lecture 6: guyton chapter 15 Flashcards
what is the definition of compliance (in terms of formula)
a change in volume has an an influence of change in pressure
ability to expand and recold
true or false: in arteries and veins, the same increase in pressure will cause a small increase in volume
false, because veins are more compliant and distensible, the same pressure increase will have a different change in volume
which is more compliant arteries or veins
veins
what is the definition of vascular distensibility
is the fractional increase in volume for each mmHg rise in pressure
how much more distensible are veins than arteries
8x
what is the eq. For vascular distensibility
=increase in volume/increase in pressure x origin volume
what makes arteries less compliant than veins
they are harder and thicker because of a larger layer of smooth muscles
what makes veins more compliant than arteries
they are thinner and less rigid (less smooth muscle cells) so they can expand easier
veins are more more distensible and therefore have a lower o r higher compliance
higher
what is the definition of vascular capacitance?
is the total quantity of blood that can be stored in a given portion of the circulation for each mmHg.
which vessel has a larger capacitance veins or arteries and why
since veins have a higher distensibility and therefore more compliant they can store a lot more blood in the venous side
how much percentage of blood is held on venous side
60-70 percent
what is the formula of capacitance
distensability x volume
small and large veins are called what type of vessels
capacitance vessels
changes in vasculature are induced by what
compliance
explain the arterial system in terms of hydraulic filter
Composed of elastic conduits (aorta and arteries) and high-resistance terminals (arterioles)
what is the function of the hydraulic filtering in the arterial system
converts intermittent output of the heart to a study flow in capillaries
what happens to part of the energy of cardiac contraction
is dissipated as forward capillary flow during systole (kinetic energy)
what is the remainder of the energy of the cardiac contraction stored as (that is not kinetic )
potential
why is the remainder of energy of cardiac contraction stored as potential energy
because of compliance
=much of the stroke volume is retained by stretching the distensible arteries
During diastole the elastic recoil of the arterial walls converts this potential energy what
into capillary blood flow
=continuous
what is the perk of the hydraulic filtering
This minimizes the workload of the heart, i.e., more work is required to pump a given flow intermittently as compared to steadily
what effect allows the conversion of intermittent blood flow to continuous
windkessel effect or elastic reservoir
true or false: The pressure curves change in arteries at different distances from the heart
true
what are the 3 major changes in the pressure curve
The high-frequency components of the pulse, such as the incisura, are damped out and soon disappear
The systolic portions of the pressure wave become narrowed and elevated
A hump may appear on the diastolic portion of the pressure wave
what happens to the high frequency components (such as insura) when increasing distance from the heart
gets dampened out and soon disappear
ass we get further from the hear what happens to the systolic portions of the pressure wave
because narrowed and elevated
what may appear on the diastolic portion of the pressure wave
a hump
what happens to the intensity of pulsations are we get to the small arteries
become progressively less intense
if no compliance what would happen to an elongated tail
it would disappear and heart would have to work harder
the degree of dampening is proportional to what
proportional to the resistance of small vessels and arterioles and the compliance of the larger vessels.
there is more dampening in smaller or larger vessels
smaller
why is the dampening importance
because it allows to go from pulsatile to continuous
what would happen if the vessels were rigid
ALL the blood the heart pumped would be immediately converted to flow
During diastole, there would be no flow (including no flow to capillaries)
pumping blood through rigid vessels creates what
more work for heart
elastic arteries ensure what
constant flow through capillaries and
reduce work of heart through the pumping
true or false: age has no effect on arterial compliance
false it has a large effect
why does BP increase as age increases
due to more stiffness in vessels which means the heart needs to work harder to combat more resistance
why is it bad if the arteries are rigid
they do not expand and recoil
as we get older our arteries get STIFFER/LOOSER and therefore more/less compliant
stiffer
Less
what is the main reason the arteries get stiffer with age
loss of elastic tissue
ellastin is all made by age 10 so after that it starts to degrade
what are 2 factors affecting pulse pressure
stroke volume
arterial compliance
explain the relationship between stroke volume and pulse pressure
increases in
stroke volume increase pulse
pressure conversely decreases
in stroke volume decrease
pulse pressure.
explain the relationship between arterial compliance and pulse pressure
decreases in compliance increases pulse pressure; increases in compliance decrease pulse pressure.
increased aortic pulse pressure is affected by what 2 main things
decreased aortic compliance
increased stroke volume
what are reason for decreased aortic compliance
age
arteriosclerosis
hypertension
what are the 4 factors that increase stroke volume
increase preload
decreased afterload
increased inotropy/contractility
decreased HR
what are 3 abnormal pressure pulse controls
arteriosclerosis
patent ductus arteriosus
aortic regurgitance
explain arteriosclerosis
decreases the compliance of arterial tree, thus leading to an increase in pulse
=build up of plaque in vessel and narrows which impedes flow and increases BP
explain patent ductus arteriosus
associated with low diastolic pressure and high systolic pressure, net result is very high pulse pressure.
=small hole means that mixing aortic and pulmonary blood
explain aortic regurtitation
a condition associated with the backward flow of blood through the aortic valve. Low diastolic and high systolic pressure leads to high pulse pressure.
=valve does not close completely, leaking blood into the heart
know the graph of pulse controls
jng
what causes resistance to flow in large peripheral veins
compressional factors
what do increases in right atrial pressure cause
causes blood to back up into the venous system, thereby increasing venous pressures.
where is the highest venous pressure
in the legs and feet
what tends to increase venous pressures in the legs
abdominal pressure
what is central venous pressure
pressure in larger veins close to the heart
what determines the filling pressure of right ventricle
CVP
explain how CVP determines filling pressure of the right ventricle
an increased CVP increase blood flow which assists in filling and increase diastolic volume
what are the 2 things that regulate CVP
A balance of the heart to pump blood out of the right atrium and right ventricle into the lungs
The tendency for blood to flow from the peripheral veins to the right atrium (venous return)
what are the 6 factors that increase CVP
Decreased Cardiac Output
Increase in Total Blood Volume
Venous Constriction
Gravity
Standing to supine position
Respiratory Activity
Increased depth and rate of respiration
Skeletal Muscle Pump
Exercise
explain how increase in total blood volume increases CVP
more blood in system=more blood to the venous side which means the heart needs more pressure to move it
explain how venous constriction increases CVP
the venous constricts which affects pressure
explain how gravity increases CVP
standing=more pressure
supine=lower pressure
with less pressure the venous return is not working against gravity which means it will increase venous return, increase stroke volume and decrease cardiac output
explain how respiratory activity increases CVP
when increase breathing rate and depth you increase the suction of blood back to the heart since it is situated above the diaphragm
explain how skeletal muscle pump/exercise increases CVP
when the skeletal muscles are working the contact on and off (pumping) which milks the veins
helps blood move back towards the heart
gravitational pressure effects pressure how
Pressure rises 1 mmHg for each 13.6 mm distance below the surface of a body of water
give an example to show the pressure difference due to gravity
feet: 90 mmHG
sagital sinus
= -10 mmHG
what can you get if you decrease pressures further from heart
you can increase venous return
what are the 3 types of respiration that effect CVP
spontaneous respiration (normal)
mechanical ventilation
valsava manoeuvre
explain the effect of spontaneous respiration
Decreased intra-thoracic pressure results in a decreased right atrial pressure which enhances venous return
= Lowering diaphram creates a negative pressure in the thoracic cavity which facilitates the filling of lungs and larger veins with blood from the lower body
explain the effect of mechanical respiration
Increased intra-thoracic pressure during positive-pressure lung inflation causes increased right atrial pressure which decreases venous return
=breathing towards positive pressure which means right atrial pressure increases since it will have a hard time pushing blood down into ventricles
high pressure in the in lungs causes alveoli will be inflated and push on capillaries and creating high resistance
= Blood will be retained in the right ventricle, right atrium won’t push blood down
=must increase venous pressure to overcome the resistance
explain the affect of valsave method on respiration
Causes a large increase in intra-thoracic pressure which impedes venous return to the right atrium lower CO
= Exhaling against closed glottis, increase pressure in the thoracic cavity so blood cannot travel easily
=no blood passing so the heart will not contract and no cardiac output = no BP
contracted skeletal muscle does what for the veins
increases venous pump
to push blood towards heart
what is the function of valves
prevent backflow
explain what contraction of muscles do
contract of muscles pushes blood up which will push open the valves
if there is an increase in right atrial pressure what is the effect on flow
flow will be decreased which means CVP must increase to compensate
60-70% of blood is stored where
in veins
under various physiological conditions what can happen to the blood
it can be transferred to the arterial system to maintain arterial pressure
=vasoconstriction
what are some examples of reservoirs
spleen, liver, large abdominal veins and venous plexus
what serves as a good special reservoir for red blood cells
spleen
what are some examples of non venous blood reservoirs
heart
lungs
