Predict the effects of a drug that blocks the parasympathetic nervous system on
ID: 3482124 • Letter: P
Question
Predict the effects of a drug that blocks the parasympathetic nervous system on blood pressure and heart rate. How would this drug affect the three factors that determine blood pressure? You are presented with a stack of ECGs on your first day of your cardiology rotation and are given a single instruction: "Read them." As you progress through the pile, you note the following abnormalities. Explain from where in the heart or cardiac conduction system each abnormality might have come: a Absent P waves b Abnormally long QRS complex c Abnormally long P-R interval d Extra QRS complexes Exploring Anatomy & Physiology in the Laboratory ·Explanation / Answer
A. Absent P wave:
On ECG P wave indicates atrial depolarization which results in atrial contraction. Absence of P wave indicates atrial fibrillation, sinoatrial block.
B. Abnormally long QRS complex:
QRS complex represents right and left ventricular depolarization. Abnormally long QRS complex may indicate bundle branch block, left ventricular hypertrophy.
C. Abnormally long PR interval:
PR interval extends from beginning of P wave to beginning of QRS complex. Long PR interval may indicate first degree heart block, hypokalemia.
D. Extra QRS complex:
This may indicate supraventricular extrasystole. In this there is premature emission of electrical impulses through the atria and ventricle which causes premature contraction.
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