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Questions and Answers
What mechanism does the baroreceptor reflex primarily utilize for short-term blood pressure control?
What mechanism does the baroreceptor reflex primarily utilize for short-term blood pressure control?
- Reduction of heart rate (correct)
- Control of cardiac output and total peripheral resistance (correct)
- Increased renal blood flow
- Enhanced blood viscosity
What characterizes primary hypertension?
What characterizes primary hypertension?
- It occurs due to other underlying factors.
- It has a known physiological cause.
- It is always accompanied by kidney dysfunction.
- The cause is not known. (correct)
Which factor is directly linked to secondary hypertension?
Which factor is directly linked to secondary hypertension?
- Dietary sodium intake
- Lifestyle choices such as exercise
- Another underlying medical condition (correct)
- Genetic predisposition
What is the blood pressure range that defines hypotension?
What is the blood pressure range that defines hypotension?
Which of the following conditions can result from heart failure?
Which of the following conditions can result from heart failure?
What happens to stroke volume when there is increased end-diastolic volume (EDV)?
What happens to stroke volume when there is increased end-diastolic volume (EDV)?
Which statement about Frank-Starling's law is true?
Which statement about Frank-Starling's law is true?
What role does the autonomic nervous system play in initiating the heartbeat?
What role does the autonomic nervous system play in initiating the heartbeat?
How does sympathetic nervous system activity affect cardiac output?
How does sympathetic nervous system activity affect cardiac output?
What is the effect of parasympathetic activity on the atria?
What is the effect of parasympathetic activity on the atria?
What effect does sympathetic stimulation have on arterioles?
What effect does sympathetic stimulation have on arterioles?
Which statement accurately describes the relationship between venous return and stroke volume?
Which statement accurately describes the relationship between venous return and stroke volume?
Which of the following best describes the function of the SA node?
Which of the following best describes the function of the SA node?
What is the formula to calculate Cardiac Output (CO)?
What is the formula to calculate Cardiac Output (CO)?
Which factor is NOT associated with increasing Heart Rate (HR)?
Which factor is NOT associated with increasing Heart Rate (HR)?
According to Frank-Starling's law, what occurs with increased venous return to the heart?
According to Frank-Starling's law, what occurs with increased venous return to the heart?
Which statement accurately describes the control of Stroke Volume (SV)?
Which statement accurately describes the control of Stroke Volume (SV)?
Which of the following conditions is likely to decrease Heart Rate (HR)?
Which of the following conditions is likely to decrease Heart Rate (HR)?
What is primarily responsible for the intrinsic control of Stroke Volume?
What is primarily responsible for the intrinsic control of Stroke Volume?
When is parasympathetic discharge dominant in controlling Heart Rate (HR)?
When is parasympathetic discharge dominant in controlling Heart Rate (HR)?
What is the expected Cardiac Output (CO) when Heart Rate (HR) is 70 BPM and Stroke Volume (SV) is 70 ml/beat?
What is the expected Cardiac Output (CO) when Heart Rate (HR) is 70 BPM and Stroke Volume (SV) is 70 ml/beat?
What role does the SA node play in the cardiac conduction system?
What role does the SA node play in the cardiac conduction system?
Which component of the cardiac conduction system has the slowest conduction velocity?
Which component of the cardiac conduction system has the slowest conduction velocity?
What is the primary purpose of AV nodal delay?
What is the primary purpose of AV nodal delay?
What does the P wave in an ECG tracing represent?
What does the P wave in an ECG tracing represent?
Which structure is responsible for rapid and simultaneous excitation of the ventricles?
Which structure is responsible for rapid and simultaneous excitation of the ventricles?
What is the relationship between End Diastolic Volume (EDV) and End Systolic Volume (ESV) in calculating Stroke Volume (SV)?
What is the relationship between End Diastolic Volume (EDV) and End Systolic Volume (ESV) in calculating Stroke Volume (SV)?
How many action potentials does the SA node typically discharge per minute?
How many action potentials does the SA node typically discharge per minute?
Which of the following statements about Heart Rate (HR) is true?
Which of the following statements about Heart Rate (HR) is true?
Which of the following statements is true regarding the electrocardiogram (ECG)?
Which of the following statements is true regarding the electrocardiogram (ECG)?
What distinguishes the AV node in terms of its function in the heart?
What distinguishes the AV node in terms of its function in the heart?
What does tachycardia indicate regarding heart rate?
What does tachycardia indicate regarding heart rate?
Which structure has a conduction velocity of 4.0 m/Sec?
Which structure has a conduction velocity of 4.0 m/Sec?
Which component of the ECG tracing signifies ventricular depolarization?
Which component of the ECG tracing signifies ventricular depolarization?
What is the average stroke volume (SV) for a healthy adult?
What is the average stroke volume (SV) for a healthy adult?
Which of the following conditions could lead to bradycardia?
Which of the following conditions could lead to bradycardia?
What characterizes cardiac output (CO)?
What characterizes cardiac output (CO)?
Study Notes
Heart - Functional Syncytium
- Heart is a functional syncytium due to the presence of gap junctions and the fast-conducting system between atria & ventricles.
Origin and Spread of Cardiac Impulse
- The SA node is the pacemaker of the heart.
Pacemaker Activity
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SA node has the fastest rate of action potential discharge (70-80/min).
-
AV node has a slower discharge rate (40-60/min).
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Bundle of His and Purkinje fibers have even slower discharge rates (20-40/min).
Conduction Velocity
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Purkinje fibers have the fastest conduction velocity (4.0 m/s).
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Bundle of His has a moderate conduction velocity (0.3 - 1 m/s).
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Nodal fibers have the slowest conduction velocity (0.02 - 0.1 m/s).
AV Nodal Delay
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The impulse is delayed in the AV node for 0.1 seconds, allowing the atria to contract completely before the impulse reaches the ventricles.
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The delay ensures that the ventricles fill completely before contraction.
Purkinje Fibers
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Purkinje fibers are the fastest conducting cells in the heart.
-
This ensures rapid and simultaneous excitation of both ventricles.
ECG (Electrocardiogram)
- ECG records the electrical activity of the heart.
- The P wave represents atrial depolarization.
- The QRS complex represents ventricular depolarization.
- The T wave represents ventricular repolarization.
Cardiac Rhythm
- An abnormal heart rhythm is known as arrhythmia.
Cardiac Output (CO)
- CO is the volume of blood pumped by each ventricle per minute.
- CO = HR x SV (Heart Rate x Stroke Volume)
Stroke Volume (SV)
- SV is the volume of blood ejected from the ventricle per heartbeat.
- SV = EDV (End Diastolic Volume) - ESV (End Systolic Volume)
Factors Regulating Heart Rate
- Factors Increasing Heart Rate:
- Sympathetic stimulation
- Epinephrine release
- Increased body temperature
- Anxiety
- Young children
- Factors Decreasing Heart Rate:
- Parasympathetic stimulation
- Decreased body temperature
- Advanced age
- Rest (parasympathetic dominance)
Factors Regulating Stroke Volume
- Intrinsic Control (Venous Return): Increased venous return leads to increased stroke volume (Frank-Starling law).
- Extrinsic Control (Autonomic Nervous System): Sympathetic stimulation increases the force of contraction.
Frank-Starling's Law of the Heart
- Increased venous return to the heart stretches the heart muscle fibers.
- Increased stretch leads to increased force of contraction.
- This results in an increased stroke volume.
Autonomic Regulation
- The autonomic nervous system does not initiate the heartbeat.
- The SA node does this spontaneously but is modulated by the autonomic nervous system.
Sympathetic Regulation
- Increases heart rate and stroke volume.
- Increases cardiac output.
- Causes vasoconstriction.
Parasympathetic Regulation
- Decreases heart rate.
- Decreases stroke volume.
- Decreases cardiac output.
Blood Pressure Control
- Short-term (within seconds): Baroreceptor reflex (adjusts CO and TPR).
- Long-term (minutes-days): Renal compensation (adjusts urine output).
Hypertension
- High blood pressure (BP > 140/90 mmHg).
- Primary (Essential) Hypertension: Cause unknown.
- Secondary Hypertension: Caused by another factor.
Hypotension
- Low blood pressure (BP < 100/60 mmHg).
Heart Failure
- Inability of the heart to supply adequate blood flow to tissues and organs.
- Causes fatigue, shortness of breath, and decreased exercise capacity.
- Can lead to organ dysfunction.
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Description
Explore the intricate functioning of the heart's conduction system in this quiz. Learn about the role of the SA node, AV node, and Purkinje fibers in maintaining heart rhythm and conduction velocity. This quiz covers essential concepts related to functional syncytium and pacemaker activity.
