BRS Phys Review Flashcards by Sarah Gillen

What is the site of highest resistance in the CV system?

Arterioles

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What part of the CV system has the largest total cross sectional and surface area?

Capillaries

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_____ are formed from merged capillaries

Venules

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What contains the highest proportion of blood in the CV system?

Veins

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How is velocity of blood flow calculated?

V = Q/A

Where Q is flow (mL/min) and A is cross sectional area

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How is blood flow (Q) calculated?

Q = change in pressure/R

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How would you calculate CO using MAP and TPR

CO = (MAP - right atrial pressure)/TPR

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Parallel resistance is illustrated by the ______ circulation; when an artery is added in parallel, the total resistance _________

Systemic; decreases

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_______ resistance is illustrated by the arrangement of blood vessels within a given organ (series or parallel?)

Series

The largest proportion of resistance in series is contributed by arterioles. As blood flows through the series of blood vessels, the pressure decreases

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When Reynolds number increases, there is greater tendency for turbulence, which causes audible vibrations called _______.

What 2 factors increase Reynold’s number?

Bruits

Decreased blood viscosity (decreased hematocrit, anemia)
Increased blood velocity (narrowing of a vessel)

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_____ is a consequence of the fact that blood travels at different velocities within a blood vessel

Velocity of blood is ______ at the wall and _______ at the center of the vessel

Shear

Zero; highest

[shear is therefore highest at the wall, where the difference in blood velocity is greatest]

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How is capacitance (compliance) calculated?

C =V/P

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Where is compliance greater, veins or arteries?

Veins (as a result more blood is contained in unstressed volume than stressed volume)

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What happens to capacitance of the arteries with age? What effect does this have?

Capacitance of the arteries decreases with age; as a person ages, the arteries become stiffer and less distensible.

Result is an increase in pulse pressure

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As blood flows through systemic circulation, pressure decreases progressively because of the resistance to blood flow. Thus, pressure is highest in the ______ and large _______, and lowest in the __________

Aorta; arteries

Vena cavae

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Where does the largest decrease in pressure occur in the CV system?

Arterioles - because they are the site of highest resistance

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What are the mean pressures in the following:

Aorta
Arterioles
Capillaries
Vena cava

Aorta = 100 mm Hg

Arterioles = 50 mm Hg

Capillaries = 20 mm Hg

Vena cava = 4 mm Hg

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________ = the difference between the systolic and diastolic presures

Pulse pressure

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What is the most important determinant of pulse pressure?

Stroke volume

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______ = average arterial pressure with respect to time

Mean arterial pressure

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How is MAP calculated?

MAP = diastolic pressure + 1/3 pulse pressure

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______ atrial pressure is estimated by pulmonary wedge pressure

Left

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Resting membrane potential of ventricles, atria, and purkinje system

-90 mV (approaches K+ equilibrium potential)

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Where is conduction velocity the fastest vs. the slowest in the heart?

Fastest in the Purkinje system

Slowest in the AV node (PR interval on ECG)

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Chronotropic effects produce changes in what?

HR (by changing the firing rate of the SA node)

Dromotropic effects produce changes in what?

Conduction velocity (primarily in the AV node) [this would increase or decrease the PR interval on ECG]

Which of the following does not have parasympathetic vagal innervation? A. SA node B. Atria C. Ventricles D. AV node

C. Ventricles

The SA node, atria, and AV node have parasympathetic innervation, where the NT is _________, which acts on _________ receptors

ACh; muscarinic

An increased heart rate occurs d/t sympathetic stimulation of _____ receptors

B1 [same receptor for sympathetic increases in conduction velocity via AV node, and contractility]

Sympathetic activity causes constriction of vascular smooth muscle of skin, splanchnic vessels, and vessels around skeletal muscles occurs via _____ receptors

Alpha1

Relaxation of vascular smooth muscle occurs via _____ receptors

What is the mechanism of a negative chronotropic effect?

Heart rate is decreased due to decreased inward Na+ current, thus decreasing the rate of phase 4 slow depolarization in the SA node

What is the mechanism of a negative chronotropic effect?

Decrease in conduction velocity through the AV node is due to decreased inward Ca+ current and increased outward K+ current, thus increasing the PR interval

Sympathetic effects on heart rate and conduction velocity occur using ______ as the NT, which acts on _____ receptors

NE; B1

A positive chronotropic effect increases heart rate due to increased inward _____ current responsible for phase 4 depolarization in the SA node

Positive dromotropic effects increase conduction velocity through the AV node due to increased inward ____ current which decreases the ______ interval on ECG

Ca+; PR

_________ is the contractile unit of the myocardial cell which runs from ______ to ______

Sarcomere; Z line to Z line

_____________ occur at the ends of myocardial muscle cells and maintain cell to cell cohesion

Intercalated disks

what are present at intercalated disks, acting as low resistance paths between cells that allow for rapid electrical spread of APs?

Gap junctions (account for heart as an electrical syncytium)

Where are mitochondria more numerous, in cardiac muscle or skeletal muscle?

Cardiac

_____ are continues with cardiac muscle cell membranes and invaginate the cells at the Z lines where they carry APs into the cell interior. They form _______ with the SR

T tubules; dyads

T tubules are well developed in the _______ of the heart, but poorly developed in the _____

Ventricles; atria

What are the sites of storage and release of Ca++ for excitation-contraction coupling in cardiac muscle cells?

During the plateau of the cardiac action potential, Ca+ conductance is increased and Ca+ enters the cell from the ECF through _____ channels, aka _______ receptors

L-type; DHP

Initial calcium entry from the ECF triggers release of even more Ca from the SR through release channels called ________ receptors

Ryanodine

The amount of Ca released from the SR depends on what 2 factors?

- amount of Ca previously stored | - size of inward Ca current during the plateau of the AP

The magnitude of the tension that develops during excitation contraction coupling is proportional to what?

The intracellular Ca concentration

______ = intrinsic ability of cardiac muscle to develop force at a given muscle length

Contractility (aka ionotropism)

Contractility is related to the intracellular Ca concentration and can be estimated by the _________

How is ejection fraction calculated? What is normal EF?

SV/EDV Normally 55%

What are the 3 major factors that have positive ionotropic effects?

Incrased heart rate (Bowditch staircase, postextrasystolic potentiation) Sympathetic stimulation (catecholamines) via B1 receptors Cardiac glycosides (digitalis)

Sympathetic stimulation (catecholamines) have positive ionotropic effects via B1 receptors. What are the 2 major mechanisms by which these increase force of contraction?

1. Increases the inward Ca current during the plateau of each cardiac AP 2. Increases activity of Ca pump of the SR by phosphorylation of phospholamban (more is accumulated in SR so that more can be released in subsequent beats)

What is the MOA of cardiac glycosides like digitalis as a positive ionotropic effector?

Increase in force of contraction by inhibiting Na/K ATPase in the cell membrane --> increasing intracellular Na and diminishing the Na gradient so that Na/Ca exchanger pumps out less Ca ,--> increasing intracellular Ca

What is the major factor that causes a negative ionotropic effect? What is the MOA?

Parasympathetic (ACh) via muscarinic receptors - decreases force of contraction in the ATRIA by decreasing inward Ca current during plateau of the AP [because ventricles do not have parasympathetic vagal innervation!]

What is preload

EDV, which is related to right atrial pressure

What is afterload for the left and right ventricles?

Afterload for LV is aortic pressure Afterload for RV is the pulmonary artery pressure

What determines the maximum number of cross-bridges that can form between actin and myosin?

Sarcomere length

Velocity of contraction at a fixed muscle length is maximal when afterload is _______. Velocity is _______ by increases in afterload.

Zero Decreased

What is the Frank Starling relationship and how does it relate EDV to CO?

FS relationship describes increases in stroke volume and CO that occur in response to an increase in venous return or EDV. Increases in EDV cause an increase in ventricular fiber length, which produces an increase in developed tension, and thus a greater cardiac output

The ventricle develops greater tension than usual during systole, causing a _______ in stroke volume, which then results in a ______ in EDV

Increase; decrease

______ is the point at which the vascular function curve intersects the x-axis

Mean systemic pressure

What determines the slope of the venous return curve?

Resistance of the arterioles [a decrease in TPR causes an increase in venous return, an increase in TPR causes a decrease in venous return]

Positive ionotropic agents cause increased contractility, a higher cardiac output, and a correspondingly _______ right atrial pressure

Lower [right atrial pressure decreases because more blood is ejected from the heart on each beat - increased stroke volume]

What effect does an increase in blood volume or decrease in venous compliance have on cardiac output and right atrial pressure?

Both are increased

How is stroke volume calculated

SV = EDV - ESV

How is CO calculated

CO = SV x HR

How is stroke work calculated

SW = aortic pressure x SV

How would changes in the following increase cardiac oxygen consumption? Afterload Size of the heart Contractility HR

Cardiac O2 consumption increases with: Increased afterload (increased aortic pressure) Increased size of the heart Increased contractility Increased HR

What is the Fick principle for measuring cardiac output based on O2 consumption?

CO = O2 consumption/[O2]pulm v. - [O2]pulm a.

What causes the fourth heart sound

Filling of the ventricle by atrial systole

During which part of the cardiac cycle would you hear the first heart sound

Isovolumetric ventricular contraction (AV valves closing)

Why might the first heart sound be split?

The mitral valve closes slightly before the tricuspid valve

During which phase of the cardiac cycle does the aortic valve open? A. Atrial systole B. Rapid ventricular ejection C. Reduced ventricular ejection D. Rapid ventricular filling

B. Rapid ventricular ejection

When is aortic pressure the greatest? A. Rapid ventricular ejection B. Reduced ventricular ejection C. Isovolumetric ventricular contraction D. Rapid ventricular filling

B. Reduced ventricular ejection

Which part of the cardiac cycle corresponds to the second heart sound?

Closure of semilunar valves; occurs in isovolumetric ventricular relaxation

The "blip" in the aortic pressure tracing occurs after closure of the aortic valve during isovolumetric relaxation and is called the _____

Dicrotic notch, or incisura

During which phase of the cardiac cycle does the mitral valve open? A. Reduced ventricular ejection B. Isovolumetric ventricular relaxation C. Rapid ventricular filling D. Atrial systole

B. Isovolumetric ventricular relaxation

What causes the third heart sound

Rapid flow of blood from the atria into the ventricles

What part of the cardiac cycle corresponds to the third heart sound?

Rapid ventricular filling

What is the longest phase of the cardiac cycle?

Reduced ventricular filling (diastasis)

What are the 4 effects of angiotensin II in the renin-angiotensin-aldosterone system?

Stimulates secretion of aldosterone (which increases Na reabsorption by DCT) Increases Na/H exchange in PCT Increases thirst Vasoconstriction of the arterioles

What is the Cushing reaction?

Response to cerebral ischemia: Increases in intracranial pressure --> compression of cerebral blood vessels --> cerebral ischemia and increased cerebral PCO2 --> vasomotor center directs an increase in sympathetic outflow which causes profound increase in Pa

What is the action of vasopressin (ADH)

Potent vasoconstrictor that increases TPR by activating V1 receptors on arterioles Increases water reabsorption by the DCT and collecting ducts by activating V2 receptors

What is the action of ANP?

Released from atria in response to increase in blood volume and atrial pressure --> causes relaxation of vascular smooth muscle and increased excretion of Na and water Also inhibits renin secretion

A decreased protein concentration in the blood would ________ filtration in capillaries

Increase

___________ = blood flow to an organ remains constant over a wide range of perfusion pressures. What organs exhibit this property

Autoregulation Brain, heart, kidney

What is active hyperemia?

Blood flow to an organ is proportional to its metabolic activity

What is reactive hyperemia?

Increase in blood flow to an organ that occurs after a period of occlusion to flow

Bradykinin causes arteriolar _______ and venous _______

Dilation; constriction [same effect as histamine]

What is the action of thromboxane A2

Vasoconstrictor

Sympathetic stimulation of ______ receptors in the heart causes vasoconstriction Sympathetic stim of _____ receptors in the heart cause vasodilation

Alpha1 Beta2