Cardiovascular System Design

Question 1

are arterioles or venous blood circulation low pressure or high pressure?

Answer 1

arteries: high pressure (delivery)
venous: low pressure (retrieval)

Question 2

percentages of blood in circulatory system

Answer 2

systemic circulation: 84%
-venous vessels >50%
heart: 7%
pulmonary vessels: 9%

Question 3

what are vessels lined with?

Answer 3

continguous sheet of endothelial cells, including heart chambers and valve leaflets

Question 4

blood flow through heart

Answer 4

Vena Cavae –> right atrium –> tricuspid valve –> right ventricle –> pulmonary valve –> lungs –> left atrium –> mitral/tricuspid valve –> left ventricle –> aortic valve

Question 5

5 requirements for effective cardiac function (ventricular pumping)

Answer 5

1. synchronized contractions of individual cardiac cells at regular intervals
2. valves must open fully
3. valves must not be leaky
4. muscle contractions must be forceful
5. ventricles must fill adequately during diastole

Question 6

equation for cardiac output (CO)

Answer 6

CO = SV * HR

typical CO is 5 L/min; SV = mL, HR = beats/minute

Question 7

major determinants of stroke volume

Answer 7

ventricular preload (length of muscle at onset of contraction)
ventricular afterload (tension of muscle during contraction)
myocardial contractility

Question 8

what effect will sleep and moderate changes in temperature have on cardiac output?

Answer 8

no change

Question 9

what effect with anxiety/excitement, eating, exercise, high temperature, pregnancy, and epinephrine have on cardiac output?

Answer 9

increase

• anxiety/excitement: 50-100%
• eating: 30%
• exercise: up to 700%

Question 10

what effect will sitting/standing from lying position, rapid arrhythmias, and heart disease have on cardiac output?

Answer 10

decrease

-sitting/standing from lying position: 20-30%

Question 11

Starling’s Law

Answer 11

the larger the ventricular end-diastolic volume (cardiac filling in diastole), the larger the stroke volume

Question 12

what does arteriolar vasoconstriction lead to?

Answer 12

increase in peripheral resistance

Question 13

what does venous vasoconstriction lead to?

Answer 13

reduced venous volume and increased cardiac output (via Starling’s Law)

Question 14

4 main variables of flow throughout circulation

Answer 14

1. flow velocity (slowest in capillaries)
2. pressure (steadily decreases from arteries to veins)
3. resistance (peaks at arterioles, then tapers)
4. volume (highest in venules/veins)

Question 15

mean arterial pressure and equation

Answer 15

average pressure over entire cardiac cycle

-MAP = DP + 1/3 (SP - DP) = DP + (1/3)(DP) = CO x TPR = HR x SV x TPR

Question 16

pulse pressure

Answer 16

difference between systolic and diastolic pressures

PP = SP - DP = SV / compliance

Question 17

systolic pressure

Answer 17

peak arterial pressure reached during ejection of blood by heart

Question 18

diastolic pressure

Answer 18

lowest arterial pressure when heart is relaxed and filling with blood

Question 19

dichrotic notch

Answer 19

also incisura: small dip caused by backfilling of aortic valve as it closes

Question 20

auscultatory method to measure BP

Answer 20

use of external blood pressure cuff

• initially no blood flow, but as cuff pressure lowered, flow is restored and pulsatile pressure changes cause detectable turbulence
• when below diastolic, flow returned to laminar and silent

Question 21

direct method to measure BP (arterial and venous)

Answer 21

arterial catheter: retrograde (against flow) for arteries, aorta, and left ventricle
venous catheter: antegrade (with flow) for veins, right atrium, and right ventricle
NOT possible to measure pulmonary venous and left atrial pressures directly, so need pulmonary capillary wedge pressure

Question 22

pulmonary artery catheterization

Answer 22

catheter passed from systemic vein thru right heart into pulmonary artery

• lumen open at distal end
• balloon inflated and pressure falls downstream
• vascular pressure equilibrates beyond balloon, and wedge pressure at catheter tip is measure of pulmonary venous and left atrium
• approximates left ventricular end-diastolic pressure

Question 23

where do changes in MAP come from?

Answer 23

changes in CO or TPR (total peripheral resistance)

Question 24

what is average PP, SV, and compliance in resting young adult

Answer 24

pulse pressure = 40 mmHg
stroke volume = 80 mL
compliance = 2 mL/mmHg

Question 25

short term control of MAP

Answer 25

altering peripheral resistance counteracts most moment-to-moment fluctuations

• vasomotor activity regulates vasomotor tone and peripheral resistance
• usually countered via baroreceptor reflex, altering CO and peripheral resistance
• both normally and neurally

Question 26

long term control of MAP

Answer 26

altering blood volume via kidneys