the sliding filament model to functioning of the heart.

10 pts   Describe Starling's forces that govern fluid movement out of and into capillaries.

What would happen to fluid movement across capillaries and why, given the following sets of circumstances:

dehydration

cardiac failure

Explanation / Answer

Cardiac Cycle ( electrical & contratile ) :-

Cardiac Cycle - it is a sequential beating cycle of heart which makes flow of blood in entire body.

Cardiac Cycle comprises of 4 phase or periods explained below -

1.1st Diastole Period :-

It is also known as relaxed phase in this period the the atria and ventricles are relaxed and atrioventicular valve are open. Right atrium starts filling with a deoxygenated blood coming from superior & inferior venacava. Then the open atrioventicular valve allows blood to pass on right ventricle. An impulse is generated through SA node to AV node then further AV node send signals and triggers both atria to contract. As a result right atrium empties its blood in right ventricle and tricuspid valve closes to stop reverse flow.

2. 1st Systole Period :-

Getting impulse from the purkinje fiber filled right ventricle undergoes contraction and as this occurs atrioventicular valve closes and semilunar valve open and deoxygenated blood pumped into the pulmonary artery then pulmonary valve closes to stop reverse flow. Further pulmonary artery carries blood into lungs.

3. 2nd Diastole Period :-

Left atrium receives the oxygented blood from pulmonary vein coming from lungs. Further semilunar valves closes and atrioventicular valves open and SA node makes trigger to contract both atriums and left atrium empties into left ventricle as side by side right atrium is also filling and emptying.

4. 2nd Systole Period :-

Atrioventicular valve closes and semilunar valve opens. Further getting impulse from purkinje fiber again ventricle contracts and oxygented blood pumped out from left ventricle to arota. And then to the other parts of the body and after that again atrium gets refilled with deoxygenated blood coming from superior and inferior vena cava.

The cardiac cycle completes here.

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