Chapter 9 Cardiac Physiology

Question 1

Circulatory System

Answer 1

the body’s transport system consisting of heart, blood vessels, and blood

Question 2

Pulmonary circulation

Answer 2

Sending blood depleted into O2 and rich in CO2 to the lungs and returns blood rich in O2 and depleted in CO2 to the heart

Question 3

Systemic circulation

Answer 3

Sends blood rich in O2 and depleted in CO2 to the whole body and returns blood depleted in O2 and rich in CO2 to the heart

Question 4

Blood circulation

Answer 4

Right atrium, right ventricle, pulmonary trunk, pulmonary arteries, lungs, pulmonary veins, left atrium, left ventricle, aorta, whole body

Question 5

What prevents the atrioventricular valves from everting?

Answer 5

By one way valves, they have chordae tendineae attached to papillary muscles

Question 6

What is the fibrous skeleton?

Answer 6

Dense connective tissue that surrounds and stabilizes position of four valves

Question 7

What are the three tissue layers of the heart?

Answer 7

Endothelium, myocardium, and epicardium

Question 8

What is the pericardial sac?

Answer 8

A tough fibrous outer covering that attaches to connective tissue in thoracic cavity and anchors the heart in place.

Question 9

What are some commonalities between cardiac and skeletal muscle fibers?

Answer 9

-They are striated (layers of thick and thin filaments)
-They contract via Ca2+ binding to troponin

Question 10

Intercalated disks contain what

Answer 10

Desmosomes (strongest cell junction) and Gap Junctions (allows action potentials to travel from one fiber to another)

Question 11

Differences between cardiac and skeletal muscle fibers?

Answer 11

• Contain many mitochondria (for oxidative phosphorylation)
  -short and slender and arranged like a spiral
  -they branch out and connect end-to end called intercalated disks

Question 12

Functional Syncytium

Answer 12

When all the cardiac muscle fibers contract together as one

Question 13

Two types of cardiac muscle cells

Answer 13

-Contractile cells- receive electrical current and provide the actual contractile force
-Autorhythmic cells- initiate the action potentials

Question 14

Do autorhythmic cells require nervous system input to fire action potentials?

Answer 14

No

Question 15

What is the potential between action potentials called?

Answer 15

pacemaker potential

Question 16

What is the weird thing about Na+ funny channels?

Answer 16

They open with hyperpolarization

Question 17

Are autorhythmic cells spread out homogenously throughout the heart? If not, where are they located?

Answer 17

Concentrated in specific sites such as the SA node, AV node, Bundle of his, and the purkinje fibers

Question 18

Why does the rhythm of the sinoatrial node drive the rest of the autorhythmic cells?

Answer 18

They are all connected to each other via gap junctions and the area with the highest bpm which is the SA node and that controls the rhythm.

Question 19

Do the atria contract at the same time as the ventricles? Why or why not?

Answer 19

No, the left and right atria contract together then after the ventricles contract together ensuring synchronous flow between pulmonary & systemic circulation loops

Question 20

Do contractile cells have a pacemaker potential? Which cell causes it to fire an action potential?

Answer 20

No, autorhythmic cells are what sends the action potential signal to the contractile cells

Question 21

Opening of which channel causes action potentials in contractiles cells to be so long in duration?

Answer 21

A slow, L-type Ca2+ channel

Question 22

How does the long-duration action potential in a contractile cell affect the contractile response?

Answer 22

Leads to increased duration of cardiac muscle fiber contraction (~3 times longer than skeletal)

Question 23

Does twitch summation occur in cardiac muscle fibers?

Answer 23

No

Question 24

Where is an ECG measured? What are the three main components of an ECG? What underlying cardiac events cause each component?

Answer 24

• Measured at skin surface arising from summed electrical activity of cardiac muscle fibers
• P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization)

Question 25

What are the two alternating periods of the cardiac cycle?

Answer 25

Systole- contracting and emptying
Diastole- relaxation and filling

Question 26

When do heart sounds occur?

Answer 26

They arise from ventricular walls oscillating as heart valves snap shut

Question 27

What valve makes the lub sound

Answer 27

atrioventricular valves

Question 28

What valve makes the dub sound

Answer 28

semilunar valves

Question 29

Isovolumetric contraction

Answer 29

Contraction is increasing in the ventricle but the volume is remaining the same

Question 29

Isovolumetric Relaxation

Answer 29

As pressure decreases volume stays constant

Question 30

Wiggers Diagram

Answer 30

Could you match the changes that occur of the following during the cardiac cycle: ventricular volume, atrial pressure, ventricular pressure, aortic pressure.

Question 31

What is cardiac output?

Answer 31

volume of blood pumped by each ventricle per minute

Question 32

What two factors determine cardiac output? What changes to these factors would increase cardiac output?

Answer 32

-Heart rate (beats/min) x Stroke volume (mL/beat)
-Increasing these would increase the cardiac output

Question 33

Cardiac output is modulated by the ______________ nervous system.

Answer 33

autonomic

Question 34

What effect does parasympathetic stimulation have on heart rate?

Answer 34

Parasympathetic fibers release ACh onto atria, not ventricles decreasing heart rate

Question 35

What effect does sympathetic stimulation have on heart rate?

Answer 35

Sympathetic fibers release NE onto atria and ventricles (and E circulating as hormone from adrenal medulla) Increasing heart rate

Question 36

What is end-diastolic volume?

Answer 36

The volume of blood in the right or left ventricle at end of filling in diastole which is amount of blood present in ventricle at the end of diastole systole.

Question 37

What is stroke volume?

Answer 37

the volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction.

Question 38

If end-diastolic volume is increased, how does stroke volume change? Why?

Answer 38

Stroke volume is increased because of the Frank-Starling law of the heart

Question 39

What effect does sympathetic stimulation have on cardiac muscle fiber contractility? How does this affect stroke volume?

Question 40

What effect does sympathetic stimulation have on venous return? How does this affect stroke volume?

Question 41

What effect does parasympathetic stimulation have on stroke volume?

Question 42

How is the heart oxygenated? Why can’t the heart receive oxygen from blood pumped through the heart?

Answer 42

The heart is oxygenated by coronary circulation
-It can’t because the endothelial lining is watertight and the myocardium is very thick and is too thick for diffusion of O2

Question 43

What are blood vessels that supply the heart called?

Answer 43

Coronary Circulation

Question 44

During exertion when more O2 to the heart is needed, what happens to coronary vessels? Which paracrine causes this?

Answer 44

Duration of diastole decreases. The vessels vasodialate from the paracrine adenosine.

Question 45

What happens to cardiac muscle in advanced coronary artery disease?

Answer 45

Changes in walls of coronary arteries that decrease blood flow

Question 46

What is atherosclerosis and how can it lead to thromboembolism?

Answer 46

Gradual, cumulative blockage of blood vessels by plaques. Thromboembolism is when there is blockage in the blood vessel due to the plaque breaking off.