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Cardiovascular II Heart

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					                                   CVII- Heart. I. Location

        Cardiovascular II- Heart     mediastinum

                                     The heart is located in the
                                     ant mediastinum.
                                     The region in the thoracic
                                     between the plueral
                                     cavities.
                                     Contains:
                                             Heart
                                             Trachea
                                             Esophagus
                                             Thymus
                                             Vessels




CVII- Heart. II.                    CVII- Heart. II.
Pericardium                         Pericardium: Inner
Or pericardial sac encloses         serous membrane
the heart and the pericardial       Parietal layer(0uter)
cavity.
                                    The outer layer of the
 Outer fibrous membrane
                                    mesothelium, under the
Is a tough protective layer         outer fibrous layer.
made of bundles of
overlapping collagen fibers.
                                    Visceral layer
                                       (inner):epicardium
Inner serous membrane
                                    The continuation of the mesothelium onto the surface of the
Called the mesothelium              heart.
makes a serous fluid called         Also produces pericardial fluid.
pericardial fluid.




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 CVII- Heart. II.                                                 CVII- Heart. II.
 Pericardium                                                      Pericardium



                                                                  Pericarditis
                                                                  Sometimes the pericardium becomes inflamed due to infection
                                                                  or damage.
                                                                  The serous membranes overproduce pericardial fluid, which fills
 Pericardial cavity                                               the pericardial cavity.
 The potential space between the parietal and visceral
 pericardial membranes.                                           cardiac tamponade
 Filled with….
                                                                  As fluid pressure increases, the heart becomes compressed,
 pericardial fluid
                                                                  creating a condition called cardiac tamponade.
 Made by the pericardial membranes.                               The efficiency of the heart declines and can lead to a serious
 The fluid acts as a lubricant, to reduce friction as the heart   drop in the amount of blood ejected from the heart into the
 moves during each beat.                                          aorta.




 CVII- Heart. III. A. Walls, chambers, vessels, and
 valves.                                                          CVII- Heart. III. A. Walls 2. Myocardium.
                                                                  trabeculae carneae
                                                                  The convoluted, inner surface of the ventricles.
                                                                  Consists of projections of myocardium which enclose spaces.
                                                                  Helps to efficiently transfer force of contraction to blood.

                                                                  papillary muscles
                                                                  Larger projections of the myocardium which help to anchor the
                                                                  cordae tendinae; see valves.
Wall has three layers
1. Epicardium
 Also called the visceral pericardium. Part of the pericardial
 membranes.
2. Myocardium
 Heart muscle itself, made of cardiocytes.
3. Endocardium
 The membrane which lines the chambers and valves of the heart.




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 CVII- Heart. III. A. Walls.                                                           CVII- Heart. III. A. Walls. 3. Endocardium
 2. Myocardium.
  Myocardial cells Or cardiocytes generate a contractile force w/i the myocardium
                                                                                        endothelial cells
  Intercalated discs These are collections of gap junctions that form a
                         functional link between adjacent cardiocytes.                  Comprise the endothelium; forms a smooth surface over which
                         Action potentials can pass easily from one cell to the next    blood flows w/o friction.
                         through the discs
  Synstitium       A tissue where all of the cells act together.
                   When one contracts, they all contract.




 CVII- Heart. III.                                                                     CVII- Heart. III.
 B. Chambers                                                                           B. Chambers
 and septa                                                                             and septa
1. Upper atria (2)                                                                      3. Septa
 Left and right.                                                                       A thick barrier between
 Upper chambers                                                                        the left and right sides
 which receive blood                                                                   of the heart..
 from veins.                                                                                fibrous trigones
 Small, with thin walls.                                                                    interatrial septum

2. Lower ventricles                                                                    Between the atria;
     (2)                                                                               usually thinner than
 Left and right.                                                                       the…
                                                                                            interventricular
 Lower chambers which get blood from atria.                                                    septum
 Large, with thick walls.
                                                                                            Between the ventricles; very thick.




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 CVII- Heart. III.                              CVII- Heart. III.
 C. Blood flow                                  C. Blood flow
 through the                                    through the
 heart                                          heart
 Enters right atrium                            Enters via pulmonary
                                                  veins
…through the sup and inf
                                               …passes into the left
vena cava.
                                               atrium.
Blood passes down
                                               Blood enters the left
through a one-way valve
                                               ventricle through
into the lower ventricle.
                                               another value.
Blood then …

 Exits via pulmonary artery                    Blood…
                                                    Exits via aorta
…and passes into the lungs to be oxygenated.         Which supplies the entire body.




                                                CVII- Heart. III.
                                                D. Valves

                                                1. Atrioventricular
                                                   (AV)valves

                                                 One-way valves between the
                                                 atrium and ventricles.
                                                   tricuspid (right AV)
                                                   bicuspid (left AV)
                                                2. Chordae tendinae &
                                                   papillary muscles

                                                 Chordae are thin, tough fibrous cords which extend from the
                                                 valve margin to muscular bumps on the wall of the ventricles
                                                 called papillary muscles.
                                                 These structures keep the AV vales pointed in the proper
                                                 direction during contraction.




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                                                                CVII- Heart. III.
                                                                D. Valves
                                                                 3. Semilunar valves
                                                                  One-way valves between the
                                                                  ventricles and the arteries.

                                                                     Pulmonary
                                                                          semilunar

                                                                  Between the right ventricle
                                                                  and the pulmonary arteries.

                                                                     aortic semilunar

                                                                  Between the left ventricle and
                                                                  the aorta.




CVII- Heart. III.                                               CVII- Heart. IV. Blood supply
D. Valves                                                         A. Coronary (cardiac) circulation:
                                                                  begins
  4. Rheumatic fever
                                                                  Right coronary artery Is one of the first branches off the aorta, just above the left
      Streptococcus pyogenes                                                               semilunar. Feeds the right atrium. A branch of the coronary
        bacteria                                                                           called…
                                                                      Posterior interventricular artery
 In some cases, during severe Streptococcal infections of                              …supplies the post side of both the right and left ventricles.
 the respiratory tract, bacteria can invade the blood supply.     Left coronary artery
 These pathogens are then transported to the heart and can                    …similar to the right but passes to the left side of the heart..
 infect the heart valves causing rheumatic fever.                     Anterior interventricular branch …supplies the ant left ventricle.
 The valves can become damaged and scarred, which                     circumflex …passes under the left atrium to the post side and supplies the
                                                                                   left atrium.
 reduces their efficiency.




                                                                                                                                                          5
CVII- Heart. IV. Blood supply
                                                                         CVII- Heart. IV. Blood supply
  B. Deoxygenated blood
      coronary sinus                                                    C. Complications of coronary
                                                                           circulation
 The veins of the heart drain deoxygenated blood from the
 myocardium. The veins converge into larger vessels and finally pass        – angina pectoris
 blood into the coronary sinus.                                          Also called “heart pains.”
 This vein delivers blood into the right atrium, where it mixes with     Caused by a slow constriction of
                                                                         blood flow.
 blood from the rest of the body.
                                                                         The pain maybe caused by the built
                                                                         up of lactic acid as the myocardium
                                                                         shifts into anaerobic glycolysis.
                                                                            – myocardial infarction (MI)
                                                                         Also called a “heart attack.”
                                                                         Here the blood flow completely stops.
                                                                         If the flow is not restored, heart
                                                                         muscle will die.
                                                                            – Serum enzymes
                                                                         During an MI myocardial enzymes are
                                                                         released, such as creatine kinase or
                                                                         lactic dehydrogenase; blood MI markers.




                                                                       CVII- Heart. V. Conduction system
 CVII- Heart. V. Conduction system
Components                                                              Components
   1. Sinatrial node(SA)                                                    3. Atrioventricular (AV)
                                                                               bundle (bundle of His)
  A region of the atrial
  myocardium where the cells                                             The AV bundle splits into
  fire slightly faster than the                                          two bundle branches which
  rest of the myocardium.                                                each pass into a ventricle.
  Sets the pace of resting
  heart contraction: called
  the pacemaker node.                                                    The branches divide into
                                                                         smaller pathways called…
   2. Atrioventricular node (AV)                                            4. Conduction myofibers
                                                                               (perkinje fibers)
   The AV node receives signals from the SA
   nodes via the internodal pathways.                                   The myofibers enter the ventricular myocardium and form close
   The AV node delays the signal for a brief                            associations with the cardiocytes.
   interval, 0.1 sec. Then passes the signals on to                     Action potentials down these fibers trigger the cardiocytes to
   the AV bundle.                                                       contract.




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                                           CVII- Heart.
                                           VI. Electrocardiogram (EKG)
                                           A cyclic electrical signal generated by the heart as it depolarizes
                                           and repolarizes (not as it contracts or relaxes.)
                                           The pattern of the EKG is based on the cardiac cycle.
                                            Cardiac cycle
                                            One complete heart beat, where both atria and then the ventricles
                                            contract.
                                            Length= about 0.8 sec at rest
                                            Consists of two major phases.
                                                1.   Systole
                                              Means contraction.
                                              Atrial systole = atrial contraction.
                                              Ventricular systole.
                                                2. Diastole
                                               Means relaxation.
                                               Atrial diastole = atrial relaxation.
                                               Ventricular diastole.
                                                Atria then ventricles
                                             Atria contract first, then the ventricles.




CVII- Heart. VI. Electrocardiogram (EKG)   CVII- Heart. VI. Electrocardiogram (EKG)




                                            1. Normal EKG
                                                P wave

                                              Atria depolarize; prepares the myocardium for contraction.
                                              Normal P wave lasts about 0.1 secs.
                                              Changes in the shape of the P wave may be caused by
                                              abnormally enlarged atria or the atria firing at the wrong
                                              time.




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CVII- Heart. VI. Electrocardiogram (EKG)                             CVII- Heart. VI. Electrocardiogram (EKG)




 1. Normal EKG                                                        1. Normal EKG
     QSR Complex                                                          T Wave

   Ventricles depolarize; Normal QRS wave lasts <0.12 secs.             Ventricles repolarize for the next cardiac cycle.
   Changes in the QRS may indicate bundle branch blocks,                Normal T wave interval varies widely; usually about 0.1 sec.
   ventricular fibrillation.                                            Changes in the T may be caused by a number of things; drinking
                                                                        ice water, anxiety.
                                                                        BTW, atrial repolarization occurs during the QRS Complex.




CVII- Heart. VI. Electrocardiogram (EKG)                             CVII- Heart. VI. Electrocardiogram (EKG)




 2. Intervals                                                         2. Intervals
     PR                                                                   QT
   Lasts about 0.12 to 0.20 secs.                                       Length about 0.42 secs; .
   A very long PR internal (>0.2 secs) may be indicate a first          A very long QT internal may be suggest a MI or other myocardial
   degree heart block; the signals have trouble reaching the right      diseases.
   ventricle from the right atrium.




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CVII- Heart. VI.
Electrocardiogram
(EKG)




3. Use

As seen before; to diagnose abnormalities of the the heart, such
as MIs, conduction pathway changes or blockages.

4. Artificial   pacemaker
If the SA node is damaged (during a MI), it may be replaced by
an artificial pacemaker: a device that generates a rhythmic
signal to set the pace of the heart.




                                                                    CV II. VII. Physiology of the cardiac cycle. A. Phases
   CV II. VII. Physiology of the cardiac cycle
                                                                    3. Ventricular systole
 A. Phases
                                                                     Is a period of time when the blood becomes pressurized.
 1. Atrial systole                                                   It has to gain enough pressure to be able to pass through the
 Atrial contraction occurs at the beginning of the cardiac cycle.    lungs or the body efficiently.
 If response to the depolarization of the heart myocardium, the
 cardiocytes contract and generate a squeezing force that              Isovolumetric     contracton
 pushes blood into the ventricle.
                                                                     Is a brief period, in both ventricles, when both the AV and
 2. Ventricular filling                                              semilunar valves are closed.
                                                                     So there is no change in blood volume, but pressure increases.
  70% of the ventricular blood volume enters through a process
  called passive filling.                                              Ejection period
  Only about 30% is actually pushed into the ventricles from the
                                                                     Occurs when the pressure in the ventricle exceeds the pressure
  atria by atrial systole.
                                                                     in the arteries; this forces the semilunar valves open.
                                                                     Blood is “ejected” at high velocity and pressure into the
                                                                     arteries.




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CV II. VII. Physiology of the cardiac cycle. A. Phases                CV II. VII. Physiology of the cardiac cycle.
 4. Ventricular diastole                                               B. Average heart rate
  As the ventricles relax the blood pressure within drops.
  It soon falls below the arterial pressure and the semilunar value
  shuts.                                                                As the ave resting cardiac cycle is 0.8 secs long, the heart rate
  The heart enters the period of…                                       works out to 72 beats per minute (bpm).
    Isovolumetric   relaxation                                          A slow heart rate is called bradycardia, <60 bpm

  Again both sets of valves are closed, but the blood pressure is       An abnormally fast rate is called tachycardia , >100 bpm.
  falling.                                                              Extremely fast rates of the ventricles, 140-220 bpm,, called
  The AV valves will open when the ventricular pressure drops
                                                                        ventricular tachycardia, may indicate damage to the
  below the atrial BP.
                                                                        myocardium of this chamber.




  CV II. VII. Physiology of the cardiac cycle.                        CV II. VII. Physiology of the cardiac cycle.
                                                                       D. Abnormal Heart sounds
  C. Ausculation
                                                                        Changes in the shape or movement of the valves may modify
  Means listening to the heart sounds using a stethoscope.
                                                                        the heart sounds, sometimes creating “murmurs.”
  Heart sounds                                                             Stenosis
  The heart sounds are caused by turbulent flow of blood around         Is a narrowing of the valve opening; the valve can’t open fully.
  the valves as they close.                                                aortic stenosis
      1. First sound                                                    Narrowing of the aortic valve; blood jets through into the aorta
  Usually designated as a low frequency “LUBB” sound.                   under very high pressure.
  Caused by the closing of the AV valves.                                  Murmur
  Larger valve, lower sound.                                            Here the valve does not close properly and there is some back
                                                                        flow of blood.
      2. Second sound
                                                                           aortic regurgitation
  Desingated as a high frequency “DUPP” sound.
                                                                        Blood back flows from the aorta into the left ventricle.
  Caused by the closing of the semilunar valves.
                                                                        This “muffles” the normally distinct DUPP sound, generating a
  Smaller valve, higher sound.
                                                                        murmur.




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VIII. Physiology of cardiac output                                   VIII. Physiology of cardiac output
                                                                       C. Stroke volume (SV)
A. Body's oxygen demands
                                                                       CO is determined by stroke volume (SV.)
  Varies with the demands placed on it.                                SV is defined as the volume of blood pumped from the left
  Exertion creates more oxygen demand and the heart has to             ventricle during one beat.
  increase its activity to delivery the additional oxygen.             SV is about 70ml/beat in the ave adult.
B. Cardiac output (CO)                                                 CO= SV x bpm : 70ml/beat x 72 beats/min = 5040 ml/min=CO
  Def: as the amount of blood pumped into the aorta, from the
  left ventricle, per minute                                              SV depends on
   Resting output                                                       …on the volume of blood in the left ventricle after atrial systole.
  Of the average adult is 5 Lt/min.                                     This is called End Diastolic Volume (EDV.)
   Syncope                                                              Diastole here refers to ventricular diastole.

  Def: a temporary loss of consciousness causing collapse and
                                                                          EDV: end diastolic volume = 110-120 ml
  quick recovery.
  If the blood flow to CNS is restricted for as little as 6-8 secs
  syncope can result.




                                                                     VIII. Physiology of cardiac output
VIII. Physiology of cardiac output
                                                                      Frank-Starling law of the heart
  ESV                                                                  “The greater the stretching of the heart, the greater the cardiac
  End Systolic Volume.                                                 output.”
  The volume of blood remaining in the left ventricle after            Greater stretch means more blood, and so, a greater CO.
  ventricular systole.
  None of the chambers are ever completely empty of blood.            stretch depends on venous return (VR)
                                                                       Venous return is defined as the volume of blood entering the
  ESV: end systolic volume= 50-60                                      right atrium each minute.
  SV=EDV-ESV= 70                                                       Important: CO depends on VR.
                                                                       Except for very brief periods, CO=VR.
  SV= 120ml-50ml=70 ml.                                                That is the volume of blood entering the heart (VR) equals the
                                                                       volume leaving (CO.)

                                                                      more return
                                                                       So the greater the VR the greater the CO.




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VIII. Physiology of cardiac output                                 VIII. Physiology of cardiac output
 Normal:                                                            Nervous stimulation
 Normal CO at rest is bout 5 lt/min.                                 Sympathetic ANS output gets the body ready for “fight or
 During exercise the both heart rate and strength of contraction     flight.”
 increase.                                                          Heart rate:
 CO can rise 3-4 x (20lt/min)
                                                                     Increases; causes CO to rise.
 Athletes:                                                           CO=SV x bpm

May be able to increase CO by up to 7x- 35lt/min.                   Contractility:
The heart muscle mass increases, so each SV is larger.               Heart contracts harder and increases SV.
At rest, athletes rate may be slower, as they don’t need as high
a rate to have normal resting CO.                                   Heart size
                                                                     Increases, allows more VR, so CO rises.

                                                                     Overall effect is to increase C) some 5-6 fold.




                                                                   VIII. Physiology of cardiac output
                                                                    D. Congestive heart failure (CHF)
                                                                    Damaged heart

                                                                    Due to MI.
                                                                    Damaged heart muscle is not readily regenerated; replaced with
                                                                    scar tissue.
                                                                    The tissue cannot contract or contribute to pumping activity.
                                                                    So CO goes down.
                                                                    Blood pools in the left ventricle and backs up into the pulmonary
                                                                    veins.
                                                                    This increases BP in the pulmonary circulation and forces fluid
                                                                    out of the blood into lungs.
                                                                    This fluid accumulates in the lung spaces and reduces O2/CO2
                                                                    exchange.
                                                                    In severe CHF the patient literally “drowns” in their own fluid.




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