Describe the proper sequence of firing events for the heart. Based on the figure

Question

Describe the proper sequence of firing events for the heart. Based on the figure in the additional pdf containing the voltages in different portions of the heart explain the origin of each of the portions of the EKG/ECG (P,QRS,T)shown in that figure 2. When the SA node fails to fire and the firings of the heart are initiated by the AV node. Explain, using mathematical arguments why the P wave in this case will be inverted. Be sure to use the curve for the membrane voltage of the atrial muscle as a function of distance in your answer 3. Sketch a cardiac muscle cell and describe how it functions as both a conductive path and a path for controlled contraction of the heart. Sketch the action potential shown in the top figure on the attached page, as a function of position if the propagation velocity is 50m/sec and the action potential is propagating in the -x direction Assume you are to find the potential on the skin generated by the action potential you sketched in part of this question. Would you treat this as a dipole source or monopole source? Explain your answer 4 5. Write the mathematical form for the source density as identified in problem 4 and solve the integral for the resulting potential which would be measured. 6. You are a cardiologist and have determined that your patient has the following problem, the SA node occasionally fails to fire. What will the EKG look like for this case? Identify/name the parts of the trace and describe how they relate to this patient's problem. In your plot, of the EKG, show a heartbeat with SA node firing followed by a heartbeat with the SA node not being the source of the excitation

Explanation / Answer

1.

An ECG records the sequential events of a heart beat. It is divided into three components mainly, the P wave, the QRS complex, and the T wave. Each of them are generated as follows:

P wave: It represents the initiation of depolarization in the Sinus node and accompanied atrial contraction. It is upright and is abt 2.5 mm tall in the electrocardiogram.

The QRS complex: It indicates the condution of bood and sequential deplarization of the ventricles. The initial Q wave depends on the leads used by the pathologist. The q wave may or may not be present.

The ST segment: It is a period of refraction during which the ventricles are isoelectric. The wave gives information on cardiac ischemia and myocardial infarction.

The T wave represents repolarization of the ventricles. The T wave gives informations about cardiac ischemia and electrolyte abnormalities.

2. SA node is the body's pacemaker. An inverted P wave indicates tha the primary pace maker has shifted to the AV node.

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