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BIOL 228 > Heart > Flashcards

Heart Flashcards

1
Q

What is the main function of the heart?

A

To pump blood to all of the cells of the body. This delivers oxygen and nutrients and takes carbon dioxide and waste away from the cells.

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2
Q

What does the right side of the heart do? What is the circulation on this side of the heart called?

A

The right side of the heart pumps blood to the lungs. This is called the pulmonary circuit.

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3
Q

What does the left side of the heart do? What is the circulation on this side of the heart called?

A

The left side of the heart pumps blood to the body. This is called the systemic circuit.

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4
Q

What are the four chambers of the heart?

A

Right and left atria and right and left ventricles.

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5
Q

Can you track blood through the heart, including the four chambers, the body and the lungs?

A

Blood leaves the right ventricle and enters the pulmonary trunk which splits into the pulmonary arteries. The pulmonary arteries carry blood to the lungs, where oxygen is picked up. The oxygenated blood returns to the heart through the pulmonary veins and enters the left atria. From there it moves through the bi-cuspid or mitral valve into the left ventricle. It leaves the left ventricle, through the aortic semi-lunar valve and enters the aorta. The aorta delivers blood to all the cells in the body. Deoxygenated blood returns from these cells in the inferior and superior vena cava. These two veins drain into the right atria. Blood moves through the tri-cuspid valve into the right ventricle.

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6
Q

Where, approximately, in the body would you find the heart?

A

In the mediastinum, between the two lungs, slightly to the left of center.

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7
Q

What are the two functions of the fibrous pericardium?

A

Protects and anchors the heart to the surrounding structures Prevents the heart from overfilling with blood.

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8
Q

What are the two layers of the serous pericardium?

A

Parietal layer is in contact with the fibrous pericardium and is continuous with the large vessels that leave and enter the heart.

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9
Q

The visceral layer is continuous with the heart wall.

What fluid is in the pericardial cavity? Where do you find this cavity?

A

Serous fluid. The cavity is between the parietal and visceral layers.

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10
Q

Epicardium -

A

this is also the visceral layer of the serous pericardium.

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11
Q

Myocardium -

A

cardiac muscle, forms the thickest layer.

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12
Q

Endocardium -

A

simple squamous epithelium lining the inside of the heart.

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13
Q

What’s the function of the myocardium?

A

To contract and move blood through the heart and body.

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14
Q

What role does connective tissue play in the myocardium?

A

The cardiac muscle cells are connected to each other by connective tissue.

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15
Q

What is the endothelium composed of?

A

Squamous epithelium on a thin layer of connective tissue.

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16
Q

What three veins enter the right atrium? Where do they come from?

A

The superior and inferior vena cava. The superior drains the head and arms and the inferior drains the rest of the body. Also, the coronary sinus, coming back from the heart muscle itself.

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17
Q

What four veins enter the left atria? Where do they come from

A

Pulmonary veins coming from the lungs.

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18
Q

What vessel leaves the left ventricle when it contracts? The right ventricle? Where do these vessels go?

A

The aorta leaves the left ventricle. The pulmonary artery leaves the right ventricle. The aorta goes to the body. The pulmonary artery goes to the lungs.

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19
Q

What type of structure makes sure that blood only flows through the heart in one direction?

A

Valves

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20
Q

Where are atrioventricular valves located?

A

Between the right atria and right ventricle (the tri-cuspid). Between the left atria and left ventricle (the bi-cuspid).

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21
Q

How do the papillary muscles and chordae tendineae make sure that the AV value works correctly?

A

The chordae tendineae attach the papillary muscle to the valves. When they contract, the valves open and when they relax, the valves close.

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22
Q

Where do you find semilunar valves in the heart?

A

The pulmonary semilunar valve is the valve between the right ventricle and the pulmonary artery. The aortic semilunar valve is between the left ventricle and the aorta.

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23
Q

Describe the structure of a semi lunar valve.-

A

It looks like a half-moon.

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24
Q

Describe how the heart itself receives blood and how it gets back to the right atria after feeding the heart tissue (describe coronary circulation).

A

Vessels are in the epicardium and then branches go inward to the myocardium. The vessels deliver blood when the heart is relaxed. When the heart contracts, it squeezes these vessels compressing them so that they can’t move blood through them. Blood leaves the aorta at its base and from there the left and right coronary arteries branch off. The left coronary artery goes to the left side of the heart and branches. The right coronary artery splits and goes to the right side.
After oxygen is delivered, cardiac veins collect deoxygenated blood. These join together to form the coronary sinus, which drains blood back into the right atria.

25
Q

What are the intercellular spaces of cardiac muscle filled with

A

Spaces are filled with connective tissue (areolar) containing capillaries (blood supply).

26
Q

What exactly is an intercalated disc? What do they contain?

A

Intercalated discs are where two cardiac muscle cells come together/connect. They contain demosomes and gap junctions.

27
Q

What’s the benefit of having a gap junction between cells?

A

Demosomes ensure that the cells don’t pull apart while contracting. Gap junctions connect the cells internal contents (allowing ions to flow from one cell to the next). This allows the action potential to spread from one cell to the next very quickly - so quickly that the heart seems to contract as one unit.

28
Q

What percent of the cell is taken up by mitochondria?

A

20-25%

29
Q

What’s a pacemaker cell? What does it do? Why is this important?

A

Pacemaker cells aren’t contractile - they don’t contract. They do spontaneously depolarize and then contract. They then spread the depolarization to nearby cells. So, the pacemaker cells set the pace of the heart without any nervous input requirement.

30
Q

Explain why the heart and all its cells, contract as a unit.

A

Because they are connected by gap junctions, which allow ions to pass quickly from one cell to its neighbor.

31
Q

Where is calcium stored in the heart muscle?

A

SR sarcoplasmic reticulum

32
Q

What does the heart rely on for energy?

A

ATP

33
Q

What arm of the nervous system innervates the heart?

A

Autonomic nervous system

34
Q

What happens in a pacemaker cell?

A

They depolarize spontaneously, spreading th edepolarizaton to the contractile cells through gap junctions.

35
Q

Pacemaker potential:

A

Hyperpolarization at the end of an action potential causes two things to happen. First, K+ channels close, so no more + charges can leave the cell. Second, slow Na+ channels open, so + charges can leak in. So, the inside of the cell becomes more and more positive. It is creeping towards depolarization, without any nervous input.

36
Q

Depolarization:

A

Threshold is reached at -40 mV. Ca++ channels open, Ca++ from the extracellular fluid enters. This creates the rising phase of the AP. This is different from skeletal muscle, where an influx of Na+ creates the rising phase.

37
Q

Repolarization:

A

Ca++ channels inactivate/close K+ channels open and K+ flows out

38
Q

Hyperpolarization:

A

K+ channels close. Slow Na+ channels open

39
Q

What are the differences between cardiac muscle contraction and skeletal muscle contraction?

A

There aren’t gap junctions in skeletal muscle. So, each muscle cell that fires has to be innervated by a nerve. Cardiac muscle cells are all connected by gap junctions, so they contract as a unit. The depolarization spreads through the gap junctions. Calcium is stored in the SR in skeletal muscle. In cardiac muscle it is stored in the extracellular fluid and in the SR.

40
Q

Tetanus

A

occurs in skeletal muscle. Muscles contract until there is so much Ca++ in the cell that one long, smooth muscle contraction occurs. No tetanus occurs in cardiac muscle. The refractory period, the time when the muscle cell can’t be stimulated to contract again, is about the same amount of time as contraction.

41
Q

What is the function of the Sino atrial (SA) node?

A

To set the pace of the heart beat.

42
Q

Define the term sinus rhythm:

A

Sinus rhythm is about 75 beats per minute.

43
Q

Describe how the depolarization spreads throughout the heart.

A

Include the SA node, the AV node, the AAV bundle, right and left bundle branches and the subendocardial conducting network (Purkinje fibers). Depolarization begins in the SA (sino atrial) node. The SA node is in the wall of the right atria. These cell depolarize. The depolarization spreads to the AV node, which is in the interatrial septum (right above the tri-cuspid valve). The impulse delays here for about a tenth of a second because the fibers that start here have a smaller diametrer and fewer gap junctions, which slows the impulse down. During this pause, the atria complete their contraction. There is no electrical connection between atria and ventricles except for the atrioventricular bundle. The impulse travels through this bundle and then the impulse spreads towards the ventricles. It travels through the bundle branches to the apex of the heart, then travels up the outside walls of the heart in the purkinje fibers.

44
Q

Why is the SA node where the contraction begins?

A

The SA node is a bundle of pacemaking cells that depolarizes the fastest. So, these cells contract first, and the contraction spreads from them.

45
Q

Systole -

A

contraction

46
Q

Diastole -

A

relaxation

47
Q

What is the cardiac cycle?

A

Blood flow through the heart during one complete contraction (atrial systole and diastole and ventricular systole and diastole).

48
Q

What happens during the ventricular filling phase of the cardiac cycle?

A

Pressure in the heart is low and blood is returning form the body and the lungs. Blood is moving into the atria (both of them) and draining into the ventricles (through the AV valves). The semilunar valves are closed. About 80% of ventricular filling occurs this way. The atria then contract, pushing the remaining blood into the ventricles. The ventricles are just about finishing up their diastole (relaxation) period. They are as full of blood as they will be. The amount of blood in them is called ‘end diastolic volume’. Atria relax. Ventricles start to depolarize.

49
Q

What does the term end diastolic volume mean?

A

The amount of blood that is in the heart at the end of a contraction.

50
Q

What happens during the isovolumetric contraction?

A

Atria relax (and begin filling with blood). Ventricles begin contracting. Ventricle walls close in on the blood, pressure in the ventricles rises. This increase in pressure causes the AV valves to close. For a moment the ventricles are completely closed off (all heart valves are closed). This is called the isovolumetric contraction phase. When pressure in the ventricles becomes higher than in the vessels leaving the ventricles, the semilunar valves open

51
Q

What happens during the ventricular ejection phase?

A

Blood enters the aorta and pulmonary artery.

52
Q

What is end diastolic volume?

A

Ventricles relax. Some blood is left in the ventricles. This is called end systolic volume.

53
Q

What happens during the isovolumetric relaxation phase?

A

The blood here isn’t compressed anymore, pressure drops. Blood in the pulmonary artery and aorta flows backwards to this area of low pressure. The semilunar valves close, directing blood in a one-way direction of flow. The atria have been filling with blood. When the pressure in the atria is higher than the ventricle, the AV valves open.

54
Q

What is cardiac output?

A

The amount of blood pumped by each ventricle in one minute. To determine this you can multiply heart rate by stroke volume.

55
Q

What is stroke volume?

A

The amount of blood moved out of each ventricle when the ventricle contracts.

56
Q

What is one effect of the sympathetic NS on the stroke volume

A

Stroke volume doesn’t change under sympathetic innervation. Heart rate does increase, which means that the cardiac output increases.

57
Q

What are the effects of the parasympathetic system on heart rate, stroke volume and cardiac output?

A

Heart rate declines, stroke volume doesn’t change, so cardiac output declines.

58
Q

What happens to the heart as it ages?

A

If the heart weakens with age, then it can’t pump out as much blood each time it contracts. In other words, stroke volume decreases. To make sure that cells are getting enough nutrients and oxygen, heart rate will increase so that cardiac output doesn’t change. Over time, this is hard on th

BIOL 228 (12 decks)

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