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Cardiac Contractility and Cardiac Output
Cardiac Contractility and Cardiac Output by Dr. Gibbons
35
Medical
Professional
10/07/2011

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Term
allows for easy travel of AP between cells and almost free diffusion of ions creating a syncytium of the heart
Definition
intercalated disc
Term
atrial and ventricular syncytium are separated by fibrous tissue called
Definition
AV node connector
Term
contractility is directly related to
Definition
intracellular Ca concentration/ handling
Term
Have you ever been so frightened that you felt your heart pounding so hard that you thought it would jump out of your chest?
What system mediates this response?
How does this system affect cardiac contractility?
Definition
Norepinephrine activates beta-adrenergic receptor /Gs-mediated activation of adenylate cyclase
NE increases cAMP levels
Increased cAMP promotes Ca influx via L-type Ca Channels
Increased cAMP promotes increased cytosolic Ca from SR.
NE effect on Ca++ induces increased cardiac contractility
Term
IIf Ca++ handling is so important to cardiac contractility; what do you predict will happen if you increase Ca influx via L-type Ca channels in cardiac myocytes through genetic engineering?
Definition
increased contractility
Term
IIf Ca++ handling is so important to cardiac contractility; what do you predict will be the inotropic effect (positive or negative) of a drug that blocks L-type Ca channels in cardiac myocytes?
Definition
Verapamil (L-type Ca channel blocker)
Reduces heart rate (negative chronotropic effect)
Reduces contractility (negative inotropic effect)
Term
on the frank starling curve a drug that blocks l type calcium channels would shift the curve
Definition
down and to the right
Term
on the frank starling curve an increase in the intrinsic ability of the heart to contract due to beta adrenergic stimulus shifts the curve
Definition
up and to the left
Term
the period of contraction that ejects blood to the lungs or the rest of the body
Definition
systole
Term
the period of relaxation when the heart fills with blood
Definition
diastole
Term
the volume of blood ejected from one ventricle in one beat
Definition
stroke volume which is about 70 ml
Term
end-diastolic volume - end systolic volume equals
Definition
stroke volume
Term
the volume of blood left in the ventricle after normal filling during diastole
Definition
end-diastolic volume
Term
volume of blood remaining in the ventricle after systole
Definition
end-systolic volume
Term
the fraction of the end-diastolic blood volume from one ventricle in one beat. which is a good index of heart contratility (normal range= 55-70%
Definition
ejection fraction
Term
stroke volume/ end-diastolic volume equals
Definition
ejection fraction
Term
the ventricular wall tension at the end of diastole, AKA the stretch on the muscle fibers just prior to contraction
Definition
preload
Term
clincial way to increase preload
Definition
IV fliud infusion
Term
the ventricular wall tension during contraction AKA the resistance that must be overcome to eject the stroke volume
Definition
afterload
Term
increased afterload in the mean aortic presure is a marker for
Definition
hypertension
Term
decreased afterload in the mean aortic pressure a marker for
Definition
hypotension
Term
peak left ventricular pressure, increased afterload is an indicator of
Definition
aortic stenosis
Term
property that accounts for changes in strength of contraction that is independent of preload and afterload, often affected by NT or hormonal influences and the contractility effect is mediated by hanges intercelluar Calcium
Definition
Contractility
Term
the 2 main factors the regulate CO
Definition
1. Intrinsic: venous return- ventricular filling pressure-preload (Frank-Starling mechanism)
2. ANS (sympatheitc and parasympatheitc nerves) regulate heart rate and strength of contraction
Term
Stroke volume X Heart rate =
Definition
cardiac output
Term
the cardiac output in an average healthy man
Definition
5L/minute
Term
expresses the functional ability of the ventricles to pump blood according to frank-starling mechanism
Definition
ventricular function curve
Term
An inrease in right and left atrial pressure leads to
Definition
increase in ventricular volume output on the right and left sides
Term
THe part of the ANS that causes an increase cardiac output at any given right atrial pressure
Definition
sympathetic stimulation
Term
The part of the ANS that leads to a decrease CO at any given right atrial pressure
Definition
parasympathetic stimulation
Term
way to measure the right atrial pressure
Definition
by measuring the length of the right jugular vein
Term
what tool can be used to measure the patient's cardiac pressure and cardiac output
Definition
Swan-Ganz catheter
Term
the method of measuring cardiac output
Definition
Oxygen Fick's
Term
In steady state:
Rate of O2 consumption in the body equal amount of O2
leaving the lung (pulmonary veins) minus amount of O2
returning to the lung (pulmonary artery)
Definition
Conservation of mass Fick's principle
Term
oxygen consumption/the change in arteriovenous oxygen concentration =
Definition
cardiac output
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