Description
Pharmacology of drugs acting on cardio vascular system
a. Introduction to hemodynamic and electrophysiology of heart.
b. Drugs used in congestive heart failure
c. Anti-hypertensive drugs.
d. Anti-anginal drugs.
e. Anti-arrhythmic drugs.
f. Anti-hyperlipidemic drugs.
impulse of their own. During diastole, the resting membrane potential remains stable (approxima-tely 90 mv negative inside). When stimulated, they depolarize very rapidly (fast 0 phase) with considerable overshoot (+ 30 mv) ï‚® rapid return to near isoelectric level (phase-1) ï‚® maintenance of membrane potential at this level for a considerable period (phase-2, plateau phase) during which Ca2+ ions flow in and bring about con- traction ï‚® relatively rapid repolarization (phase- 3) during which membrane Na+K+ pump gets activated and tends to restore ionic distribution to the resting pattern. Resting membrane potential, once attained, does not decay (stable phase-4). (b) Automatic fibres These are present in the sinoatrial (SA) and atrioventricular (A-V) nodes, and in the His-Purkinje system, i.e. especialized conducting tissue. In addition, patches of automatic tissue are present in the interatrial septum, A-V ring and around openings of the great veins.
The most characteristic feature of these fibres is phase-4 or slow diastolic depolarization, i.e. after repolarizing to the maximum value, the membrane potential decays spontaneously. When it reaches a critical threshold value—sudden depolarization occurs automatically. Thus, they are capable of generating their own impulse. The rate of impulse generation by a particular fibre depends on the value of maximal diastolic potential, the slope of phase-4 depolarization and the value of threshold potential.
