Cardiac Physiology

Question 1

What are the four chambers of the heart?

Answer 1

Right atrium (RA)
Right ventricle (RV)
Left atrium (LA)
Left ventricle (LV):

Question 2

What are the functions of the right atrium of the heart?

Answer 2

Receives deoxygenated blood from the body via the superior and inferior vena cava.

Question 3

What is the function of the Right ventricle (RV)?

Answer 3

Pumps deoxygenated blood to the lungs for oxygenation via the pulmonary artery.

Question 4

What is the function of the Left atrium (LA)?

Answer 4

Receives oxygenated blood from the lungs via the pulmonary veins

Question 5

What is the function of the Left ventricle (LV)?

Answer 5

Pumps oxygenated blood to the systemic circulation via the aorta.

Question 6

What are the heart valves and their locations?

Answer 6

Tricuspid valve: Between the right atrium and right ventricle.
Pulmonary valve: Between the right ventricle and pulmonary artery.
Mitral (bicuspid) valve: Between the left atrium and left ventricle.
Aortic valve: Between the left ventricle and the aorta.

Question 7

Describe the path of blood through the heart.

Answer 7

1. Deoxygenated blood enters the right atrium via the superior and inferior vena cava.
   
   2. Blood passes through the tricuspid valve into the right ventricle.
   3. The right ventricle pumps blood through the pulmonary valve into the pulmonary artery to the lungs.
   4. Oxygenated blood returns from the lungs to the left atrium via the pulmonary veins.
   5. Blood flows through the mitral valve into the left ventricle.
   6. The left ventricle pumps blood through the aortic valve into the aorta and systemic circulation.

Question 8

What is the cardiac cycle?

Answer 8

refers to the sequence of events that occur during one heartbeat. It is characterized by electrical and mechanical events that ensure proper filling and ejection of blood.

Question 9

What are the Phases of the Cardiac Cycle?

Answer 9

•Systole
•Diastole

Question 10

What is systole?

Answer 10

The contraction phase, during which the ventricles eject blood into the pulmonary and systemic circulations.

Question 11

What is diastole?

Answer 11

The relaxation phase, during which the heart chambers fill with blood.

Question 12

What occurs during the Atrial Systole (Active Filling)?

Answer 12

• The atria contract to fill the ventricles with blood.
• This occurs late in diastole, contributing to about 20% of the ventricular filling.

Question 13

What are the phases within the cardiac cycle?

Answer 13

Atrial Systole (Active Filling)
Isovolumetric Contraction
Ventricular Ejection
Isovolumetric Relaxation
Ventricular Filling (Passive and Active)

Question 14

What happens during Isovolumetric Contraction:?

Answer 14

• The ventricles begin to contract, but the volume remains unchanged because all valves are closed.
• Ventricular pressure rises as blood is prepared to be ejected.

Question 15

What happens during Ventricular Ejection:?

Answer 15

• The ventricular pressure exceeds the pressure in the pulmonary artery and aorta, causing the semilunar valves (pulmonary and aortic) to open.
• Blood is ejected from the ventricles into the pulmonary and systemic circulations.

Question 16

What happens during Isovolumetric Relaxation?

Answer 16

• The ventricles relax, but all valves are closed, preventing blood flow.
• Ventricular pressure decreases while volume remains constant.

Question 17

What happens during Ventricular Ejection:?

Answer 17

• The ventricular pressure exceeds the pressure in the pulmonary artery and aorta, causing the semilunar valves (pulmonary and aortic) to open.
• Blood is ejected from the ventricles into the pulmonary and systemic circulations.

Question 18

What happens during Ventricular Filling (Passive and Active)?

Answer 18

• The AV valves open, and blood flows passively from the atria into the ventricles.
• This is followed by atrial contraction, which further fills the ventricles before the next cycle begins.

Question 19

What are heart sounds produced by?

Answer 19

the closing of heart valves during the cardiac cycle

Question 20

What events are associated with the S1 and S2 heart sounds?

Answer 20

S1: “Lub “Caused by the closure of the AV valves (mitral and tricuspid) at the beginning of ventricular systole.
•S2: “Dub “Caused by the closure of the semilunar valves (aortic and pulmonary) at the end of ventricular systole.

Question 21

What is the electrical system of the heart responsible for?

Answer 21

initiating and coordinating heart contractions.

Question 22

What do the action potentials generated by the electrical system of the heart do?

Answer 22

spread through specialized conductive tissue, ensuring that the heart contracts in a rhythmic and synchronized manner.

Question 23

What causes S3 and in what situations is it abnormal?

Answer 23

S3 is caused by rapid ventricular filling during early diastole and is abnormal in adults, typically indicating heart failure or volume overload.

Question 24

What are the Components of the Conduction System?

Answer 24

Sinoatrial (SA) Node
Atrioventricular (AV) Node
Bundle of His
Right and Left Bundle Branches
Purkinje Fibers

Question 25

What is the Sinoatrial (SA) Node?

Answer 25

The heart’s natural pacemaker, located in the right atrium. It initiates the action potential at a rate of 60-100 beats per minute (bpm)

Question 26

What is the Atrioventricular (AV) Node?

Answer 26

Located at the junction of the atria and ventricles. It delays the signal from the SA node, allowing the ventricles time to fill with blood.

Question 27

What is the function of the Bundle of His?

Answer 27

Conducts the action potential from the AV node to the right and left bundle branches.

Question 28

What is the function of the Right and Left Bundle Branches?

Answer 28

Carry the electrical signal to the right and left ventricles, respectively.

Question 29

Describe the phases of a ventricular myocyte action potential.

Answer 29

1. Phase 0: Rapid Na⁺ influx, leading to depolarization. 2. Phase 1: K⁺ efflux and initial repolarization. 3. Phase 2: Ca²⁺ influx and K⁺ efflux, creating a plateau phase. 4. Phase 3: K⁺ efflux leads to full repolarization. 5. Phase 4: The resting membrane potential is re-established.

Question 30

What is the function of the Purkinje Fibers?

Answer 30

Spread the electrical impulse throughout the ventricles, ensuring a coordinated contraction.

Question 31

Describe the conduction pathway of the heart.

Answer 31

1. SA node initiates the action potential. 2. The signal spreads across the atria to the AV node. 3. The AV node delays the signal slightly to allow atrial contraction. 4. The signal moves through the Bundle of His. 5. The signal travels along the right and left bundle branches. 6. The signal reaches the Purkinje fibers, which distribute it through the ventricles.

Question 33

Describe the pacemaker action potential in the SA node.

Answer 33

1. Phase 4: Slow, spontaneous Na⁺ influx (funny current, If) leads to gradual depolarization. 2. Phase 0: Ca²⁺ influx leads to rapid depolarization. 3. Phase 3: K⁺ efflux causes repolarization.

Question 34

What is cardiac output (CO), and how is it calculated?

Answer 34

O is the amount of blood the heart pumps per minute. • CO = Stroke Volume (SV) × Heart Rate (HR)

Question 35

What is stroke volume?

Answer 35

is the amount of blood ejected by the ventricles per heartbeat

Question 36

What is stroke volume influenced by?

Answer 36

Preload ,Afterload and Contractility

Question 37

What is Preload?

Answer 37

The volume of blood in the ventricles at the end of diastole.

Question 38

What is Afterload?

Answer 38

The resistance the heart must overcome to eject blood.

Question 39

What is Contractility?

Answer 39

The intrinsic ability of the heart muscle to contract, which is influenced by sympathetic stimulation and calcium availability.

Question 40

The heart muscle (myocardium) requires a constant supply of oxygen and nutrients, which is provided by ?

Answer 40

The coronary arteries.

Question 41

Where do the coronary arteries arise from?

Answer 41

arise from the base of the aorta and branch to supply the myocardium with blood

Question 42

What is ejection fraction (EF), and what is the normal range?

Answer 42

EF is the percentage of blood ejected from the left ventricle with each contraction EF = Stroke Volume (SV) / End-Diastolic Volume (EDV) •Normal EF is 55-70%.

Question 43

When does coronary blood flow occur?

Answer 43

Coronary blood flow predominantly occurs during diastole, when the ventricles are relaxed and the coronary arteries are not compressed.

Question 44

How is coronary blood flow regulated?

Answer 44

It is regulated by factors such as vascular resistance, pressure changes during the cardiac cycle, and metabolic demand for oxygen.

Question 45

What is the significance of S4 heart sound

Answer 45

S4 is caused by atrial contraction against a stiff, non-compliant ventricle and is often associated with conditions such as left ventricular hypertrophy or diastolic dysfunction.

Question 46

The heart rate and contractility are regulated by?

Answer 46

the autonomic nervous system and various hormones

Question 47

How does the sympathetic nervous system affect heart function?

Answer 47

The sympathetic nervous system increases heart rate (positive chronotropy), contractility (positive inotropy), and conduction velocity (positive dromotropy) via β1 adrenergic receptors.

Question 48

How does the sympathetic nervous system affect heart function?

Answer 48

The sympathetic nervous system increases heart rate (positive chronotropy), contractility (positive inotropy), and conduction velocity (positive dromotropy) via β1 adrenergic receptors.

Question 49

How does the parasympathetic nervous system affect heart function?

Answer 49

The parasympathetic nervous system decreases heart rate (negative chronotropy) and conduction velocity (negative dromotropy) via muscarinic receptors.

Question 50

How does endocrine control affect heart rate and Contractility?

Answer 50

Hormones such as epinephrine (from the adrenal glands) and thyroid hormones can also influence heart rate and contractility.

Question 51

What is heart failure?

Answer 51

Heart failure is Characterized by a reduction in the heart’s ability to pump blood

Question 52

how does it differ between systolic and diastolic dysfunction?

Answer 52

•Systolic heart failure: Reduced ejection fraction (EF) due to impaired contractility of the heart. •Diastolic heart failure: Normal EF, but impaired ventricular filling due to stiff or thickened ventricles.

Question 53

What is atrial fibrillation?

Answer 53

an arrhythmia characterized by irregular, rapid electrical impulses in the atria, causing inefficient atrial contraction and an irregular ventricular response.

Question 54

What is the difference between first-degree heart block and other degrees of heart block?

Answer 54

First-degree heart block is characterized by a prolonged PR interval (>0.20 seconds) without dropped beats, while second-degree and third-degree blocks involve some degree of conduction failure.

Question 55

What is the pressure-volume loop, and what does it represent?

Answer 55

The pressure-volume (PV) loop represents the relationship between ventricular pressure and volume during one cardiac cycle. It shows phases of isovolumetric contraction, ventricular ejection, isovolumetric relaxation, and ventricular filling.

Question 56

How does preload affect the PV loop?

Answer 56

Increased preload results in an increase in end-diastolic volume (EDV) and a larger stroke volume, causing a wider loop.

Question 57

How does afterload affect the PV loop?

Answer 57

Increased afterload (e.g., higher blood pressure) increases ventricular pressure, leading to a narrower loop as the heart works harder to eject blood.