The Heart

1
The Heart
Chapter 20
2
Interesting Facts

• At rest, the heart pumps 30xs its own weight each
  minute.
• There are 60,000 miles of blood vessels.
• In one day, the heart can pump 7000 L.
• In one year, the heart pumps about 5 million L.
• The average body contains about 5 L of blood
  volume.

3
Functions of the Heart

• Generating blood pressure
• Routing blood
• Heart separates pulmonary (lungs to left side)
  and systemic (O2 nutrients) circulations
• Ensuring one-way blood flow
• Heart valves ensure one-way flow
• Regulating blood supply
• Changes in contraction rate and force match blood
  delivery to changing metabolic needs

4
Size, Shape, Location of the Heart

• Size of a closed fist
• Shape
• Apex Blunt rounded point of cone (pointed
  bottom)
• Base Flat part at opposite of end of cone
  (rounded top)
• Located in thoracic cavity in mediastinum (b/w
  the lungs 2/3 to left of center)

5
Pericardium

• Encloses the heart and holds it in place
• Two layers
• Outer, fibrous pericardium prevents the heart
  from overstretching
• The inner, serous pericardium contains
  pericardial fluid to prevent friction

6
Heart Wall

• Three layers
• Epicardiumthin, transparent outer layer
• Myocardiumcardiac muscle tissue bulk of the
  heart
• Endocardiumlines the inside of the myocardium
  and covers the valves

7
Heart Chambers

• Two upper chambers Atria
• Receiving chambers
• Separated by interatrial septum
• Two lower chambers Ventricles
• Pumping chambers
• Separated by interventricular septum

8
Thickness of Heart Chambers

• Vary according to each chambers functions.
• Atriathin walls because they only pump blood to
  ventricles
• Right ventriclepumps blood to lungs slightly
  bigger than atria
• Left ventriclepump blood to entire body and keep
  up with the other chambers thickest of the four
  chambers

9
Concept Check

• What are the functions of the heart?
• Blood pressure, routing blood, one-way blood
  flow, regulating blood supply
• Name and describe the 3 layers of the heart.
• Epicardium (thin/transparent outer layer),
  myocardium (cardiac muscle tisssue bulk),
  endocardium (lines inside of myocardium covers
  valves)
• What is the difference between atria and
  ventricles?
• Atria receives blood ventricles pumps blood

10
Blood Vessel Structure

• Arteries
• Elastic, muscular, arterioles
• Capillaries
• Blood flows from arterioles to capillaries
• Most of exchange between blood and interstitial
  spaces occurs across the walls
• Blood flows from capillaries to venous system
• Veins
• Venules, small veins, medium or
• large veins

11
Valves of the Heart

• Four valves one for each chamber
• They keep blood from flowing back to where it
  came from
• They open and close in response to the pressure
  of blood against them

12
Valves of the Heart

• Atrioventricular (cuspid) valves
• Tricuspid valve between right atrium and right
  ventricle 3 flaps or cusps
• Chordae tendinae tendon-like cords that prevent
  the cusps from being pushed back
• Bicuspid valve between left atrium and left
  ventricle two cusps

13
Path of Blood

• Right atrium receives deoxygenated blood from 3
  veins
• Superior Vena Cavablood from above the heart
• Inferior Vena Cavablood from below the heart
• Coronary Sinusblood from the heart wall

14
Vessels of the Heart
15
Right Ventricle

• Blood goes from to the pulmonary trunk
• Pulmonary trunk divides into left and right
  pulmonary arteries
• Pulmonary arteries lead to the lungs

16
From the Lungs

• Oxygenated blood enters the left atrium via four
  pulmonary veins

17
From the Left Ventricle

• Blood enters the ascending aorta
• To the coronary arteries
• To the arch of the aorta
• To the thoracic aorta
• To the abdominal aorta

18
Valves of the Heart

• Semilunar Valves
• Pulmonary semilunar valve between right
  ventricle and pulmonary artery
• Aortic semilunar valve between left ventricle
  and the aorta

19
Blood Supply of the Heart

• Coronary Circulationblood flow through the
  myocardium
• Left and right coronary arteries bring blood to
  the tissue
• Coronary sinus take deoxygenated blood from the
  tissue

20
Blood Flow Through Heart
21
Concept Check

• What are the 3 types of blood vessels?
• Arteries, veins, capillaries
• Describe the flow of blood through the heart
  starting w/ the body.
• Body, (SVC, IVC, CS), R Atrium, Tricuspid Valve,
  Chordae Tendinae, R Ventricle, Pulmonary SLV,
  Pulmonary Trunck, Pulmonary Arteries, Lungs,
  Pulmonary Veins, L Atrium, Bicuspid Valve,
  Chordae Tendinae, L Ventricle, Aortic SLV, Aorta,
  Body

22
Disorders ?

• Ischemia faulty circulation weakens cells due to
  lack of oxygen, but the cells dont die
• Angina Pectoris chest pain resulting from
  ischemia also from stress, over exertion, high
  blood pressure, or narrow arteries

23
Disorders ?

• Myocardial Infarction (MI) heart attack
• Infarction is the death of an area due to
  interrupted blood supply usually from a clot
• Tissue beyond the clot will die and become scar
  tissue
• Location of the infarction area is key to how
  serious it is

24
Conduction System of the Heart

• This is an intrinsic regulating system
• It does not need a stimulus from the nervous
  system
• All cardiac muscle is capable of self-excitation
• Cardiac muscle generates its own action potential

25
Sinoatrial (SA) Node

• Located in the right atrial wall just below the
  superior vena cava
• Known as the pacemaker of the heart
• Rate of self-excitation is faster than all other
  heart fibers
• Its impulses are spread to all the other areas
  thus setting the rhythm of the heart
• Both atria will contract at the same time
• This will then depolarize the AV node (ventricles
  contract)

26
Atrioventricular (AV) Node

• Located in the interatrial septum
• Last part of atria to depolarize
• This impulse will depolarize fibers in the
  interventricular septum bundle of His
• This is the only electrical connection between
  the atria and ventricles

27
Atrioventricular (AV) Node

• The impulse passes toward the apex through left
  and right bundle branches to the ventricles
• The actual contraction of the ventricles is done
  by the Purkinje fibers

28
Conducting System of Heart
29
Electrocardiogram (ECG)

• A record of the electrical changes that accompany
  the heartbeat.

30
Electrocardiogram

• Action potentials through myocardium during
  cardiac cycle produces electric currents than can
  be measured
• Pattern
• P wave
• Atria depolarization
• QRS complex
• Ventricle depolarization
• Atria repolarization
• T wave
• Ventricle repolarization

31
Cardiac Arrhythmias

• Tachycardia Heart rate in excess of 100bpm
• Bradycardia Heart rate less than 60 bpm
• Sinus arrhythmia Heart rate varies 5 during
  respiratory cycle and up to 30 during deep
  respiration
• Premature atrial contractions Occasional
  shortened intervals between one contraction and
  succeeding, frequently occurs in healthy people

32
Alterations in Electrocardiogram
33
Cardiac Cycle
34
Cardiac Cycle

• Heart is two pumps that work together, right and
  left half
• Repetitive contraction (systole) and relaxation
  (diastole) of heart chambers
• Blood moves through circulatory system from areas
  of higher to lower pressure.
• Contraction of heart produces the pressure

35
Concept Check

• Why does the SA node act as the pacemaker?
• Impulses are spread to other areas setting the
  rhythm of the heart
• How does the heart contract without an impulse
  from the brain?
• Intrinsic regulation / Self-excitation / Cardiac
  muscle generates own action potentials
• What actually contracts the myocardium of the
  ventricles?
• Purkinje fibers
• What is an infarct?
• Death of an area due to interrupted blood supply
  usually a clot

36
Concept Check

• What does an EKG measure?
• Electrical changes in the heart that accompany
  heart beat
• Why is QRS bigger than P?
• QRS contraction of ventricles
• P contraction of atria
• What is a fibrillation or arrhythmia?
• Fibrillation hearts electrical activity has
  become disordered contraction rapid,
  unsynchronized flutter rather than beat heart
  pumps little or no blood

37
Heart Rate

• Cardiac Output amount of blood ejected from the
  left ventricle into the aorta per minute
• Stroke volume amount of blood ejected from the
  left ventricle per contraction

38
Factors Affecting Heart Rate

• Autonomic control baroreceptorsneurons
  sensitive to blood pressure changes
• Chemicals too much or too little K, Na, or Ca
  either increases or decreases heart rate oxygen
  demands
• Temperature increase temperature, increase heart
  rate lower temperature, decrease heart rate
• Emotions fear, anxiety, anger all increase heart
  rate while depression and grief lower heart rate
• Sex and age faster in females fastest at birth
  but slows as one gets older

39
More Disorders ?

• Arteriosclerosis - thickening of the walls of the
  arteries and loss of elasticity
• Atherosclerosis - Deposition of plaque on walls
• Congenital defectsa defect that exists at birth
• Interventricular septal defecthole in septum
• Valvular stenosisnarrowing of a valve
• Arrthymiaany irregularity in heart rhythm

40
Effects of Aging on the Heart

• Gradual changes in heart function, minor under
  resting condition, more significant during
  exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
• Increased tendency for valves to function
  abnormally and arrhythmias to occur
• Increased oxygen consumption required to pump
  same amount of blood

41
Heart Sounds

• First heart sound or lubb
• Atrioventricular valves and surrounding fluid
  vibrations as valves close at beginning of
  ventricular systole
• Second heart sound or dupp
• Results from closure of aortic and pulmonary
  semilunar valves at beginning of ventricular
  diastole, lasts longer
• Third heart sound (occasional)
• Caused by turbulent blood flow into ventricles
  and detected near end of first one-third of
  diastole

42
Blood Pressure

• Measure of force exerted by blood against the
  wall
• Blood moves through vessels because of blood
  pressure
• Measured by listening for Korotkoff sounds
  produced by turbulent flow in arteries as
  pressure released from blood pressure cuff

43
Pulse Pressure

• Difference between systolic (contraction of
  ventricles) and diastolic (relaxation of
  ventricles) pressures
• Increases when stroke volume increases or
  vascular compliance decreases
• Pulse pressure can be used to take a pulse to
  determine heart rate and rhythmicity

44
Concept Check

• What types of things would increase your heart
  rate? Decrease?
• What is a congenital disorder? Describe the
  problems with interventricular septal defect.
• What is the difference between systole and
  diastole if they both measure on the arteries?
• What causes the heart sounds?