Mod 5 - Lesson 30 Cardiac Output Assignment

Question 1

1) What is cardiac output?

Answer 1

amount of blood pumped by blood per min

CO unit = mL/min

Question 2

2) What is stroke volume?

SV - volume of blood pumped w/each ventricle or beat of heart (mL/beat)

Answer 2

3) What is the formula for calculating Cardiac Output?

CO = HR X SV

2 variables
HR - number of heart beat per min
SV - volume of blood pumped w/each ventricle or beat of heart

Question 3

4) What is the average cardiac output per minute for an average adult male?

5 L/min

avg amount of blood passing through the heart per min = 4-6 liters

Answer 3

5) What is the term that describes factors that increase or decrease heart rate?

positive chronotropic/increase factor:
sympathetic stimulation:secretion of adrenaline & epinephrine, hypercapnia (increase CO2), hypocalcemia (decrease calcium), drug –> atropine

Sign: tachycardia (fast heart rate, > 100 bpm)

Negative chronotropic/decrease factor:
parasympathetic stimulation: secretion of acetylcholine, hypoxia (decrease O2), hypercalcemia (increase calcium)

Sign: bradycardia (low heart rate, <60 bpm)

hyper/hypocalcemia: these usually don’t have much an affect on heart rate, but more on muscles of heart

Question 4

6) What are the four determinants of cardiac output?

heart rate, (SV) preload, after load, contractility

Answer 4

7) Describe preload.

volume of blood entering the ventricles

Increase in preload:
More blood enter heart ventricle = more myocardial stretching (stretching outward) = increase in preload = increase in SV if everything else is normal

Frank-starling mechanism: the amount of blood entering the ventricles will be the amount of blood ejected by the ventricles to the body

In other words, end diastolic volume = SV

Question 5

8) Describe afterload.

resistance the ventricles must overcome to circulate blood around the body

if person has AO2 pressure = afterload increase = decrease in SV

since more in resistance = increase in blood pressure

Answer 5

9) What is contractility?

how hard the myocardium contracts for a given preload or
how hard heart muscle contract to pump blood

decrease contract = decrease in cardiac output

positive ionotropic/ increase factor:
sympathetic stimulation, caffeine, hypercalcemia (essential for muscle contraction)

negative ionotropic/ decrease factor:
parasympathetic stimulation, hypocalcemia, increase in potassium, myocardial hypoxia (not enough O2 in heart muscle cells)