A&p 18

Front 1

Heart Anatomy

Back 1

Fist-sized; Enclosed in pericardium (doubled walled sac)

Front 2

Superficial Fibrous Pericardium

Back 2

Protects, anchors, prevents overfilling

Front 3

Deep 2-Layered Serous Pericardium

Back 3

Parietal layer lines internal surface of fibrous pericardium; Visceral layer (epicardium) on external surface of heart; Separated by fluid filled pericardial cavity (decreases friction

Front 4

Epicardium

Back 4

Visceral layer of serous pericardium

Front 5

Myocardium

Back 5

Main wall of heart; Spiral bundles of cardiac muscle cells; Fibrous skeleton of heart anchors cardiac muscle fibers, supports great vessels and valves, limits spread of action potentials to specific paths

Front 6

Endocardium

Back 6

Continuous with endothelium

Front 7

Ventricles

Back 7

Two; Separated by interventricular septum; Anterior and posterior interventricular sulci mark position of septum externally

Front 8

Atria

Back 8

Two; Separated internally by interatrial deptum; Coronary sulcus (atrioventricular groove) encircles junction of atria and ventricles; Auricles increase atrial volume

Front 9

Blood Pathway through Heart

Back 9

Heart is 2 side-by-side pumps; Circuits are interconnected; Right ventricle is pump for pulmonary circuit; Left ventricle is pump for systemic circuit; Equal volumes of blood are pumped to both circuits

Front 10

Pulmonary Circuit

Back 10

Vessels that carry blood to and from lungs, pumped by the right ventricle; Short, low-pressure circulation

Front 11

Systemic Circuit

Back 11

Vessels that carry blood to and from all body tissues, pumped by left ventricle; Long pathways cause resistance, high pressure circuit; Left ventricle has more robust walls due to high pressure demands

Front 12

Blood Flow

Back 12

RIght atrium to tricuspid valve to right ventricle; to pulmonary semilunar valve to pulmonary trunk to pulmonary arteries to lung; to pulmonary veins to left atrium; to bicuspid valve to left ventricle; to aortic semilunar valve to aorta; to systemic circulation

Front 13

Coronary Circulation

Back 13

Function blood supply to heart muscle; Arterial supply varies considerably and contains many anastomoses (junctions) among branches; Collateral routes provide additional routes for blood deliveries

Front 14

Atrioventricular (AV) Valves

Back 14

Prevent backflow into atria when ventricles contract; Tricuspid and mitral valve; Chordae tendineas anchor AV valve cusps to papillary muscles

Front 15

Semilunar (SL) Valves

Back 15

Prevent backflow into the ventricles when atrias relax; Aortic and pulmonary semilunar valves

Front 16

Cardiac Muscle

Back 16

Cells are striated, short, fat, branched, interconnected; Connective tissue matrix (endomysium) connects to fibrous skeleton; T tubules are wide but less numerous - SR is simpler than in skeletal muscle; Numerous large mitochondria (25-35% of cell vol.)

Front 17

Intercalated Discs

Back 17

Junctions between cells anchor cardia cells

Front 18

Desmosomes

Back 18

Prevent cells from separating during contraction

Front 19

Gap Junctions

Back 19

Allow ions to pass, electrically couple adjacent cells

Front 20

Cytoskeletal Cardiac Cell Bands

Back 20

Actin - thin filaments; Myosin - thick filaments

Front 21

Cardiac Muscle Contraction

Back 21

Depolarization of heart is rhythmic and spontaneous; About 1& of cardiac cells have automaticity (are self-excitable); Gap junctions ensure heart contracts as a unit; Long absolute refractory period (250 ms) - promotes complete relaxation and opportunity for refilling of heart with blood

Front 22

Depolarization

Back 22

Opens voltage gated fast Na+ channels in sarcolemma; Reversal of membrane potential form -90 mV to +30 mV; Depolarization wave causes Ca2+ surge which prolongs depolarization

Front 23

Repolarization

Back 23

Ca2+ causes EC coupling as Ca2+ binds to toponin; sliding of filaments begins; Repolarization results from inactivation of Ca2 channels and opening of voltage gated K+ channels

Front 24

Intrinsic Cardiac Conduction System

Back 24

Network of noncontractile (autorhythmic) cells that initiate and distribute impulses to coordinate depolarization and contraction of heart

Front 25

Autorhythmic Cells

Back 25

Populate SA node; Have unstable resting potentials; At threshold, Ca2+ channels open; Ca2+ influx produces rising phase of action potential; Repolarization results from inactivation of Ca2+ channels and opening of voltage gated K+ channels

Front 26

SInoatrial (SA) Node

Back 26

Pacemaker; Generates impulses about 75 times/minute (sinus rhythm)

Front 27

Atrioventricular (AV) Node

Back 27

Smaller diameter fibers, fewer gap junctions; Delays impulses approximately .1 second; Depolarizes 50 times per minute in absence of SA node input

Front 28

Atrioventriucular Bundle

Back 28

Only electrical connection between atria and ventricles

Front 29

Right/Left Bundle Branches

Back 29

Two pathways in interventricular septum carry impulses toward apex of heart

Front 30

Purkinje Fibers

Back 30

Complete pathway into apex and ventricular walls; AV bundle and Purkinje fibers depolarize only 30 times per minute in absence of AV node input

Front 31

Heart Sequence of Excitation

Back 31

SA node to AV node to AV bundle to Right/Left bundle branches to Purkinje fibers

Front 32

Extrinsic Innervation of Heart

Back 32

Heartbeat modified by ANS; Cardiac centers are located in medulla oblongata

Front 33

Caridoacceleratory Center

Back 33

Innervates SA and AV nodes, heart muscle, and coronary arteries through sympathetic neurons

Front 34

Cardioinhibitory Center

Back 34

Inhibits SA and Av nodes through parasympathetic fibers in vagus nerves

Front 35

Electrocardiogram (EKG)

Back 35

Composite of all action potentials generated by nodal and contractile cells at a given time

Front 36

P Wave

Back 36

Depolarization of SA node

Front 37

QRS Complex

Back 37

Ventricular depolarization

Front 38

T Wave

Back 38

Ventricular repolarization

Front 39

Heart Sounds

Back 39

Two sounds (lub-dup) associated with clsing of heart valves; First sound occurs as AV valves close - signifies beginning of systole; Second sound occurs when SL valves close at beginning of ventricular diastole

Front 40

Heart Murmurs

Back 40

Abnormal heart sounds most often indicative of valve problems; Leakage of blood in wrong direction - malformed during embryonic development or disease/mechanical trauma to valve

Front 41

Cardiac Cycle

Back 41

All events associated with blood flow through the heart during one complete heartbeat

Front 42

Systole

Back 42

Contraction

Front 43

Diastole

Back 43

Relaxation

Front 44

Mechanical Events of Cardiac Cycle

Back 44

1. Atrial systole and ventricular diastole to 2. Ventricular systole and atrial diastole to 3. Atrial/Ventricular diastole

Front 45

(1) Atrial Systole with Ventricular Diastole

Back 45

AV valves open; 80% or more of blood passively flows into ventricles; Atrial systole occurs near end, delivering remaining 20%

Front 46

End Diastolic Volume (EDV)

Back 46

Volume of blood in each ventricle immediately before starting ventricular systole, occurs at end of phase 1 of the cardiac mechanical cycle

Front 47

(2) Ventricular Systole with Atrial Diastole

Back 47

Atria relax, ventricles begin to contract; Rising ventricular pressure results in closed AV valves; Isovolumetric contraction phase (all valves are closed); IN ejection phase, ventricular pressure exceeds pressure in large arteries, forcing SL valves open

Front 48

End Systolic Volume (ESV)

Back 48

Volume of blood remaining in each ventricle at the end of phase 2 of the cardiac mechanical cycle

Front 49

(3) Atrial and Ventricular Diastole

Back 49

Isovolumetric relaxation; Ventricles relax; Backflow of blood in aorta and pulmonary trunk closes SL valves and causes dicrotic notch (brief rise in aortic pressure)

Front 50

Cardiac Output (CO)

Back 50

Volume of blood pumped by each ventricle in one minute; CO = HR (Heart Rate) x SV (Stroke Volume)

Front 51

Heart Rate (HR)

Back 51

number of beats per minute

Front 52

Stroke Volume (SV)

Back 52

Volume of blood pumped out by a ventricle with each beat

Front 53

Cardiac Output Statistics

Back 53

At rest CO (ml/min) = HR (75 bpm) x SV (70 ml per beat), most adults use 5 to 6 L per circuit; Maximal CO is 4 to 5 times resting CO in nonathletes; Maximal CO may reach 35 L/min in athletes

Front 54

Cardiac Reserve

Back 54

Difference between resting and maximal CO

Front 55

Regulation of Stroke Volume

Back 55

SV = EDV - ESV; Main factors are preload, contractility, and afterload

Front 56

Preload

Back 56

The degree to which cardiac muscle cells can stretch before the contract (Frank Starling law of the heart; Slow heartbeat and exercise increase venous return, which in turn stretches ventricles and increases contraction force

Front 57

Contractility

Back 57

Contractile strength at a given muscle length, independent of muscle stretch and EDV

Front 58

Positive Inotropic Agents of Contractility

Back 58

Increase contractility (epinephrine and norepinephrine or secondary hormone actions like thyroxine)

Front 59

Negative Inotropic Agents

Back 59

Decrease contractility (Acidosis, increased extracellular K+, Calcium channel blockers - propanolol)

Front 60

Afterload

Back 60

Pressure that must be overcome for ventricles to eject blood

Front 61

Hypertension

Back 61

Increases afterload, resulting in increased ESV and reduced SV; Increases chronic workload of cardiac system; Promotes abnormal ventricular hypertrophy

Front 62

Heart Rate Regulation

Back 62

Positive chronotropic factors increase heart rate, negative chronotropic factors decrease heat rate

Front 63

Autonmic Nervous System Regulation

Back 63

Sympathetic nervous system activated by emotional/physical stressors; Norephinephrine causes pacemaker to fire more rapidly and increase contractility; Parasympathetic NS opposes sympathetic effects - acetylcholine hyperpolarizes pacemaker cells by opening K+ channels; Heart at rest exhibits vagal tone

Front 64

Atrial (Bainbridge) Reflex

Back 64

Sympathetic reflex initiated by increased benous return; Stretch of atrial walls stimulates SA nodes and atrial stretch receptors activating sympathetic reflexes

Front 65

Epinephrine

Back 65

Chemical from adrenal medulla that enhances heart rate and contractility

Front 66

Thyroxine

Back 66

Increases heart rate and enhances effects of norepinephrine and epinephrine

Front 67

Intra/Extracelluar Ion Concentration

Back 67

Ca2+ and K+ concentrations must be maintained for normal heart functions

Front 68

Other Factors for Heart Rate

Back 68

Age; Gender; Exercise; Body Temp.

Front 69

Arrhythmmias

Back 69

Irregular heart rhythms

Front 70

Fibrilliation

Back 70

Rapid, irregular contractions -useless for pumping blood

Front 71

Uncoordinated Atrial/Ventricular Contractions

Back 71

Result of defect in intrinsic conduction system

Front 72

Defective SA Node

Back 72

Can result in ectopic focus - abnormal pacemaker takes over ; AV node take over - junctional rhythm

Front 73

Defective AV Node

Back 73

Can result in heart block; Few or no impulses from SA node reach ventricles

Front 74

Tachycardia

Back 74

Abnormall fast heart rate (more than 100 bpm)

Front 75

Bradycardia

Back 75

Heart rate slower than 60 bpm - may result in inadequate blood circulation

Front 76

Angina Pectoris

Back 76

Thoracic pain caused by fleeting deficiency in blood delivery to myocardium - cells are weakened

Front 77

Myocardial Infarction (Heart Attack)

Back 77

Prolonged coronary blockage; Areas of cell death are repaired with noncontractile scar tissue

Front 78

Congestive Heart Failure (CHF)

Back 78

Progressive condition where CO is so low that blood circulation is inadequate to meet tissue needs; Caused by coronary atherosclerosis, persistent high blood pressure, multiple myocardial infarcts, dilated cardiomyopathy (DCM)