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Lexotan Sau Xanax
In some severe anemias, the reticulocytes may account for as much as 30 of the total red cell count. In some situations, red cell
production is so accelerated that numerous erythroblasts appear in the blood.
Pharmacologic management includes the use of 5. - reductase
inhibitors and. 1-adrenergic blocking drugs. 39 The 5.
-reductase inhibitors, such as finasteride, reduce prostate size
by blocking the effect of androgens on the prostate.
5 mm, which is located slightly beneath the right atrial endocardium, anterior to the opening of the coronary sinus, and
immediately above the insertion of the septal leaflet of the tricuspid valve. Lexotan sau xanax In 85 to 90 of people, blood
supply to the AV node is provided by the right coronary artery.
1 The AV node is divided into three functional regions: the AN, or transitional, zone between the atria and the rest of the node;
the middle N, or nodal, zone; and the NH, or upper, zone of the ventricular conduction system. 5 Within the AN portion of the
node, atrial fibers connect with very small junctional fibers of the node itself. The velocity of conduction through the AN lexotan
sau xanax N fibers is very slow, which greatly delays transmission of the impulse.
5,6 A further delay occurs as the impulse travels through the nodal region into the NH region, which connects with the bundle of
His. This delay provides a mechanical advantage whereby the atria complete their ejection of blood before ventricular
contraction begins. Under normal circumstances, the AV node provides the only connection between the atrial and 582 UNIT VI
Cardiovascular Function SA node AV node Bundle of His Left posterior fascicle Left anterior fascicle Purkinje fibers Right bundle
branch Left bundle branch A B C FIGURE 27-1 Conduction system of the heart and action potentials.
Action potential of sinoatrial and atrioventricular nodes; atrial muscle action potential; action potential of ventricular muscle and
Purkinje fibers. CARDIAC CONDUCTION SYSTEM. The cardiac conduction system controls the rate and direction of electrical
impulse conduction in the heart. Normally, impulses are generated in the SA node, which has the fastest rate of firing, and travel
via the AV node to the Purkinje system in the ventricles.
Cardiac action potentials are divided into five phases: phase 0, or the rapid upstroke of the action potential; phase 1, or early
repolarization; phase 2, or the plateau; phase 3, or final repolarization period; and phase 4, or diastolic repolarization period.
Cardiac muscle has two types of ion channels that function in producing the voltage changes that occur during the
depolarization phase of the action potential: the fast sodium channels and the slow calcium channels.
There are two types of cardiac action potentials: the fast response, which occurs in atrial and ventricular muscle cells and the
Purkinje conduction system and uses the fast lexotan sau xanax channels; and the slow response of the SA and AV nodes,
which uses the slow calcium channels. ventricular conduction systems. The atria and ventricles would beat independently of
each other if the transmission of impulses through the AV node were blocked.
The Purkinje system, which lexotan sau xanax the ventricles, has large fibers that allow for rapid conduction and almost
simultaneous excitation of the entire right and left ventricles. 6 Lexotan sau xanax rapid rate of conduction throughout the
Purkinje system is necessary for the swift and efficient ejection of blood from the heart. The fibers of the Purkinje system
originate in the AV node and proceed to form the bundle of His, which extends through the fibrous tissue between the valves of
the heart and into the ventricular system.
Because of its proximity to the aortic valve and the mitral valve lexotan sau xanax, the bundle of His is predisposed to
inflammation and deposits of calcified debris that can interfere with impulse conduction. 6 The bundle of His penetrates into the
ventricles and almost immediately divides into right and left bundle branches that straddle the interventricular septum. Branches
from the anterior and posterior descending coronary arteries provide blood supply for the His bundle, making this conduction
site less susceptible to ischemic damage, unless the damage is extensive.
1 The bundle branches move through the subendocardial tissues toward the papillary muscles and then subdivide into the
Lexotan sau xanax fibers, which branch out and supply the outer walls of the ventricles. The main trunk of the left bundle branch
extends for approximately Lexotan sau xanax to 2 cm before fanning out as it enters the septal area and divides further into
two segments: the left posterior and anterior fascicles.
The left bundle branch is supplied with blood from both the left anterior descending artery and the posterior descending artery,
whereas the right bundle branch receives its blood from both the right and left anterior descending coronary arterial systems. 1
The AV nodal fibers, when not stimulated, discharge at an intrinsic discharge rate of 40 lexotan sau xanax 60 times a minute,
and the Purkinje fibers discharge at 15 to 40 times per minute.
Although the AV node and Purkinje system have the ability to control the rhythm of the heart, they do not normally do so
because the discharge rate of the SA node is considerably faster. Each time the Lexotan sau xanax node discharges, its
impulses are conducted into the AV node and Purkinje fibers, causing them to fire. The AV node can assume the pacemaker
function of the heart should the SA node fail to discharge, and the Purkinje system can assume the pacemaker function of the
ventricles should the AV node fail to conduct impulses from the atria to the ventricles.