10.28.08: Cardiac Muscle
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Author(s): Louis D’Alecy, 2009
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Citation Key for more information see: http://open.umich.edu/wiki/CitationPolicy
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Cardiac Muscle I
M1- Cardiovascular/Respiratory Sequence
Louis D’Alecy, Ph.D.
Fall 2008
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Tuesday 10/28/08, 10:00Cardiac Muscle I
19 Slides, 50 min 1. CM structure 2. CM contractile function 3. Ca++ induced Ca++ release 4. Isometric contraction 5. Isotonic contraction 6. Afterloaded contraction
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Mc-Graw-Hill Companies, Inc.
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Requirements for Effective Cardiac Pumping
1) Synchronized not arrhythmic
2) Valves open fully not stenotic
3) Valves don't leak not insufficient or regurgitant
4) Forceful not failing
5) Must fill Not "dry"
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Cardiac myocyte
Purkinje fibers
SA node - pacemaker
AV node
One heart - ~ 1 billion cells
Intercalated Disc = Firm mechanical connection Low resistance electrical connection
Source Undetermined (All Images)
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Functional syncytium
Source Undetermined
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9 Source Undetermined
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CALCIUM-INDUCED CALCIUM RELEASE 1. “Excitation” (Depolarization of plasma membrane) 2. Opening of voltage-sensitive Ca++ channels in
transverse tubules 3. Flow of Ca++ into cytosol (small amount ~20%) 4. Ca++ binds to Ca++ receptors (Ryanodine receptor) on
the external surface of the sarcoplasmic reticulum within the cell
5. Opening of Ca++ channels (large amount of calcium release ~ 80%)
6. Flow of Ca++ into cytosol 7. Cytosolic Ca++ conc. increases (10-7M to ~10-5M) 8. Contraction
0.1 µM to 100 µM
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Calcium-Induced Calcium Release
Essentially defines ʻcontractility”.
Source Undetermined
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12 Source Undetermined
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ISOMETRIC LENGTH-TENSION TE
NSIO
N
Source Undetermined
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14 Source Undetermined
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Optimized stretching
Good
“Over stretched” Bad
Source Undetermined
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Passive stretch & Isometric contraction
2.8 MH Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Inactive Active “At rest” Diastole
Contracting Systole
Same tension (load) but shorter length. Source Undetermined
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1 to 3 Isotonic at 1 g tension
2.9 MH
Isotonic = Shortening at same tension
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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2g 2g 2g
2.9 MH Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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2g 2g 2g
2.9 MH Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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1-2-3 Isotonic 1-4-5 Afterloaded
2.9 MH
Relaxation
“COUNTER CLOCKWISE ROTATION”
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Terms Related to Cardiac Performance
Preload - The ventricular wall tension at the end of diastole.
Afterload -- The ventricular wall tension during contraction; the resistance that must be overcome for the ventricle to eject its contents. Approximated clinically by systolic ventricular or arterial pressure.
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1. Afterloaded contraction (length-tension) 2. Afterloaded contraction (volume-pressure) 3. LaPlace 4. Wiggers diagram 5. Stroke volume & Ejection Fraction 6. Cardiac Output 7. Right pump 8. Preload (Frank-Starling), Afterload, & Contractility
Tuesday 10/28/08, 11:00Cardiac Muscle II
22 Slides, 50 min
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24 3.3 MH
active
passive stretch
COUNTER CLOCKWISE ROTATION
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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3.3 MH
Ejection Fraction = 70/130 = 54%
ventricular systole
diastolic filling
COUNTER CLOCKWISE ROTATION
Pressure increases as radius decreases.
LV end-diastolic Volume
**** LVEDV ****
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Law of La Place T = P x r (see page 44 of M&H)
The tension (T) in the ventricular wall depends upon both the pressure (P) in the chamber and
the radius (r) of the chamber. Thus as the ventricle gets smaller during
ejection the pressure within increases even at the same muscle tension.
Same T = P x r
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COUNTER CLOCKWISE ROTATION
Source Undetermined
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Top 3.1 MH
C = isovolumetric contraction D = isovolumetric relaxation
Ventricular A = diastole B = ventricular systole
Time on x axis
2
1
3
Three Pressures
mmHg
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Systole & Diastole Text books vary in definitions but the more common uses of the unmodified
terms “systole” and “diastole” are:
Systole is the period from the closing of the atrio-ventricular valve (mitral) to the closing of the aortic valve (ventricular contraction).
Diastole is the period from the closing of the aortic valve to the closing of the atrio-ventricular valve (ventricular relaxation and filling).
M & H NOTE: Your text distinguishes ventricular systole from arterial systole:
Ventricular systole is the period from the closing of the atrio-ventricular valve (mitral) until its opening. (Fig 3.1 M &H)
Arterial systole is the period from the opening of the aortic valve until its closing.
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3.1 MH
Ventricular Filling
(volume mL)
Ventricular ejection
Flow mL /min
LV end-diastolic Volume
****LVEDV****
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Small P & V Contribution from Atrial contraction.
Source Undetermined
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Heart Rate X Stroke Volume = Cardiac Output
HR X SV = CO b/min X mL / b = mL / min
Heart is a Pressure Pump but also pumps volume/time.
Stroke Volume = volume pumped with each beat of the heart.
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The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
Capillaries
Lungs RV
= Volume Pumped LV
Volume Pumped
DʼAlecy
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Not 125 mmHg
3.2
Squares
Circles
Solid line Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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35 Source Undetermined
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+ and (-) CHRONOTROPIC EFFECTS
McGraw-Hill
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Terms Related to Cardiac Performance Preload - The ventricular wall tension at the end of diastole.
Afterload -- The ventricular wall tension during contraction; the resistance that must be overcome for the ventricle to eject its contents. Approximated by systolic ventricular or arterial pressure.
Contractility -- Property of heart muscle that accounts for changes in strength of contraction independent of preload and afterload.
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Stroke Volume
Contractility
Afterload
Preload
+
+
-- Complex interactions so
we will treat each separately with others held constant.
DʼAlecy
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Increased Preload Increases Stroke Volume Frank -Starling
3.5 MH
Contractility & Afterload ~
CONSTANT
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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3.5 MH
LV Pressure
Contractility & Afterload ~
CONSTANT
Preload
Increased Preload ~ Increases SV (Frank-Starling Mechanism)
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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However ! Excessive Diastolic Volume or Pressure Decreases Developed Tension
Source Undetermined
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42 3.6 MH
Increased Afterload Decreases SV
Contractility & Preload ~
CONSTANT
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Increased Afterload Decreases SV
3.6 MH
Contractility & Preload ~
CONSTANT
Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed.
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Stroke Volume
Contractility
Afterload
Preload
+
+
-- Complex interactions so
we will treat each separately with others held constant.
√
√
Next hour.
DʼAlecy
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Additional Source Information for more information see: http://open.umich.edu/wiki/CitationPolicy
Slide 5: Mc-Graw-Hill Companies, Inc. Slide 7: Source Undetermined Slide 8: Source Undetermined Slide 9: Source Undetermined Slide 11: Source Undetermined Slide 12: Source Undetermined Slide 13: Source Undetermined Slide 14: Source Undetermined Slide 15: Source Undetermined Slide 16: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 18: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 19: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 20: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 21: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 24: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 25: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 27: Source Undetermined Slide 28: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 30: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 31: Source Undetermined Slide 33: D’Alecy Slide 34: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 35: Source Undetermined Slide 36: McGraw-Hill Slide 38: D’Alecy Slide 39: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 40: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 41: Source Undetermined Slide 42: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 43: Mohrman and Heller. Cardiovascular Physiology. McGraw-Hill, 2006. 6th ed. Slide 44: D’Alecy