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PNB 277 6 LECTURE 3 &4 (HEART) EXAM WITH COMPLETE
SOLUTIONS 1 00 % VERIFIED!!
when comparing a ECG to a muscular diagram of heart contraction, the ______ comes before _______ electrical signal; muscular action
The Wiggers Diagram focuses on which ventricle? What does it track? the left ventricle; it tracks the ECG, blood pressure, heart sounds, blood volume, and heart cycle
read left to right because it shows you how things change over time
what is stroke volume? how is it calculated? the amount of blood pumped out from a ventricle during one contraction
calculated by subtracting ESV from EDV
this value is the same for the L and R ventricle***
what is ejection fraction? what does it tell us? %stroke volume/EDV
gives us an idea of how much blood is ejected on every cycle
what is cardiac output? how is it calculated? the blood volume pumped via ventricle during a period of time
heart rate*stroke volume
how do you find the stroke volume in a pressure/volume curve? the stroke volume is found by subtracting point D from point C (the distance between the two)
three key factors of heart rate regulation -depolarization speed of myocardial autorhythmic cells (pacemaker cells)
-autonomic nervous system
-hormones (epinephrine from adrenals)
NT, and receptors involved in the parasympathetic nervous system "rest and digest"
-acetylcholine -muscarinic
Channels & effect from the adrenal medulla releasing epinephrine "fight or flight"
-increase If; increase Ca -depolarization; higher potential
Two main ways stroke volume is regulatef -length of cardiac muscle fiber
-contractility of heart muscle fibers (ionotropic agents)
how does the length of cardiac muscle fiber regulate stroke volume? the loner the muscle fiber, the greater the tension created upon contraction
what is preload? how is it determined? the degree of myocardial stretch before heart contraction begins.
this is determined by the amount of blood flowing into the ventricle
the Frank-Starling law of the heart states that.... the heart pumps out all the blood that returns to it
stroke volume is proportional to the EDV
what determines EDV? (venous return) aka "what determines how much blood comes into the heart"
the superior and inferior vena cava supply the heart
three pumps:
- skeletal muscle pump
- respiratory pump
- sympathetic venous innervation
what do inotropic agents change? heart contractility (positive increases FOC, negative decreases FOC)
how does epinephrine/norepinephrine affect heart contractility (cardiomyocyte)? positive inotropic agent
binds to ß1 receptors which activates cAMP, phosphorylating two things:
- VG Ca2+ channels (stay open for longer)
- PLN (inhibits inhibiter, so more Ca2+ in SR and Ca2+ removed faster) -more forceful, shorter contractions
endothelial cells
venules are composed of.... a connective tissue surrounding the endothelial layer
arterioles are composed of.... smooth muscle wrapped around endothelial layer
_____ are considered the volume reservoir of the circulatory system because ____________- veins; they are more compliant (larger diameter, thinner wall, less elastic tissue, more abundant = can accommodate increases in blood volume with little change in pressure)
they contain most (70%) of our total blood volume
which have valves, veins or arteries? veins; they have to push blood back to the heart working against gravity
why would you see varicose veins? valve insufficiency results in blood pooling
three types of capillaries are... continuous
-ex. brain
fenestrated
-fenestrations in endothelial layer
-ex. organs that produce hormones (thyroid)
sinusoid
-intercellular gaps in endothelial layer
-incomplete basement membrane
-ex. liver
some arterioles branch into ________ which have ________ that all them to _______ which
metarterioles; muscle rings;
relax or constrict based on environmental signals;
the lowest pressure is found in the..... left ventricle and aorta
vena cava and R atrium
∆P is.... and is calculated by..... pressure gradient
(pressure 1 - pressure 2)
∆P is the driving force that pushes the blood to flow forward
relationship of flow to ∆P and resistance (R) flow is proportional to ∆P and inversely proportional to R
how to determine R? what does it tell us about its relationship to length, fluid viscosity, and radius? poiseuille's law
resistance is proportional to length, fluid viscosity (thickness) and inversely proportional to radius
how is resistance regulated in the cardiovascular system? via changes in vasodilation or vasoconstriction (∆R)
systolic vs. diastolic pressure systolic pressure: pressure when the heart contracts (120)
diastolic pressure: pressure when the heart relaxes (80)
how does the aorta react to ventricular contraction and relaxation? aorta expands to accommodate blood volume (systolic), then recoils and propels the blood forward (diastolic)
during diastolic phase, the aortic valve closes***
what is the windkessel effect? explains why our blood flow is continuous
elastic arteries store kinetic energy in their walls to smooth and use that energy to push the blood forward when the heart is relaxing
(*) shows energy stored in aortic artery
cardiac output
resistance
blood distribution
