Cardiac contraction Flashcards by Joe Pence

what are the two key elements of excitation-contraction coupling

structure

CICR

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what two structures are most important to EC coupling

T tubules

sarcoplasmic reticulum

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what is the general process of calcium induced calcium release CICR

Calcium enters the the cell during phase two, triggering the release of calcium from the SR and producing a contraction

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trigger calcium

calcium that enters the cell through a calcium channel that bings to ryanodine receptors and triggers CICR

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what is the function of a ryanodine receptor

binds with calcium to allow for the release of calcium from the SR

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what does SERCA do

uses ATP to pump calcium back into the SR afer a contraction to allow the muscle to relax

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what is necessary for cardiac muscle relaxation

a decrease in intracellular calcium concentration

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T/F contractility is dependent on preload and afterload

false, it is an intrinsic capability of the heart dependent on calcium

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contractility

the intrinisic contractile force of the heart a given preload and afterload

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Frank-Starlings law

increased ventricular filling (preload) will increase tension in the heart muscle and increase contraction force

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what is the difference between contractility and Frank-Starlings law

contractility is intrinsic and Ca dependant

Frank-Starling is dependent on preload, not calcium

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Describe the calcium signalling process

Ca enters the cell

trigger calcium binds to ryanodine triggering CICR

depolarization and muscle contraction

repolarization through calcium sequestering by SERCA

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what protein regulates SERCA activity

phosopholamban

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describe how phospholamban works

at rest phospholamban inhibits SERCA

stimulation of beta adrenergic receptors releases cAMP

cAMP phosphorylates phospholamban

phosphorylation allows SERCA to function

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what is the function of phospholamban at rest

inhibition of SERCA

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what is the function of phospholamban in response to sympathetic beta receptor stimulation

phosphorylation by cAMP will disassociated phospholamband from SERCA to allow calcium to be removed from the cytoplasm

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what are the functions of cAMP in regards to contractility of the heart

it stimulates L type calcium channels to increase Ca influx

phosphorylation of phospholamban to increase SERCA activilty

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how does SERCA allow for enhanced contractility

increased SERCA activation will increase the amount of Ca in the SR and allow for a greater release, whch will trigger a stronger contraction

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what is the effect of digitalis on the heart

it increases contractility

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how does digitalis (digoxin) produce greater contractility in the heart

it increases intracellular Na concentration, decreasing the activty of the Ca/Na exchanger and increasing the amount of intracellular calcium

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why does intracellular calcium increased contractility

more calcium means there are more Ca bound to troponin which will allow for more myosin binding sites

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describe the path of blood through the heart

vena cava

right atrium

tricuspid valve

right ventricle

pulmonary semilunar valve

pulmonary artery

lungs

pulmonary vein

left atria

mitral valve

left ventricle

aortic valve

aorta

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two phases of the cardiac cycle

systole

diastole

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two parts of systole

isovolumic contraction

ejection

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three parts of diastole

isovolumic relaxation passive ventricular filling atrial systole

what are the four phases of the **ventricular cycle**

filling isovolumic contraction ejection isovolumic relatxation

what is the driving force behind the movement of blood during the cardiac cycle

pressure

ejection fraction

the amount of blood ejected from the left ventricle each beat

what is the formula for EF

SV/EDV

what is a normal ejection fraction what would it mean if EF were low

+50% lower values indicate heart failure

EDV vs ESV

EDV: the amount of blood in heart during ventricular filling ESV: the amount of blood remaining in the heart after a contraction

when is pressure the highest in the ventricles and aorta

during ventricular systole

incisura

the point on a ventricular pressure graph where the aortic valve closes, indicated by a small increase in pressure followed by a stedy decline

what would a high slope on a pressure/time graph indicate

increased contractility

what is measured by a pressure/volume loop

the efficiency and work performed by the heart

what is this? define the variables

a pressure time graph of the left ventricle A diastolic filling M1 mitral valve closes B isovolumic contraction A1 aortic valve opens C ejection A2 aortic valve closes D isovolumic relaxation M2 mitral valve opens

what is this? define the variables

a pressure volume loop ## Footnote A diastolic filling M1 mitral valve closes B isovolumic contraction A1 aortic valve opens C ejection A2 aortic valve closes D isovolumic relaxation M2 mitral valve opens

define the variables

1. mitral valve opens 2. diastolic filling 3. mitral valve closes 4. isovolumic contraction 5. aortic valve opens 6. ejection 7. aortic valve closes 8. isovolumic relaxation 9. stroke volume

what is stroke volume how do you calculate it

the volume of blood ejected each beat SV = EDV-ESV

what is cardiac output how do you calculate it

the total volume of blood ejected from the heart each minute CO = SV x HR

what is ejection fraction indicative of

the effectiveness of ventricular ejection

normal vs impaired EF%

55-65% = 40%

what point on a pressure/volume loop indicate LVEDV and LVESV

mitral valve closing aortic valve close

what six things can be evaluated looking at a PV loop

* stroke volume * cardiac output * ejection fraction * contracility * ventricular wall compliance * ventricular preload an afterload

how can stroke volume be evaluated from a PV loop

SV = the width of the loop

how can cardiac output be evaulated on a PV loop

CO = SV x HR

how can EF% be determined using a PV loop

dividing the width of the loop (stroke volume) by the volume when the aortic valve closes (LVESV)

how can you determine the contractility of the heart from a PV loop

the systolic pressure (upper) line will have an increased slope with increased contractility

how can you determine ventricle wall compliance from a PV loop

the diastolic compliance curve (lower line) will have a flatter slope

what would a steeper diastolic compliance curve on a PV loop indicate

a decreased level of compliance indicated by less volume filling at a given pressure and preload

T/F compliance always goes up in the heart

false it always go down

compliance formula

change in volume/change in pressure

positive inotropic effect what type of drugs would cause this

increased contractility of the heart Beta adrenergic agonists

negative inotropic effect what would cause this

decreased contractility beta blockers

what effect would increased contractility have on a PV loop what would be the result

the systolic pressure curve would sift to the upper left, indicating a higher pressure per volume increasing stroke volume

T/F increasing contractility would affect LVEDV

false

Laplace Law for a sphere

tension in the ventricular wall is equal to the pressure multiplied by the radius divided by the width of the ventricle

Laplace Law formula

T = (P x r)/w

how can Laplace Law be manipulated to find pressure

P = (w/r)(T)

what would be the effect of increased preload on a PV loop what would be the result

it would increase the LVEDV, increasing the amount of tension in the wall and increasing contraction force increased stroke volume

T/F changing the filling (venous) pressure of the system alters stroke volume by increase LVESV

false, on LVEDV will be changed with an increase in venous pressure

afterload

the force that opposes ventricular shortening against aortic pressure

what will be the effect of increasing afterload on a PV Loop what is the result

it will move the point of aortic valve closing to the right due to higher pressure required with less volume ejected decreased stroke volume

what is a condition that would cause decreased compliance in the left ventricle? the aorta? what would cause an increase?

myocardial infarction HTN nothing

what would be effect of decreased compliance on a PV loop what is the result

decreased compliance would require more pressure with less filling, resulting in a steeper diastolic loop decreased stroke volume

what is effect of compliance on end systolic volume? end diastolic volume?

no effect decreased volume

which part of the cardiac cycle is longer? as HR increases, which part get shorter?

diastole diastole

a patient presents with an HR +200bpm why would this need to be treated immediately

because over 180bpm increasing HR causes a decrease, not an increase in CO

what is ficks principle used for? what is the equation

to determine CO by the amount of O2 consumed divided by the difference of arterial and venous PO2 CO = (VO2)/(Cpv - Cpa) \*high minus low

what are the four areas of auscultation over the heart

aortic pulmonic tricuspid mitral

where is the aortic area of ausculation? pulmonic? mitral? tricuspid?

2nd right intercostal space 2nd left intercostal space 5th intercostal space at the sternm 5th intercostal space at the mid clavicle

what is the "LUB" sound what is the "DUB" sound

mitral and tricupsid valve closure aortic and pulmonic valve closure

three examples of conditions that might cause a murmur

high blood flow through a valve in pregnancy systemic disease such as anemia valvular heart disease

if you hear a systolic murmur over the 2nd right sternal intercostal space, what would this most likely be

aortic vale stenosis

if you hear systolic murmur over the 5th intercostal space at the midclavicular line, what would be the expected cause what if it were at the 5th sternal intercostal space

mitral valve incompetance tricuspid valve incompetence

two systolic murmurs

aortic valve stenosis mitral or tricuspid valve incompetance

what type of murmur would be heard with aortic valve incompetance

diastolic murmur over the 2nd right intercostal space

Cardiac contraction Flashcards

(77 cards)