heart

where is the heart positioned in the body

mediastinum of thorax, just deep of sternum with 2/3 lying to left of median plan and is triangular/pyramidal in shape with base on superior and apex on inferior tip of left ventricle

double walled sac that encloses the heart with three layers

pericardium

tough, superficial outer layer of the heart that anchors the sac to the diaphragm and prevents overfilling

fibrous pericardium

portion of the pericardium that contains two layers

serous pericardium

lines the inner surface of fibrous pericardium

parietal layer

covers surface of the heart

visceral layer/ epicardium

space between two layers of serous pericardium with pericardial fluid exuded from serous layers

pericardial cavity

what is the purpose of the pericardial fluid

decreases friction to allow the heart to beat

inflammation of the pericardial layers

pericarditis

so much excess fluid (pericardial effusion) that it affects pumping function/ physiology

cardiac tampanode

what are the three layers of the heart wall

epicardium, myocardium, and endocardium

visceral layer of serous pericardium and can have an epicardial layer of fat

epicardium

where do the coronary vessels of the heart travel through

epicardium

thick muscular layer of the heart where fibers have spiral orientation to push blood up and out

myocardium

lines inner heart chambers, covers valves and is continuous with endothelium of blood vessels

endocardium

what are the plates of fibrous connective tissue between the atria and ventricles

fibrous skeleton of the heart

what is the functions of the fibrous skeleton of the heart

provide support of tissues around valves, site for cardiac muscle attachment, and electrical insulation between atria and ventricles to control path of conduction

what is the primary job of the right and left atria

receive blood coming back to the heart via the pulmonary or vena cava veins

what heart chambers have extensions (auricles) and muscular ridges (pectinate muscles)

right and left atria

what is the primary job of the right and left ventricles

pumps that eject blood into great arteries (pulmonary trunk or aorta)

what heart chambers have internal ridges or trabeculae carnae

right and left ventricles

what are the right and left sides of the heart separated by

interatrial and interventricular septum

what is the role of the atrioventricular valves

provide one way flow from atria to ventricles and the cusps are pulled into the ventricles by the papillary muscles and chorda tendinea

which portion of the heart contains the 3 cusps valve tricuspid

right atrioventricular valve

which portion of the heart contains the 2 cusps valve mitral/bicuspid

left atrioventricular valve

what is the purpose of the semilunar valves

ensure one way flow from ventricles to great arteries

what occurs to the semilunar valves’ three cusps during systole or diastole since they are not anchored

the cusps are pushed up and out of the way when blood is being pushed out and then meet in the middle during relaxation

where is the pulmonary valve located

the right ventricle to the pulmonary artery

where is the aortic valve located

the left ventricle to the aorta

carries O2 poor blood to lungs for gas exchange; enters the RA and leaves RV to travel to the pulmonary arteries and veins to become oxygenated

pulmonary circuit

supplies O2 rich blood to all organs: enters LA and leaves LV to travel through the aorta and systemic circulation

systemic circuit

where does the heart receive its own arterial supply and venous network

coronary arteries that come from aorta within the aortic valve cusps

when do the coronary arteries that give the heart its own arterial supply fill

ventricular diastole when aortic valve is closed

which coronary artery supplies the SA node

right coronary artery

what supplies the lateral aspect of RV

right marginal artery

what supplies the posterior walls of ventricles and septum

posterior interventricular artery/ posterior descending artery

what is the major artery supplying anterior walls of RV and LV and anterior 2/3 of interventricular septum

anterior interventricular artery/left anterior descending artery off of the left main coronary artery

where majority of the coronary veins drain into and is located within the posterior coronary sulcus before draining into the RA; 5-10% of venous blood sumps directly into RA

coronary sinus

striated muscle made of cardiomyocytes

cardiac muscle

branched cells that contact several other cells

cardiomyocytes

how are the cardiomyocytes of cardiac muscle joined

intercalated disc

what do the intercalated discs contain

interdigiting folds, desmosomes, gap junctions

increases surface area of intercellular contact

interdigiting folds

mechanical junctions that prevent cells from pulling apart

desmosomes

electrical junctions that allow each cell to electrically stimulate other cells in contact quickly

gap junctions

what type of respiration does cardiac muscle depend on to make ATP and is rich in myoglobin and glycogen to do this

aerobic respiration

at rest, where does the heart get majority of its energy to produce ATP

fatty acids and glucose

what are the pros and cons to the heart only relying on aerobic respiration

prone to O2 deficiency but not as much fatigue because of no anaerobic fermentation

why is the heart considered myogenic

it does not require the nervous system to initiate a heartbeat because the signal to depolarize originated within itself due to auto rhythmicity

what is the path of the conduction system in the heart

SA node →interatrial pathway→AV node→AV bundle (bundle of His)→ left and right bundle branches→purkinje fibers(subendocardial fibers)

where does the membrane potential start around in the pacemaker cell

-60mV

what is the pacemaker potential that it is slowly increasing to

-40 mV

once the pacemaker cells reach -40 mV, what occurs

voltage gated calcium channels open and calcium flows into the cell

in an action potential of the pacemaker cells, what happens once the membrane potential reaches 0 mV

K+ channels open and flow out for the cycle to then automaticallly restart

what is the resting membrane potential for the cardiomyocytes

-90 mV and only depolarizes once stimulated

what prevents wave summation/ tetanus of the cardiomyocytes to allow the cardiac muscle to complete its contraction

absolute refractory period of 250ms

atrial depolarization

p-wave

ventricular depolarization and atrial repolarization

QRS complex

ventricular repolarization

T wave

time required for signal to travel from SA node through AV node

PR interval

depolarization through the AV node

PR/PQ segment

beginning of atrial systole

P wave

duration of atrial systole

PR interval

beginning of ventricular systole while atrial diastole occurs

QRS complex

entirety of ventricular systole

QT interval

when does ventricular diastole occur in the ECG

end of T to beginning of QRS

series of electrical and mechanical events that allow heart to pump and move blood; one complete contraction and relaxation phase

cardiac cycle

causes systole and must occur first before contraction of the muscle

depolarization

once completed, diastole occurs

repolarization

as the size of the chamber increases during diastole, how does this affect the pressure

decreases so fluid comes in

as the size of the chamber decreases during systole, how does this affect the pressure

increases so fluid pushes out

what are heart sounds the result of

closing of the valves

closing of AV valves (mitral and tricuspid)

S1 “lubb”

closing of SL valves (aortic and pulmonary)

S2 “dubb”

what happens if a valve is too tight so the opening narrows

stenosis

what happens if the valve is too loose

regurgitant so the opening isnt tight enough and allows backwards flow during diastole

what is phase one of the cardiac cycle

ventricular filling

ventricular diastole where cavity size increases and pressure decreases below that of the atria

ventricular filling

during ventricular filling, what is the flow of blood and which valves are open/closed

AV valves open and blood flows from atria into ventricles

what are the three phases to ventricular filling

rapid filling, diastasis, and atrial systole

what occurs during rapid filling of phase 1

blood stored in atria rushes into the ventricles due to the AV valves opening

what occurs during diastasis of phase 1

slower filling

what occurs during atrial systole of phase 1

atria contracts to increase the pressure within the atria and push more blood into the ventricles (30% of ventricular filling)

what is phase 2 of the cardiac cycle

isovolumetric contraction

what is phase 3 of the cardiac cycle

ventricular ejection

what is phase 4 of the cardiac cycle

isovolumetric relaxation

what occurs during isovolumetric contraction

atria repolarize and relax while the ventricles begin to depolarize and begin systole; the pressure in ventricles increases sharply; no change in volume

what valves are open/closed during isovolumetric contraction

both are closed

what occurs during ventricular ejection

ventricular pressure exceeds the great arteries to allow blood to flow quickly out

what valves are open/ closed during ventricular ejection

AV are closed and SL are open

what occurs during isovolumetric relaxation

beginning of ventricular diastole where the pressure becomes lower than the great arteries; no change in blood amount in ventricles, just increasing diameter of the chamber

which valves are open/ closed during isovolumetric relaxation

both are closed

amount of blood left over within ventricle after systole (apprx. 60mL)

end-systolic volume

amount of blood within the ventricle after diastole (apprx. 130mL)

end-diastolic volume

what does the end- diastolic volume include

end-systolic volume (60mL), amount added during atrial diastole (30mL) and systole (40mL)

amount of blood ejected from ventricles during systole (apprx. 70mL)

stroke volume

how do you calculate the stroke volume

end diastolic - end systolic volume

if there is left sided heart failure, where would extra fluid end up

the LA and then the lungs/pulmonary circuit

if there is right sided heart failure, where would extra fluid end up

the RA and then the systemic system through the vena cava

since the heart does not need nerves for contraction, how does it have physiological adjustments to the heart rate and force of contraction

parasympathetic and sympathetic