Final-Chapter 12 Cardiac Physiology

Question 1

Describe the cardiovascular system.

Answer 1

The cardiovascular system is composed of blood and fluid that carries materials to and from cells. Blood vessels - a series of tubes including Veins, arteries, venules, arterioles, and capillaries. Lastly, is the heart. Humans have a closed circulatory system where blood stays inside these vessels at all times. Things move from high pressure to low pressure but when dealing with these chambers of the heart (atria or ventricles), there’s only two ways that you can build pressure in a chamber. Add more blood, or contract that chamber.

Question 2

What is blood?

Answer 2

Blood cells include:

1. Erythrocytes (red blood cells) that carry oxygen bound to hemoglobin. It makes up about 90% of blood cells. Anemic means you are not getting enough iron in your diet or you could have a problem when you’re not producing enough RBCs. Since oxygen is needed to produce oxygen, you are lowering your ability to produce ATP, so you’ll be tired all the time. You will also run out of breath.
2. Leukocytes (white blood cells) which mediate immune responses. Leukemia is a disease where bony marrow produces too many leukocytes.
3. Platelets (cell fragments) aid in blood clotting. Plasma is the liquid portion of blood.

Question 3

What are the vessels transporting blood away from the heart?

Answer 3

Vessels transporting blood away from heart include:

1. Arteries which are big, thick in diameter (fast) and have thick walls (difficult diffusion). They branch off into arterioles.
2. Arterioles are small, and all flow into capillaries. When an arteriole is cut, the blood squirts because the blood is coming directly form the heart.
3. Capillaries are the smallest. Every living cell in your body is no farther than a few millimeters from a capillary. Capillaries are very leaky with thin walls, this is where exchange of oxygen and glucose into the blood occurs. They give your body time to transport blood to your cell. Blood moves slowly to allow for things to diffuse in and out of the blood and move into venues.

Question 4

What are the vessels transporting blood to the heart?

Answer 4

Vessels transporting blood to heart include:

1. Venules are small and branch into veins.
2. Veins are big and carry blood back to the heart. Every one of these blood vessels, except capillaries, have very tight seals. They are impermeable and are just used for transport.

Question 5

Describe the heart?

Answer 5

The heart has four chambers:
the left and right atria and the left and right ventricles. Two separate pumps next to each other (separated by septum). The septum is very beneficial to us because it keeps oxygenated and deoxygenated blood from mixing.
The left heart, were blood finishes, composed of left atrium and left ventricle: supplies blood to systemic circuit (body) and carries oxygenated blood to every cell in the body.
Right heart, where blood starts, is composed of right atrium and right ventricle supplying blood to pulmonary circuit (lungs) and pumps deoxygenated blood to the lungs and then back to the heart.

Question 6

What are the two largest veins in the body?

Answer 6

The two largest veins in the body is vena cava composed of the superior and inferior vena cava. The superior vena cava is located above the heart while the inferior vena cava lies below the heart.

Question 7

What is the largest artery?

Answer 7

The largest artery (and blood vessel) in the body is the aorta. It is largest because it has to travel the greatest difference, physical distance is furthest. Ex.heart to toes.

Question 8

What ventricle is the most muscular?

Answer 8

The left ventricle is the most muscular because it has to generate enough force to transport blood from your heart to your toes. Generates the most force, has the most muscle.

Question 9

What does pulmonary refer to?

Answer 9

Pulmonary refers to your lungs, and deoxygenated blood.

Question 10

What does systemic refer to?

Answer 10

Systemic refers to everywhere, but the lungs.

Question 11

How does blood flow through the heart?

Answer 11

1. Blood enters the heart at the Vena Cava—biggest vein in the body. Blood in the vena cava will be low in oxygen and high in CO2 and will undergo pulmonary circulation first.
2. Blood will enter the right atrium.
3. Then will enter the tricuspid valve into the right ventricle.
4. Blood leaves right ventricle and moves into pulmonary artery. It enters the artery through the pulmonary semilunar valve.
5. Blood in the pulmonary artery goes to the lungs, oxygen moves into the blood and CO2 moves into the lungs.
6. After blood leaves the lungs and enters the pulmonary vein. Blood enters the left atrium.
7. Blood then enters left ventricle by passing through the bicuspid valve.
8. Blood then enters the aorta through the aortic semilunar valve to send blood to systemic organs. It delivers oxygen to these cells and picks up CO2. It has so much blood in it, a tiny rupture would be fatal.

Question 12

Describe the heart valves?

Answer 12

The opening and closing of heart valves is controlled by pressure difference between chambers. This allows unidirectional blood flow preventing the backflow of blood.
There are two types of valves:
1. Atrioventricular (AV) valves separate the atria from ventricles. Left AV valve (bicuspid/mitral) and right AV valve (tricuspid)
2. Semilunar (SL) valves: separate ventricles from arteries. Pulmonary SL valve separates right ventricle from pulmonary artery. Aortic SL valve separates left ventricle from Aorta.

Question 13

How does the AV valves work?

Answer 13

When the ventricle is relaxed, the atrial pressure is greater than the ventricular pressure (open). When the ventricle is contracting (close), the ventricular pressure is greater than the atrial pressure.

Question 14

How does the SL valves work?

Answer 14

When the ventricle is contracting (open), the ventricular pressure is greater than aortic pressure. When the ventricle is relaxed (close), the aortic pressure is higher than the ventricular pressure.

Question 15

Describe the series flow through pulmonary and systemic circuits.

Answer 15

1. Left ventricle pumps blood through the aortic semilunar valve into the aorta. The valve prevents backflow of blood into the left ventricle.
2. The aorta branches and carries blood to all organs and tissues in the systemic circuit.
3. Blood is deoxygenated in organ capillary beds and travels back to the heart through the superior and inferior vena cava into the right atrium-goes through pulmonary circulation. It drops of oxygen and picks up CO2 in systemic organs. (blood is always higher in vena cava, than in atrium, no risk of back flow, no valve)
4. From right atrium, blood goes through the tricuspid valve to the right ventricle. The valve prevents backflow of blood into the atrium. What physically opens or closes any valve is pressure. (Atria only fills up blood, so it can contract and force blood to ventricles.)
5. The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary artery, (the only artery carrying deoxygenated blood-pulmonary SV opens when when right ventricle pressure is higher.)
6. Blood is oxygenated in the lungs and goes to left atrium through the pulmonary vein (the only vein in the body carrying oxygenated blood)
7. From left atrium, blood goes through bicuspid valve (aka mitral valve) into the left ventricle. And now the cycle begins again.

Question 16

Describe the contraction of the myocardium?

Answer 16

1. Atria contracts first then force blood into the ventricles.
2. Ventricles contract second and force blood into arteries. (This is called the cardiac cycle.)
3. Pulmonary and systemic circulation are happening at the same time.
4. Right atrium and left atrium contract at the same time, then the ventricles contract at the same time.
   The ultimate goal of the heart is to get as much blood leaving the ventricles per heart beat to get more blood to cells.

Question 17

How does the heart achieve sequential contraction of atria and ventricles?

Answer 17

The heart contracts w/out neural input—it is myogenic. You don’t consciously make your heart beat, making the the heart a unique muscle. Your heart needs to beat every second. If the brain was busy, it might forget to tell the heart to beat – then you die. The rhythm of heartbeat is due to activity of pacemaker cells (which produce AP down conducting fibers) and conduction fibers. They determine how much time goes by between the beats – how fast. Force of heartbeat is due to activity of contractile cells. Contractile cells act more like muscle cells, they generate the force needed for the heart to contract, i.e. how hard the heart beats. Most of our muscles in the body are neurogenic – the brain tells them to contract.

Question 18

Describe cardiac muscles?

Answer 18

Cardiac muscles contains sarcomeres—same contraction machinery as skeletal muscle and are striated as well as skeletal muscles. cardiac muscles contains gap junction where multiple cells can contract together. They are physically and electrically coupled. Allows for synchronized activity allowing charge can spread easily and large groups of cells can be activated in sync. Action potentials are longer than in skeletal muscle cells. Longer in terms of how long they last. This is because skeletal muscle [leg muscle] can reach tetanus [maximum contraction of the muscle] this isn’t possible in the heart. Leg cramps are painful but not life threatening… If you get a heart cramp, you could die. These longer APs basically mean longer refractory periods. If you have longer APs, you have time to contract and relax before it has to contract again which makes summation impossible.

Question 19

What are the three types of cardiac muscle cells?

Answer 19

The three types of cardiac muscle cells include:

1. Cardiac pacemaker cells which sets rhythm of heartbeat and act more like neurons than muscle cells because they generate their own APs. Pacemaker cells are found in the Sinoatrial node(SA) and the Atrioventricular (AV) node.
2. Cardiac conduction fibers are the electrical wiring. They transmit rhythm of heartbeat -(inter-nodal pathway, inter-atrial pathway, Purkinje fibers)
3. Cardiac contractile cells generate the contractile force.

Question 20

What is the conduction system of the heart?

Answer 20

1. An AP is initiated in the SA node.
2. From there, AP spread from SA to both atria and they are given the signal to contract.
3. After that, the conduction slows and the AV node has to generate another AP that tells the ventricles to contract. Right about now, there is a brief pause – nothing is happening. This is known as the AV nodal delay. Why is there a pause and what is the purpose? The atria have contracted and the ultimate goal of all of this is to get as much blood leaving the ventricles as possible. In order to do that, these ventricles need to fill up with blood completely. The purpose of this delay is to allow the atria to completely empty into the ventricles allowing for complete filling of the ventricles. Conduction is slow because if it wasn’t slow, you have atria contracting immediately followed by ventricle contracting. You want the ventricles to be relaxed enough to completely filled with blood, and if they’re contracting they won’t be. Big Picture – if the Delay was shorted – less blood output per heartbeat. Ideally, you want every heartbeat to pump as much blood as possible, which means your heart wouldn’t have to work as hard.
4. Following the delay, APs travel rapidly through the conduction system to the apex of the heart. 5. AP spread upward through the ventricular muscle through the Purkinje fibers. This causes ventricles to contract, forcing blood into the arteries. Like squeezing a tube of toothpaste from the bottom—forcing out as much as you can. Eventually, the entire heart returns to the resting state, remaining that way until another AP is generated in the SA node.

Question 21

What way is the heart beats based on?

Answer 21

The way the heart beats is based on flow of ions. Pacemaker cell create AP, Cardiac contractile AP.