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Questions and Answers
What is the role of systemic circulation?
Which structure returns deoxygenated blood from the head and upper limbs to the heart?
What prevents the backflow of blood into the ventricles during contraction?
What is the primary function of the atrioventricular (AV) node in the heart's electrical conduction system?
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Which of the following correctly describes the function of desmosomes in cardiac muscle fibers?
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Where is the sinoatrial (SA) node located?
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Which statement accurately describes the action potential in cardiac muscle cells as compared to pacemaker cells?
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What is the function of gap junctions in cardiac muscle fibers?
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What initiates the action potential that causes the heart to contract in pacemaker cells?
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Which artery carries oxygenated blood from the left ventricle to the rest of the body?
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What role do Purkinje fibers play in the heart's electrical conduction system?
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What is the main role of the specialized conduction system of the heart?
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Study Notes
The Circulatory System
- Transports materials throughout the body
- Consists of two main circuits: systemic and pulmonary
- Systemic circulation: delivers oxygenated blood to tissues and returns deoxygenated blood to the heart
- Pulmonary circulation: delivers deoxygenated blood to the lungs and returns oxygenated blood to the heart
- Capillary networks are located in the lungs and throughout the body
Blood Flow Through Heart
- Deoxygenated blood enters the right atrium from the superior vena cava (head and upper limbs) and inferior vena cava (trunk and legs)
- Blood flows from the right atrium through the right atrioventricular valve into the right ventricle
- The right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary artery
- Deoxygenated blood travels to the lungs in the right and left pulmonary arteries
- Oxygenated blood returns from the lungs through the right and left pulmonary veins to the left atrium
- Oxygenated blood flows from the left atrium through the left atrioventricular valve into the left ventricle
- The left ventricle pumps oxygenated blood through the aortic semilunar valve into the aorta
- The aorta, the largest artery, distributes oxygenated blood to the body
Cardiac Muscle Fibers
- Are branched and interconnected by intercalated discs
- Intercalated discs contain desmosomes and gap junctions
- Desmosomes hold muscle fibers together, preventing them from separating during contraction
- Gap junctions allow ions to flow between cells, creating a functional syncytium – a network that contracts as a unit
Specialized Conduction System of the Heart
- Controls heart rate and ensures coordinated contraction of the atria and ventricles
- Sinoatrial (SA) node: the heart's pacemaker, initiates electrical impulses
- Internodal pathway: conducts impulses from the SA node to the AV node
- Atrioventricular (AV) node: delays impulses briefly, allowing the atria to contract before the ventricles
- Bundle of His: conducts impulses from the AV node to the ventricles
- Right and left branches of the bundle of His: conduct impulses to the right and left ventricles
- Purkinje fibers: spread impulses throughout the ventricles, causing ventricular contraction
Pacemaker Cells
- Generate electrical impulses that cause the heart to beat
- Possess unique ion channels that create a slow depolarization called the pacemaker potential
- Pacemaker potential triggers an action potential, initiating heart contraction
Cardiac Muscle Cells
- Have different action potentials than pacemaker cells
- Rapid rising phase: due to the opening of fast sodium channels
- Plateau phase: due to the opening of slow calcium channels
- Falling phase: due to the opening of potassium channels
Excitation-Contraction Coupling in Cardiac Contractile Cells
- Links electrical activity of cardiac muscle to its mechanical contraction
- Action potential travels down T tubules
- Ca2+ enters cytoplasm through L-type calcium channels, triggering the release of more Ca2+ from the sarcoplasmic reticulum through ryanodine receptors
- Increased cytosolic Ca2+ binds to troponin, moving tropomyosin away from the myosin-binding sites on actin
- Cross-bridge cycling occurs, causing filament sliding and muscle contraction
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Description
Test your knowledge on the circulatory system, including its main components and functions. This quiz covers systemic and pulmonary circulation, as well as the flow of blood through the heart. Challenge yourself to understand how blood is transported throughout the body!
