Fundamentals to Cardiovascular Pathophysiology

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Questions and Answers

Which chamber of the heart receives deoxygenated blood from the body?

Right Ventricle

Left Ventricle

Right Atrium (correct)

Left Atrium

What is the correct sequence of blood flow from the Right Atrium to the Lungs?

Right Atrium, Right Ventricle, Aortic Valve, Pulmonary Artery

Right Ventricle, Pulmonary Valve, Left Atrium, Pulmonary Vein

Right Atrium, Tricuspid Valve, Right Ventricle, Pulmonary Valve (correct)

Right Atrium, Pulmonary Vein, Left Atrium, Left Ventricle

Which of the following valves is located between the Left Atrium and Left Ventricle?

Mitral (Bicuspid) Valve (correct)

Aortic Valve

Tricuspid Valve

Pulmonary Valve

How many valves are found in the human heart?

4 Signup and view all the answers

Which vessels are considered 'great vessels' of the heart?

Aorta, Superior Vena Cava, Inferior Vena Cava, Pulmonary Arteries, and Pulmonary Veins Signup and view all the answers

What is the primary function of the renin-angiotensin-aldosterone system?

To regulate blood pressure Signup and view all the answers

Which factor does NOT influence cardiac output?

Body Temperature Signup and view all the answers

What is the primary role of the atrioventricular valves?

To prevent backflow of blood into the atria Signup and view all the answers

What is the primary function of the mitral valve?

To control blood flow from the left atrium to the left ventricle Signup and view all the answers

Which electrical impulse structure initiates the heartbeat?

Sinoatrial Node Signup and view all the answers

What occurs in the lungs that changes the blood's composition?

Oxygen is exchanged for Carbon Dioxide Signup and view all the answers

What occurs during the systole phase of the cardiac cycle?

Ventricles contract and pump blood into arteries Signup and view all the answers

Which valve prevents backflow from the right ventricle to the right atrium?

Tricuspid valve Signup and view all the answers

What describes the role of the chordae tendineae in the heart?

To prevent prolapse of the valve cusps into the atria Signup and view all the answers

Which structure acts as the primary pacemaker of the heart?

Sinoatrial (SA) node Signup and view all the answers

During which part of the cardiac cycle do the AV valves close, producing the first heart sound (S1)?

Ventricular systole Signup and view all the answers

What is the layer of the heart wall that is responsible for contractile forces?

Myocardium Signup and view all the answers

Which valves must be closed while the ventricles are contracting to maintain unidirectional blood flow?

Atrioventricular valves only Signup and view all the answers

What function does the pericardial fluid serve?

To reduce friction between the heart and surrounding structures Signup and view all the answers

What is the role of the coronary veins in the cardiovascular system?

To drain deoxygenated blood from the heart muscle Signup and view all the answers

What is the primary function of the SA node in cardiac physiology?

Generating electrical impulses Signup and view all the answers

What does the QRS wave on an ECG represent?

Ventricular contraction Signup and view all the answers

Which of the following factors does NOT affect stroke volume?

Depolarization rate Signup and view all the answers

What is the normal range for the PR interval on an ECG?

0.12-0.20 seconds Signup and view all the answers

What does an increased afterload lead to in terms of cardiac output?

Decreased stroke volume Signup and view all the answers

What cardiac event is primarily measured by the ejection fraction (EF)?

Amount of blood ejected per beat Signup and view all the answers

During which phase of the cardiac cycle does preload mainly occur?

Diastole Signup and view all the answers

How is the cardiac output (CO) calculated?

Heart Rate multiplied by Stroke Volume Signup and view all the answers

What is the role of the Purkinje fibers in the cardiac conduction system?

They assist in the rapid spread of impulses to ventricles Signup and view all the answers

What does the T wave on an electrocardiogram signify?

Repolarization of ventricles Signup and view all the answers

Study Notes

The Cardiac Cycle

The cardiac cycle refers to each ventricular contraction and relaxation.
Diastole is when the muscles are relaxed.
Systole is when the muscles contract.
The five phases of the cardiac cycle include:
- Atrial contraction, pushing blood through the AV valves.
- Ventricular contraction, closing the AV valves (causing the first heart sound, S1).
- Ventricular pressure exceeding arterial pressure, opening the semilunar valves.
- Ventricular pressure falling, closing the semilunar valves (causing the second heart sound, S2).
- Blood flowing from veins into relaxed atria.

Structures that Direct Circulation Through the Heart

Valves of the Heart
- Two atrioventricular (AV) valves open when ventricles are relaxed, allowing blood to flow from higher pressure in the atria to lower pressure in the ventricles.
- Tricuspid: from the right atrium to the right ventricle.
- Mitral: from the left atrium to the left ventricle.
- The semilunar valves of the heart open when pressure in the ventricles exceeds aortic and pulmonary pressures.
- Pulmonary Valve: from the right ventricle to the lungs.
- Aortic Valve: from the left ventricle to the systemic circulation.
- The AV valves close to prevent backflow when ventricles contract.
- The semilunar valves close to prevent backflow after ventricular contraction and ejection.
- Chordae tendineae "heart strings" attach the valve cusps to the papillary muscles. These muscles hold the cusps together and prevent prolapse into the atria.
The Heart Wall
- Three layers: epicardium (outer), myocardium (middle), endocardium (inner).
- Myocardium (thickest layer) contains contractile forces needed for blood flow.
- Pericardium: double-walled sac that encloses the heart wall.
- Pericardial Cavity: fluid-containing space that separates the parietal and visceral pericardium.
- Pericardial Fluid: allows lubrication to decrease friction while the heart beats.
- Functions of the Pericardial Sac
  - Prevents displacement of the heart.
  - Serves as a physical barrier to protect the heart.
  - Contains pain receptors and mechanoreceptors that can affect blood pressure (BP) and heart rate (HR).
Coronary Arteries
- Right Coronary Artery (RCA)
- Left Coronary Artery (LCA)
- Left Anterior Descending (LAD)
- Circumflex Artery
Coronary Veins
- Blood from the arteries drain into the veins alongside them.
- Veins feed into the Great Cardiac Vein and the Coronary Sinus.

The Conduction System

Electrical impulses normally arise in the sinoatrial (SA) node.
Sympathetic (increase HR) and parasympathetic (decrease HR) nerve fibres innervate the SA node.
SA node sets the pace (60-100 bpm) in a healthy, resting adult.
The SA node causes atria to contract.
The impulse moves to the atrioventricular (AV) node.
The vagus nerve innervates the AV node, slowing impulse conduction (40-60 bpm).
The impulse moves to the Bundle of His, which breaks into the right bundle branch and the left bundle branch.
The branches further branch off into Purkinje Fibers.
Purkinje Fibers promote rapid spread of the impulse to the ventricular apexes (contraction).
These fibers conduct at 20-40 bpm.

Cardiac Action Potentials

The movement of ions (Na, K, Ca, Cl) across the cardiac cell membranes causes the electrical activation of the muscle cells known as depolarization.
Deactivation of muscle cells, known as repolarization, occurs in the same way.

The Electrocardiogram (ECG)

A diagnostic test that records all cardiac action potential from myocardial cell activity.
Electrodes placed on the skin interpret waves printed on a strip of paper.

ECG Rhythms

Sinus Rhythm (normal conduction)
- Electrical stimuli are initiated in the SA node, conducted through the AV node and bundle of His, bundle branches, and Purkinje fibers.
- Depolarization and repolarization of the atria and ventricles are shown as 3 distinct waves:
  - P Wave: atrial contraction.
  - QRS Wave: ventricular contraction.
  - T Wave: relaxation of ventricles.
PR Interval: starts with atrial contraction, ends at the beginning of ventricular contraction (0.12-0.20 seconds).
QRS Complex (Duration): ventricular contraction (0.06-0.10 seconds).
ST Segment: starts at the "J point" (end of ventricular contraction), ends right before the T wave (important for diagnosing myocardial infarction).
RR Interval: used to measure regularity of impulses.
QT Interval: total ventricular contraction and relaxation (some medications prolong this and can cause dysrhythmias).

Factors Affecting Cardiac Output

Measured by multiplying Heart Rate (BPM) by Stroke Volume (L/beat).
This is known as Starling's Law.
Factors Affecting Stroke Volume
- Preload (Stretch of Ventricle)
- Afterload (Resistance in Vessels)
- Contractility (Force)
Factors Affecting Hear Rate
- Autonomic Nervous System Activity
- Hormones
- Physical Activity

Preload (Stretch of Ventricle)

Known as the left ventricular end-diastolic pressure.
The amount of stretch on the muscle at the end of diastole.
Greater preload leads to greater volume and stretch, resulting in a "boggy" heart that doesn't eject as effectively (heart failure).
Lower preload results in a heart that works faster and squeezes harder.

Afterload (Resistance in Vessels)

Systemic Vascular Resistance (SVR): amount of resistance the heart must overcome to open the aortic valve and push blood into systemic circulation.
Pulmonary Vascular Resistance (PVR): amount of resistance the heart must overcome to open the pulmonic valve.
Increased Afterload decreases stroke volume (hypertension, aortic/pulmonic stenosis, vasoconstriction).
Decreased Afterload increases stroke volume (vasodilation).

Contractility (Force)

Ability of the myocardium to increase the extent and force of muscle fiber shortening.
Force of contraction depends on:
- Changes in ventricle stretching caused by preload.
- Alterations in the inotropic stimuli of the ventricles.
- Adequacy of myocardial oxygen supply.

Ejection Fraction (EF)

Diagnostic finding obtained by echocardiography.
Measures how much blood is ejected out of the ventricles per beat.
Normal EF is 66-68% for women and 58-60% for men.
Lower EF can indicate the ventricles (usually left) do not pump blood effectively.

Systemic Circulation

Veins → Venules → Capillaries
- Thin-walled, less elastic tissue
- Contain valves that facilitate one-way blood flow toward the heart.
- Contraction of muscles around the veins compresses and assists blood flow.
Arteries → Arterioles → Capillaries
- Elastic or muscular.
- Smooth muscle can contract and relax (vasoconstriction/vasodilation).

Blood Pressure

Systolic Blood Pressure: highest pressure after ventricular contraction.
Diastolic Blood Pressure: lowest pressure during ventricular filling.
Mean Arterial Pressure (MAP): average pressure in the arteries throughout the cardiac cycle (normal range 70-110 mmHg).
If MAP is lower than this, organs are not adequately perfused.
Regulation of BP
- Cardiac Output
- Systemic Vascular Resistance
- Hormones (RAAS)

The Lymphatic System

One-way network of lymphatic vessels and lymph nodes.
Important for:
- Immune function, fluid balance, transport of lipids, hormones, and cytokines.
Lymph consists of water, small amounts of dissolved proteins (albumin), and immune system cells.

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Description

This quiz covers the fundamentals of the cardiac cycle, including the phases of systole and diastole, as well as the structures that direct circulation through the heart such as the AV valves. Test your knowledge on how blood flows through the heart and the important sounds produced during the cardiac cycle.