Cardiovascular System-1 : Introduction - Anatomy and Hemodynamics

True or False: With endurance training, the heart can increase its size and force of contraction.

True

Describe the position of the heart in the chest

-bwtn 2 lungs

-rest on the diaphragm

-apex points to the left

-2/3 of the heart is to the left of the midline

-enclosed in pericardium

pericardium

fibrous sac interspersed with fat that surrounds the heart

Why can the heart be considered 2 pumps arranged side by side?

-right side --> pulmonary circulation

-left side --> system circulation

*output of right side = output of left side & output of one side returns to the other

Which atrioventricular valve is on the right side?

tricuspid valve

True or False: The mitral valve is also known as the tricuspid valve, the atrioventricular valve on the left side of the body.

False ==> The AV valve on the left side = bicuspid valve = mitral valve

bicuspid valve

left AV valve = mitral valve

What is the function of the chordae tendinae & papillary muscles?

chordae tendinae attaches the underside of the tricuspid & mitral valves to the papillary muscles in the ventricular wall ==> papillary muscles contract when the ventricles contract --> chordae tendinae become taut --> prevent AV valve cusps from everting into the atria --> prevent retrograd flow (blackflow of blood from the ventricles back into the atria)

Explain how the coronary arteries are perfused.

coronary arteries branch from the aorta at the same level as the aortic valve ==> aortic valve open during ventricular contraction --> blood pumped into aorta --> ventricular dystole (relaxation)--> aortic valve closes --> blood pools into the semilunar cusps of aortic valve & runs down the openings of the coronary artery

*perfusion of coronary artery happens during dystole

epicardium

visceral layer of serous pericardium (outer layer of the heart that's continuous with the pericardium)

endocardium

inner lining of the heart

How does the orientation of myocardial fibers influence contraction?

orientation of fibers allows for the heart to propel blood upwards (towards base of ventricles & up thru the pulmonary artery & aorta)

*fibers arranged in different directions & direction of contraction is a sum of the pull of all the directions ==> total direction of contraction is kind of obliquely & upwards (like wringing out a towel upwards)

-circular/circumferential fibers --> wrap around heart & squeezes in inward

-longitudinal fibers --> shortens fibers vertically (brings apex closer to the base)

-oblique fibers --> up & sideways

What is the electrical connectivity of the heart?

gap junctions

*reason stimulating one area of the heart stimulates the entire heart to contract

Features of Myocardial Cells

-individual cells arranged into fibers

-fibers are branched

-intercalated disks connect the cells end to end

-gap junctions --> electrically connect the cells

cardiac output (CO)

total volume of blood flow thru systemic or pulmonary circulation

CO = HR x Stroke Volume

_________________ is the amount of blood ejected from either the right or left ventricle in one beat.

stroke volume

What is the typical unit of measurement for fluid flow (Q) ?

L/min (or mL/min)

When fluid is flowing down a tube, why is the potential energy of the fluid at a point downstream of the starting point less than the fluid's potential energy at the starting point?

some of the fluid's potential energy at starting point is used up to overcome the resistance to flowing thru the tube to make it to downstream point

(* it takes energy to move thru the tube)

Total Peripheral Resistance (TPR)

the frictional resistance to blood flow provided by all vessels between the aorta and right atrium

How are resistances of vessels in a series calculated?

sum of resistances

R = R(aorta) + R (arteries)+ Rcapillaries . . .

How are the resistances of parallel vessels calculated.

sum of the reciprocals of their individual resistances

R = 1/(R1 + R2 +R3)

Poiseuille's Equation

equation to understand the factors that contribute to resistance when fluid flows through a cylindrical tube ==> arterial resistance flows this equation

R = 8nl/pir^4

-n = viscosity

-l = length

-r = radius of tube (blood vessel) ==> vasoconstriction/dilation has a 4-fold effect on resistance!

*n & l remain constant for blood vessels so they don't often contribute to change in resistance

conductance

how easily blood flows through a vessel for a given pressure (or pressure difference)

= 1/resistance

(defn from google; equation from slides)

When does systolic pressure occur?

when the left ventricle contracts

When does diastolic pressure occur?

when the left ventricle relaxes

mean arterial pressure (MAP)

the driving force of blood flow averaged over the time of heart beat (average of all the pressure in the body's arterioles --> the main driver of blood pressure & flow into tissues)

MAP = DP + (SP-DP)/3

-DP = diastolic pressure

-SP = systolic pressure

True or False: The velocity of blood flow is greater in blood vessels with a bigger diameter, and less in blood vessels with a smaller diameter.

False ==> velocity of blood is greater in small diameter blood vessels (gotta be faster to go the same distance in tighter space)

*velocity of blood flow thru a vessel varies inversely w/ the total cross sectional area of that segment

The velocity of blood flow is greater in blood vessels that have a small diameter --however, blood flow is the slowest in the capillaries and the fastest in the aorta. How is this possible?

Due to all the branching of the capillaries (& the other microvessels before the capillaries) the total cross-sectional area is much greater of all the capillaries than the cross sectional area of the aorta, making aorta the vessel with smaller diameter ==> blood flow faster in aorta

Doppler ultrasound

non-invasive test that can be used to estimate your blood flow thru blood vessels by bouncing high frequency sound waves (ultrasound) off circulating red blood cells & measuring the frequency change in reflected sound

*measures cardiac output - coronary circulation (minus the blood the perfuses the heart)

True or False: Pressure drop is directly proportional to the resistance in each segment of the vasculature

True

Why are veins called capacitance vessels?

b/c they can expand & store blood

Which blood vessels have the highest resistance in the body?

arterioles

Greatest pressure is in the ___________________.

arterioles

(rewatch to make sure it's not the aorta cuz . . .)

What is the function of the aorta?

pulse dampening & distribution

what is the function of large arteries?

distribution of arterial blood

What is the function of small arteries?

distribution & resistance

What is the function of arterioles?

resistance for pressure & blood flow regulation

what is the function of capillaries?

exchange

what is the function of venules?

exchange, collection, & capacitance

what is the function of the veins?

capacitance function (blood volume)

What is the function of the vena cava?

collection of venous blood

Law of LaPlace

measures the tension a blood vessel needs to prevent the wall from splitting due to distending pressure (the stretching pressure of the blood inside of it)

P = T/r

*the smaller the radius, the smaller the tension needed to balance the distending pressure (small vessels like capillaries don't need as much wall tension to prevent splitting; the bigger vessels the more tension needed)