Cardio Physiology Flashcards by Michael Yee

What is Poiseuille’s equation? What is it used to measure?

It is used to measure flow.

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Fill in the blanks.
Adrenergic sympathetic fibers release ______ which interacts with the B1 adrenergic receptors on the heart.

Parasympathetic fibers release ____ which acts on the muscarinic receptors on the SA/AV nodes and atrial muscle

Adrenergic sympathetic fibers release norepinephrine which interacts with the B1 adrenergic receptors on the heart.

Parasympathetic fibers release Acetylcholine which acts on the muscarinic receptors on the SA/AV nodes and atrial muscle

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Describe what is happening during Phases 0 through 4

Phase 0- rapid depolarization, Na channels open and Na enters the cell
Phase 1- Na channels close, K channels open allowing K out of the cell
Phase 2- K channels remains open, Ca channels open, allowing Ca2+ into the cell
Phase 3- Ca Channels close, K remains open to repolarize
Phase4- K channels close, resting membrane potential

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Describe what is happening during phase 4, 0 and a3

Phase 4- Funny currents allow slows depolarization of Na, Ca also open to further depolarize the cell
Phase 0- Depolarization is caused by the Ca 2+ inward
Phase 3- K channels open to hyperpolarize the cell

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Cardiac muscle is connected by end- to end structures known as

Intercalated discs

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Where is Ca2+ sequestered within cardiac muscles

Sarcoplasmic reticulum

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What is Calcium- induced calcium release

Release of stored Ca from within the Sarcoplasmic reticulum following Ca entry into the cell

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Describe the steps in Cardiac excitation-contraction coupling

Increase in Ca leads to Ca induced Ca release.
Calcium binds to troponin C which releases the inhibition of Actin
Actin crosslinks to Myosin
Thick and thin filaments slide over each other
Calcium is taken back into SR via Ca ATPase

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What is the Staircase Phenomenon/Bowditch effect?

As HR increases, more and more Ca is stored in the SR resulting in higher and high contractility

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What are the 6 phases of the Cardiac cycle?

Atrial systole, isovolumetric contraction, ejection, isovolumetric relaxation, Diastasis

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What is/causes the dicrotic notch/Incisura?

Closing of the aortic valve

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Fill in the graph

a wave- atrial contraction
c wave- Ventricular contraction
x descent- Atrial relaxation, pulling of tricuspid valve towards RV
v wave- End of RA filling towards end of systole
y descent- RA emptying into RV

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The V wave on CVP measurements corresponds with what on an ECG?

T wave

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What causes the 4 heart sounds?

S1= AV valves closing
S2: Aortic valves closing
S3: End of early diastolic filling
S4: Atrial contraction and rapid ventricular filling

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What is the equation for delivery of Oxygen?

DO2= CaO2*CO

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What is the equation for CaO2?

CaO2= (0.003PaO2)+ (1.34Hgb*SaO2)

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What is happening during each phase of the Ventricular PV loop?

Phase 1–>2 isovolumetric contraction
Phase 2–>3 ejection
Phase 3–>4 isovolumetric relaxation
Phase 4–>0 Ventricular filling

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How will changes in Preload, afterload and contractility affect the ventricular PV loop?

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What is the law of LaPlace? What is it used to measure?

A measure of wall stress
Wall stress= Pressure* radius/2(thickness of wall)

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What are ways to measure cardiac output?

Ficks principle
Thermodilution
Lithium thermodilution

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Explain how you can use Fick’s principle to measure cardiac output

Fick’s principle states that ‘total uptake of substance is equal to blood flow * concentration gradient’

CO= (VO2)/ (CaO2-CvO2)

You can measure inhaled vs. exhaled oxygen to get VO2 and arterial and venous oxygenation to determine extraction

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What is ejection fraction? What is fractional shortening?

Ejection fraction is the volume of blood pumped by the ventricle
Fractional shortening is the % of contraction by the ventricles

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How is ejection fraction measured?

SV/End diastolic volume

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What is the equation for Mean Arterial Pressure?

MAP= (2*DP+SP)/3

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What is the difference between absolute refractory period and relative refractory period?

The relative refractory period can be overridden

How will Changes in inotropy, blood volume and total peripheral resistance affect the CO/vascular function curve?

Where are baroreceptors located?

Carotid sinus and aortic arch

Where is renin synthesized and stored?

Juxtoglomerular cells of kidneys

What is the most important hormone in inhibition of Renin release?

Angiotensin II

What are causes for renin release?

Decreased afferent arteriole stretch, decreased NaCl concentrations within the Macula Densa

What are 4 effects of Angiotensin II?

Vasoconstriction Increased thirst Increased salt and water retention Promotes ADH secretion

What are the primary functions of aldosterone?

Na/water resorption, K excretion

What are 3 classes of drugs that can suppress RAAS?

ACE inhibitors Angiotensin II receptor blockers Mineralocorticoid receptor antagonist

What is the Bainbridge effect? What causes it

Bainbridge effect is a drop in heart rate following rapid venous volume expansion. This occurs due to low pressure baroreceptors within the veins.

What are 2 potential hypotheses for control of regional blood flow?

Myogenic hypothesis-- arterial stretch--> arterial contraction Metabolic hypothesis-- As a result of increased metabolic activity, vasodilatory metabolites are released

What is ANP and BNP? What are their functions?

Atrial Natriuretic peptide and B-type natriuretic peptide. They are produced 2' to stretch of stress of myocardial tissue. Their functions are natriuresis, diuresis, and vasodilation

In cases of heart failure, the heart uses ______ as a the preferential energy source?

Glucose

What is the difference between Class B1 and B2 in heart disease?

Class B1 indicates underlying heart disease with no structural changes. Class B2 has structural heart changes

What is considered a normal fractional shortening in dogs? Cats?

Dogs 28-45%, cats 30-50%

List 4 causes of LV hypertrophy.

HCM, Systemic hypertension, hyperthyroidism, congenital aortic stenosis, pseudohypertrophy

Label the following diagram with the correct anatomic locations for the pressure tracings

List 4 options for cardiac output measurement

Thermodilution Lithium dilution CO2 rebreathing Bioreactance

What is a pulmonary wedge pressure?

Measures the pressure within pulmonary capillaries

What are 3 hormones responsible for cardiac remodeling in CHF?

Norepinephrine, Aldosterone, Angiotensin II

How can we use cardiac troponins to diagnose myocardial infarction?

Cardiac trop will result in an acute massive spike in troponins vs. CHF which typically results in a slow release

What are the 5 major classifications of Cardiomyopathy?

HCM, DCM, ARVC, RCM, nonspecific

Which of the cardiomyopathy phenotypes is predisposed to PTE?

ARVC (Maybe this isnt that important)

What does Pro-BNP measure? How is this different from troponins?

ProBNP measures cardiac stretch. Troponins are intracellular proteins of sarcomeres

What is Commotio Cordis?

Blunt force trauma to the precordium during ventricular repolarization result in cardiac arrest (The Damar Hamlin)

What is the most significant cause of exudative pericardial effusion in cats?

FIP

What is pulsus paradoxus? When is it seen?

Changes in arterial pressure which are exaggerated with respirations. Pericardial effusion

What is the hepatojugular reflex?

Jugular distension when pressure is applied to the cranial abdomen.

Why is pericardial effusion typically approached from the right side?

Cardiac notch, less risk of lacerating coronary circulation

What is the role of cardiac troponins in pericardial effusion?

Cardiac troponins may be used to differentiate HSA from other causes of pericardial effusion

What is the Bezold- Jarish reflex?

Stimulation of LV--> results in bradycardia, vasodilation, hypotension

What is the most common cause for AV block in dogs?

Age related fibrodegenerative disease

What is the ventricular escape rate in dogs? Cats?

Dogs= 30-40bpm Cats= 60-130bpm

What is overdrive suppression?

The faster rhythm will inhibit the slower rhythm

BNP is secreted in response to ____

Myocardial stretch

What are non-cardiac causes for an elevated Pro-BNP?

Renal dz, systemic hypertension, hyperthyroidism, IVF administration

Elevated troponins with arrhythmias in the absence of an obvious cause=

Myocarditis

What are treatment goals with patients in hypertensive crisis?

Reduce systolic BP by 10% over the first hour then 15% over the next several hours