chapter 20

Pericardium

Consists of fibrous pericardium and serous pericardium

Fibrous Pericardium

Prevents overstretching of the ❤ , protection, anchors ❤ to mediastinum. Made of inelastic dense irregular connective tissue.

serous pericardium

Has 2 layers, Parietal pericardium + Visceral pericardium. Separated by Pericardial cavity (fluid filled space)

3 layers of heart

Epicardium, Myocardium, Endocardium

Pericarditis, Myocarditis, Endocarditis

Inflammation of the 3 layers of heart

Heart Pathway

• Right atrium

• Right ventricle

• Pulmonary arteries/trunk

• Pulmonary capillaries (gas exchange)

• Pulmonary veins

• Left atrium

• Left ventricle

• Aorta

• Systemic capillaries (gas exchange)

• Cava (back to right atrium)

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Fibrous Skeleton

4 connective tissue rings surrounding the heart valves, fused together and merged with the interventricular septum

Myocardial Ischemia

Reduced blood flow to the myocardium. Can cause hypoxia + pain in chest, neck, etc

Myocardial Infarction

Heart attack, blocked coronary artery causing death of tissues, Treatment = thrombolytic injection angioplasty, bypass grafting

Autorhythmic Fibers

repeatedly generate spontaneous action potentials that then trigger heart contractions

Heart Conduction

SA node

Atrioventricular node

right/left Bundle Branches

Subendocardial conducting network

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Artifical Pacemakers

sends out small electrical current to stimulate the heart to contract

Epinephrine

Can modify heart rate, force of contraction and blood vessel size to increase blood flow during stress

Action Potential in a Ventricular Fiber

rapid depolarization, plateau, and repolarization

Rapid Depolarization in Ventricular Fiber

Na rushes into the cell, causes electrical charge to ↑, triggers cell to contract

Plateau in Ventricular Fiber

Ca2 flows in cells (keeping it ↑), K+ starts flowing out (bring ↓), balance then keeps cell contracted longer

Repolarization in Ventricular Fiber

Ca2 channel close, K+ flows out, charge ↓, cell relax

ATP Production in Cardiac Muscle

via aerobic cellular respiration (most) and creatine phosphate (some)

Electrocardiogram (EKG or ECG)

recording of the electrical changes that accompany each heart beat

Action Potential Propagation Through the Heart - 1

P wave = Depolar of atrial contractile fibers

Action Potential Propagation Through the Heart - 2

Atrial systole (contract)

Action Potential Propagation Through the Heart - 3

QRS = Depolar of ventricular contractile fibers

Action Potential Propagation Through the Heart - 4

Ventricular systole (contraction)

Action Potential Propagation Through the Heart - 5

T waves = Repolar of ventricular contractile fibers

Action Potential Propagation Through the Heart - 6

Ventricular diastole (relaxation)

Phase of cardiac cycle - 1

Atrial contraction - Atria squeeze blood ↓ → ventricle. Ventricle are relax and filling up

Phase of cardiac cycle - 2

Isovolumetric (same vol) contraction - Ventricles strat contracting, pressure ↑, Biscupid valve close (no backflow into atria), no blood leave yet (vol same)

Phase of cardiac cycle - 3

Ventricular ejection -Ventricular pressure gets ↑ enough to force aortic valve open, blood gets pumped out into aorta and pulmonary artery (Pumping phase)

Phase of cardiac cycle - 4

Isovolumetric (same vol) relaxation - Ventricles relax, pressure drops, aortic valve close (no backflow from aorta), no blood moving (vol same)

Phase of cardiac cycle - 5

Ventricular filling - Bicuspid valve opens, blood flows from artia back into ventricles, ventricles refill

Phase of cardiac cycle - 6

Atrial contraction - cycle repeats

Isovolumetric

All valves closed, no blood moving, just pressure changing

Cardiac Output

CO (mL/min) = SV (mL/beat) x HR (beats/min)

Stroke Volume (SV)

amount of blood pumped out of ventricle in one beat

Preload

Stretch of ventricles b4 contraction, depends on end diastolic volume (EDV), More filling = ↑ SV.
Ex: Slow HR = more filling = bigger SV

Contractility

Strength of ventricular contraction

↑ Ca²⁺ = stronger contraction = ↑ SV

Afterload

Pressure in aorta + pulmon trunk that must be overcome for semilunar valve open, lower afterload = ↑ SV

Ex: ↑ BP = ↑ after load = ↓ SV

End Diastolic Volume (EDV)

the amount of blood in a ventricle right before it contracts

Coroanry Artery Disease

Blocks coronary arteries, causes hypoxia

Atherosclerotic plaques:

Structures developed in arteries, fat deposits, arteries become clogged, can occur in coronary arteries (coronary artery disease)

Congenital Heart Disease

Foramen ovale does not close upon birth

Arrthymia

Lack of normal heart rhythm, examine ECG to see arrythmia or stethoscope to hear irregular rhythm

Congestive heart failure

Left, right or both ventricles do not contract strong enough, does not pump enough blood throughout body counteracted by the devices previously mentioned