The Cardiovascular System

Practice flashcards reviewing heart anatomy, blood flow pathways, coronary circulation, cardiac cycle phases, electrical conduction, and ECG wave representations based on the lecture notes.

What is the main job of the cardiovascular system?

To propel blood through the body via the heart, blood, and blood vessels, delivering oxygen and nutrients to cells while carrying away waste products.

Where is the heart located in the human body, and what structures are near it?

The heart is in the thoracic cavity, in the mediastinum, between the lungs and slightly left of the body’s midline. The sternum is in front of it, the spine is behind it, the lungs are on both sides, and the diaphragm is below it. The heart it also surrounded by Pericardium, a protective, fluid-filled sac.

What are the two top chambers of the heart and what blood do they receive?

The Right Atrium receives deoxygenated blood from the body and coronary circulation, and the Left Atrium receives oxygenated blood from the lungs.

What are the two bottom chambers of the heart and where do they push blood?

The Right Ventricle pushes deoxygenated blood toward the lungs, and the Left Ventricle pushes oxygenated blood toward the body.

Why is the left ventricle wall 3x thicker than the right ventricle wall?

The left ventricle has a thicker wall because it pumps blood to the whole body and needs more pressure. The right ventricle only pumps blood to the lungs, so it needs less pressure.

Which valves make up the Atrioventricular (AV) valves and Semilunar valves?

AV valves include the Tricuspid Valve and Bicuspid/Mitral Valve; Semilunar valves include the Pulmonary Valve and Aortic Valve.

What is the function of the four heart valves?

The valves keep blood flowing in one direction. Pressure causes the valves to open and close, preventing blood from flowing backward.

How are the base and apex of the heart defined?

The Base is the largest part, mostly formed from both atria; the Apex is the pointy area made from the left ventricle.

What is the pathway of blood flow through the right side of the heart to the lungs?

Oxgen-poor Blood:

Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve (AV Valve) → Right Ventricle → Pulmonary Valve (Semilunar Valve) → Pulmonary Trunk → Pulmonary Arteries → Lungs

What is the pathway of blood flow from the lungs through the left side of the heart to the body?

Oxygen-rich Blood:

Lungs → Pulmonary Veins → Left Atrium → Mitral Valve (AV Valve) → Left Ventricle → Aortic Valve (Semilunar Valve) → Aorta → Body

What muscular walls separate the chambers of the heart?

The Interatrial Septum separates the two atria, and the Interventricular Septum separates the two ventricles.

What is the functional difference between arteries and veins?

Arteries carry blood away from the heart, whereas veins carry blood toward the heart.

Which main veins bring deoxygenated blood to the right atrium?

The Superior Vena Cava (from the head, neck, and upper extremities) and Inferior Vena Cava (from the trunk and lower body).

What is the role of the coronary system?

To supply oxygenated blood and nutrients directly to the heart muscle (myocardium) and carry away waste products like CO₂ (carbon dioxide).

When do the coronary arteries receive blood?

During diastole, blood enters the coronary arteries through openings in the aorta just above the aortic valve.

Where does deoxygenated blood from the coronary system empty?

It flows to the Large Coronary Vein, then to the Coronary Sinus, which empties it into the Right Atrium.

Where do the Pulmonary circuits and Systemic circuits begin, and what is the difference between them?

Both begin in the ventricles:

Pulmonary circuit → begins at the right ventricle and sends blood to the lungs (low pressure).
Systemic circuit → begins at the left ventricle and sends blood to the body (high pressure).

What serous membrane surrounds the heart?

The serous membrane surrounding the heart is the Pericardium.

Fibrous pericardium = tough outer layer

Parietal pericardium = lines inside of fibrous pericardium

Pericardial cavity = space containing fluid

Visceral pericardium (epicardium) = directly covers heart

What three layers make up the heart wall?

The Epicardium (outermost layer), Myocardium (middle muscular layer; contracts/pumps blood), and Endocardium (innermost layer).

What is the role of the pericardium and pericardial fluid?

The Pericardium is a sac enclosing the heart that releases pericardial fluid to lubricate and reduce friction between layers.

What do pacemaker cells and cardiac muscle cells do?

Pacemaker (nodal) cells → Create the electrical impulses that start the heartbeat.

Cardiac muscle (contractile) cells → Receive those electrical impulses and contract, which pumps the blood.

What is the SA node, where is it located, and what is its impulse rate?

The Sinoatrial Node (SA node) is the primary pacemaker located in the right atrium that generates impulses at 60–100 BPM.

What function does the AV node serve if the SA node fails?

The Atrioventricular Node (AV node) acts as a secondary pacemaker, generating 40–60 BPM to keep blood flowing and sustain life.

What is the pathway of an electrical impulse through the conduction system?

SA Node → Atria → AV Node → Bundle of His (AV Bundle) → Right & Left Bundle Branches → Purkinje Fibers

Why is the electrical impulse briefly delayed at the AV node?

To give the ventricles enough time to fill completely with blood before contracting.

What constitutes one cardiac cycle and how long does it take?

One complete cycle of systole and diastole, representing 1 heartbeat, which takes an average of 0.8 seconds.

What happens during Systole and Diastole in the cardiac cycle?

Systole → Both ventricles CONTRACT, pushing blood into the Pulmonary Artery and Aorta. (Semilunar Valves OPEN)

Diastole → Both ventricles RELAX, allowing blood to flow from the Atria into the Ventricles. (AV valves OPEN)

What causes the “Lub” and “Dub” heart sounds?

“Lub” is the sound of the AV Valves closing, and “Dub” is the sound of the Semilunar Valves closing.

What are bradycardia and tachycardia? How is heart rate calculated?

Bradycardia = Slow heart rate below 60 bpm
Tachycardia = Fast heart rate above 100 bpm

Calculation: Heart rate (bpm) = number of beats ÷ time (seconds) × 60

What do the P wave, QRS complex, and T wave represent on an ECG?

P Wave = Atrial Depolarization
QRS Complex = Ventricular Depolarization
T Wave = Ventricular Repolarization

Abnormal ECG waves or rhythms can show Arrhythmias (abnormal heart rhythms).

Why does atrial repolarization not appear as a distinct wave on an ECG?

Because it occurs at the same time as ventricular depolarization, so the much larger QRS complex covers it up.

How do the electrical events on an ECG relate to heart contraction and relaxation?

P wave → Atria depolarize, then contract.
QRS complex → Ventricles depolarize, then contract.
T wave → Ventricles repolarize, then relax.

What do systolic and diastolic blood pressure measure?

Systolic → Measures arterial pressure during ventricular contraction (higher number).

Diastolic → Measures arterial pressure during ventricular relaxation (lower number).

What does a typical cardiac muscle cell look like? Does it need a nervous signal to contract?

Cardiac muscle cells are short, branched, striated, and connected by intercalated discs. They do not need a nervous signal to start each heartbeat.

What is the function of intercalated discs and gap junctions in cardiac muscle?

Intercalated Discs = Connect cardiac muscle cells together.

Gap Junctions = Allow electrical signals to quickly pass from one cardiac muscle cell to the next.

What is the difference between pacemaker cells and contractile cardiac muscle cells? Which are more common?

Pacemaker cells create electrical signals. Contractile cells receive nearby signals and contract/pump blood. The heart has more contractile cells (99%).

How is an action potential generated in a pacemaker cell?

1. Na⁺ slowly enters the cell, causing automatic depolarization.

2. Ca²⁺ enters and causes rapid depolarization.

3. K⁺ leaves the cell, causing repolarization.

How is an action potential generated in a contractile cardiac muscle cell?

1. Na⁺ enters the cell, causing depolarization.

2. Ca²⁺ enters, creating the plateau phase and helping contraction.

3. K⁺ leaves the cell, causing repolarization.

How is a contractile-cell action potential different from a pacemaker-cell action potential?

Pacemaker cells create their own electrical signals. Contractile cells receive a nearby signal that causes them to depolarize and contract.

What is the refractory period, and why is it important in cardiac muscle?

It is the time when a cardiac cell cannot immediately contract again. It is longer than in skeletal muscle, allows the heart to relax and refill with blood, and prevents sustained contraction (tetanus).

What are the four phases of the cardiac cycle, and which valves are open or closed?

1. Ventricular Filling → Blood flows from the Atria into the Ventricles.
   (AV valves OPEN)

2. Isovolumetric Contraction → Ventricles begin contracting and pressure rises, but no blood leaves yet.
   (ALL valves CLOSED)

3. Ventricular Ejection → Ventricles push blood into the Pulmonary Trunk and Aorta.
   (Semilunar valves OPEN)

4. Isovolumetric Relaxation → Ventricles relax and pressure falls, but they are not filling yet.
   (ALL valves CLOSED)

What is stroke volume and how is it calculated?

Stroke volume is the amount of blood pumped by one ventricle per heartbeat.

EDV = Bood in the ventricle before contraction
ESV = Blood left after contraction

Calculation: SV = EDV − ESV

What three factors affect stroke volume?

Preload, Contractility, and Afterload.

More Preload → ↑ SV (increases)

More Contractility → ↑ SV (increases)

More Afterload → ↓ SV (decreases)

How does the autonomic nervous system affect heart rate?

Sympathetic stimulation increases heart rate. Parasympathetic stimulation decreases heart rate.

Sympathetic = Speeds up
Parasympathetic = Slows down