Lecture #1 - Part 2 Flashcards
What does Excitation-Contraction coupling refer to?
Connection leading from electrical changes in the PM to initiation of contraction.
Cause of cardiac muscle contraction?
Increase in intracellular Ca+
Talk through the steps of muscular contraction
Depolarization along Sarcolema into T Tubules
Trigger Ca enters via L-Type Voltage-sensitive channels
Trigger Ca opens Calcium release channels
Calcium leaves SR –> Calcium “spark”
Calcium Binds Troponin subunit C
Another name for L-type voltage sensitive channels?
DHP receptors
Another name for calcium release channels?
Ryanodyne Receptors
Two proteins associated with Ryanodine receptors?
Junctin
Triadin
How are heart contractile activities dysregulated in heart failure?
SR Calcium Stores Depleted
Weakened Contractility
How does cardiac muscle relax?
cAMP dependent protein kinase P’s troponin I
Tropomyosin can now reblock the binding site
Calcium removed from sarcoplasm by SERCA
What causes SERCA activation?
phospholamban
How do catecholamines affect the heart?
Speeding the phosphorylation rate of Troponin I and Phospholamban
What is lusitropy?
Relaxation of the heart
What happens to Ca after it is pumped into the SR?
Binding to calsequestrin
Other than SERCA, where else might Ca go?
Pumped out in NA-Ca exchange pump (Coupled with Na/K)
(much less important) Ca ATP-ase
Increasing available intracellular calcium has what effect on the heart?
More vigorous contraction
What is the Cardiac Inotropic State?
Myocardial Contractility, The Force Developed by the Heart Muscle at a given length.
Ca influence on the heart’s ionotropic state?
Higher with increased intracellular calcium
Four primary influences on intracellular calcium?
Extracellular Calcium
Positive Inotropic Agents
Heart Rate
Negative Inotropic Agents (Ca channel blockers)
Effects of increased and decreased extracellular calcium?
Increased – Initial inc. in contractility, eventually arrest in systole
Decrease – Initial dec in contractility, eventual arrest in diastole
Give two examples of positive inotropic agents.
Catecholamines (Inc. P of Ca channels to let Ca in)
Digitalis (inhibits Na/K pump, less Ca pumped out)
Why would increasing the heart rate increase calcium levels?
Not enough time to return it all to the SR between contractions.
What does the force-frequency relationship refer to?
Increase in contractility with the increase in the HR due to remnant Ca
Two ways Calcium channel blockers influence the CV system
Contractility reduced, as less Ca gets in
No Ca for smooth muscle –> Vasodilation and lost Per. Resistance.
Four types of Cardiomyopathy?
Dilated cardiomyopathy
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Arrhythmogenic RV Dysplasia
Six Steps in Heart Contraction
Filling Atrial Systole Isovolumetric Ventricular Contraction Ejection (Rapid, then reduced) Isovolumetric Relaxation Filling Again
Define End Diastolic Volume
Volume in the Ventricle following Atrial Systole
Role of papillary muscles?
Pull on chordae tendinae to prevent AV values from inversion
Define End Systolic Volume
Blood volume remaining in the ventricle following Systolic Contraction in the isovolumetric relaxation phase
How does end diastolic volume relate to heart rate?
Higher heart rate means that diastolic filling time is reduced
Approx. fractions for blood movement in a healthy heart?
1/3 End Systolic Volume
2/3 Pumped Out
Relationship of SV, End Diastolic, and End Systolic Volumes
SV=EDV-ESV
Equation for Ejection Fraction.
(SV/EDV) x 100 (for percentage)
What does the incisura reflect?
Closure of the aortic semilunar valves
Memorize pg 8 figure
plz.
What is the Pulse Pressure?
The difference between the systolic and diastolic pressure.
Difference in pressure between R and L Heart?
Much lower systolic pressure
Why does the drop in pressure in reduced ejection occur?
Onset on physiological systole
Equation for CO
CO = HR x SV
Low ejection fraction may indicate…
Heart Failure
Relationship of SV, EDV, and Ejection Fraction
SV= (EF) (EDV)
Equation for Cardiac Index.
Cardiac Output/Body Area
Equation for Stroke Index.
Stroke Volume/Body Area
Equation for Stroke Work
(SV) (Mean Arterial Pressure)
Equation for Pulse Pressure
Systolic Pressure - Diastolic Pressure
Equation for MAP (with Diastolic)
Diastolic + 1/3 (Pulse Pressure)
Equation for MAP (with CO)
CO X Systemic Vascular Resistance
Equation for MAP (with HR)
(HR)(SV)(Systemic Vascular Resistance)
What is compliance? (concept)
A measure of wall stiffness
What is compliance (equation)?
Change in V / Change in P
SV/PP (for full system)
Increasing compliance will have what affect on pulse pressure.
Inc Stiffness will cause inc. pressure
Non-Compliant arteries will have _______ pulse wave velocity
Higher
Source of reflected waves
Bifurcations and diameter changes
Relationship of Diastolic Run Off to SVR (Total Peripheral Resistance)
Inverse
Central Venous Pressure is equal to (for all intents and purposes)
RA Pressure
How can Central Venous Pressure be determined?
Measurement of Jugular Vein Filling
Direct catheterization of the right internal jugular
Name the five venous waves
Positive - a,c,v
Negative - x,y
Cause of A-Wave
R Atrial Systole
Cause of C-Wave
Tricuspid Closes
Cause of X-wave
Atrial Relaxation, Early Ventricular Ejection
Cause of V-Wave
Increased Pressure from Passive Atrial Filling
Cause of Y-Wave
Tricuspid Opens
