NUR1112 Heart Anatomy & Physiology

82 Questions

What causes the atrioventricular (AV) valves to open?

Atrial pressure > ventricular pressure

What causes the semilunar (SL) valves to close?

Arterial pressure > ventricular pressure

Heart valves receive oxygen and nutrients from the blood passing through the heart.

False

What does the pulmonary circuit carry oxygen-poor blood to?

lungs

Which artery supplies oxygenated blood to the anterior ventricles?

Left coronary artery

What is the primary function of the aortic semilunar valve?

To deliver oxygen-rich blood to the body

Coronary sinus empties into the __ atrium.

right

During ventricular systole, the atria are in a state of relaxation.

True

Phase 3 of the cardiac cycle is known as ventricular diastole (early)–______ relaxation.

isovolumetric

What is the typical length of the heart?

12-14 cm

What is the typical weight range of the heart?

250-350 grams

Where is the heart typically located?

In the thoracic cavity

The heart is a single pump organ.

False

The ___________ collects blood from the pulmonary circuit and empties it into the left ventricle.

left atrium

Match the following components of the heart wall with their descriptions:

Epicardium = Outermost layer of epithelial tissue Myocardium = Middle layer of cardiac muscle cells Endocardium = Inner layer of endothelial cells

During isovolumetric relaxation, what is the state of the AV valves?

Closed

What initiates the mechanical activity of the heart?

Electrical activity (action potential in myocardial cells)

The autonomic nervous system is part of the extrinsic innervation that controls myocardial activity.

True

The ____ node depolarizes approximately 100 times per minute.

sinoatrial

What is bradycardia?

Bradycardia is a condition in which the heart rate is slower than normal.

What is tachycardia?

Tachycardia is a condition in which the heart rate is faster than normal.

What are some factors that affect heart rate?

All of the above

Thyroxine (T4) is released from the adrenal medulla and __ HR.

increases

What determines the heart rate in a healthy individual?

SA node

What is the function of the Atrioventricular node?

Delays depolarization during atrial contraction

The heart will stop beating if separated from the body, even if supplied with oxygen.

False

Cardiac output is calculated as stroke volume x ____?

heart rate

Match the factor affecting End Diastolic Volume (EDV) with its description:

Venous return = Amount of blood returning to the heart Passive filling time = Time both the atria and ventricles are in diastole Total blood volume = Determines the amount of venous return

What is the typical length of the heart?

12-14 cm

How much does the heart typically weigh?

250-350 grams

What is the position of the heart apex typically located in?

5th intercostal space

The myocardium is the inner layer of the heart wall.

False

What is the outermost layer of the heart wall called?

Epicardium

What causes the atrioventricular (AV) valves to open?

Pressure of incoming blood

AV valves close when atrial pressure is greater than ventricular pressure. (True/False)

False

What causes the semilunar valves to close?

Arterial pressure greater than ventricular pressure

Coronary circulation ensures the myocardium has its own blood supply because it does not receive oxygen or nutrients from the _____ that passes through the heart.

blood

What phase of the cardiac cycle involves passive filling until atrial systole which completes ventricular filling?

Ventricular and atrial diastole

What is the purpose of the intrinsic conduction system in the heart?

Generating action potentials in the myocardial cells

During ventricular diastole (mid-late), the __________ continue to relax, and the ventricular pressure drops below atrial pressure.

ventricles

T/F: A heart murmur is produced by the closure of the semilunar valves.

False

What is the purpose of the pulmonary circuit?

To oxygenate blood by carrying oxygen-poor blood to the lungs and oxygen-rich blood to the heart.

Which heart valve is responsible for preventing blood backflow into the left ventricle?

Mitral valve

During ventricular systole, the AV valves are open and the SL valves are closed.

True

Ventricular filling occurs during ____-to-late diastole.

mid

Match the phase of the cardiac cycle with its description:

Ventricular filling = Mid-to-late diastole Atrial contraction = Systole Isovolumetric contraction = No change in ventricular blood volume Ventricular ejection = Blood forced into aorta and pulmonary trunk

What is the main function of the SA node in the heart?

Acts as pacemaker and determines heart rate.

Which node becomes the pacemaker if the SA node is damaged?

Atrioventricular node

The bundle branches are the only electrical connection between the atria and ventricles.

True

Cardiac output is calculated by multiplying stroke volume by ___________.

heart rate

What is bradycardia?

Bradycardia is a condition in which the heart rate is slower than normal.

What is tachycardia?

Tachycardia indicates a heart rate that is faster-than-normal.

Increasing body temperature leads to a decrease in heart rate.

False

Which hormones affect heart rate?

Thyroxine

Body temperature and _______ affect heart rate.

plasma electrolytes

What is the typical weight range of the heart?

250-350 grams

Where does the heart sit in the body?

In the mediastinum

The heart is typically the size of ____________. (Fill in the blank)

your fist

Match the heart coverings with their descriptions:

Parietal pericardium = Outer fibrous tissue Epithelial layer = Inner epithelial tissue Epicardium = Outermost layer of epithelial tissue

What is the purpose of the pulmonary circuit?

To oxygenate oxygen-poor blood by carrying it to the lungs.

What is the main function of atrial systole during the cardiac cycle?

To fill the ventricles with blood

What is the function of atrioventricular (AV) valves?

To prevent backflow of blood from the ventricles to the atria

During ventricular systole, the AV valves are closed.

True

When do semi-lunar valves close?

When arterial pressure is higher than ventricular pressure

In Phase 2b of the cardiac cycle, ventricular ejection occurs when ventricular pressure increases above _______ pressure.

arterial

Is it true that coronary circulation provides oxygen and nutrients to the myocardium?

True

Coronary sinus empties into the ________.

right atrium

Match the following heart valves with their corresponding location/function:

Aortic valve = Left ventricle Mitral valve = Left atrium Tricuspid valve = Right ventricle Pulmonary semilunar valve = Right ventricle

What is the term for the phase in which ventricles relax and ventricular pressure drops below atrial pressure?

Ventricular diastole

What causes the 'lubb' sound in the heartbeat?

Closure of the AV valves

The intrinsic conduction system of the heart stimulates its own contractions.

True

The myocardial activity is controlled by two separate electrical systems: the intrinsic conduction system and ________ innervation.

extrinsic

What is the role of the SA node in the heart?

Acts as pacemaker and determines heart rate (sinus rhythm)

What is the function of the atrioventricular node?

At the junction between the atria and ventricles, delays depolarization for 0.1s while atria complete contraction

What happens if the bundle of His is damaged?

SA node becomes the pacemaker

The Purkinje fibers penetrate ventricle walls and depolarize ventricular myocardium.

True

Cardiac output is calculated by multiplying stroke volume by __________.

heart rate

What is bradycardia?

Bradycardia is a condition in which the heart rate is slower than normal.

What factors affect heart rate?

All of the above

Increased body temperature leads to a decreased heart rate.

False

Thyroxine (T4) and thyroid hormones affect heart rate by increasing cellular metabolism, leading to an increase in heart rate.

thyroxine

Match the following factors affecting heart rate:

Adrenalin and noradrenalin = Released from the adrenal medulla, increase heart rate Thyroxine (T4) and thyroid hormones = Increase cellular metabolism, increase heart rate Increased temperature = Increases heart rate Plasma electrolytes = Affect heart rate based on electrolyte levels

Study Notes

Heart Anatomy and Physiology

The heart is a double pump that simultaneously supplies both the pulmonary and systemic circuits.
The cardiac structure facilitates function, enabling one-way blood flow through the heart.

Cardiac Cycle

The cardiac cycle is a series of continually repeated mechanical (muscle contraction) events.
The cardiac cycle is essential for understanding the anatomy and physiology of the heart.

Anatomy of the Heart

The heart is a cone-shaped, muscular organ that is approximately 12-14 cm long, 9 cm wide, and weighs 250-350 grams.
The heart is located in the mediastinum, which is the cavity between the two pleural cavities, and rests on the superior surface of the diaphragm.
The heart sits posterior to the sternum and anterior to the vertebral column.

Coverings of the Heart

The heart has three layers of coverings: the epicardium (or visceral pericardium), the myocardium, and the endocardium.
The epicardium is the outermost layer of epithelial tissue, the myocardium is the middle layer of cardiac muscle cells, and the endocardium is the inner layer of endothelial cells.

Components of the Heart Wall

The heart wall consists of three components: the epicardium, the myocardium, and the endocardium.
The epicardium is the outermost layer, the myocardium is the middle layer, and the endocardium is the inner layer.

External Anatomy - Anterior View

The anterior view of the heart shows the ascending aorta, superior vena cava, auricle of the left atrium, and the right and left ventricles.

External Anatomy - Posterior View

The posterior view of the heart shows the aortic arch, left pulmonary artery, left pulmonary veins, and the right and left ventricles.

Internal Anatomy

The internal anatomy of the heart shows the right and left atria, the right and left ventricles, and the atrioventricular valves.

Heart Valves

The heart valves are responsible for ensuring one-way blood flow through the heart.
There are two types of heart valves: atrioventricular (AV) valves and semilunar (SL) valves.

Atrioventricular (AV) Valves

The atrioventricular valves are located between the atria and ventricles and ensure that blood flows from the atria to the ventricles.
The AV valves are closed when the atrial pressure is less than the ventricular pressure.

Semilunar (SL) Valves

The semilunar valves are located between the ventricles and the pulmonary artery and aorta, and ensure that blood flows from the ventricles to the pulmonary artery and aorta.
The SL valves are closed when the arterial pressure is greater than the ventricular pressure.

Coronary Circulation

The coronary circulation is responsible for supplying oxygenated blood to the myocardium.
The coronary arteries arise from the base of the aorta and encircle the heart in the coronary sulcus.
The coronary veins drain deoxygenated blood from the myocardium and empty into the right atrium.

Coronary Artery Disease (CAD)

Coronary artery disease occurs when the coronary arteries become narrowed and hardened, reducing blood flow to the myocardium.
CAD is often caused by atherosclerosis, which is the buildup of fatty plaques in the arteries.

Unidirectional Pathway of Blood Flow

The unidirectional pathway of blood flow through the heart is essential for understanding the anatomy and physiology of the heart.
The pathway of blood flow through the heart is from the superior and inferior vena cavae to the right atrium, then to the tricuspid valve, then to the right ventricle, then to the pulmonary valve, then to the pulmonary artery, then to the lungs, then to the pulmonary veins, then to the left atrium, then to the mitral valve, then to the left ventricle, and finally to the aortic valve and the aorta.### Cardiac Cycle
The cardiac cycle involves alternating periods of contraction and relaxation, producing pressure and blood volume changes in the heart chambers.
Systole is the period of contraction, increasing pressure and forcing blood out of the chambers, while diastole is the period of relaxation, allowing chambers to refill.

Cardiac Cycle Events

The cardiac cycle consists of one complete heartbeat, involving atrial diastole and systole, and ventricular diastole and systole.
The sequence of events includes: relaxation, atrial contraction, ventricular contraction, and relaxation.

Phases of the Cardiac Cycle

The cardiac cycle can be divided into three phases: ventricular filling, ventricular systole, and ventricular diastole.

Phase 1: Ventricular Filling

All four chambers are relaxed, and the AV valves are open, allowing blood to flow directly into the ventricles.
Blood fills the ventricles to 70-80% capacity through passive filling.
Atrial systole occurs, filling the ventricles with blood, and the atrial systole ends, beginning atrial diastole.

Phase 2a: Ventricular Systole – Isovolumetric Contraction

Ventricular systole begins, and the ventricles contract, increasing pressure and closing the AV valves.
The ventricular pressure is not yet great enough to open the SL valves, resulting in isovolumetric contraction.

Phase 2b: Ventricular Systole – Ventricular Ejection

Increasing ventricular contraction increases pressure, opening the SL valves, and blood is ejected into the aorta and pulmonary trunk.
The volume ejected is the stroke volume (SV), and the volume remaining is the end-systolic volume (ESV).

Phase 3: Ventricular Diastole (Early) – Isovolumetric Relaxation

Ventricular diastole begins, and the ventricles relax, decreasing pressure, and the SL valves close.
Isovolumetric relaxation occurs, and the AV valves remain closed, preventing blood from flowing into the ventricles.
The ventricular pressure drops below arterial pressure, and the SL valves close, producing the heart sound S2.### Ventricular Diastole
During mid-late ventricular diastole, ventricles continue to relax, and pressure drops below atrial pressure, causing AV valves to open and allow blood to flow from atria to ventricles.
This phase is known as passive ventricular filling (Phase 1).
The cardiac cycle consists of four phases: atrial systole, ventricular systole, ventricular diastole, and atrial diastole.

Heart Sounds

Heartbeat is characterized by the "lubb-dubb" sound, corresponding to S1 and S2 heart sounds, which occur when AV valves and SL valves close, respectively.
There are four heart sounds (S1-S4), with S1 and S2 being the most prominent.
Heart murmurs occur when blood backflows through an incompetent valve, producing a swishing sound.

Phases of the Cardiac Cycle

Phase 1: Atrial and ventricular diastole, during which AV valves open, allowing blood to flow from atria to ventricles.
Phase 2a: Ventricular systole, during which ventricles contract, pushing blood up and closing AV valves (heart sound S1).
Phase 2b: Ventricular systole, during which SL valves open, and blood is ejected into the aorta and pulmonary trunk.
Phase 3: Ventricular diastole, during which ventricular pressure drops, and SL valves close (heart sound S2).

Innervation of the Heart

The heart has two electrical systems: intrinsic conduction system (myocardium) and extrinsic innervation (autonomic nervous system).
Intrinsic conduction system:
- Sinoatrial node (SA node) acts as the pacemaker, setting the heart rate.
- Atrioventricular node (AV node) delays depolarization for 0.1 seconds.
- Atrioventricular bundle (Bundle of His) connects atria and ventricles.
- Bundle branches and Purkinje fibers conduct depolarization to ventricular myocardium.
Extrinsic innervation:
- Autonomic nervous system modifies myocardial activity.
- Cardioacceleratory center increases heart rate and force of contraction.
- Cardioinhibitory center decreases heart rate.

Cardiac Output

Cardiac output (CO) is the volume of blood pumped by the left ventricle in one minute.
CO = stroke volume (SV) x heart rate (HR)
Factors that determine SV and thus CO:
- Heart rate
- Stroke volume (EDV - ESV)
- End-diastolic volume (EDV) and end-systolic volume (ESV)
- Venous return
- Passive filling time
- Contractility
- Plasma electrolytes
- Sympathetic nervous system

Heart Anatomy and Physiology

The heart is a double pump that simultaneously supplies both the pulmonary and systemic circuits.
The cardiac structure facilitates function, enabling one-way blood flow through the heart.

Cardiac Cycle

The cardiac cycle is a series of continually repeated mechanical (muscle contraction) events.
The cardiac cycle is essential for understanding the anatomy and physiology of the heart.

Anatomy of the Heart

The heart is a cone-shaped, muscular organ that is approximately 12-14 cm long, 9 cm wide, and weighs 250-350 grams.
The heart is located in the mediastinum, which is the cavity between the two pleural cavities, and rests on the superior surface of the diaphragm.
The heart sits posterior to the sternum and anterior to the vertebral column.

Coverings of the Heart

The heart has three layers of coverings: the epicardium (or visceral pericardium), the myocardium, and the endocardium.
The epicardium is the outermost layer of epithelial tissue, the myocardium is the middle layer of cardiac muscle cells, and the endocardium is the inner layer of endothelial cells.

Components of the Heart Wall

The heart wall consists of three components: the epicardium, the myocardium, and the endocardium.
The epicardium is the outermost layer, the myocardium is the middle layer, and the endocardium is the inner layer.

External Anatomy - Anterior View

The anterior view of the heart shows the ascending aorta, superior vena cava, auricle of the left atrium, and the right and left ventricles.

External Anatomy - Posterior View

The posterior view of the heart shows the aortic arch, left pulmonary artery, left pulmonary veins, and the right and left ventricles.

Internal Anatomy

The internal anatomy of the heart shows the right and left atria, the right and left ventricles, and the atrioventricular valves.

Heart Valves

The heart valves are responsible for ensuring one-way blood flow through the heart.
There are two types of heart valves: atrioventricular (AV) valves and semilunar (SL) valves.

Atrioventricular (AV) Valves

The atrioventricular valves are located between the atria and ventricles and ensure that blood flows from the atria to the ventricles.
The AV valves are closed when the atrial pressure is less than the ventricular pressure.

Semilunar (SL) Valves

The semilunar valves are located between the ventricles and the pulmonary artery and aorta, and ensure that blood flows from the ventricles to the pulmonary artery and aorta.
The SL valves are closed when the arterial pressure is greater than the ventricular pressure.

Coronary Circulation

The coronary circulation is responsible for supplying oxygenated blood to the myocardium.
The coronary arteries arise from the base of the aorta and encircle the heart in the coronary sulcus.
The coronary veins drain deoxygenated blood from the myocardium and empty into the right atrium.

Coronary Artery Disease (CAD)

Coronary artery disease occurs when the coronary arteries become narrowed and hardened, reducing blood flow to the myocardium.
CAD is often caused by atherosclerosis, which is the buildup of fatty plaques in the arteries.

Unidirectional Pathway of Blood Flow

The unidirectional pathway of blood flow through the heart is essential for understanding the anatomy and physiology of the heart.
The pathway of blood flow through the heart is from the superior and inferior vena cavae to the right atrium, then to the tricuspid valve, then to the right ventricle, then to the pulmonary valve, then to the pulmonary artery, then to the lungs, then to the pulmonary veins, then to the left atrium, then to the mitral valve, then to the left ventricle, and finally to the aortic valve and the aorta.### Cardiac Cycle
The cardiac cycle involves alternating periods of contraction and relaxation, producing pressure and blood volume changes in the heart chambers.
Systole is the period of contraction, increasing pressure and forcing blood out of the chambers, while diastole is the period of relaxation, allowing chambers to refill.

Cardiac Cycle Events

The cardiac cycle consists of one complete heartbeat, involving atrial diastole and systole, and ventricular diastole and systole.
The sequence of events includes: relaxation, atrial contraction, ventricular contraction, and relaxation.

Phases of the Cardiac Cycle

The cardiac cycle can be divided into three phases: ventricular filling, ventricular systole, and ventricular diastole.

Phase 1: Ventricular Filling

All four chambers are relaxed, and the AV valves are open, allowing blood to flow directly into the ventricles.
Blood fills the ventricles to 70-80% capacity through passive filling.
Atrial systole occurs, filling the ventricles with blood, and the atrial systole ends, beginning atrial diastole.

Phase 2a: Ventricular Systole – Isovolumetric Contraction

Ventricular systole begins, and the ventricles contract, increasing pressure and closing the AV valves.
The ventricular pressure is not yet great enough to open the SL valves, resulting in isovolumetric contraction.

Phase 2b: Ventricular Systole – Ventricular Ejection

Increasing ventricular contraction increases pressure, opening the SL valves, and blood is ejected into the aorta and pulmonary trunk.
The volume ejected is the stroke volume (SV), and the volume remaining is the end-systolic volume (ESV).

Phase 3: Ventricular Diastole (Early) – Isovolumetric Relaxation

Ventricular diastole begins, and the ventricles relax, decreasing pressure, and the SL valves close.
Isovolumetric relaxation occurs, and the AV valves remain closed, preventing blood from flowing into the ventricles.
The ventricular pressure drops below arterial pressure, and the SL valves close, producing the heart sound S2.### Ventricular Diastole
During mid-late ventricular diastole, ventricles continue to relax, and pressure drops below atrial pressure, causing AV valves to open and allow blood to flow from atria to ventricles.
This phase is known as passive ventricular filling (Phase 1).
The cardiac cycle consists of four phases: atrial systole, ventricular systole, ventricular diastole, and atrial diastole.

Heart Sounds

Heartbeat is characterized by the "lubb-dubb" sound, corresponding to S1 and S2 heart sounds, which occur when AV valves and SL valves close, respectively.
There are four heart sounds (S1-S4), with S1 and S2 being the most prominent.
Heart murmurs occur when blood backflows through an incompetent valve, producing a swishing sound.

Phases of the Cardiac Cycle

Phase 1: Atrial and ventricular diastole, during which AV valves open, allowing blood to flow from atria to ventricles.
Phase 2a: Ventricular systole, during which ventricles contract, pushing blood up and closing AV valves (heart sound S1).
Phase 2b: Ventricular systole, during which SL valves open, and blood is ejected into the aorta and pulmonary trunk.
Phase 3: Ventricular diastole, during which ventricular pressure drops, and SL valves close (heart sound S2).

Innervation of the Heart

The heart has two electrical systems: intrinsic conduction system (myocardium) and extrinsic innervation (autonomic nervous system).
Intrinsic conduction system:
- Sinoatrial node (SA node) acts as the pacemaker, setting the heart rate.
- Atrioventricular node (AV node) delays depolarization for 0.1 seconds.
- Atrioventricular bundle (Bundle of His) connects atria and ventricles.
- Bundle branches and Purkinje fibers conduct depolarization to ventricular myocardium.
Extrinsic innervation:
- Autonomic nervous system modifies myocardial activity.
- Cardioacceleratory center increases heart rate and force of contraction.
- Cardioinhibitory center decreases heart rate.

Cardiac Output

Cardiac output (CO) is the volume of blood pumped by the left ventricle in one minute.
CO = stroke volume (SV) x heart rate (HR)
Factors that determine SV and thus CO:
- Heart rate
- Stroke volume (EDV - ESV)
- End-diastolic volume (EDV) and end-systolic volume (ESV)
- Venous return
- Passive filling time
- Contractility
- Plasma electrolytes
- Sympathetic nervous system

Heart Anatomy and Physiology

The heart is a double pump that simultaneously supplies both the pulmonary and systemic circuits.
The cardiac structure facilitates function, enabling one-way blood flow through the heart.

Cardiac Cycle

The cardiac cycle is a series of continually repeated mechanical (muscle contraction) events.
The cardiac cycle is essential for understanding the anatomy and physiology of the heart.

Anatomy of the Heart

The heart is a cone-shaped, muscular organ that is approximately 12-14 cm long, 9 cm wide, and weighs 250-350 grams.
The heart is located in the mediastinum, which is the cavity between the two pleural cavities, and rests on the superior surface of the diaphragm.
The heart sits posterior to the sternum and anterior to the vertebral column.

Coverings of the Heart

The heart has three layers of coverings: the epicardium (or visceral pericardium), the myocardium, and the endocardium.
The epicardium is the outermost layer of epithelial tissue, the myocardium is the middle layer of cardiac muscle cells, and the endocardium is the inner layer of endothelial cells.

Components of the Heart Wall

The heart wall consists of three components: the epicardium, the myocardium, and the endocardium.
The epicardium is the outermost layer, the myocardium is the middle layer, and the endocardium is the inner layer.

External Anatomy - Anterior View

The anterior view of the heart shows the ascending aorta, superior vena cava, auricle of the left atrium, and the right and left ventricles.

External Anatomy - Posterior View

The posterior view of the heart shows the aortic arch, left pulmonary artery, left pulmonary veins, and the right and left ventricles.

Internal Anatomy

The internal anatomy of the heart shows the right and left atria, the right and left ventricles, and the atrioventricular valves.

Heart Valves

The heart valves are responsible for ensuring one-way blood flow through the heart.
There are two types of heart valves: atrioventricular (AV) valves and semilunar (SL) valves.

Atrioventricular (AV) Valves

The atrioventricular valves are located between the atria and ventricles and ensure that blood flows from the atria to the ventricles.
The AV valves are closed when the atrial pressure is less than the ventricular pressure.

Semilunar (SL) Valves

The semilunar valves are located between the ventricles and the pulmonary artery and aorta, and ensure that blood flows from the ventricles to the pulmonary artery and aorta.
The SL valves are closed when the arterial pressure is greater than the ventricular pressure.

Coronary Circulation

The coronary circulation is responsible for supplying oxygenated blood to the myocardium.
The coronary arteries arise from the base of the aorta and encircle the heart in the coronary sulcus.
The coronary veins drain deoxygenated blood from the myocardium and empty into the right atrium.

Coronary Artery Disease (CAD)

Coronary artery disease occurs when the coronary arteries become narrowed and hardened, reducing blood flow to the myocardium.
CAD is often caused by atherosclerosis, which is the buildup of fatty plaques in the arteries.

Unidirectional Pathway of Blood Flow

The unidirectional pathway of blood flow through the heart is essential for understanding the anatomy and physiology of the heart.
The pathway of blood flow through the heart is from the superior and inferior vena cavae to the right atrium, then to the tricuspid valve, then to the right ventricle, then to the pulmonary valve, then to the pulmonary artery, then to the lungs, then to the pulmonary veins, then to the left atrium, then to the mitral valve, then to the left ventricle, and finally to the aortic valve and the aorta.### Cardiac Cycle
The cardiac cycle involves alternating periods of contraction and relaxation, producing pressure and blood volume changes in the heart chambers.
Systole is the period of contraction, increasing pressure and forcing blood out of the chambers, while diastole is the period of relaxation, allowing chambers to refill.

Cardiac Cycle Events

The cardiac cycle consists of one complete heartbeat, involving atrial diastole and systole, and ventricular diastole and systole.
The sequence of events includes: relaxation, atrial contraction, ventricular contraction, and relaxation.

Phases of the Cardiac Cycle

The cardiac cycle can be divided into three phases: ventricular filling, ventricular systole, and ventricular diastole.

Phase 1: Ventricular Filling

All four chambers are relaxed, and the AV valves are open, allowing blood to flow directly into the ventricles.
Blood fills the ventricles to 70-80% capacity through passive filling.
Atrial systole occurs, filling the ventricles with blood, and the atrial systole ends, beginning atrial diastole.

Phase 2a: Ventricular Systole – Isovolumetric Contraction

Ventricular systole begins, and the ventricles contract, increasing pressure and closing the AV valves.
The ventricular pressure is not yet great enough to open the SL valves, resulting in isovolumetric contraction.

Phase 2b: Ventricular Systole – Ventricular Ejection

Increasing ventricular contraction increases pressure, opening the SL valves, and blood is ejected into the aorta and pulmonary trunk.
The volume ejected is the stroke volume (SV), and the volume remaining is the end-systolic volume (ESV).

Phase 3: Ventricular Diastole (Early) – Isovolumetric Relaxation

Ventricular diastole begins, and the ventricles relax, decreasing pressure, and the SL valves close.
Isovolumetric relaxation occurs, and the AV valves remain closed, preventing blood from flowing into the ventricles.
The ventricular pressure drops below arterial pressure, and the SL valves close, producing the heart sound S2.### Ventricular Diastole
During mid-late ventricular diastole, ventricles continue to relax, and pressure drops below atrial pressure, causing AV valves to open and allow blood to flow from atria to ventricles.
This phase is known as passive ventricular filling (Phase 1).
The cardiac cycle consists of four phases: atrial systole, ventricular systole, ventricular diastole, and atrial diastole.

Heart Sounds

Heartbeat is characterized by the "lubb-dubb" sound, corresponding to S1 and S2 heart sounds, which occur when AV valves and SL valves close, respectively.
There are four heart sounds (S1-S4), with S1 and S2 being the most prominent.
Heart murmurs occur when blood backflows through an incompetent valve, producing a swishing sound.

Phases of the Cardiac Cycle

Phase 1: Atrial and ventricular diastole, during which AV valves open, allowing blood to flow from atria to ventricles.
Phase 2a: Ventricular systole, during which ventricles contract, pushing blood up and closing AV valves (heart sound S1).
Phase 2b: Ventricular systole, during which SL valves open, and blood is ejected into the aorta and pulmonary trunk.
Phase 3: Ventricular diastole, during which ventricular pressure drops, and SL valves close (heart sound S2).

Innervation of the Heart

The heart has two electrical systems: intrinsic conduction system (myocardium) and extrinsic innervation (autonomic nervous system).
Intrinsic conduction system:
- Sinoatrial node (SA node) acts as the pacemaker, setting the heart rate.
- Atrioventricular node (AV node) delays depolarization for 0.1 seconds.
- Atrioventricular bundle (Bundle of His) connects atria and ventricles.
- Bundle branches and Purkinje fibers conduct depolarization to ventricular myocardium.
Extrinsic innervation:
- Autonomic nervous system modifies myocardial activity.
- Cardioacceleratory center increases heart rate and force of contraction.
- Cardioinhibitory center decreases heart rate.

Cardiac Output

Cardiac output (CO) is the volume of blood pumped by the left ventricle in one minute.
CO = stroke volume (SV) x heart rate (HR)
Factors that determine SV and thus CO:
- Heart rate
- Stroke volume (EDV - ESV)
- End-diastolic volume (EDV) and end-systolic volume (ESV)
- Venous return
- Passive filling time
- Contractility
- Plasma electrolytes
- Sympathetic nervous system

This quiz is based on the lecture notes of NUR1112, covering the fundamental skills and knowledge of heart anatomy and physiology for nursing and midwifery practice.

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