The Heart

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The Heart
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The Heart

• Heart pumps over 1 million gallons per year
• Over 60,000 miles of blood vessels

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I. Layers of Heart Wall

• Pericardium
• protects and anchors the heart, prevents
  overstretching
• Myocardium
• cardiac muscle layer is the bulk of the heart
• Endocardium
• chamber lining valves

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II. Structures of the Heart
Left common carrotid
Left subclavian artery
Brachiocephalic trunk
aorta
left pulmonary artery
Superior vena cava
Mitral/bicuspid
pulmonary semi-lunar
Right atrium
Left atrium
Right pulmonary vein
Aortic semi-lunar
tricuspid
Chordae tendinae
myocardium
Papillary muscle
Left ventricle
inferior vena cava
Interventricular septum
Right ventricle
Descending aorta
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III. Blood Circulation

• Two closed circuits, the systemic and pulmonic
• Pulmonary circulation
• Right atrium pumps blood through the tricuspid
  valve to the right ventricle
• Right ventricle pumps blood through the pulmonary
  semi-lunar valve to pulmonary trunk
• pulmonary trunk branches into left and right
  pulmonary arteries
• Pulmonary arteries carry blood to lungs for
  exchange of gases
• Which gases and in what direction?
• Oxygenated blood returns to the heart through the
  pulmonary veins into the left ventricle

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Blood Circulation (cont)

• Systemic circulation
• Left atrium pumps blood though the mitral valve
  (bicuspid) to the left ventricle
• Why is this valve replaced the most often?
• left ventricle pumps oxygenated blood through the
  aortic semi-lunar valve into aorta
• Why is the myocardium of this chamber the
  thickest?
• Aorta branches into many arteries that travel to
  organs
• Arteries branch into many arterioles in tissue.
• Arterioles branch into thin-walled capillaries
  for exchange of gases and nutrients
• Deoxygenated blood begins its return in venules
• Venules merge into veins and return to right
  atrium via the vena cavas

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IV. Blood Flow Off Descending Aorta

• Common carotid artery (left)
• First branch coming off of the aorta and it
  carries blood to head and brain
• Returns through jugular veins to superior vena
  cava
• Left right Subclavian arteries carries blood to
  the arms and the subclavian veins return blood to
  the superior vena cava.

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Blood flow off Descending Aorta (2)

• Celiac artery carries blood to stomach, spleen
  and liver
• Portal vein leads to the liver and leaves through
  the hepatic (liver) vein to inferior vena cava.
• Superior mesenteric artery carries blood to the
  small intestine, which in turn connects to the
  portal vein.
• This way all materials entering the blood stream
  from the digestive tract are sent directly to the
  liver for detoxification.

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Blood flow off Descending Aorta (3)

• Inferior mesenteric artery leads to large
  intestine (and small, but mostly large)
• Large intestine leads to internal iliac vein
  (hypogastric) that connects to the inferior vena
  cava
• The Iliac arteries branches to supply blood to
  reproductive and excretory organs, as well as the
  legs
• Blood returns through iliac veins to inferior
  vena cava

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HEART QUESTIONS

• How many times will your heart beat in 80 years?
• How much blood is pumped with each heart beat?

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V. Cardiac Cycle

• Atrial diastole
• both atria fill with blood
• atrioventricular valves are open and the
  semilunar valves are closed
• 75 of ventricular filling occurs now
• lasts about 0.7 seconds
• Atrial systole
• atria contract forcing the remaining 25 of the
  blood into the ventricles
• lasts about 0.1 seconds

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Cardiac Cycle (2)

• Ventricular diastole
• ventricles are relaxing
• lasts about 0.5 seconds
• Ventricular systole
• ventricles are contracting
• blood is being forced into the aorta and
  pulmonary arteries.
• the semilunar valves are open and the
  atrioventricular valves are closed.
• lasts about 0.3 seconds

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VI. Cardiac Conduction System

1. Impulse originates in sinoatrial node (SA node or
   pacemaker) which is located in the superior
   region of the right atrium.
2. Impulse spreads across both atria which causes
   them to contract at the same time.
3. The impulse reaches atrioventricular node (AV
   node) located at the top of the right ventricle.

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Cardiac Conduction System (cont)

1. From the AV node the impulse passes through the
   atrioventricular bundle node to (Bundle of His).
2. The Bundle of His branches off into right and
   left bundle branches.
3. The impulse now flows through the many branches
   of the Purkinje fibers which pass deep into the
   ventricular myocardium.

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Pacemaker
Bundle of His
AV node
Purkinje fibers
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VII. Electrocardiogram-ECG or EKG

• Action potentials of all active cells can be
  detected and recorded
• The machine amplifies electrical impulses
  generated by your muscles.
• 4 basic parts to analyze
• P wave
• P to Q interval
• QRS complex
• T wave

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VIII. ECG Analysis

• Parameters
• Horizontal Axis
• Measures time of duration.
• Each box or mm 0.04 seconds

• Vertical Axis
• Measures voltage or amplitude
• Each box or mm 0.1 mV

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P-Wave

1. Depolarization of the atria (atrial systole)
2. Amplitude of P-Wave should be less than 0.2 mV to
   0.3 mV
3. Duration of P-Wave should be less than 0.11
   seconds

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QRS Complex

1. Atria repolarization (atrial diastole)
2. Ventricle depolarization (ventricular systole)
3. Amplitude should be greater than 0.5 mV in leads
   1, 2, or 3
4. Measured from tip of R to bottom of S
5. Duration should be less than 0.12 secs.

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T-Wave (isoelectric)

• Repolarization of ventricles (ventricular
  diastole)
• Amplitude should be less than 0.5 and greater
  than 1/10 of R wave for that segment.
• T-wave should be on the isoelectric line
• Duration not a concern
• T-wave should be in the same direction as the
  R-wave

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P-Q Interval

1. Measured from beginning of P to beginning of Q.
2. Between 0.12 and 0.2 second duration.
3. Too long indicates AV block.

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ST Segment

• Amplitude should be isoelectric
• If depressed more than 2 mm indicates ischemic
  heart.
• Most often caused by atherosclerosis.
• Duration should be between 0.13 - 0.16 sec.

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Heart Rate

1. HR 60/(R to R Interval in seconds)

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Cardiac Cycle
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Regulation of Heart Rate
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I. Cardiac Output (CO)

• The amount of blood the heart pumps in 1 minute.
• stroke volume (SV) amount of blood pumped per
  beat

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II. Influences on Stroke Volume

• Preload (affect of stretching heart muscle)
• Frank-Starling Law of Heart
• The longer the filling time, the greater the
  stretch of cardiac muscle
• more muscle is stretched, greater force of
  contraction
• This explains why athletes have lower resting
  heart rates but the same cardiac output
• more blood more force of contraction results
• Contractility
• autonomic nerves, hormones, Ca2 or K levels
• Afterload
• amount of pressure created by the blood in the
  way
• high blood pressure creates high afterload

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III. Control Centers for Heart Rate

• Two centers found in the medulla
• Cardioacceleratory center
• has a sympathetic nerve (cardioaccelerator nerve)
  that connects to the SA node of the heart.
• Cardioinhibitory center
• has a parasympathetic nerve (vagus nerve) that
  connects to the SA node of the heart.

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IV. Factors that effect heart rate

• Blood Pressure (BP)
• Carotid Sinus Reflex
• As the BP in the carotid sinus rises the walls of
  the carotid sinuses stretch (baroreceptors)
• Stretching increases stimulation of the
  glossopharyngeal nerve, which leads to the
  cardioinhibitory center in the medulla.
• The inhibitory center stimulates the Vagus nerve
  which slows down the heart rate
• Therefore a drop in HR, produced a drop in CO,
  which produced a drop in blood pressure, that
  reduced the amount of stretch in the carotid
  sinus.
• What happens if there is a drop in blood pressure
  in the carotid sinus?

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Factors that effect heart rate (cont)

• Aortic reflex (regulates BP to rest of body)
• Right Atrial (Bainbridge) reflex
• There are baroreceptors located in the right
  atrium and in the superior and inferior vena
  cavas.
• When these are stimulated heart rate increases.
• Why increase heart rate instead of decrease?

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Factors that effect heart rate (cont)

• Chemical Factors
• CO2
• increases heart rate
• Adrenaline (epinephrine)
• increases heart rate
• Ca 2
• increases heart rate
• Na and K
• lower heart rate

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Factors that effect heart rate (cont)

• Other factors
• Sex
• females have higher heart rates
• Age
• older-slower
• Exercise
• increase
• person who exercises regularly has a lower
  resting heart rate than one who doesn't - called
  Bradycardia
• Temperature
• Higher temperature, higher heart rate

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Cardiovascular Disease (CVD)

• In the U.S.1 million deaths/year

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I. Coronary heart disease (56)

• Cause
• Slow build up of fatty plaque (atherosclerosis)
  along the walls of the coronary blood vessels
  which reduces blood flow to heart
• The drop in O2 levels (ischemia) causes a angina
  which could lead to myocardial infarction.

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B. Diagnosis

• Outward symptoms of a heart attack
• pain in chest and left arm
• cyanosis of lips
• nausea
• dizziness
• shortness of breath
• cold sweat
• denial

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Diagnosis (cont)

• Exercise ECG
• ST Depression
• Problems with PR interval
• Angiogram
• A catheter is inserted into femoral artery of
  pelvis and worked into the aorta.
• Then dye is injected through catheter.
• A fluoroscope will show the dye pathway.
• Any narrowing or blockages will show up on the
  fluoroscope.

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C. Treatment

• Bypass surgery
• remove a vein from the leg and use it to bypass a
  blockage in heart vessel
• stop heart and put on a heart lung machine
• Angioplasty (see angiogram)
• Catheter with specialized tip is positioned where
  the coronary artery is narrowed or blocked.
• Use syringe to blow up catheters balloon (fig.
  20-14, page 599).
• Balloon presses the plaque up against the walls
  of the vessel.

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By-pass Graft
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Coronary Angioplasty
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CVD

• Stroke 20
• The interruption of blood flow to the brain
• Causes
• thrombus vs. embolus
• atherosclerosis (has no symptoms)
• aneurysm-broken blood vessel

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Stent in an Artery

• Maintains patency of blood vessel

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CVD

• Hypertension 7
• Chronic high blood pressure
• More common in black males than white.
• Myocardial degeneration 5
• Heart muscle degenerates
• Arteriosclerosis 4
• Hardening of the arteries
• Rheumatic fever 2
• Childhood disease that damages heart valves

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Risk Factors associated with Cardiovascular
Disease

1. age
2. sex
3. genetics
4. diets high in fat (hyperlipidemia)
5. high blood pressure
6. smoking
7. stress
8. alcohol
9. obesity
10. inactivity

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First Heart Attack Risk Test

• Age
• Men 0 pts Less than 35, 1 pt 35 to39, 2 pts
  40 to 48, 3 pts 49 to 53, 4 pts 54.
• Women 0 pts Less than 42, 1 pt 43 to 45, 2
  pts 46 to 54, 3 pts 55 to 73, 4 pts 74.
• Family History 2 pts if family has a history
  (parents and/or grandparents) of heart disease or
  heart attack before age 60.
• Inactivity 1 pt if you rarely exercise or do
  anything physically demanding.
• Weight 1 pt if you are more than 20 pounds
  overweight.

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First Heart Attack Risk Test (cont)

1. Inactivity 1 pt if you rarely exercise or do
   anything physically demanding.
2. Weight 1 pt if you are more than 20 pounds
   overweight.
3. Smoker 1 pts if you smoke
4. Diabetes 1 pt if you are male, 2 pts if your are
   female.
5. Total Cholesterol Level 0 pts if you are less
   than 240 mg/dl, 1 pt if you are 240-315 mg/dl and
   2pts if you are greater than 315 mg/dl.

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First Heart Attack Risk Test (cont)

1. HDL Level 2 pts if you are under 30 mg/dl, 1
   pt if you are 30-38 mg/dl or 1 pt if you are over
   60 mg/dl, and 0 pts if you are 38-59 mg/dl.
2. Blood Pressure (Systolic) 0 pts if less than
   140 mmhg, 1 pt if 140-170 mm/hg and 2 pts if
   greater than 170 mmhg.
3. Scoring the test Any value above four represents
   an above average risk the higher the number, the
   greater the risk.

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IX. Benefits of Aerobic Exercise

• Normalizes BP
• Bradycardia
• heart pumps more blood per beat
• more efficient
• Increases the number of RBC's
• Increases caloric output
• Decreases LDL's and increases HDL's
• High density lipoproteins (HDL's) contain more
  protein than fat and HDL's are able to remove low
  density lipoproteins (LDL's) from the blood
  stream
• LDL's have a higher proportion of fat and tend
  to accumulate along the walls of the arteries of
  the body, and heart in cerebral arteries

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X. Designing A Good Exercise Program

• Correct intensity as measured by heart rate
• Heart must work
• athlete 80-90 of the max. HR
• normal 70-80 of the max. HR
• older 60-70 of the max. HR
• Maximum HR 220 age
• e.g. a normal person 40 years of age(220-40) x
  70180 x 0.7 126.0 beats/min.180 x 0.8144
  beats/min.

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Designing A Good Exercise Program (cont)

• Correct duration
• 20 minutes or longer at target heart rate
• Frequency
• 3-4 times a week or every other day