Bio261 Lecture 14 Q's- Cardiac System

Front 1

Are the ventricles empty before the atria contract?

Back 1

- No, the ventricles are actually only ~70% full, and the atria "top them off".

Front 2

Which side of the heart delivers blood to the pulmonary circuit?

Back 2

-Right side

Front 3

Which side of the heart delivers blood to the systemic circuit?

Back 3

-Left side

Front 4

Do the pulmonary and systemic circuits contain the same amount of blood?

Back 4

-No

Front 5

Are both circuits at the same pressure?

Back 5

-No, the systemic circuit is under much greater pressure. (Systemic systolic pressure ~120 mmHg; Pulmonary systolic pressure ~ 12-14 mmHg).

Front 6

Do both circuits pump the same amount of blood at the same rate?

Back 6

- Yes, both the pulmonary and systemic circuits must pump the same amount of blood through each circuit so that neither one "backs up" the other - they both pump about 70 ml/beat

Front 7

Are left and right ventricles the same size?

Back 7

No, the left ventricle is considerably larger than the right.

Front 8

Which is longer: diastole or systole?

Back 8

During normal contractions, diastole is longer than systole (normal heart beat - diastole 0.5 sec and systole 0.3 sec).

Front 9

Do the left and right atria contract at the same time?

Back 9

-yES

Front 10

Do the left and right ventricles contract at the same time?

Back 10

-Yes

Front 11

Do the left and right atria & ventricles contract at the same time?

Back 11

- No, atria contract 0.1-0.2 sec before ventricles

Front 12

How long is an average cardiac cycle at rest (non-exercising)?

Back 12

-0.8 sec

Front 13

What is occurring during isovolumetric ventricular contraction?

Back 13

The ventricles begin contracting, which closes the AV valves. As isovolumetric contraction continues, pressure is built up within the ventricle until the pressure in the ventricles is great enough to open the semilunar valves

Front 14

What are heart murmurs?

Back 14

- Heart murmurs are abnormal heart sounds produced by abnormal blood flow in the heart.

Front 15

What does congenital mean?

Back 15

-Congenital means present at birth, but not necessarily hereditary.

Front 16

What is mitral stenosis?

Back 16

- This a condition in which the mitral valves become calcified and thickened.

Front 17

What can happen as a result of mitral stenosis?

Back 17

- If the mitral valve is calcified and thickened, it does not open properly, so blood can not enter the left ventricle easily, this can cause blood to remain in the atria, and eventually back up into the pulmonary system causing pulmonary hypertension.

Front 18

What happens to the length of diastole during exercise?

Back 18

- During exercise the length of diastole decreases.

Front 19

If rate is over 200bts/min does it affect the ability of the ventricles to fill?

Back 19

- Yes, if the heart rate is over 200 beats/min there is insufficient time for the ventricles to fill.

Front 20

Where is the majority of the blood in your body contained when you are at rest?

Back 20

- In the veins of the systemic system.

Front 21

Do all of the cells of the heart contract?

Back 21

- No, the conducting cells do not contract.

Front 22

Do all of the contractile heart cells contract with each cardiac cycle? (all-or-nothing)

Back 22

Yes, once one cell is committed to contract, all the cells in one syncitium become committed to contract because they are all connected by gap junctions, however, the atria acts as one syncitium (like one giant cell) and the ventricles act as another, so the contraction of the atria does NOT commit the ventricles to directly contract, this is why you must have the conducting cells to send the depolarization from the atria to the ventricles.

Front 23

Do heart cells always contract with the same force?

Back 23

- No, the sympathetic system can cause an increase in availability of internal Ca++. If there is more Ca++, that means that cross bridging can happen faster which will cause the cells collectively to contract more forcibly and more quickly.

Front 24

-Is there only one area of the heart with cells that generate spontaneous action potentials?

Back 24

-No, all of the conducting cells of the heart can generate spontaneous action potentials. Even the contracting cells can generate ABNORMAL action potentials called ectopic beats, these are the primary causes of PVC's. These are abnormal only because the contracting cells don't generally generate spontaneous action potentials, not because they are connected with a specific disease state.

Front 25

At what part of the heart is the heart rate normally determined?

Back 25

- Normally the SA node sets the pace of the heart because it is depolarizing the quickest.

Front 26

What does “cardiac output” mean?

Back 26

- Cardiac output (CO) is the volume of blood pumped per minute from each ventricle

Front 27

What is the equation for cardiac output?

Back 27

- CO = HR x SV (Cardiac output = Heart rate x stroke volume).

Front 28

What factors affect Heart rate?

Back 28

-Heart rate is controlled by the ANS (autonomic nervous system).

Front 29

What factors affect stroke volume?

Back 29

3 factors affect stroke volume 1. EDV (end diastolic volume) 2. TPR (total peripheral resistance) and 3. Contractility of the heart

Front 30

What is the average resting cardiac output?

Back 30

- At rest, the average CO is about 5.25L of blood (slightly more than our total blood volume is pumped through the heart every minute).

Front 31

At rest the c.o. is what % of the total blood volume?

Back 31

~ 105%.

Front 32

During strenuous exercise, the c.o. is what % of total blood volume?

Back 32

- During strenuous exercise up to 25-30L/min of blood can be pumped through the heart ~500% of our total blood volume.

Front 33

How does the sympathetic n.s. influence the heart rate?

Back 33

-The sympathetic nervous system releases NE onto the SA node cells and causes the HR to increase.

Front 34

How does the parasympathetic n.s. influence the heart rate?

Back 34

- The parasympathetic system releases ACh onto the SA node cells and causes the HR to slow down.

Front 35

What is stroke volume?

Back 35

-Stroke volume is the amount of blood ejected per each beat of the heart

Front 36

Is stroke volume consistent?

Back 36

-no

Front 37

What can change stroke volume?

Back 37

-The EDV (end diastolic volume) - the amount of blood that has returned to the heart, which can be affected, for example, by the amount of sympathetic activity causing vasoconstriction of arteries and veins or the activity of the "skeletal muscle pumps". Furthermore, the stroke volume can be affected by the contractility of the heart. Or the blood pressure of the arteries (if the pressure in the arteries is too high, not as much blood can be pumped out of the heart).

Front 38

What is the major intrinsic regulator of the force of contraction (stroke volume)?

Back 38

- The EDV

Front 39

What is the Frank-Starling law of the heart?

Back 39

- Basically, the more blood returned to the heart (the more EDV), the more blood will be ejected with each beat, this is based on the relationship of the stretch of the sarcomeres and the ability of actin and myosin to form cross-bridges. W

Front 40

What are chronotropic effects?

Back 40

- Chronotropic effects are those which affect heart rate. (Chronos = time)

Front 41

What are inotropic effects?

Back 41

- Inotropic effects are those which affect the contractility of the heart, these are usually associated with ions, such as Ca++.

Front 42

What % of the blood that enters the ventricle during diastole is pumped out during systole?

Back 42

- This is referred to as the "Ejection Fraction" and is usually about 60%.

Front 43

Is the ventricle empty at the end of systole?

Back 43

- No, if the ejection fraction is ~60%, that means that about 40% of the blood is still remaining in the ventricles at the end of systole.

Front 44

How do skeletal muscles affect EDV?

Back 44

-Without skeletal muscles (especially of the lower extremities) blood would not be able to return to the heart, and would pool in the foot and lower leg area. The more skeletal muscle activity, the more blood is returned to the heart. In other words, when you go out and run, you muscles are being used to not only move you but also to return more blood to the heart at a quicker rate.

Front 45

Pulmonary

Back 45

-part of the circulatory system concerned with the transportation of oxygen from and carbon dioxide to the lungs.

Front 46

Systemic

Back 46

-denoting the part of the circulatory system concerned with the transportation of oxygen to and carbon dioxide from the body in general

Front 47

Atria

Back 47

-receive blood from venous system

Front 48

Ventricle

Back 48

-pump blood to arteries

Front 49

Septum

Back 49

-separates the 2 sides of the heart

Front 50

Myocardium

Back 50

-entire muscle that forms a chamber

-AKA functional syncitium

Front 51

Aorta

Back 51

- the main artery in the human body

- distributes oxygenated blood to all parts of the body through the systemic circulation

Front 52

Pulmonary artery

Back 52

- carries deoxygenated blood from the heart to the lungs

-one of the only arteries to carry deoxygenated blood

Front 53

Pulmonary vein

Back 53

-large blood vessels that receive oxygenated blood from the lungs and drain into the left atrium of the heart.

-one of the few veins that carry oxygenated blood

Front 54

AV (atrioventricular) valves

Back 54

-one-way valves in between the atria and ventricles

-blood flows from atria to ventricles

-contain tricuspid& bicuspid valves

Front 55

Tricuspid

Back 55

-b/n right atrium & ventrical

Front 56

Bicuspid/mitral

Back 56

-b/n left atrium & ventrical

Front 57

Semilunar valves

Back 57

-blood is pumped thru these valves during ventricular contraction

-close during relaxation

Front 58

SA (sinoatrial) node

Back 58

-a small, specialized region in the right atrial wll

Front 59

Internodal pathway

Back 59

-the pathway b/n the SA node and the AV node

Front 60

AV (atrioventricular) node

Back 60

-a small bundle of specialized cardiac muscle cells located at the base of the right atrium near the septum

Front 61

Bundle of His

Back 61

-a tract of specialized cells that originates at the AV node and enters the septum b/n the ventricles.

-divides to form the left & right bundle branches that travel down the septum, curve around the tip of the ventricular chambers, and travel back toward the atria along the outer walls

Front 62

Purkinje Fibers

Back 62

-small terminal fibers that extend from the bundle of His and spread throughout the ventricular myocardium much like small twigs of a tree branch

Front 63

HCN - hyperpolarization activated cyclic-nucleotide gated

Back 63

"funny channels"

-V-g channels that open when the potential becomes more negative (hyperpolarizes), rather than when it becomes more positive (depolarizes) as with usual v-g channels.

-Na+ moves inward, depolarizing the cells and moves the pacemaker cell's potential toward threshold again.

Front 64

Absolute refractory period

Back 64

-the period where cells cannot be retimulated to undergo another AP

Front 65

Plateau phase (Ca++)

Back 65

-MP rapidly declines to -15mV and stays there for 200-300 msec

-results from balance b/n slow Ca++ influx & K+ efflux

Front 66

CO - cardiac output

Back 66

-volume of blood pumped/min by each ventricle

Front 67

SV - stroke volume

Back 67

blood pumped/beat by each ventricle

Front 68

EDV - end diastolic volume

Back 68

-volume of blood in ventricles at end of diastole

Front 69

Ejection fraction

Back 69

-SV/EDV

Front 70

Frank-Starling Law of the Heart

Back 70

-a state of myocardial sarcomeres just b4 filling

-actins overlap, actin-myosin interactions are reduced & contraction would be weak

-state that strength of ventricular contraction varies directly w/EDV

Front 71

Chronotropic effect

Back 71

-sympathetic and parasympathetic nerve fibers modify rate of spontaneous depolarization at the SA node

-the name for how both influence heart rate

Front 72

Inotropic

Back 72

-Affecting the force of muscle contraction.

-An inotropic heart drug is one that affects the force with which the heart muscle contracts.

-positive or negative

Front 73

Intrinisic

Back 73

-referes to the heart's inherent ability to vary stroke volume, depends on the direct correlation b/n end-diastolic volume and stroke volume.

Front 74

Extrinsic

Back 74

-control of SV by factors originating outside the heart, most important of which are actions of the cardiac sympathetic nerves and epinephrine

Front 75

Skeletal pump

Back 75

-blood is moved toward heart by contraction of surrounding skeletal muscles

Front 76

Venous return

Back 76

-refers to the volume of blood per minute entering each atrium from the veins.

Front 77

Capacitance vessels

Back 77

the blood vessels that hold the major portion of the intravascular blood volume.

-they are elastic and distensable

Front 78

Compliance

Back 78

-a measure of the ease with which the heart may be distended.

-the quality of yielding to pressure w/o disruption

Front 79

Isovolumetric contraction

Back 79

-a period where all valves are closed, no blood can enter/leave the ventricle during this time.

Front 80

Isovolumetric relaxation

Back 80

-a brief period where all valves are closed

Front 81

Heart murmurs

Back 81

-abnormal sounds produced by abnormal patterns of blood flow in heart

-many caused by defective heart valves

Front 82

Rheumatic fever

Back 82

-Valve damage due to the thickened valve not opening fully, impairing blood flow from left atrium to left ventricle.

Front 83

Mitral stenosis

Back 83

-a type of valve damage where the mitral valve becomes thickened & calcified very often due to secondary damage from rheumatic fever.

Front 84

TPR-total peripheral resistance

Back 84

-impedance to blood flow in arteries

Front 85

systole

Back 85

contraction phase of the heart

~0.3 sec

Front 86

Diastole

Back 86

relaxation phase of the heart

~0.5 sec