Cardiovascular System

Primary function

Transport O₂, nutrients, and hormones to tissues; remove CO₂ and metabolic wastes

Major components

Pump = heart, generates pressure

Pipes = arteries, veins, capillaries

Transport medium = blood

Three types of circulation

Pulmonary circulation: right side → lungs → left side

Systemic circulation: left side → body → right side

Coronary circulation: blood supply to the heart itself

Location and size of the heart

Mediastinum, between the lungs, behind the sternum

Roughly the size of a fist; ~250–350 g in adults

Endocardium

Inner lining for chambers and valves; smooth endothelial lining helps minimize friction

Myocardium

Thickest layer composed of contractile cardiac muscle; contains many mitochondria and branched cells connected by intercalated discs and gap junctions

Epicardium

Outer most layer of the heart wall; forms the innermost layer of the serous pericardium

Pericardium

A tough, double-walled sac around the heart filled with pericardial fluid; reduces friction and limits overfilling

What do intercalated discs and gap junctions do in the heart muscle?

Connect cardiac muscle cells and allow electrical coupling (coordinated contraction)

Why is the left ventricular myocardium thicker than the right?

The left ventricle pumps against high systemic resistance; the right ventricle pumps to the low-pressure pulmonary circui

What separates the right and left ventricles?

The interventricular septum

Right atrium: receives from, pumps to, blood type?

Receives from superior/inferior vena cava and coronary sinus

Pumps to right ventricle

Deoxygenated blood

Right ventricle: receives from, pumps to, blood type?

Receives from right atrium

Pumps to pulmonary trunk → pulmonary arteries → lungs

Deoxygenated blood

Left atrium: receives from, pumps to, blood type?

Receives from pulmonary veins

Pumps to left ventricle

Oxygenated blood

Left ventricle: receives from, pumps to, blood type?

Receives from left atrium; pumps to aorta → systemic circulation; oxygenated blood

What are the roles of atria vs ventricles?

Atria are receiving/reservoir chambers; ventricles are pumping chambers

Where does the coronary sinus drain?

Into the right atrium

Tricuspid valve: location and function?

Between the right atrium and and right ventricle; prevents backflow from ventricle to atrium

Pulmonary semilunar valve: location and function?

Between right ventricle and pulmonary trunk; prevents backflow from pulmonary artery to ventricle

Mitral/bicuspid valve: location and function?

Between left atrium and left ventricle; prevents backflow from ventricle to atrium

Aortic semilunar valve: location and function?

Between left ventricle and aorta; prevents backflow from aorta to ventricle

What is the full blood-flow sequence through the heart and body?

SVC/IVC/coronary sinus → RA → tricuspid valve → RV → pulmonary semilunar valve → pulmonary trunk → pulmonary arteries → lungs → pulmonary veins → LA → mitral valve → LV → aortic semilunar valve → aorta → body

What three vessels empty into the right atrium?

Superior vena cava (upper body), inferior vena cava (lower body), and coronary sinus (heart’s own circulation)

What happens once blood is received into the right atrium?

Right atrium contracts, pushing blood through the tricuspid valve into the right ventricle

After receiving blood from the right atrium, what does the right ventricle do?

Right ventricle contracts, forcing blood through the pulmonary semilunar valve into the pulmonary trunk/pulmonary arteries

What happens to the blood once it reaches the lungs?

Gas exchange occurs: CO₂ out, O₂ in

How does oxygenated blood return to the heart?

Pulmonary veins to the left atrium

What does the left atrium do upon receiving oxygenated blood from the lungs?

Left atrium contracts, sending blood through the mitral/bicuspid valve into the left ventricle

What happens once oxygenated blood arrives in the left ventricle?

Left ventricle contracts powerfully, ejecting blood through the aortic semilunar valve into the aorta and then to the body (initiates systemic circulaton)

What drives blood flow through the heart?

Pressure gradients

What is the pathway of the heart’s electrical conduction system?

SA node → AV node → Bundle of His → R & L bundle branches → Purkinje fibers

Sinoatrial (SA) Node: location and function?

Specialized clump of myocardial conducting cells located iin the upper right wall of the atrium, near the entrance of the superior vena cava; the pacemaker of the heart that establishes normal cardiac rhythm

Atrioventricular (AV) Node: location and function?

A second clump of specialized myocardial conductive cells located in the inferior portion of the right atrium within the atrioventricular septum; receives electrical impulses generated from the SA node via internodal pathways

What is the importance of the atrioventricular septum in the heart’s conducting system?

The septum prevents the impulse from spreading directly to the ventricles without passing through the AV node

Bundle of His: location and function?

Arises from the AV node, proceeds through the interventricular septum before dividing into two branches; the primary electrical bridge carrying signals from the AV node to the ventricles

Purkinje fibers: location and function?

Deep inside the heart ventricles branching out from the Bundle of His; transmit cardiac action potentials to contract ventricles and pump blood

What system is activated during stress, fear, or exercise, releasing chemicals that make the heart beat faster and work harder?

Sympathetic nervous system

What system operates mostly though the vagus nerve, releasing signals that slow down the heart and calm cardiovascular activity?

Parasympathetic nervous system

What are the five prominent points on the ECG?

The P wave, the QRS complex, and the T wave

P wave

Small wave that represents the atrial depolarization

QRS complex

Larger wave that represents depolarization of ventricles

T wave

Represents that depolarization of the ventricles

Cardiac cycle

Period of time that begins with contraction of the atria and ends with ventricular relaxation

Systole

Period of contraction that the heart undergoes while it pumps blood into circulation

Diastole

Period of relaxation that occurs as the chambers fill with blood

What are the 3 phases of the cardiac cycle?

Atrial systole/diastole

Ventricular systole

Ventricular diastole

The first “lub” heart sound (S₁)

AV valves closing

The second “dub” heart sound (S₂)

Semilunar valves closing

SV (stroke volume): definition and equation?

The amount of blood ejected by ne ventricle of the heart into the bloodstream during a single cardiac contraction

EDV (end diastolic volume) – ESV (end systolic volume)

CO (cardiac output): definition and equation?

The total volume of blood the heart pumps out of each ventricle in one minute

HR (heart rate) * SV (stroke volume)

Ejection fraction = ?

SV (stroke volume) / EDV (end diastolic volume)

Normal around 55-70%

MAP (mean arterial pressure) ≈ ?

Diastolic pressure + 1/3(systolic pressure – diastolic pressure)

Arteries

Pressure vessels

Arterioles

Resistance vessels; major site of blood flow control

Capillaries

Exchange vessels

Veins

Capacitance vessels, hold about 65% of blood volume

What is one of the body’s short-term regulation strategies?

Pressure sensors in the aortic arch and carotid sinus detect a change in pressure and triggers parasympathetic activity via the vagus nerve

What is one of the body’s long-term regulation strategies?

Kidney uses renin-angiotensin system to regulate blood volume