Cardiovascular Physiology 1 Flashcards
Average size people have how many liters of blood
5.5 liters
What separates the blood into the components
centrifugation
Components of the blood and their percentages
erythrocytes: 45%, buffy coat: <1%, plasma: 55%
What is the buffy coat made of?
leukocytes and platelets; necessary for fighting infection and blood clotting respectively
What is in the plasma?
water, dissolved proteins like albumin, ions, metabolites, hormones, antibodies
What are eythrocytes?
red blood cells, used for oxygen transport
What is heart failure defined as
heart cannot pump enough blood to meet the body’s basal demands
- it is a progressive disease
- 35% die within 1 year of diagnosis
What is end-stage heart failure
medical treatment has failed, patient needs heart transplant
What is hematocrit?
portion of the blood taken up by red blood cells, typically 45%
-depends on ration of RBC’s to plasma
What happens to hematocrit when you are dehydrated?
you lose water from your body so your plasma levels go down but red blood cells stay the same level, so the percentage increases (higher than 45%)
Heart beat is divided into two phases:
systole and diastole
systolic phase of cardiac cycle
blood is pumped out of the ventricles
diastolic phase of the cardiac cycle
blood flows from atria into the ventricles
The atria are
collecting chambers
the ventricles are
pumps
the valves do what
control direction
The heart has billions of cells, most are what kind
myocytes that look like skeletal muscles fibers
-they are nucleated
What is functional syncytium
system of the heart that pumps blood most effectively with a synchronous contraction, coordinated by the electrical system of the heart
Humans have a ___ circulatory system
double
Blood is pumped from the right ventricle to the ____
lungs; deoxygenated blood goes there for oxygenation
blood is pumped from the lungs to the ____
left atrium (returns oxygenated)
the left ventricle pumps freshly oxygenated blood through ____
systemic circulation
blood comes from systemic circulation back to _____
right atrium (deoxygenated again at this point)
double circulation ensures:
every tissue bed in the systemic circulation receives fresh blood, blood flow can be diverted to different parts of the body as demanded by metabolic requirements
the two ventricles pump the same amount or different amounts of blood
same amount
How do arterial and venous pressures differ?
arterial pressure is a lot more than venous pressures
- if an artery was exposed, the pressure would make the blood hit the ceiling
- if a vein was exposed, you would just have bleeding on the surface
Venous pressure is really low because you can change its direction based on?
position of your body parts (holding your hand up in the air vs down towards the ground)
If venous pressure rises, what is this a sign of?
congestion
Which is higher, pulmonary or venous pressure?
pulmonary, although it is still low; typically systolic might be 25
If pulmonary arterial pressure gets too high, what might happen?
you could bleed into your lungs
The body can/cannot store blood and unless you are ____, you don’t lose any
cannot; bleeding
Cardiac output is defined as
the amount of blood pumped by a ventricle per unit time
at rest, the heart typically pumps about _____ per minute
5 liters of blood
Since humans have about 5 liters of blood, it takes about __ minute(s) for a red blood cell to return to the left ventricle after is has been pumped out of the aorta
one
to leave the left ventricle, blood must travel through the
aorta
typical amount of time spent in systole versus diastole
1/3 time in systole (1/3 second), 2/3 time in diastole (2/3 second)
overview of systemic circulation pressures from left ventricle back to right atrium
left ventricle: pressures alternate between high up to 120 and low 0
large arteries: arterial pressure is high, stays closer to 120 most of the time
resistance vessels (arterials): lower pressure
capillaries: lower pressure
veins: lowest pressure
Resistance vessels (arterials) have a lower or high cross sectional area
lower
capillaries have a lower or high cross sectional area? why?
higher because you want to blood to move slow here to allow time for gas exchange
A man is sleeping horizontally. What is the mean pressure in his left ventricle?
a. 5 mmHg
b. 55 mmHg
c. 95 mmHg
d. 120 mmHg
mean pressure means the average pressure in the left ventricle. we know that pressure alternates between 0 and 120 in the ventricle, so the average cannot be 5 or 120, but 55 is close to being right in the middle (55+55=110) so that is close to 120 total
*we would not use the MAP calculation here because it is not asking about mean ARTERIAL pressure, it is asking about mean ventricle pressure
common cause of heart attack (myocardial infarction)
blockage in coronary artery
symptoms of heart failure
exercise intolerance, peripheral and pulmonary edema
Two ways to classify heart failure
systolic heart failure: ventricles don’t eject blood properly
diastolic heart failure: heart failure with preserved ejection fraction, ventricles cannot pump because they are not filling properly
left sided heart failure symptoms
- respiratory problems because blood backs up in the lungs when it is not pumped onwards by the left ventricle
- dyspnea (shortness of breath)
right sided heart failure symptoms
occurs when blood backs up in the systemic circulation
-ascites (fluid accumulation in the abdomen)
symptoms of heart attack
chest, neck, should pain and a crushing pressure on the chest; symptoms in women are more vague, often confused with GI issues and heart burn
what happens during a myocardial infarction
- blood flow to heart is restricted
- the affected part becomes ischemic
- when the flow is restored, the tissue is often damaged as a result of reperfusion injury
Why are patients who survive a heart attack left with damaged ventricles and a higher risk of heart failure?
Because heart muscle cannot repair itself the same way skeletal muscle can so it puts them at a higher risk for failure later on
flow=
linear speed of fluid times cross sectional area
How can you increase flow?
by making fluid move faster or having a bigger pipe
why does blood flow through systemic circulation
systolic contractions produce a pressure difference between the left ventricle and right atrium
Ohm’s law defines flow for a given pressure difference as
flow= pressure difference/resistance
pressure difference is the pressure at the beginning of the pipe minus the pressure at the end of the pipe
resistance is how hard it is to move the fluid through the pipe, can be affected by diameter
Poiseuille’s law defines resistance as
8(n= viscosity) x Length / pi (radius to fourth power)
flow increases or decreases with the pressure drop along the tube
increases
flow increases or decreases with the 4th power of the radius
increases
flow decreases or increases with fluid viscosity
decreases as viscosity goes up
flow decreases or increases with the length of the tube
decreases as the tube gets longer
if resistance increases, flow
decreases
if the pressure difference increases, flow rate
increases
what happens to resistance with a wider pipe (increased radius)
resistance decreases with increasing radius
how can we increase fluid viscosity
increase hematocrit (normal is 45%)
Why does poiseuille’s law not apply to capillary blood flow?
because the red blood cells have to squeeze through the small capillaries and flow becomes non-newtonian
Some participants in endurance sporting events illicitly increase the number of red blood cells in their circulation by blood doping. Why does this elevate their physical performance? How does their hematocrit change? What happens to their total peripheral resistance (the resistance of their systemic circulation)?
- blood doping increases their ability to transport oxygen to their muscles
- hematocrit increases
- total peripheral resistance goes up because hematocrit increases viscosity
Blood is flowing through an artery at a rate of 20 cubic centimeters per second. The artery has a cross sectional area of 4 cm2. What is the blood’s average velocity?
5 cm s-1
Blood is flowing out of a reservoir through a tube. The length of the tube us suddenly doubled. The flow rate changes to ____% of its original value.
50%; flow decreases
Is the average pressure in the right atria greater than, less than, or equal to the average pressure in the aorta?
less than- the pressure difference between the aorta and right atrium is driving blood around the systemic circulation
Most numerous cell type in the blood
erythrocytes
what do erythrocytes do
- oxygen molecules from the lungs to other tissues
2. carbon dioxide molecules produced by tissues back to the lungs
What do leukocytes do
white blood cells that fight infection, 5 different types
What are platelets
cell fragments that play a crucial role in the mechanisms that stop bleeding (blood clotting)
how big is a erythrocyte
about 7um
do erythrocytes have a high or low surface area? what does this allow for?
high surface area, allows gases to move quickly in and out of their interiors
What is in the plasma membrane of an erythrocyte
contain polysaccharides and proteins that define a person’s blood type
Do erythrocytes have a nucleus and organelles
No nucleus and lack most organelles
Can red blood cells repair themselves?
No, due to the lack of nucleus and most organelles
How long does a RBC typically last?
about 120 days which means that 1% of them (250 billion) have to be replaced every 24 hours
What hormone regulates red blood cell replacement
erythropoietin
state the negative feedback loop for restoration of O2 delivery
decreased O2 delivery to kidneys -> kidneys increase erythropoietin secretion -> plasma erythropoietin is increased -> bone marrow increases production of erythrocytes -> blood hemoglobin concentration is increased -> blood oxygen carrying capacity is increased -> restoration of O2 delivery
sickle cell anemia
a genetic disorder which is manifested fully only in people who are homozygous to the mutation, heterozygotes are protected from malaria (because malaria doesn’t do well in jagged cells)
Why is there an evolutionary pressure for sickle cell anemia in places with high malaria rates?
malaria cannot live in jagged cells, therefore this gene might be selected in order to prevent people from contracting malaria; however, they would have sick cell anemia and would likely die in their 40s, but would still live longer than if they caught malaria
Why is sickle cell anemia painful?
the shape of the red blood cells causes them to get stuck in the capillaries so the tissue is not properly oxygenated and this causes severe pain
neutrophil percentage and broad overview
65%, kill bacteria and fungi by phagocytosis, release chemicals involved in inflammation, main constituent of pus
eosinophil percentage and overview
4%, destroy parasites, predominate inflammatory cells in allergic reaction
If eosinophil percentage increases, what might this indicate?
that a person might have a parasitic infection
basophil percentage and overview
less than 1%, release histamine and other chemicals involved in inflammation; similar to mast cells
monocytes percentage and overview
6%, phagocytosis; similar to macrophages in other tissues
lymphocytes percentage and overview
25%, 3 classes- b cells, t cells, nk cells
-responsible for immune response, production of antibodies, etc.
What is the normal range for white blood cells (leukocytes)?
4.5 to 11.0 x 10^9 cells per liter, a person that is 1.5 x 10^9 cells per liter can leave an individual susceptible to infection
Why are blood counts often reduced during anti-cancer treatments such as radiation or chemotherapy?
cancer is uncontrolled cell growth and the treatment targets rapidly dividing cells and it cannot differentiate between rapidly dividing blood cells and rapidly dividing cancer cells
hemostasis is
prevention of blood loss
Two mechanisms for hemostasis by the body
formation of platelet plug and blood coagulation, both involving platelets
Which mechanism of hemostasis occurs first?
platelet plug
how do platelets become activated in plugging?
when they encounter exposed collagen
is platelet plug formation positive or negative feedback?
positive
chemical that platelets release to promote further aggregation
thromboxane A2
how do endothelial cells prevent too much platelet plugging so that the entire pipe is not blocked?
away from damage, the endothelial cells release NO and PGl2 to prevent platelet activation in good tissue
NO and PGI2 do what?
prevent platelet adhesion, activation, and aggregation
clotting involves a complex cascade that turns soluble fibrinogen into ____ which forms ____
loose fibrin which forms stabilized fibrin
fibrin acts as a ____ around the platelet plug
mesh
What happens if a clot breaks free from the vascular wall?
it can circulate in the blood-stream before lodging in a critical vessel
What happens if a blood clot gets lodged in a vessel within the brain
could result in a stroke
What happens if a blood clot blocks the coronary artery
can result in myocardial infarction
What is warfarin (coumadin)?
a blood thinner uses to reduce the probability of clot formation in the blood by inhibiting certain chemical factors; commonly used in patients with atrial fibrillation who are at increased risk of developing clots in their atria because of altered flow patterns
why is aspirin taken to reduce risk of heart attack and stroke?
reduces production of thromboxane A2
Vioxx is a pain killing drug that has the potential to do what
increase the risk of blood clot formation
which cells initiate heart beat?
pacemaker cells in the SA node; these cells have the fastest spontaneous rhythm in the heart
if the SA node fails, what takes over
pacemaker cells in the AV node can set a slower ventricular rhythm
Ventricular myocytes are/are not autorhythmic
are not autorhythmic and need to be triggered to contract
general pathway of pacemaker heart cycle
SA node depolarizes, AP propagated through atria to AV node, AV node causes pause and can filter out AP’s from SA node if needed, AV node sends AP’s down septum through bundle of His, AP spreads through perkinje fibers causing ventricles to depolarize and contract, then ventricles return to resting state (electrically silent ventricles)
excitation contraction coupling pathway
start with excitation (depolarization of plasma membrane) -> opening of plasma membrane L type Ca2+ channels in T-tubules -> flow of calcium into cytosol -> 50% increases cytosolic calcium concentration -> 50% of Ca2+ binds to ryanodine receptors on external surface of SR -> opens calcium channels intrinsic to these receptors -> flow of calcium into cytosol –> increased calcium concentration which leads to contraction
Why is the excitation contraction coupling pathway considered to be calium-induced calcium-release?
because calcium is required to open more calcium channels in the sarcoplasmic reticulum to release calcium into the cytosol
How are myocytes relaxed during diastole?
By SERCA pumping calcium ions back into the sarcoplasmic reticulum
What molecule regulates SERCA?
phospholamban
during systole, the free calcium concentration in the cytoplasm increases/decreases/stays the same
increases (200 nM in diastole, to 5-10 micro molar in systole)
increasing the peak calcium concentration during systole causes the muscle to develop more or less force
more force; this is different than skeletal muscle because the amount of calcium released form the SR is always more than enough to produce maximal force
why are calcium channel blockers sometimes used to control blood pressure?
they reduce the peak systolic calcium concentration so the amount of pressure the heart generates during systole goes down
how is contraction reduced
pumping calcium back into the SR by SERCA or outside the cell
Ventricular myocytes have a resting membrane potential around
-80 mV
-80 mV is close to the equilibrium potential for K+ and reflects
the tendency of K+ ions to diffuse out of the cell through open potassium channels down their concentration gradient
Why does membrane potential change?
due to the opening and closing of channels and similarly, ion channels will open or close based on changes in the membrane potential
when the cell depolarizes, the membrane permeability of K+ ____
decreases, minimizing number of K+ ions leaving the cell helping to preserve the plateau phase of the action potential
rapid upstroke of the action potential is primarily due to opening of
voltage gated sodium channels
the calcium ions that enter the cell initiate
calcium induced calcium release (CICR), also help maintain plateau phase of ventricular action potential
cells in the conducting system exhibit
automaticity- they are rhythmically self exciting
pacemaker cells in the what set the rate at which the heart beats
SA node
conducting system cells (pacemaker cells) completely lack
rapidly acting voltage gated Na channels
instead of the fast Na channels, conducting system cells have
F-type Na+ channels
F type Na+ channels open when
the cell is hyperpolarized, which is unusual so the associated current is often referred to as the funny current
Nodal cells contain ____ channels that help raise the membrane potential towards threshold
T-type Ca2+ channels
The upstroke of action potential in nodal cells is determined primarily by inward current through _____ channels
L type Ca2+ channels
Inside the cell, there is ____ concentrations of Na+, K+, Ca2+
low Na+, High K+, Low Ca2+ inside the cell
What happens during each phase of cardiac myocite action potential
Phase 0: rapid depolarization Phase 1: initial repolarization Phase 2: plateau Phase 3: repolarization Phase 4: resting potential restored
ECGs are commonly used to
diagnose arrhythmia or electrophysiological problems with the heart
heart trace components on ECG
P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization)
The refractory period for a cardiac ventricular cell is much longer than that of a skeletal muscle cell. Why is that helpful?
stops the heart from going into tetanic contraction
True or False: The t wave on an ECG trace indicates opening of the aortic valve
false. T wave is ventricular repolarzation which is the end of systole
which part of the heart would set the ventricular rhythm if the SA node was damaged?
AV node
Most of the current flowing through the cell membrane in the late plateau of a ventricular myocyte action potential passes through
voltage gated L type calcium channels
note: The L-type calcium channel is responsible for normal myocardial contractility and for vascular smooth muscle contractility. In contrast, T-type calcium channels are not normally present in the adult myocardium, but are prominent in conducting and pacemaking cells (so not in the ventricular myocyte)
On an ECG where someone’s heart was being ran by the AV node, why would they not have p-waves?
because p-wave comes from the SA node
-HR would also be slower in this case
valve stenosis is when
fail to open properly leaving a narrowed opening
valve insufficiency is when
valves do not close completely; does not prevent blood from flowing backwards
Both valve stenosis and insufficiency can be diagnosed how?
by listening to the heart for murmurs which are extra sounds in the cardiac cycle
-the timing of the murmur can tell you which valves might be at fault
AV valves can prolapse, which means what? and what happens?
valves do not seal and the leaflets bend upwards so that they point towards the atria, which leads to insufficiency so some blood flows backwards into the atrium during systole
isovolumetric ventricular contraction
has a constant volume because the valves are closed
-AV valves closed, aortic and pulmonary valves closed
Ventricular ejection (systole)
blood flows out of ventricle because the ventricular pressure rises further and aortic valve pops open
-AV valve is closed because the pressure in the ventricle is larger than the pressure in the atria
Isovolumetric ventricular relaxation (diastole)
AV valves closed
-aortic and pulmonary valves closed
Ventricular filling (diastole)
blood flows into the ventricles
- atria contract after depolarization
- pressure is higher in atria
- AV valves open
- ventricles are relaxed and they fill
- aortic and pulmonary valves are closed
EDV
the filled volume of the ventricle prior to contraction
ESV
the residual volume of blood remaining in the ventricle after ejection
