Cardio V

Question 1

How does the internal structure of an artery compare to that of a vein?

Answer 1

The artery has a narrow lumen and many layers of smooth muscle and connective tissue, while the vein has a wide lumen and less muscle/connective tissue.

Question 2

What is the formula for compliance?

Answer 2

Compliance = dV/dP

Question 3

How do veins and arteries differ in terms of compliance?

Answer 3

Veins have a higher compliance than arteries

Question 4

How can compliance be calculated from a volume vs transmural pressure graph?

Answer 4

Compliance is the inverse of the slope.

Question 5

On a volume vs pressure diagram, how does the slope compare between veins and arteries?

Answer 5

Since arteries have a lower compliance than veins and slope = 1/compliance, we expect the arteries to have a much steeper pressure/volume (slope) than veins

Question 6

How many pulmonary veins do we have?

Answer 6

4 total. 2 that come from the left lung and 2 that come from the right lung.

Question 7

How many pulmonary arteries do we have?

Answer 7

1 pulmonary artery that splits into a left pulmonary artery and a right pulmonary artery.

Question 8

How many arteries branch off from the aortic arch?

Answer 8

3

Question 9

How many chordae tendinae attached to the tricuspid valve and the bicuspid value?

Answer 9

3 each (according to diagram)

Question 10

Compare the thickness of the right ventricular wall, the left ventricular wall, and the interventricular septum.

Answer 10

The left ventricular wall and the interventricular septum are much thicker than the right ventricular wall.

Question 11

Name the 4 valves and where they’re located.

Answer 11

Mitral (bicuspid) valve: between left atrium and ventricle
Tricuspid valve: between right atrium and ventricle
Aortic valve: between left ventricle and aorta
Pulmonary valve: between right ventricle and pulmonary trunnk

Question 12

What is the fibrous ring and what is its function?

Answer 12

It is a barrier that prevents action potentials from circulating directly between the atria and the ventricles.

Question 13

What is the function of the papillary muscle and chordae tendinae? Include what they are made of in your answer.

Answer 13

Papillary muscle is cardiac muscle that is an extension of the muscle from the ventricular free wall. Action potentials can travel up them and cause them to contract. They contract by the top moving down, which pulls on the chordae tendinae. Because the CT are made of the same substance as tendons, they don’t really stretch. They will therefore pull down on the leaflets of the valve, ensuring that it remains sealed shut.

If you didn’t have this structure, the valves would be pushed up and the blood would flow backwards. When the ventricles are contracting and generating a high force, they pull down on the leaflets to ensure that blood doesn’t flow backwards.

Question 14

What is the endocardium?

Answer 14

It is a single layer of endothelial cells that lines the inside of the heart.

Question 15

What is the pericardium? What is its function?

Answer 15

It consists of two layers with pericardial fluid/space in between them. They are in turn attached to the epicardium, which is the innermost outer layer. The function of the structure is to constrain the size of the ventricle, thus preventing overfilling, and protecting cardiac muscle from the other things in the chest.

Question 16

The activation sequence of the heart begins in […]

Answer 16

the sinoatrial node

Question 17

The fibrous ring is made of […]

Answer 17

Connective tissue

Question 18

The action potential in the heart travels along what kind of tissue?

Answer 18

The entire “circuitry” of the heart is made of specialized muscle (NOT neural)

Question 19

Describe the sequence by which an action potential travels throughout the heart after being initiated. Include the major anatomical structures involved.

Answer 19

Action potentials start in the SN node and then enter into the right atrium in a wave that spread over the atrium. It will also slowly enter through and enter the bundle of His/atrioventricular bundle. This bundle goes into the septum and breaks into two branches. One goes down the left side of the septum and the other goes down the right. The action potential picks up speed and it goes through the Bundle of His and down the branches, and travels through both branches at the same time. It ends up in fine structures called Purkinje fibers in the subendocardial muscle. The action potential then travels through the thickness of the ventricular free walls.

Question 20

Explain the timing of the contraction of the ventricles after an action potential is sent through.

Answer 20

Both ventricles contract throughout at the same time.

Question 21

The bundle branches are enclosed by […]

Answer 21

connective tissue

Question 22

How does the insulation of the left bundle branch compare to that of the right bundle branch? How does this affect the travel of action potentials in the heart?

Answer 22

The right bundle brunch is completely sealed, so there is no leakage of action potentials into the septum. On the other hand, the left bundle brunch is imperfectly sealed, so there can be leakage into the septum. The septum can therefore become depolarized from top to bottom and left to right (heart directions).

Question 23

Adjacent cardiac cells are connected by the […]

Answer 23

intercalated disk

Question 24

Intercalated discs have several […], whose function is […]

Answer 24

nexi or gap junctions, to allow for communication between cardiomyocytes

Question 25

Describe the organization of gap-junctional channels.

Answer 25

The gap-functional channels come in hemi-channels (half channels). These two channels stick together. Each is made of 6 identical protein subunits. When two link up, they create a tunnel that connects the interior of one cell to the interior of another cell, and it is filled with cytoplasm. This is how the cells communicate.

Question 26

Describe the flow of ions within and outside cells during local circuit currents

Answer 26

In the excited cell, there will be positive ions (such as K+), and on the outside there will be negative ions.

The next cell over, which has not yet received the action potential, has negative ions inside and positive ions outside.

When the local current spreads to the next cell over, positive ions from inside the first cell will flow into the second cell. Meanwhile, the positive ions outside the second cell will flow towards the outside of the first cell. The opposite will be true for negative ions: the negative ions in cell B will flow into cell A, and the negative ions outside cell A will flow to the outside of cell B.

Question 27

What species of ions flow during local circuit currents?

Answer 27

All species of ions do. K+ is the dominant intracellular ion and Na+ is the dominant extracellular ion.