GENERAL ANATOMY
CARDIOVASCULAR SYSTEM
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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initiates atrial depolarization
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boosts the electrical signal to the ventricles
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causes contraction of the ventricles
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are the purkinje fibers
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Detailed explanation-1: -The firing of the SA node sends out an electrical impulse via its neurons to the right atrium, left atrium, and AV node simultaneously. Since the right atrium is closer to the SA node, it depolarizes first, resulting in pumping action by the right atrium before the left atrium.
Detailed explanation-2: -Every cardiac cycle (heartbeat) begins with the sinus node sending an electrical signal across both atria through specialized conduction tracts, which causes the atrial muscle to depolarize and contract.
Detailed explanation-3: -Left: Normal excitation originates in the sinoatrial (SA) node then propagates through both atria. The atrial depolarization spreads to the atrioventricular (AV) node, and passes through the bundle of His to the bundle branches/Purkinje fibers.
Detailed explanation-4: -The sinoatrial node (SA node) is a specialized myocardial structure that initiates the electrical impulses to stimulate contraction, and is found in the atrial wall at the junction of superior caval vein and the right atrium (Mikawa and Hurtado, 2007).
Detailed explanation-5: -SA nodal action potentials are divided into three phases. Phase 4 is the spontaneous depolarization (pacemaker potential) that triggers the action potential once the membrane potential reaches threshold between-40 and-30 mV). Phase 0 is the depolarization phase of the action potential.