Cardiovascular System Overview and Functionality

Superior vena cava

Major vein returning deoxygenated blood to heart.

Right atrium

Receives deoxygenated blood from body.

Tricuspid valve

Valves between right atrium and ventricle.

Right ventricle

Pumps deoxygenated blood to lungs.

Pulmonary semilunar valve

Prevents backflow into right ventricle.

Pulmonary trunk

Carries deoxygenated blood to pulmonary arteries.

Pulmonary arteries

Transport deoxygenated blood to lungs.

Lungs

Site for gas exchange in blood.

Pulmonary veins

Carry oxygenated blood from lungs to heart.

Left atrium

Receives oxygenated blood from pulmonary veins.

Bicuspid valve

Valves between left atrium and ventricle.

Left ventricle

Pumps oxygenated blood to body.

Aortic semilunar valve

Prevents backflow into left ventricle.

Aorta

Major artery delivering oxygenated blood to body.

Vasculature

Network for blood transport and exchange.

Arteries

Carry blood away from the heart.

Veins

Bring blood back to the heart.

Capillaries

Tiny vessels for gas and nutrient exchange.

Diffusion

Movement of substances following concentration gradients.

Blood volume

Humans have about 5 liters of blood.

Double pump

Heart structure with two atria and two ventricles.

Pulmonary circuit

Pathway from heart to lungs and back.

Systemic circuit

Pathway delivering blood throughout the body.

Heart valves

Prevent backflow; ensure unidirectional blood flow.

Right ventricle function

Pumps blood into pulmonary circulation.

Normal pathway

Artery → capillary → vein blood flow.

Portal system

Artery → capillary → portal vessel → capillary → vein.

Pericardium

Tough outer layer surrounding the heart.

Myocardium

Muscle layer responsible for heart contractions.

Endocardium

Innermost layer lining the heart chambers.

Sinoatrial Node (SA node)

Heart's natural pacemaker located in right atrium.

Atrioventricular node (AV node)

Coordinates contraction between atria and ventricles.

Action potential

Electrical signal triggering muscle contraction.

Purkinje fibers

Conduct impulses to coordinate ventricular contractions.

Bundle branches

Transmit electrical impulses to ventricles.

SA Node

Primary pacemaker generating heart rhythm.

AV Node

Delays electrical signal between atria and ventricles.

Atrioventricular Bundles

Conducts impulses from AV node to ventricles.

Purkinje Fibers

Distributes electrical impulses throughout ventricles.

Contractile Cells

Muscle cells generating force in heart.

Intercalated Disks

Connects adjacent cardiac muscle cells.

Desmosomes

Structures allowing quick electrical signal passage.

Gap Junctions

Facilitates synchronized heart muscle contractions.

Resting Membrane Potential

Stable voltage across cell membrane at rest.

Action Potential

Electrical impulse triggering muscle contraction.

Pacemaker Potential

Unstable resting potential in autorhythmic cells.

Rapid Depolarization Phase

Initial phase of action potential with Na+ influx.

Plateau Phase

Prolonged depolarization due to Ca2+ influx.

Repolarization Phase

Return to resting potential after contraction.

Tetanic Contraction

Sustained muscle contraction; dangerous for heart.

Calcium Ions (Ca2+)

Essential for cardiac muscle contraction.

Voltage-Gated Channels

Regulate ion flow during action potentials.

Apex Muscle Cells

First to contract, pushing blood upward.

Mitochondria

Powerhouse of the cell, abundant in cardiac cells.

Autorhythmic Cells

Generate and conduct electrical impulses autonomously.

Funny Ion Channels

Na+ channels contributing to pacemaker potential.

L-Type Calcium Channels

Open during plateau phase for prolonged contraction.

T-Type Calcium Channels

Transient channels aiding in rapid depolarization.

Ventricular Myofibrils

Contractile fibers in ventricular muscle cells.

Plateau phase

No tetanus occurs during cardiac muscle contraction.

L type voltage gated Ca2+ channels

Channels in conduction fibers for calcium influx.

SA Node

Initiates heartbeat by generating electrical impulses.

AV Node

Receives signal from SA node, activates septum.

Contraction of atria

Atria contract to push blood into ventricles.

Contraction of ventricles

Ventricles contract starting from the apex.

Atrioventricular valves

Valves that close during ventricular contraction.

Electrocardiogram (ECG)

Recording of electrical activity of the heart.

Einthoven's triangle

Triangle formed by limb leads for ECG.

Lead 1

Right arm (-) to left arm (+) configuration.

Lead 2

Right arm (-) to left leg (+) configuration.

Lead 3

Left arm (-) to left leg (+) configuration.

P wave

Represents atrial depolarization in ECG.

QRS complex

Indicates ventricular depolarization and atrial repolarization.

T wave

Represents ventricular repolarization in ECG.

PR interval

Time from atrial depolarization to ventricular depolarization.

PR segment

Time between end of atrial depolarization and ventricular depolarization.

ST segment

Time between end of ventricular depolarization and start of repolarization.

QT interval

Duration from ventricular depolarization to repolarization.

Isoelectric line

Baseline in ECG with no electrical activity.

Systole

Phase of contraction in the cardiac cycle.

Diastole

Phase of relaxation in the cardiac cycle.

Cardiac cycle

Sequence of events in one heartbeat.

******* diagram

Graphical representation of cardiac cycle events over time.

Ventricular pressure-volume changes

Changes during different phases of the cardiac cycle.

Ejection fraction

Percentage of blood ejected from ventricles.

Stroke volume (SV)

Volume of blood ejected during ventricular systole.

End diastolic volume (EDV)

Volume in ventricles at end of diastole.

End systolic volume (ESV)

Volume remaining in ventricles after contraction.

Cardiac output (CO)

Volume of blood pumped by each ventricle per minute.

Cardiac Output (CO)

Volume of blood pumped per minute.

Stroke Volume (SV)

Volume of blood ejected per heartbeat.

Heart Rate (HR)

Number of beats per minute.

Parasympathetic System

Reduces heart rate via vagus nerve.

Sympathetic System

Increases heart rate and contractility.

Vagus Nerve

Innervates heart, releases acetylcholine.

Cardiac Nerve

Innervates heart, releases norepinephrine.

Tonic Control

Maintains resting heart rate at 70 bpm.

If Channels

Increase Na+ and Ca2+ permeability.

Frank-Starling Law

SV increases with increased EDV.

Preload

End diastolic volume returning to heart.