Understanding Heart Function and Blood Circulation

Heart

Muscular organ that pumps blood throughout the body.

Excitation

Initial electrical impulse triggering heart muscle contraction.

Contraction

Shortening of cardiac muscle cells to pump blood.

Pressure

Force generated by heart contractions driving blood flow.

Flow

Movement of blood through the circulatory system.

Sinoatrial node

Heart's natural pacemaker initiating electrical impulses.

Action potential

Electrical signal causing muscle contraction in the heart.

Atria

Upper chambers of the heart receiving blood.

Atrioventricular node

Node relaying signals from atria to ventricles.

Bundle of His

Pathway for electrical signals from AV node.

Purkinje Fibers

Fibers spreading electrical impulses throughout ventricles.

Apex

Lowest point of the heart where contraction begins.

Electrocardiogram (ECG)

Recording of heart's electrical activity over time.

P-wave

Represents atrial contraction in ECG readings.

QRS complex

Indicates ventricular contraction and atrial relaxation.

T-wave

Shows ventricular relaxation and return to rest.

Isoelectric line

Represents heart's electrical inactivity or relaxation.

Right Atrioventricular valve

Valve allowing blood flow from right atrium to ventricle.

Pulmonary valve

Valve directing blood from right ventricle to lungs.

Coronary circulation

Blood supply specifically for heart muscle tissue.

Systemic circuit

Pathway delivering oxygenated blood to body tissues.

Unidirectional blood flow

Blood moves in one direction due to valves.

Semilunar valves

Valves preventing backflow from arteries to ventricles.

Atrioventricular valves

Valves separating atria from ventricles, ensuring flow.

Chordae Tendineae

Connective cords linking heart valve flaps to muscles.

Papillary Muscle

Cardiac muscle projections stabilizing heart valve flaps.

Atria

Upper heart chambers that receive blood.

Ventricles

Lower heart chambers that pump blood out.

AV Valves

Valves between atria and ventricles, controlling blood flow.

Pressure Gradient

Difference in pressure driving fluid movement.

Bulk Flow

Fluid movement driven by pressure differences.

Heart Sounds

Sounds produced by closing heart valves.

S1 Sound

First heart sound, occurs when AV valves close.

S2 Sound

Second heart sound, occurs when aortic valve closes.

Heart Murmur

Abnormal heart sound indicating potential issues.

Ventricular Pressure

Pressure within ventricles during contraction.

Aortic Pressure

Pressure in the aorta during heart cycles.

Atrial Pressure

Pressure within atria during heart cycles.

Ejection Fraction

Percentage of blood ejected from ventricles.

Cardiac Cycle

Sequence of events in one heartbeat.

QRS Complex

ECG representation of ventricular depolarization.

Isoelectric Line

Period of no electrical activity in heart.

Ventricular Filling

Phase where blood fills ventricles from atria.

Turbulence

Disordered flow causing sound around valve rims.

Connective Tissue Skeleton

Structural support for semilunar valves.

Vena Cava

Large veins returning blood to the heart.

Lumen

Inside space of a hollow organ.

Endocardium

Thin tissue layer separating lumen from myocardium.

Myocardium

Cardiac muscle layer responsible for heart contraction.

Serous cavity

Fluid-filled space allowing heart movement.

Pericardium

Membrane surrounding and protecting the heart.

Coronary circulation

Blood supply circuit for the myocardium.

Coronary vessels

Blood vessels supplying myocardium externally.

Acute myocardial infarction

Rapid tissue death in myocardium due to blood flow loss.

EKG

Electrocardiogram measuring heart's electrical activity.

Junctional Rhythm

Heart rhythm from AV node when SA node fails.

Second-degree heart block

AV node partially blocks SA node impulses.

Ventricular fibrillation

Disorganized electrical activity in ventricles.

Cardiac Output

Volume of blood heart pumps per minute.

Heart rate

Number of heartbeats per minute.

Stroke volume

Volume of blood ejected per heartbeat.

End Diastolic Volume

Blood volume in heart at relaxation's end.

End Systolic Volume

Minimum blood volume in heart after contraction.

Ejection Fraction

Stroke volume divided by end diastolic volume.

Single cardiac cycle

One complete heartbeat or stroke.

Preload

Volume of blood filling heart before contraction.

Sympathetic influence

Increases heart rate and stroke volume.

Diastolic phase

Heart muscle relaxation phase.

Contraction force

Strength of heart muscle contraction.

End Diastolic Volume (EDV)

Volume of blood in heart before contraction.

Frank-Starling Law

EDV determines heart muscle stretch and contraction.

Venous Return

Amount of blood entering the right atrium.

Skeletal Muscle Pump

Muscle contractions increase venous pressure, aiding return.

Constriction of Veins

Sympathetic ANS activation increases venous return.

Respiratory Pump

Pressure changes during breathing enhance venous return.

Ejection Fraction

Percentage of blood ejected during heart contraction.

Contractility

Force of heart contraction independent of stretch.

Norepinephrine

Neurotransmitter increasing heart muscle contraction force.

Epinephrine

Hormone enhancing heart muscle contraction strength.

G-Protein

Mediates neurotransmitter signals in heart muscle.

Calcium Concentration

Increased calcium enhances crossbridge formation in myocardium.

Elastic Arteries

Expand to absorb pressure from heart's output.

Muscular Arteries

Contain smooth muscle to regulate blood flow.

Arterioles

Connect larger arteries to capillary networks.

Crossbridge Formation

Interaction between actin and myosin for contraction.

Pressure Gradient

Difference in pressure driving blood flow.

Sarcoplasmic Reticulum

Stores calcium for muscle contraction in myocardium.

Inspiration

Breathing in creates lower pressure aiding venous return.

Blood Flow Patterns

Arterioles influence flow into specific capillary beds.

Muscle Veins

Return more blood to heart during contraction.

Sympathetic Nervous System

Regulates heart contractility and blood vessel constriction.

Volume of Blood

Total blood in heart influences stroke volume.

Venules

Small vessels that collect blood from capillaries.

Veins

Blood vessels returning blood to the heart.

Inferior Vena Cava

Vein carrying blood from lower body to heart.

Superior Vena Cava

Vein carrying blood from upper body to heart.

Capillaries

Tiny vessels where exchange of substances occurs.

Blood Volume in Veins

60% of total blood volume resides in veins.

Valves in Veins

Prevent backflow of blood towards the heart.

Pressure Generation by Heart

Heart creates pressure to move blood through arteries.