Lecture 3 The Heart Flashcards
fibrous pericardium?
- dense irregular CT
- protects and anchors the heart, prevents overstretching
where is the HT located?
in mediastinum - area from the sternum to the vertebral column and bt LU
what is thin, delicate membrane containing:
- parietal layer - outer layer
- pericardial cavity with pericardial fluid
- visceral layer (epicardium)
serous pericardium
what are the layers of the Heart?
epicardium
myocardium
endocardium
which layer of the HT is the visceral layer of serous pericardium?
epicardium
which layer of the heart is the cardiac muscle layer and is the bulk layer of the heart?
myocardium
which layer lines the chamber and valves of the heart?
endocardium
the thickness of myocarium varies according to the function of what?
the function of chamber of heart
what is the thickness of atria wall, why?
Atria are thin walled, because they deliver blood to adjacent ventricles
what is the thickness of ventricle walls, why?
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
which chamber of the HT, receives blood from 3 sources? what are they?
right atrium
- superior vena cava, inferior vena cava, coronary sinus, blood flows through the tricuspid valve to the right ventricle
the right ventricle?
receives blood from right atrium, blood goes through pulmonary semilunar valve; blood flows into pulmonary trunk
the left atrium?
receives blood from lungs (through 4 pulmonary venins, 2 right and 2 left) and through the bicuspid valves blood passes through into left ventricle
left ventricle
receives blood from left atrium, sends blood through aortic semilunar valve into ascending aorta
the systemic circulation is on which side of the heart? and does what?
- 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
pulmonary circulation
- 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
what is the function of the dense CT rings surrounding the valves of the heart, and that fuses and merges with the interventricular septum?
- 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)
what is coronary circulation?
- 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
what is anastomoses?
- connection between arteries supplying blood to same region, provide alternate routes if one artery becomes occluded
which cells fire spontaneously, and act as pacemaker and form conduction system for the heart?
autorhythmic cells
what are cluster of cells in wall of Right Atria,
- begins heart activity that spreads to both atria
- pacemaker of heart (why?)
SA node
it’s the pacemaker, bc SA node is the fastest it sets the pace
what is the connection bt atria and ventricles and divides into bundle branches & purkinje fibers (large diameter fibers that conduct signals quickly)
AV bundle of His
SA nodes fires spontaneously how many times per min?
90-100 x/min
AV nodes fires how many times per min?
40-50 x/mins
if both SA and AV nodes are suppressed, how many times per min does the ventricles fire by themselves?
20- 40 x/min
if extra beats form at other sites, this is called?
ectopic pacemaker
what is the cardiac cell resting membrane potential?
-90 mv
what happens during depolarization?
- excitation spreads through gap junctions
- fast Na+ channels open for rapid depolarization
what happens during plateau phase?
- 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
what is repolarization?
- Ca+2 channels close and K+ channels open & -90mv is restored as potassium leaves the cell
how long is the refractory period? why?
very long so heart can fill
what records action potential of all active cells?
EKG
P wave
atrial depolarization
P to Q interval
conduction time from atrial to ventricular excitation
QRS complex
ventricular depolarization
T wave
ventricular repolarization
what is one cardiac cycle?
75 beats/min, one cycle requires .8 sec
what is end diastole volume (EDV)?
volume in ventricle at end of diastole, about 130 ml
what is end systolic volume (ESV)?
volume in ventricle at end of systole, about 60ml
what is stroke volume (SV)
the volume ejected per beat from each ventricle, about 70 ml
SV = EDV-ESV
what is a brief period when volume in ventricles does not change - as ventricles relax, pressure drops and AV open?
isovolumetric relaxation
what are the phases of cardiac cycle?
- isovolumetric relaxation
- ventricular filling (rapid ventricular filling)
- ventricular systole
what happens during ventricular filling?
- 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
what happens during ventricular systole?
- ventricular systole
- isovolumetric contraction: brief period, AV valves close before SL valves open
- ventricular ejection: as SL valves open and blood is ejected out
what is the blood pressure in aorta?
120 mm Hg
what is the blood pressure in pulmonary trunk?
30 mm Hg
the difference in ventricle wall thickness allows heart to do what? what is the volume of blood ejected from each ventricle?
pushes the same amount of blood with more force from left ventricle
- 70 ml (stroke volume)
the first heart sound that is created with the closing of atrioventricular valves?
lubb
the second heart sound, created with closing of semilunar valves is?
dupp
what is the amount of blood pushed into aorta or pulmonary trunk by ventricle?
cardiac output
cardiac output is determined by?
what is the equation?
determined by stroke volume and heart rate
CO = SV x HR
what influences stroke volume?
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
what are the causes of CHF?
coronary artery disease, hypertension, MI, valve disorders, congenital defects
what happens in a left side heart failure?
- 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
what happens in right side failure?
- fluid builds up in tissues as peripheral edema
how does the nervous control from cardiovascular center in the medulla affect heart rate?
- 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)
what hormones affect heart rate?
- epinephrine, norepinephrine, thyroid hormones
- ions (Na+, K+, Ca+2)
what is in atrial septum and transmits signal to bundle of His?
AV node
