Cardiopulmonary Physiology

Question 1

What is the normal pacemaker of the heart?

Answer 1

The SA node

Question 2

How does a nerve impulse travel after being fired from the SA node?

Answer 2

• Impulse travels into the Atria and both atria contract (right then left)
• Impulse goes from Atria to the AV node
• Impulse enters Bundle of his before splitting into left and right bundle branches
• Impulse travels into purkinje fibers from bundle branches and contract ventricles

Question 3

What are baroreceptors?

Where are they typically located in the circulatory system?

Answer 3

mechanoreceptors that detect changes in pressure

Carotid sinus, aortic arch and origin of the right subclavian artery

Question 4

How does the baroreceptor reflex work to control blood pressure?

Answer 4

• baroreceptors (BRs) react to increased BP
• BRs send increased signals to CNS via cranial nerves 9 and 10
• CNS increases parasypathetic activity to heart and decreases sympathetic activity to the heart
• Both increased PNS activity and decreased SNS activity lower BP

Question 5

What is the Bainbridge Reflex?

Answer 5

reflex to increase cardiac output via increased HR via inhibition of PNS system due to increased pressure in right atrium

Question 6

How does the chemoreceptor Reflex control BP?

Answer 6

• Chemoreceptors in aorta and carotid arteries sense increases or decreases in pH via increased/decreased blood O2/ blood CO2
• In case of decreased O2, decreased CO2, and decreased pH the SNS activity is increased to increase cardiac output the PNS is also inhibited which further increases HR and cardiac output

Question 7

What are the two main nerves which send information from the heart to the CNS?

Answer 7

Glossopharyngeal and Vagus

Question 8

What is the difference between systole and diastole?

Answer 8

systole refers to a contraction of a heart segment which forces blood out of the segment

diastole refers to the relaxation of a heart segment when the segment is re-polarizing

Question 9

What is cardiac pre-load?

Answer 9

the tension in the ventricular walls at the end of diastole which reflects the venous filling pressure that fills the left ventricle during diastole

Question 10

What is cardiac afterload?

Answer 10

the forces that impede the flow of blood out of the heart, primarily the pressure in the peripheral vasculature, the compliance of the aorta, and the mass and viscosity of blood

Question 11

What is stroke volume?

Answer 11

volume of blood ejected by each contraction of the left ventricle which normally ranges between 60-80 ml

Question 12

What is cardiac output?

Answer 12

amount of blood pumped from the left ventricle per minute, it is the product of HR x SV and in adults males is normally between 4.5-5 L/min with females being slightly less

Question 13

How much oxygen is usually dissolved in 100 mL of arterial blood?

Answer 13

~0.3 mL

Question 14

How is 80-90% of CO2 transported in blood?

How is the other 10-20% transported?

Answer 14

as bicarbonate ions

5-10% is dissolved in blood
5-10% is in the form of carbamino compounds

Question 15

What is Rate Pressure Product an index of? What does it provide?

Answer 15

myocardial oxygen consumption and coronary blood flow

Provides an easy to measure way to find causes of the onset of angina pectoris or the development of ECG abnormalities in patient’s with heart disease

Question 16

How do you find the Rate Pressure Product (RPP)?

Answer 16

• measure SBP and HR during the same exercise workload

- RPP = HR x SBP

Question 17

What is the Ejection Fraction?

What is the norm for Ejection Fraction?

Answer 17

a measure of left ventricular contractility which is determined by dividing stroke volume by left ventricular end-diastolic volume.

Normal ejection fraction is approximately 55-70%