1- Cardiovascular Physiology

The cardiovascular system is primarily a ____ system for __________

Transport, oxygen and carbon dioxide

The heart consists of 4 chambers that function as a system of 2 serial pumps, what are the 2 circulation?

Systemic and pulmonary

systemic circulation flow from

Heart to organs/tissues

Pulmonary circulation flow from

Organs/tissues to Lung

Cardiac Output (CO)

Total blood flow circulating in the system, which is determined by the product of heart rate and stroke volume

(CO = HRxSV)

If HR is 60 beats/min and SV is 100mL, what is the estimated CO?

6000mL/min —> or 6L/min

Cardiac output must change with metabolic demands. Oxygen uptake is the global metabolic demand. Now, CO =

VO2/ C(a-v)O2

Hemodynamics

The study of the physical law that govern the movement of blood - involves the relationship between pressure, flow, and resistance

A pressure gradient creates flow, pressure is:

change in pressure between 2 points in a system
- change in P = (P1-P2)

Blood flow is dependent on:

Pressure gradient and resistance

Flow

Movement of blood over time in relation to the opposing force provided by blood vessels. (F = change in P/R)

Resistance

The force opposing the movement of fluid (R = change in P/F)

CO is affected by arterial pressure/mean arterial pressure (MAP) and overall vascular resistance (TPR). CO =

CO = MAP/TPR

What are the key parameters related to hemodynamics?

-pressure: change in pressure in a system
-resistance: force opposing the movement of fluid
-flow: movement of fluid

What are the steps of cardiac output?

1. Oxygen enters lung

2. Oxygen travels to heart

3. Heart pumps out oxygenated blood

4. Tissues extract oxygen from oxygenated blood

5. Deoxygenated blood and CO2 return to heart

6. Heart pumps deoxygenated blood and CO2 to lungs

7. CO2 is eliminated

8. Back to Step 1

Cardiac (heart) and skeletal muscles are both made of what type of fibers? How is cardiac tension produced?

Striated fibers, tension is produced by actin-myosin interactions

Cardiac muscle characteristics

1. Intercalated discs

2. Syncytial

3. Large T-tubules

4. Extracellular Ca2+ important for contraction

5. Calcium-induced calcium release

Cardiac muscle functions

1. Range of work is less compared to skeletal muscle (10-fold vs. 1000-fold increase)

2. The heart cannot rest

3. Output is essentially generated by twitches

4. Does not fatigue

What are the 3 tissue layers of the heart?

Pericardium, myocardium, endocardium

Pericardium (fibrous layer) contains _________

• Parietal pericardium

• Visceral pericardium (also called epicardium)

• Between these two layers is the pericardial space, where pericardial fluid resides

Myocardium (contractile layer) is _________

Muscular layer that facilitates the pumping action of the heart

Endocardium (endothelial layer) is ________

Innermost layer that is continuous with tissue of the valves

What is the general orientation of the heart in the thorax?

Base: superior and posterior

Apex: inferior and lateral

The 4 chambers work together to function as a dual pump system that sustains circulation. The atria pumps blood to the _____, ventricle pump blood to _____, blood returns from circulation to ______ and so on.....

Ventricles, circulation, atria

Atriventricular valves are ________

Tricuspid and mitral

Tricuspid valve is between ________

right atrium and right ventricle

Mitral/bicuspid valve is between ________

left atrium and left ventricle

Semilunar valves are ______

Pulmonary and aortic

Pulmonary valve is between ______

right ventricle and pulmonary artery

Aortic valve is between _______

left ventricle and aorta

The left side of the heart receives ___________ from _________ and ________

oxygenated blood, lungs, pumps it to the body

The right side of the heart:

receives deoxygenated blood from the body and pumps it to the lungs

The atria of each side receives

blood coming into heart

The ventricles of each side ________

Pump blood out of the heart

The systemic circulation delivers _____ blood to muscles and end organs and returns _____ blood to the heart

Oxygenated; deoxygenated

The pulmonary circulation delivers _____ blood to the lungs and returns _____ blood to the heart

Deoxygenated; oxygenated

When upstream pressure exceeds downstream pressure, valves:

Open passively

When downstream pressure exceeds upstream pressure, valves:

Close passively

Systole

Ventricles contract

Diastole

Ventricles relax

In the heart, blood moves in what gradient?

High concentration to low concentration

Function of the chordae tendineae

Provide tension during closure to prevent prolapse (failure of valve to keep flow in one direction)

The cardiac cycle

Isovolumetric ventricular relaxation occurs when all valves are:

Closed

"Lub"

First sound (S1)

• Tricuspid valve closing

• Mitral valve closing

• Pulmonary valve opening

• Aortic valve opening

"Dub"

Second sound (S2)

• Tricuspid valve opening

• Mitral valve opening

• Pulmonary valve closing

• Aortic valve closing

What contracts like a bellows?

Right ventricle

What contracts like a hand squeezing toothpaste?

Left ventricle

Cardiac performance depends on

Volume, pressure, flow

Stroke volume (SV) =

EDV - ESV (end diastolic volume - end systolic volume)

Ejection fraction (EF) =

SV/EDV

Pressure-volume loop illustrates ejection

Starlings law

greater fiber length leads to greater mechanical energy

Preload

initial sarcomere length and EDV just before blood is ejected from the ventricle

After load

force that contracting myocytes must overcome as blood is ejected from the ventricle. Arterial pressure is this opposing force.

Contractility

intrinsic measure (not affected by external factors) of cardiac performance. End-systolic pressure can be used as a measurement of contractility

Increase in preload (at constant contractility) =

Increase in SV

Increase in afterload (at constant contractility) =

Decrease in SV

Increase in contractility =

Increase in SV