Chapter 18 The Heart

Question 1

Pulmonary and Systemetic Circuts

Answer 1

• Pulmonary Circut) Blood pumps to lungs to remove CO2 and pick up O2
  
  • Right Atrium) Recives blood returning from systemic citcut and delivers to Right ventricle
  • Right Ventricle) Pumps blood through the pulmonary Circut.
• Systemic Circut) Pumps blood through the body to deliver O2 and picks up CO2 for the lungs
  
  • Left Atrium) recives blood from pulmonary circut and moves it to the Left ventricle
  • Left Ventricle) Pumps blood through the systemic circut.

Question 2

Size, Location and Orentation

Answer 2

• About the size of a fist (One pound or so)
• Location
  
  • In mediastinum; between second and fith ribs intercostal space
  • Superior surface of diaphragm
  • 2/3 of the heart is left of midsternal line
• Base (Posterior Surface) leans toward right shoulder
• Apex) Points toward the left hip

Question 3

Pericardium

Answer 3

Double-Walled sac that surrounds the heart

• Superficial Fibrous pericardium) protects heart, anchors surrounding structures, prevents overfilling
• Serous Pericardium (two layers)
  
  • Parietal layer) Lines surface of fibrous pericardium
  • Visceral layer (epicardium) on external surface of heart
  • Seperated by pericardial Cavity (decreases friction)

Question 4

Pericardial Homestatic Imbalance

Answer 4

• Pericardiatis) Inflammation of pericardium
  
  • Pericardial Frictin Rub) creaking sound caused
• Cardiac Tamponade) Excess fluid compresses heart
  
  • Limited pumping ability
  • Fluid is drawn from cavity.

Question 5

Layers of the Heart Wall

Answer 5

• Epicardium) Visceral (organ) layer of serous pericardium
• Myocardium) Circular bundles of cadriac muscle cells
  
  • Teathered to one another (cardiac skeleton)
  • Anchors muscle fibers, supports vessels and calves, keeps AP on specific paths
• Endocardium) continous with lining of blood vessels
  
  • lines heart chambers

Question 6

Atria

Answer 6

• Receiving chambers of the heart
  
  • small, thin-walled chambers
  • Do not pump blood
• Auricles) Increase atrial volume
• Right Atrium) recives deoxygenated blood from the body
  
  • Anterior portion is smooth walled
  • Containes ridges formed by pectinate muscles
  • Superior (above diaphragm) and Inferior (below diaphragm) Vena Cava’s and Cornary Sinus (cornary veins) empty blood into the Right artium
• Left Atrium) recives oxygnated blood from lungs
  
  • Mostly smooth muscles with few pectinate muslces
  • Four pulmonary veins return blood from the lungs (2 right 2 left)

Question 7

Ventricles

Answer 7

• The Pumping chambers of the heart
  
  • Make up most of the hearts volume
• Right Ventricle) most of the anterior surface
  
  • Pumps blood into pumonary trunk
• Left Ventricle) Posteroinferior surface
  
  • Pumps blood into the aorta (largest artery in body)
• Trabeculae Carneae) ridges of muscle on ventricular walls
• Papillary Muscles) Project into the venticular cavity
  
  • Achor chordae tendinae mucles that control valves
• Features
  
  • Thicker walls than atria

Question 8

Heart Valves

Answer 8

• Atrioventricular valves) located between atria and ventricles
  
  • Tricuspid Valves) Between Right artium and aorta
    
    • made of 3 cusps (lips)
  • Mitral valvue) Between Right artium and aorta
    
    • made of 2 cusps
  • Chordae muscles anchor cusps to valves
• Semilunar (SL) valves
  
  • Pulmonary Semilunor valve) Between right ventricle and pulmonary trunk
  • Aortic Semilunar valve) Between left ventricle and aorta.

Question 9

Blood Pathway

Answer 9

Question 10

Cornary Circulation

Answer 10

Functional Blood suply of the heart itself

• Cornary Artieries
  
  • Both Left and Right
  • Arise from base of aorta and supply blood to heart
  • Encirrcle heart in coronary sulcus
• Cornary Veins
  
  • Colelct blood from capliary beds
  • Cornary Sinus) empties into right atrium (merges with cardiac veins)

Question 11

Cardiac Muscle Cells

Answer 11

• Striated, Branched, and connected. have one central nucleus and tons of mitochondria.
• Intercalated Discs) connecting juction between cardiac cells
  
  • Demosomes hold cells togehter and prevent seperation
  • Gap junctions allow ions to pass from cell to cell
  • Allows heart to be a functional syncytium
• Contraction of Muscle cells is through the action of an Action potential
• Some heart muscle cells are self excitable
  
  • Contractile cells) responsible for contraction
  • Pacemaker cells) noncontractile; initate deploraztion and do not need nervous stimulation
• Heart contacts as a unit

Question 12

Cardiac Rythym) Conduction System

Answer 12

• AP for heart contraction is iniated by pacemaker cells
  
  • have unstable reting membrane potentials called pacemaker potentials (prepotentials)
• Three steps of an AP
  
  • Pacemaker potential) Inside is more positive (K+ down, Na+ up)
  • Depolarization) Ca2+ floods in and causes AP
  • Repolarization) K+ floods back in and cell becomes more negative

Question 13

Sequence of Heart Excitation

Answer 13

1. Sinoatrial (SA) Node
   
   • Pacemaker of heart in right atrial wall
   • Depolarizes faster than myocardium so it sets the pace for contraction (sinus rhythm)
2. AtrioVentricular (AV) Node
   
   • Delays impulse appozimately .1 of a sec
   • Allows atrial contraction before ventricular contraction
3. Atriventricular (AV) Bundle
   
   • Eletrical connection between atria and ventrile
4. Right and Left Bundle Branches
   
   • Splits into two pathways
   • Carry impulses to the apex of the heart
5. Subendocardial conducting network (Punkije Fibers)
   
   • Complete pathway and extend into ventricle walls and out of apex
     *

Question 14

Extrensic innervation of Heart

• Medulla Oblongota
  
  • sympathetic) Up rate and force
  • Parasymptahtetic) down rate and force
• Cardioaccelratory Center) Stimulares heart to increace rate and force
• Cardioinhibitory Center) Parasympathetic signals to decrease rate.

Question 15

Eletrocardiograph Readings

Answer 15

• Singular
  
  • P wave) Depolarization of SA node and Atria
  • QRS Complex) ventricular depolarization and atrial repolarization
  • T wave) Ventrical repolarization
• Compelxes
  
  • P-R interval) Begining of atrial extiation to begining of ventricular extitation
  • S-T segment) entire ventricular myocardium depolarized
  • Q-T interval) beginning of ventricular depolarization through ventricular repolarization.

Question 16

Mechanical Events

Answer 16

• Systole) period of Contraction
• Diastole) period of Relaxation
• Cardiac Cycle) one complete heartbeat
• Mechanical Events

1. Ventricular Filling: mid-to-late diastole
   
   • Blood flows into ventricle from atria (AV valves open) (SL valves closed)
   • Rest of blood is pushed by atrial depolrization
   • End Diastolic Volume) volume of blood in ventricle at end of phase
2. Isovolumetric Contraction
   
   • Atria Relax; Ventricles Contract
   • Ventricular pressure rises
3. Ventricular Ejection)
   
   • SL valves are forced open
4. Isovolumetric Relxation (Early diastole)
   
   • Ventricles relax and pressure drops
   • End Systolic volume) Volume of blood in each ventricle after systole.