Lecture 3 The Heart

Question 0

fibrous pericardium?

Answer 0

• dense irregular CT

- protects and anchors the heart, prevents overstretching

Question 1

where is the HT located?

Answer 1

in mediastinum - area from the sternum to the vertebral column and bt LU

Question 2

what is thin, delicate membrane containing:

• parietal layer - outer layer
• pericardial cavity with pericardial fluid
• visceral layer (epicardium)

Answer 2

serous pericardium

Question 3

what are the layers of the Heart?

Answer 3

epicardium
myocardium
endocardium

Question 4

which layer of the HT is the visceral layer of serous pericardium?

Answer 4

epicardium

Question 5

which layer of the heart is the cardiac muscle layer and is the bulk layer of the heart?

Answer 5

myocardium

Question 6

which layer lines the chamber and valves of the heart?

Answer 6

endocardium

Question 7

the thickness of myocarium varies according to the function of what?

Answer 7

the function of chamber of heart

Question 8

what is the thickness of atria wall, why?

Answer 8

Atria are thin walled, because they deliver blood to adjacent ventricles

Question 9

what is the thickness of ventricle walls, why?

Answer 9

ventricle walls are much thicker and stronger

• the right ventricles supplies blood to the lung (little flow resistance)
• left ventricle wall is the thickest to supply systemic circulation

Question 10

which chamber of the HT, receives blood from 3 sources? what are they?

Answer 10

right atrium

- superior vena cava, inferior vena cava, coronary sinus, blood flows through the tricuspid valve to the right ventricle

Question 11

the right ventricle?

Answer 11

receives blood from right atrium, blood goes through pulmonary semilunar valve; blood flows into pulmonary trunk

Question 12

the left atrium?

Answer 12

receives blood from lungs (through 4 pulmonary venins, 2 right and 2 left) and through the bicuspid valves blood passes through into left ventricle

Question 13

left ventricle

Answer 13

receives blood from left atrium, sends blood through aortic semilunar valve into ascending aorta

Question 14

the systemic circulation is on which side of the heart? and does what?

Answer 14

• the left side of heart pumps blood through body
• left ventricle pumps oxygenated blood into aorta
• aorta branches into many arteries that travel to organs
• arteries branch into many arterioles in tissue
• arterioles branch into thin-walled capillaries for exchange of gases and nutrients
• deoxygenated blood begins its return in venules
• venules merge into veins and return to right atrium

Question 15

pulmonary circulation

Answer 15

• right side of heart pumps deoxygenated blood to lungs
• right ventricle pumps blood to pulmonary trunk
• pulmonary trunk branches into pulmonary arteries of gases
• oxygenated blood returns to heart in pulmonary veins

Question 16

what is the function of the dense CT rings surrounding the valves of the heart, and that fuses and merges with the interventricular septum?

Answer 16

• the fibrous skeleton of the heart support structure for heart valves
• it is an insertion pt for cardiac muscle bundles
• it acts as an electrical insulator bt atria and ventricles (prevents direct propagation of AP’s to ventricles)

Question 17

what is coronary circulation?

Answer 17

• coronary circulation is blood supply to the heart
• heart is a very active muscle and needs lot of O2
• when heart relaxes high pressure of blood in aorta pushes blood into coronary vessels
• there are many anastomoses in coronary circulation

Question 18

what is anastomoses?

Answer 18

• connection between arteries supplying blood to same region, provide alternate routes if one artery becomes occluded

Question 19

which cells fire spontaneously, and act as pacemaker and form conduction system for the heart?

Answer 19

autorhythmic cells

Question 20

what are cluster of cells in wall of Right Atria,

• begins heart activity that spreads to both atria
• pacemaker of heart (why?)

Answer 20

SA node

it’s the pacemaker, bc SA node is the fastest it sets the pace

Question 21

what is the connection bt atria and ventricles and divides into bundle branches & purkinje fibers (large diameter fibers that conduct signals quickly)

Answer 21

AV bundle of His

Question 22

SA nodes fires spontaneously how many times per min?

Answer 22

90-100 x/min

Question 23

AV nodes fires how many times per min?

Answer 23

40-50 x/mins

Question 24

if both SA and AV nodes are suppressed, how many times per min does the ventricles fire by themselves?

Answer 24

20- 40 x/min

Question 25

if extra beats form at other sites, this is called?

Answer 25

ectopic pacemaker

Question 26

what is the cardiac cell resting membrane potential?

Answer 26

-90 mv

Question 27

what happens during depolarization?

Answer 27

- excitation spreads through gap junctions | - fast Na+ channels open for rapid depolarization

Question 28

what happens during plateau phase?

Answer 28

- 250 msec (only 1 msec in neuron) - slow Ca+2 channels open, let Ca+2 enter from outside cell and from storage in sarcoplasmic reticulum, while K+ channels close - Ca+2 binds to troponin to allow for actin-myosin cross bridge formation & tension development

Question 29

what is repolarization?

Answer 29

- Ca+2 channels close and K+ channels open & -90mv is restored as potassium leaves the cell

Question 30

how long is the refractory period? why?

Answer 30

very long so heart can fill

Question 31

what records action potential of all active cells?

Answer 31

EKG

Question 32

P wave

Answer 32

atrial depolarization

Question 33

P to Q interval

Answer 33

conduction time from atrial to ventricular excitation

Question 34

QRS complex

Answer 34

ventricular depolarization

Question 35

T wave

Answer 35

ventricular repolarization

Question 36

what is one cardiac cycle?

Answer 36

75 beats/min, one cycle requires .8 sec

Question 37

what is end diastole volume (EDV)?

Answer 37

volume in ventricle at end of diastole, about 130 ml

Question 38

what is end systolic volume (ESV)?

Answer 38

volume in ventricle at end of systole, about 60ml

Question 39

what is stroke volume (SV)

Answer 39

the volume ejected per beat from each ventricle, about 70 ml SV = EDV-ESV

Question 40

what is a brief period when volume in ventricles does not change - as ventricles relax, pressure drops and AV open?

Answer 40

isovolumetric relaxation

Question 41

what are the phases of cardiac cycle?

Answer 41

- isovolumetric relaxation - ventricular filling (rapid ventricular filling) - ventricular systole

Question 42

what happens during ventricular filling?

Answer 42

- rapid ventricular filling: as blood flows from full atria - diastasis: as blood flows from atria in smaller volume - atrial systole pushes final 20 - 25 ml blood into ventricle

Question 43

what happens during ventricular systole?

Answer 43

- ventricular systole - isovolumetric contraction: brief period, AV valves close before SL valves open - ventricular ejection: as SL valves open and blood is ejected out

Question 44

what is the blood pressure in aorta?

Answer 44

120 mm Hg

Question 45

what is the blood pressure in pulmonary trunk?

Answer 45

30 mm Hg

Question 46

the difference in ventricle wall thickness allows heart to do what? what is the volume of blood ejected from each ventricle?

Answer 46

pushes the same amount of blood with more force from left ventricle - 70 ml (stroke volume)

Question 47

the first heart sound that is created with the closing of atrioventricular valves?

Answer 47

lubb

Question 48

the second heart sound, created with closing of semilunar valves is?

Answer 48

dupp

Question 49

what is the amount of blood pushed into aorta or pulmonary trunk by ventricle?

Answer 49

cardiac output

Question 50

cardiac output is determined by? | what is the equation?

Answer 50

determined by stroke volume and heart rate CO = SV x HR

Question 51

what influences stroke volume?

Answer 51

preload (affect stretching; Frank-Starling Law of Heart: more blood more force of contraction) contractility (autonomic nerves, hormones, Ca+2 or K+ levels) afterload (amount of pressure created by the blood in the way

Question 52

what are the causes of CHF?

Answer 52

coronary artery disease, hypertension, MI, valve disorders, congenital defects

Question 53

what happens in a left side heart failure?

Answer 53

- less effective pump so more blood remains in ventricle - heart is overstretched & even more blood remains - blood backs up into lungs as pulmonary edema - suffocation & lack of oxygen to the tissues

Question 54

what happens in right side failure?

Answer 54

- fluid builds up in tissues as peripheral edema

Question 55

how does the nervous control from cardiovascular center in the medulla affect heart rate?

Answer 55

- sympathetic impulses increase heart rate and force of contraction - parasympathetic impulses decrease heart rate - baroreceptros (pressure receptors) detect change in BP and send info to cardiovascular center (located in arch of the aorta and carotid arteries)

Question 56

what hormones affect heart rate?

Answer 56

- epinephrine, norepinephrine, thyroid hormones | - ions (Na+, K+, Ca+2)

Question 57

what is in atrial septum and transmits signal to bundle of His?

Answer 57

AV node