chapter 19: heart Flashcards
Functions of the heart
-generate BP
-route blood
-ensure one way flow by way of valves
-regulate blood supply
where is the heart located?
mediastinum
apex
blunt rounded point of cone
base
flat part at opposite end of cone
What are the two parts of the pericardial sac?
fibrous pericardium and serous pericardium
fibrous pericardium
tough fibrous outer layer and prevents over dstention
serous pericardium
thin transparent inner layer that includes parietal and visceral pericardium
epicardium
serous membrane, smooth outer surface of heart,
-aka visceral layer
myocardium
middle layer, heart contractions
endocardium
lines the inner chamber of the heart, simple squamous epithelium
What is the function of the atria?
receive blood
What is the function of the ventricles?
pump blood
pulmonary circuit
-deliver blood to the lungs
-right side of the heart
-poor in O2 but rich in CO2
-
Pulmonary Circuit Blood Pathway
blood from body—>right atrium—>tricuspid valve—>right ventricle—> pulmonary valve—> pulmonary trunk—> pulmonary arteries—> lungs—> pulmonary veins—> left atrium
systemic circuit
-deliver blood to the rest of the body
-left side of heart
-rich in oxygen and poor in CO2
Systemic Circuit Blood Pathway
left atrium—>bicuspid valve—>left ventricle—>aortic valve—>aorta—> systemic circuit
Why are the walls of the left ventricle thicker?
it is pumping over a greater distance but both circuits pump the same amount of blood
AV valves
prevent backflow into the atria and regulates passage of blood from the atria to the ventricles
How many cusps does the right AV valve have?
3
How many cusps does the left AV valve have?
2
semilunar valves
control flow into great arteries and prevent backflow into ventricles
pulmonary valve pathway
right ventricle—>pulmonary trunk
aortic valve pathway
left ventricle—> aorta
What determines the opening of the valves?
depends on pressure in ventricle
Diastole
ventricles relax
-pressure drops and semilunar valves close
-AV valves open and blood flows from atria to ventricles
Systole
ventricles contract
pressure increases and AV valves close
semilunar valves open and blood flows into the vessels
coronary circulation
supplies heart muscle itselfq
anastomoses
junctions, alternate routes for blood to get to the tissues
arteries
carry blood away from the heart
veins
carry blood to the heart
angina pectoris
thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium
myocardial infarction
heart attack, prolonged coronary blockage
desmosomes
type of intercalated discs that prevents cells from separating during contraction
gap junctions
allow ions to pass and pass electrical signals from cell to cell
Electrical event of the cardiac cycle
cardiac action potential which increases calcium
-ECG
mechanical event of the cardiac cycle
contraction and generation of pressure
Pathway of Blood
superior/inferior vena cava—>right atrium—> tricuspid valve—>right ventricle—>pulmonary valve–>pulmonary artery—>lungs—>pulmonary veins–>left atrium—>bicuspid valve—> left ventricle—> aortic valve—> aorta
Conducting system of heart
-causes contractions
1. The SA node or the pacemaker initiates the heartbeat and fires the fastest
2.The AV node will fire second and the action potential is slower
3. The AV bundle reaches interventricular septum
4.right and left bundle branches extend beneath endocardium
5. purkinje fibers
Where is the SA node?
atrium
action potential
electrical signal on a nerve
depolarization
contraction
repolarization
relaxation
What is the benefit of long refractory periods?
prevents tetanic contractions
ECG
record of an electrical event in the myocardium that can be circulated w/ mechanical events
P wave
depolarization of atrial myocardium
SA node
QRS complex
ventricular depolarization
AV node
T wave
repolarization of ventricles
PQ interval
atria contracts and begins to relax
QT interval
ventricles contract and begin to relax
blood pressure
force exerted on the wall of a blood vessel by its contained blood
What 3 things affect BP?
cardiac contractililty
peripheral resistance
blood volume
Where does blood move?
high to low pressure
What causes the valves to open and close?
the pressure of the ventricles
first heart sound
AV valves close and signals systole
second heart sound
SL valves close
Quiescent period of Cardiac cycle
all chambers relaxed, AV valves open, blood flowing in ventricles
atrial systole of cardiac cycle
SA node fires, atria depolarizes
P wave appears
atria contracts and forces additional blood into ventricles
end diastolic volume
amount of blood in ventricles before they contract
isovolumetric contraction
atria repolarizes and relax
ventricles depolarize
QRS complex appears
ventricles contract
pressure rises rapidly closing AV valve, hear first heart sound
ventricular ejection, pressure in ventricle exceeds aorta
rising pressure opens SL valve
rapid ejection of blood
stroke volume
volume of blood pumped out of left ventricle
end-systolic volume
amount of blood left in heart
isovolumetric relaxation
T wave appears
ventricles repolarize
Sl valves close and hear 2nd heart sound
AV valves stay closed
ventricles expand but don’t fill
dicrotic notch
when the aortic SL valves closes, pressure in the aorta increases slightly
cardiac output
amount ejected by each ventricle in 1 minute
What is the formula for cardiac output?
HR x SV
cardiac reserve
difference between a persons maximum and resting CO
What effect does the sympathetic nervous system have on the heart?
it increases heart rate with norepinephrine
What effect does the parasympathetic nervous system have on the heart?
it slows the heart rate down w/ acetylcholine and stimulates vagus nerves
What would happen if a vagus nerve was severed?
the SA node would fire at an intrinsic rate of 100 BPM
vagus nerves
cranial nerve associated with cardiac
What 3 components affect stroke volume?
preload, contractility, and afterload
preload
increases SV
-the amount of tension in the ventricular myocardium before it contracts
venous return
amount of blood that returns to your heart
Frank Starling Law of Heart
ventricles eject as much blood as they receive
What is the formula for the Frank Starling Law?
SV=EDV
contractility
how hard the heart is pumping, increases SV but decreases ESV
What can increase contractility?
hypercalcemia
What can decrease contractility?
hyperkalemia and hypocalcemia
afterload
pressure in arteries above SL valves and opposes the opening of the valves
-decreases SV and ESV
vagal tone
steady background firing of the vagus nerve to the heart
What is the biggest contributor to afterload?
BP
