Physio Ch 09 Flashcards
pumps blood through the lungs
right heart
pumps blood through the peripheral organs
left heart
pulsatile two-chamber pump
heart
weak primer pump for the ventricle, helping to move blood into the ventricle
Atrium
Ventricles supply the main pumping force that propels the blood either
- through the pulmonary circulation by the right ventricle
- through peripheral circulation by the left ventricle
continuing succession of heart contractions transmitting action potentials throughout the cardiac muscle to cause the heart’s rhythmical beat
cardiac rhythm
Three major types of cardiac muscle
- atrial muscle
- ventricular muscle
- specialized excitatory and conductive muscle fibers
provide excitatory system that controls the rhythmical beating of the heart
excitatory and conductive
fibers
dark areas crossing the cardiac muscle fibers
intercalated discs
cell membranes that separate individual cardiac muscle cells from one another
intercalated discs
At each intercalated disc the cell membranes fuse with one another and form this structure that allow rapid diffusion of ions
gap junctions
causes ventricular contraction to last as much as 15 times as long in cardiac muscle as in skeletal muscle
plateau
.
.
velocity of conduction in the specialized heart conductive system
4 m/sec
interval time which a normal cardiac impulse cannot reexcite an already excited area of cardiac muscle
refractory period
normal refractory period of the ventricle
0.25 to 0.30 secs
period which muscle is more difficult than normal to excite but can be excited by very strong excitatory signal
relative refractory period
refractory period of atrial muscle
0.15 seconds
refractory period of ventricular muscles
0.25 to 0.30 seconds
mechanism by which the action potential causes the myofibrils of muscle to contract
excitation-contraction coupling
velocity of conduction of the excitatory action potential signal along both atrial and ventricular muscle fibers
0.3 - 0.5 m/sec or 1/250 in large nerve fibers or 1/10 in skeletal muscle fibers
calcium entering the cell activates these channels to release calcium from sarcoplasmic reticulum
calcium release channels, ryanodine receptor channels
Inside is a large quantity of mucopolysaccharides that are electronegatively charged and bind an abundant store of calcium ions
T tubules
Transport of calcium back into
the sarcoplasmic reticulum is achieved with the help of a
calcium-ATPase pump
cardiac events that occur from the beginning of one heartbeat to the beginning of the next are called
cardiac cycle
Each cardiac cycle is initiated by spontaneous generation of an action potential in the?
sinus node
act as primer pumps for the ventricles
atria
period of relaxation during which the heart fills with blood
diastole
total duration of the cardiac cycle, including systole and diastole, is the reciprocal of the?
heart rate
At a normal heart rate of 72 beats/min, systole comprises about ____ of the entire cardiac cycle.
0.4
At three times the normal heart rate, systole is about ____ of the entire cardiac cycle.
0.65
a wave in the electrocardiogram caused by spread of depolarization through the atria
P wave
How many seconds will the QRS waves appear after the onset of the P wave?
0.16 sec
appear as a result of electrical depolarization
of the ventricles
QRS waves
this complex begins slightly before the onset of ventricular systole
QRS
represents the stage of repolarization of the ventricles when the ventricular muscle
fibers begin to relax
ventricular T wave
a wave is caused by
atrial contraction
During pressure change, right atrial pressure increases ______ during atrial
contraction, while left atrial pressure increases _____
4 to 6 mm Hg; 7 to
8 mm Hg
c wave occurs when the ventricles begin to?
contract
pressure change wave caused partly by slight backflow of blood into the atria
mainly by bulging of the A-V valves backward toward the atria due to
increasing pressure in the ventricles
c wave
pressure change wave which occurs toward the end of ventricular contraction that results from slow flow of blood into the atria from the veins
v wave
It is the filling of ventricles due to pressure accumulated in the atrium during ventricular systole which pushed the AV valves open
period of rapid filling of the ventricles
during this period, contraction is occurring in the ventricles, but there is no emptyingq
Period of isovolumic (isometric) contraction
the tension is increasing in the muscle but little or no shortening of the muscle fibers is occurring
isovolumic or isometric contraction
How many % of blood is poured out of the ventricles on the first third or period of rapid ejection?
70%
This the remaining 30% of blood emptied at the ventricles during the next two thirds of ejection
period of slow ejection
When ventricular relaxation occurs after the end of systole, this pressure decreases rapidly
intraventricular pressures
During this period, the intraventricular pressures decrease rapidly back to their low diastolic levels
isovolumic or isometric relaxation
During diastole, normal filling of the ventricles increases the volume of each ventricle to how many ml
110 to 120 ml
as the ventricles empty during systole, the volume decreases about 70 ml, which is
called …..
stroke volume output
normal filling of the ventricles which increases the volume of each ventricle, called as?
end diastolic volume
remaining volume in each ventricle after systole, about 40 to 50 ml, is called
end systolic volume
It is the fraction of the end-diastolic volume that is ejected
ejection fraction
When the heart contracts strongly, the end-systolic volume can be decreased to as little as
10 to 20 ml
In a healthy heart, when large amounts of blood flow into the ventricles during diastole, the ventricular end-diastolic volumes can
become as great as
150 to 180 ml
prevent backflow of blood from the
ventricles to the atria during systole
AV valves
prevent backflow from the aorta and pulmonary arteries into the ventricles during diastole
semilunar valves
occurs in the aortic pressure curve
when the aortic valve closes
incisura
pull the vanes of the valves
inward toward the ventricles to prevent their bulging too far backward toward the atria during ventricular contraction
papillary muscle
What is the diastolic pressure of the aortic pressure before the ventricle contracts again?
80 mm Hg
Sound of closure of the A-V valves with its low vibration and relatively low lasting
first heart sound
aortic and pulmonary valves close at the end
of systole bearing a rapid snap because the valves close rapidly
second heart sound
amount of energy that the heart converts to work during each heartbeat while pumping blood into the arteries
stroke work output
total amount of energy converted to work in 1 minute
minute work output
Two forms of work output of the heart
- volume-pressure work or external work
- kinetic energy of blood flow
major proportion is used to move the blood from the low-pressure veins to the high-pressure arteries
volume-pressure work
form of output which minor proportion of the energy is used to accelerate the blood to its
velocity of ejection through the aortic and pulmonary valves
kinetic energy of blood flow
determined by filling the heart with progressively greater volumes of blood
diastolic pressure curve
It is the measuring of the diastolic pressure immediately before ventricular contraction occurs
end diastolic pressure
determined by recording the systolic pressure achieved during ventricular contraction at each volume of filling
systolic pressure curve
What is the maximum systolic pressure for the normal left ventricle
250-300 mm Hg
What is the maximum systolic pressure of a normal right ventricle?
60-80 mm Hg
Phase I or Period of filling in the volume-pressure diagram begins at a ventricular volume of about ____ and diastolic pressure of ____ ?
50 ml and a diastolic pressure of 2 to 3 mm Hg
The amount of blood that remains in the ventricle after the previous heartbeat, 50 ml, is called
end systolic volum
Phase of cardiac cycle wherein the pressure inside the ventricle increases to equal the pressure in the aorta, at a pressure value of about 80 mm Hg
Period of isovolumic contraction
the LOAD considered to be the end-diastolic pressure when the ventricle has become filled
preload
what type of load describes by the pressure in the aorta leading from the ventricle
afterload
Enumerate the sources of energy of heart muscles with their respective %
- Oxidative metabolism of fatty acids - 70-90%
- Lactate and glucose - 10-30%
represents additional work that could be accomplished by contraction of the ventricle if the ventricle should empty completely all
the blood in its chamber with each contraction
potential energy
Basic means by which the volume pumped
by the heart is regulated (2)
(1) intrinsic cardiac regulation of pumping in response to changes in volume of
blood flowing into the heart
(2) control of heart rate and strength of heart pumping by the autonomic nervous system
During heart muscle contraction, most of the expended chemical energy is converted into ____ and a much smaller portion into _____-
heat; work output
ratio of work output to total chemical energy
expenditure is called
efficiency of cardiac contraction or efficiency of the heart
Maximum efficiency of the normal heart is between ……
20-25%
In heart failure, maximum efficiency of the heart can decrease to as low as ____
5-10%
heart is composed of two syncytiums;
atrial syncytium and ventricular syncytium
constitutes the walls of the two atria
atrial syncytium
constitutes the walls of the two ventricles
ventricular syncytium
a bundle of conductive fibers several millimeters of ventricular contraction. they are conducted only by way of a specialized conductive system
A-V bundle
also called calcium-sodium channels
slow calcium channels
the atria act as ___________ for the ventricles, and the ventricles in turn provide the major source of power for moving the blood through the body’s vascular system
primer pumps
