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Questions and Answers
What is the role of the chordae tendinae in the heart?
What is the role of the chordae tendinae in the heart?
Which valves are classified as atrioventricular valves?
Which valves are classified as atrioventricular valves?
How does the heart receive its blood supply?
How does the heart receive its blood supply?
What does the 'T' wave represent in an electrocardiogram (ECG)?
What does the 'T' wave represent in an electrocardiogram (ECG)?
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Which factor typically causes the left ventricle to have thicker walls compared to the right ventricle?
Which factor typically causes the left ventricle to have thicker walls compared to the right ventricle?
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What unique feature do about 1% of cardiac muscle cells possess?
What unique feature do about 1% of cardiac muscle cells possess?
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What is the role of the autonomic nervous system in heart function?
What is the role of the autonomic nervous system in heart function?
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What does the term 'functional blood supply' to the heart muscle refer to?
What does the term 'functional blood supply' to the heart muscle refer to?
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What type of respiration does the heart primarily rely on?
What type of respiration does the heart primarily rely on?
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What does stroke volume describe?
What does stroke volume describe?
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In the context of cardiac output, what does the formula HR x SV represent?
In the context of cardiac output, what does the formula HR x SV represent?
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Why is the coronary circulation considered the shortest in the body?
Why is the coronary circulation considered the shortest in the body?
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Where do both the left and right coronary arteries originate?
Where do both the left and right coronary arteries originate?
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Which condition is characterized by uncoordinated atrial and ventricular contractions?
Which condition is characterized by uncoordinated atrial and ventricular contractions?
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What normally happens when the sympathetic nervous system is activated?
What normally happens when the sympathetic nervous system is activated?
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What can occur due to a defective SA node?
What can occur due to a defective SA node?
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What is the main function of the left atrium?
What is the main function of the left atrium?
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Which statement accurately describes the role of the ventricles?
Which statement accurately describes the role of the ventricles?
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What is the purpose of the valves within the heart?
What is the purpose of the valves within the heart?
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Which of the following best describes the right atrium?
Which of the following best describes the right atrium?
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What chambers of the heart are referred to as the receiving chambers?
What chambers of the heart are referred to as the receiving chambers?
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The pulmonary circuit is responsible for which of the following?
The pulmonary circuit is responsible for which of the following?
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What is the structure called that attaches to the heart valves?
What is the structure called that attaches to the heart valves?
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Which vessel is responsible for returning blood from the head and arms to the right atrium?
Which vessel is responsible for returning blood from the head and arms to the right atrium?
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What feature is primarily responsible for the thickness of the ventricular walls?
What feature is primarily responsible for the thickness of the ventricular walls?
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How does deoxygenated blood reach the right atrium?
How does deoxygenated blood reach the right atrium?
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Study Notes
The Cardiovascular System
- The heart is a transport system with two pumps
- The right side receives oxygen-poor blood from tissues and pumps it to the lungs to remove CO2 and pick up O2 (pulmonary circuit)
- The left side receives oxygenated blood from the lungs and pumps it to body tissues through the systemic circuit
Heart Anatomy
- The heart has four chambers: two atria and two ventricles
- The atria are thin-walled, receiving chambers
- The ventricles are thick-walled, pumping chambers, with the left ventricle being thicker due to greater pressure
- Valves (tricuspid, mitral/bicuspid, pulmonary, aortic) prevent backflow of blood
Heart Location
- The heart sits in the mediastinum, the central area of the chest.
- More precisely, it's located between the lungs, behind the sternum, and above the diaphragm.
Heart Layers
- Pericardium: Sac-like structure that encloses the heart.
- Myocardium: Thick muscle layer that forms the heart walls.
- Endocardium: Inner layer lining the heart chambers
Receiving Chambers - Atria
- Small, thin-walled chambers
- Left atrium: Receives oxygenated blood from the lungs (4 pulmonary veins)
- Right atrium: Receives deoxygenated blood from the body (Superior vena cava, Inferior vena cava, coronary sinus)
Discharging Chambers - Ventricles
- Thicker walls than atria, the actual pumps of the heart
- Right ventricle: Pumps deoxygenated blood to the lungs
- Left ventricle: Pumps oxygenated blood to the body
Valves
- Prevent backflow of blood
- Atrioventricular (AV) valves: Tricuspid (right side), Mitral/Bicuspid (left side)
- Semilunar valves: Pulmonary (right side), Aortic (left side)
Blood Flow Through Heart
- Blood flows into the right atrium (Superior and Inferior vena cava, Coronary sinus)
- Through tricuspid valve to right ventricle
- To pulmonary semi-lunar valve to pulmonary trunk (pulmonary circulation)
- To lungs to pick up oxygen
- Oxygenated blood returns to the left atrium (pulmonary veins)
- Through mitral/bicuspid valve to left ventricle
- Through aortic semi-lunar valve into the aorta (systemic circulation)
- To the body tissues
Coronary Arteries
- Functional blood supply to the heart muscle itself, delivered when the heart is relaxed
- Left main coronary artery, circumflex, and left anterior descending coronary arteries are crucial supply routes
- Both the left and the right coronary arteries arise from the base of the aorta
Cardiac Muscle
- Cardiac cells tightly encircle heart chambers
- Striated muscle, 1% specialized for electrical excitation (conduction system)
Cardiac vs. Skeletal Muscles
- Cardiac muscle relies almost exclusively on aerobic respiration
- Skeletal muscle can use both aerobic and anaerobic respiration
- Cardiac muscle has more mitochondria, is more adaptable to other fuels
The Conduction System
- Specialized cells that initiate and conduct electrical impulses, rapidly spreading via gap junctions throughout the heart to ensure coordinated contractions.
- Sinoatrial node (SA node): The pacemaker of the heart, initiating impulses.
- Atrioventricular node (AV node): Delays the impulse to allow the atria to empty before ventricles contract
- Bundle of His, bundles branches, and Purkinje fibers conduct the impulse throughout the ventricles
Intrinsic Conduction System
- Non-contractile cells initiate and distribute impulses
- Pacemaker cells generate the heartbeat with an unstable resting potential (continuous depolarization)
The Heartbeat
- Action potentials spread from cell to cell through the heart
- The SA node is the pacemaker: initial depolarization begins, setting the contraction rate
- Atrioventricular node (AV node): delays the impulse, allowing the atria to fully empty to improve blood pumping efficiency
The ECG
- Tool to measure electrical events:
- P wave: Atrial depolarization
- QRS complex: Ventricular depolarization
- T wave: Ventricular repolarization
Sinus Rhythm and Electrocardiography (ECG)
- Sinus rhythm: Normal heart rhythm, initiated by the SA node
- Arrhythmias: Irregular heart rhythms; some examples include fibrillations or ectopic beats
- Defibrillation or pacemakers: Medical devices used to restore regular heart contractions if needed
Anatomical Differences Between Ventricles
- Left ventricle walls are 3 times thicker than the right to generate the greater pressure needed to pump blood throughout the body
- The right ventricle pumps blood to the lungs, requiring less pressure
Phases of Cardiac Cycle
- Series of events during one heartbeat. Four stages: atrial systole, atrial diastole, ventricular systole, ventricular diastole.
- Pressure changes in chambers, driving blood flow
Extrinsic Innervation
- Autonomic Nervous System modifies heart rate and force
- Sympathetic stimulation increases rate/force
- Parasympathetic stimulation slows heart rate through the vagus nerve.
Cardiac Output
- Volume of blood pumped by each ventricle per minute
- Determined by Heart Rate x Stroke Volume.
Stroke Volume
- Volume of blood expelled during each contraction.
- Affected by end-diastolic volume/preload, Starling's Law, and afterload.
Physiotherapy
- Physical activity can help lower blood pressure, strengthen the heart, control weight, increase circulation, and enhance cellular oxygen usage.
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