Cardiovascular System Properties Quiz

Properties of the Heart Related to its Function

• The heart is a muscular organ that pumps blood throughout the body
• It has a high degree of automatism, meaning it can generate its own rhythmic contractions
• The heart is also a highly vascularized organ, receiving about 5% of the total cardiac output

Substrate of Automatism in the Heart

• The substrate of automatism in the heart is the sinoatrial (SA) node
• The SA node is a group of cells located in the right atrium that generates the electrical impulses that control the heart's rhythm

Components of the Substrate of Automatism

• The SA node is composed of pacemaker cells, which are specialized cardiomyocytes that have the ability to generate electrical impulses
• The SA node is also richly innervated by the autonomic nervous system, which modulates the heart's rhythm

Phases of the Action Potential (AMP) of a Cardiomyocyte

• The action potential of a cardiomyocyte has five distinct phases: Phase 0 (depolarization), Phase 1 (rapid repolarization), Phase 2 (plateau), Phase 3 (final rapid repolarization), and Phase 4 (diastole)
• Phase 0 is characterized by a rapid depolarization of the cardiomyocyte, triggered by the opening of voltage-gated calcium channels
• Phase 1 is a rapid repolarization of the cardiomyocyte, due to the closure of voltage-gated calcium channels and the opening of voltage-gated potassium channels
• Phase 2 is a prolonged plateau phase, during which the cardiomyocyte is contracted and the membrane potential is relatively stable
• Phase 3 is a rapid repolarization of the cardiomyocyte, caused by the closure of voltage-gated sodium channels and the opening of voltage-gated potassium channels
• Phase 4 is the diastolic phase, during which the cardiomyocyte is at rest and the membrane potential is stable