22.7
심장주기
심장은 수축(수축기(systole))과 이완(이완기(diastole))의 빠른 조정인 심장 주기라고 불리는 순서대로 리듬감 있게 박동합니다.
과정
오른심방벽(right atrial wall)의 동방결절(sinoatrial node, 줄여서 SA node)에서 오른심방(…
- [강사] 심장은 주기적으로박동을 합니다.수축의 빠른 조정, 심장수축.그리고 이완, 심장확장.우심실 벽 근처의 심방 결절점에서 보내진 전기 신호는 두 심방을 동시에수축시켜 심실로혈액을 밀어 넣습니다.맥박이 우심방과 우심실사이의 방실 결절에 도달하면약 1/10 초 동안 중단되어 혈액이 심방에서 완전히 비울 수 있습니다.그다음 요금은 히스 다발을 통해뇌실 중격 아래로 퍼진다.그리고 오른쪽 및 왼쪽 번들 가지를 통과한 다음 심실의벽을 통해 푸르킨제 섬유가 갑니다.따라서 심실 수축을 유도하고 심장으로부터폐동맥 및 대동맥으로 혈액을 펌핑한다.심장 근육이 이완된 후, 심방이 혈액으로 채워지고주기가 반복됩니다.
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Q1: What is the cardiac cycle and how does it work?
The cardiac cycle is a rhythmic sequence of heart contractions and relaxations that pumps blood throughout the body. It consists of systole, when the heart muscle contracts, and diastole, when it relaxes and refills. This coordinated process ensures blood continuously circulates through the circulatory system heart and blood vessels.
Q2: Where does the electrical signal that starts the cardiac cycle originate?
The sinoatrial node, located near the right atrial wall, generates the electrical signal that initiates the cardiac cycle. This signal causes both atria to contract simultaneously, pushing blood into the ventricles. The signal then travels to the atrioventricular node, where it pauses briefly to allow complete blood emptying.
Q3: What is the purpose of the pause at the atrioventricular node?
The atrioventricular node pauses the electrical signal for approximately one-tenth of a second, allowing the atria to fully contract and empty all blood into the ventricles before ventricular contraction begins. This timing ensures efficient blood flow and prevents backflow, optimizing the heart's pumping efficiency.
Q4: How does the electrical impulse travel through the ventricles?
After passing through the atrioventricular node, the electrical signal travels through the Bundle of His and splits into right and left bundle branches along the intraventricular septum. The signal then spreads through Purkinje fibers in the ventricular walls, triggering coordinated ventricular contraction that pumps blood into the pulmonary artery and aorta.
Q5: What happens during diastole in the cardiac cycle?
During diastole, the ventricles relax and the atria continue filling with blood returning from the body and lungs. As ventricular pressure drops, blood flows passively into the ventricles from the atria. This relaxation phase prepares the heart for the next contraction cycle.
Q6: Why is the coordination between atrial and ventricular contractions important?
Coordinated atrial and ventricular contractions ensure blood moves efficiently through the heart chambers in one direction. The brief delay at the atrioventricular node allows atria to empty completely before ventricles contract, maximizing blood volume pumped with each heartbeat and maintaining consistent circulation throughout the body.
Q7: What role do Purkinje fibers play in the cardiac cycle?
Purkinje fibers are specialized conduction pathways in the ventricular walls that rapidly spread the electrical signal throughout both ventricles. This ensures synchronized ventricular contraction, allowing the ventricles to contract as a unified unit and effectively pump blood out of the heart with maximum force.