1 Heart Basics

what does the right atrium do

Receives "dirty" deoxygenated blood from your body

what does the left atrium do

Receives "clean" oxygenated blood from your lungs (red blood on diagrams)

what does the right ventricle do

Pumps deoxygenated blood TO your lungs to get oxygen

what does the left ventricle do

Pumps oxygenated blood TO your entire body

which ventricle wall is thicker and why

left - needs more muscle power to pump blood to your ENTIRE body (right only goes to lungs)

layers if the heart wall inside to outside

endocardium - myocardium - epicardium - pericardium

name the AV valves

• tricuspid - right side & 3 flaps

• bicuspid - left side & 2 flaps

name the semilunar valves

• pulmonic valve - between right ventricle and pulmonary artery (goes to lungs)

• aortic valve - Between left ventricle and aorta (goes to body)

Chordae tendineae

String-like cords that anchor valves (like parachute strings)

Papillary muscles

Muscles that pull on the chordae tendineae to open/close valves

right side journey (deoxygenated blood)

1. Body → Superior/Inferior vena cava (large veins)

2. Right Atrium

3. Tricuspid valve

4. Right Ventricle

5. Pulmonic valve

6. Pulmonary artery

7. LUNGS (picks up oxygen, drops o CO₂)

Left Side Journey (Oxygenated Blood):

1. Lungs → Pulmonary veins

2. Left Atrium

3. Mitral valve

4. Left Ventricle

5. Aortic valve

6. Aorta

7. BODY (delivers oxygen, picks up CO₂)

Pulmonary artery exception

carries DEoxygenated blood

Pulmonary veins exception

carry Oxygenated blood

coronary arteries job

deliver oxygen-rich blood to the heart muscle

what are the main coronary arteries

• Right Coronary Artery (RCA)

• Left Coronary Artery (LCA)

Right Coronary Artery (RCA)

Supplies right side of heart

Left Coronary Artery (LCA) splits into:

• Left Anterior Descending (LAD) - Supplies front of left ventricle

• Circumex artery - Supplies side and back of left ventricle

what happens when coronary arteries get blocked

you get a heart attack (myocardial infarction) because part of the heart muscle doesn't get oxygen

Coronary veins job

drain the "used" blood back into the right atrium through the coronary sinus

conduction pathway

1. SA Node (Sinoatrial node) - The "pacemaker"

2. Internodal pathways

3. AV Node (Atrioventricular node) - The "gatekeeper"

4. Bundle of His - Highway for signal

5. Right and Left Bundle Branches - Splits into two paths

6. Purkinje Fibers - Spreads throughout ventricles

SA node job

• Located in right atrium

• Fires electrical signal 60-100 times per minute

• Sets your heart rate

Internodal pathways job

• Spreads signal across both atria

• Makes atria contract together

AV Node (Atrioventricular node) job

• The "gatekeeper"

• Located between atria and ventricles

• Delays signal slightly so ventricles ll with blood before contracting

Bundle of His job

• Highway for signal

• Travels down the interventricular septum (wall between ventricles)

Purkinje Fibers job

• Spreads throughout ventricles

• Makes ventricles contract from bottom up (squeezing blood UP and OUT)

P Wave (rst small bump)

• Atria depolarizing (receiving electrical signal)

• Atria are contracting

PR Interval

• Time from atrial contraction to ventricular contraction

• Normal: 0.12-0.20 seconds

QRS Complex (big spike)

• Ventricles depolarizing (receiving electrical signal)

• Ventricles are contracting

• This is the main heartbeat you feel

QRS Interval

• How long ventricular contraction takes

• Normal: less than 0.12 seconds

T Wave (small bump after QRS)

• Ventricles repolarizing (resetting, getting ready for next beat)

• Ventricles are relaxing

Systole

• Heart muscle contracts

• Blood is PUMPED OUT of chambers

Diastole

• Heart muscle relaxes

• Blood FILLS the chambers

Stroke Volume (SV)

• Amount of blood pumped out with EACH heartbeat

• Normal: about 70 mL per beat

Cardiac Output (CO)

• Amount of blood pumped by each ventricle in ONE MINUTE

• Formula: CO = Heart Rate × Stroke Volume

• Normal: 4-8 L/min

• Example: If HR = 70 beats/min and SV = 70 mL, then CO = 4,900 mL/min (about 5 L/min)

Cardiac Index (CI)

• Cardiac output adjusted for body size

• Formula: CI = CO ÷ Body Surface Area

• Normal: 2.8-4.2 L/min/m²

• More accurate than CO for comparing dierent-sized people

Preload

The volume of blood in the ventricles at the END of diastole (when they're full)

What increases preload

• Hypervolemia (too much uid)

• Lying down (blood returns to heart easier)

What decreases preload

• Hypovolemia (dehydration, bleeding)

• Standing up quickly

• Diuretics (water pills)

Contractility

The force/strength of heart muscle contraction (independent of preload)

What increases contractility (Positive Inotropes):

• Epinephrine (adrenaline)

• Calcium

• Digoxin (heart medication)

• Exercise

What decreases contractility (Negative Inotropes):

• Heart failure

• Beta-blockers (certain blood pressure meds)

• Calcium channel blockers

• Acidosis (blood too acidic)

Afterload

The resistance the left ventricle must pump AGAINST to eject blood (like pushing against a door)

What increases afterload:

• Hypertension (high blood pressure)

• Vasoconstriction (blood vessels tightening)

• Aortic stenosis (narrowed aortic valve)

What decreases afterload:

• Vasodilators (blood pressure meds that relax vessels)

• Shock (blood vessels dilate)

Arteries

• Carry blood AWAY from the heart

• High pressure

• Thick, muscular, elastic walls

• Can withstand high pressure

Arterioles

• Smaller branches of arteries

• Can constrict (narrow) or dilate (widen) to control blood ow

• Main controllers of blood pressure

Veins

• Carry blood BACK TO the heart

• Low pressure

• Thinner walls than arteries

• Have VALVES to prevent backow (gravity would pull blood down in your legs!)

• Hold most of your blood volume (about 60-70%)

Venules

Smaller branches that drain into veins

Capillaries

• Tiniest blood vessels (one cell thick!)

• Where the actual exchange happens:

• Oxygen and nutrients OUT to tissues

• Carbon dioxide and waste IN from tissues

• So small that red blood cells travel single-le

Arterial capillaries

Oxygen-rich blood entering

Venous capillaries

Oxygen-poor blood leaving

Pulse Pressure

• Formula: Pulse Pressure = SBP - DBP

• Normal: About 1/3 of the SBP

• Example: If BP is 120/80, pulse pressure = 40 mm Hg

• Represents the "surge" of blood with each heartbeat

Mean Arterial Pressure (MAP)

• The AVERAGE pressure in arteries during one cardiac cycle

• Formula: MAP = (SBP + 2 × DBP) ÷ 3

• Example: If BP is 120/80, MAP = (120 + 160) ÷ 3 = 93 mm Hg

• Important: Organs need MAP of at least 60-65 to get adequate blood ow

Baroreceptors

• Location: Aortic arch and carotid sinus (in neck)

• What they do: Sense when blood pressure is TOO HIGH

• Response: When stretched (high BP detected):

  • Turn OFF sympathetic nervous system (slows heart down)

  • Turn ON parasympathetic nervous system (relaxes vessels)

  • Result: Blood pressure DECREASES

Chemoreceptors

• Location: Aortic arch and carotid bodies

• What they do: Sense when oxygen is TOO LOW

• Response: When low O₂ detected:

  • INCREASE heart rate

  • INCREASE blood pressure

  • INCREASE breathing rate

  • Goal: Get more oxygen to tissues faster