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PHGY 210 Midterm Study Set Exam
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PHGY 210 Midterm Study Set ExamOstium/Ostia - Answer Smaller opening(s) in insects through which hemolymph returns
to circulation
Spiracles - Answer breathing tubes of insects located on abdomen, allow co2 & o2
exchange
why is the venous system called capacitance system? - Answer ~15% of our blood is in
the arteries, and the arterioles. So, The venous system is sometimes called the
capacitance system because that's the place where you have the capacity to store more
blood. And these vessels are called capacitance vessels, whereas on the arterial side
there's almost no capacity it and the main purpose of the arteries is to bring the
oxygenated blood To the organs & to provide a certain amount of resistance to flow
t/f- flux is not affected by area - Answer true- flux is not affected by area, but flow is
How many capillaries are in the body? - Answer ~10 billion
Largest vessel in the body - Answer aorta
distribution vessels - Answer large arteries, low resistance, distribute blood from aorta
to organs
resistance vessels - Answer Small arteries and arterioles
- Large pressure change/drop occurs between large arteries to small arteries &
arterioles (drop in pressure in systemic circulation is 10x higher than in pulmonary circ)
- highest resistance
exercise induced changes - Answer arteriovenous o2 difference increases, TPR
decreases, CO & SV increases, heart rate decreases,
what are the two vena cava? - Answer There are two vena cava: inferior and superior
which bring deoxygenated blood back to
the right atrium from the body
O Inferior vena cava brings blood back from the lower half of the body (limbs)
O Superior vena cava brings blood back from the upper half of the body (head, neck
what are the advantages of branching? - Answer Advantages of branching
O High total area of the walls of capillaries - increase the wall area which is
where diffusion occurs (Fick's law)
O A low blood flow velocity in capillaries - allows for efficient gas exchange
,between RBCs
O A high total cross-sectional area - smaller resistance
-Any cell is very close to a capillary
systemic vs pulmonary circulation - Answer Average pressure in systemic circulation is
around 100mmHg
Average pressure in pulmonary circulation is around 15mmHg
why does pressure energy decrease? - Answer average pressure is always falling as
you move through the vascular tree, and it must, because the fluid has viscosity & there
is friction to flow- this is producing heat and reducing pressure energy, so the pressure
has to fall down.
central venous pressure - Answer equivalent to pressure in the right atrium, 5-10cm of
h20. Can be measured by inserting an IV line into a vein, & it is pushed so it goes to the
right atrium.
hydrostatic pressure - Answer Pressure exerted by a volume of fluid against a wall,
membrane, or some other structure that encloses the fluid due to gravity. Changes due
to diff in height/gravity- so pressure at bottom is greater than pressure at the top
perfusion pressure - Answer pressure gradient needed to maintain blood flow through a
local tissue. Pin - Pout. For an organ, this is Pa-Pv (arterial-venous pressure) but since
venous pressure is so low, we assume perfusion pressure through an organ = arteriole
pressure
concentration gradient - Answer Cout-Cin/thickness of membrane that diffusion is
occuring through
arteriole vs venous pressure - Answer 100mmHg vs 5 mmHg
describe laminar & parabolic flow - Answer Poiseuille's Law applies to laminar flow.
Blood is flowing in a series of concentric circles called lamina. So there are parallel
layers with no disruption between layers.
The blood closer to the center is moving faster than the blood closer to the cell walls.
Near the blood vessel walls, the further u go from midline, the blood is barely moving at
all so laminar flow is decreasing. Also known as parabolic flow/parabolic velocity.
There is friction between the laminae & thus there is loss of pressure energy due to heat
generated from friction. The sliding of the lamina on each other generates the friction.
So pressure decreases continuously down the length of the vessel, there is pressure
gradientL
Resistance is affected by - Answer blood viscosity, vessel length, vessel radius
If you increase radius, resistance is falling, hence flow is increasing (if perfusion
,pressure remains constant). If you blow through a more narrow tube, you have greater
resistance to flow. Through a larger tube, you can displace same amount of air but in
shorter period of time due to less resistance.
When length of tube decreases, resistance decreases.
When viscosity increases, resistance increases.
how do we maintain same CO & flow on both sides of the heart? - Answer Cardiac output
must be equal on both sides, but on one side (systemic circ) we have a high pressure.
Whereas in the pulmonary circulation, we have a low pressure. But we have same flow &
CO, bc of differences in vascular resistance
The blood vessels in the pulmonary circulation (lower pressure) are thinner and they
contain less smooth muscle then vessels of comparable size in the systemic circulation.
So basically in the pulmonary circulation, it is easy to dilate these vessels, so that more
blood can flow per unit of time, less resistance so you can get the same flow for a low
resistance, therefore, for low pressure. So even though the radius of the blood vessels
is smaller, the fact that the walls are much thinner reduces the resistance. Pulmonary
circ resistance is 1/10th that of systemic circulation. And this lower resistance & higher
compliance of vessels helps to maintain comparable flow in pulm circulation as that of
systemic, despite lower pressure.
actual control of vessel resistance - Answer Since length & viscosity cant be changed,
only the radius of the resistance vessels can be changed.
Local metabolites- when you exercise, for instance, there is a buildup of the waste
products in the muscle those will act on the smooth muscle to make it relax and you get
an increase in in the radius and therefore a fall in the resistance and, therefore, an
increase in flow.
Innervation- Almost all arteries & arterioles (these are the resistance muscles) all have
smooth muscle in the walls and all of them are innervated by the autonomic nervous
system. These smooth muscles contract to increase resistance & relax to decrease
resistance.
Hormones- there are all sorts of hormones that are floating around in the blood and they
have an action on the smooth muscle to either make a contract or relax so there's also a
hormonal control Of the size or the diameter.
hormones that affect vascular resistance - Answer Norepinephrine, serotonin,
histamine cause vasoconstriction by contracting smooth muscle, & increase in vasc
resistance
Acetylcholine (and Nitric Oxide) cause vasodilation
Poiseuille's Law - Answer -calculates rate of flow through a pipe of confined space
(laminar flow)
, Q= (πr^4 ∆P)/8ηL
η: viscosity of the fluid
Q: flow rate (volume flowing per time)
ΔP: pressure gradient/perfusion pressure.
r: radius of tube
L: length of tube
resistance is inversely prop to r^4
organs in series - Answer -they have the same flow. Right Heart & lung are in series &
both have same flow - 5L/min. Their individual resistances are added to give total
resistance. Their perfusion pressures are added to give total.
Organs in parallel - Answer have differing flow, have same perfusion pressures.
compliance - Answer delta v/delta pressure, compliance = 1/slope
Slope of change in volm by change in pressure curve decreases with increase in volm -
indicating that the more you stretch vessels/lung, the harder it gets to stretch,
compliance decreases. Compliance is the tendency to stretch, the greater the pressure
needed to stretch an object, the lower the compliance & higher the elastance (tendency
to recoil)
elastance= 1/compliance
transmural pressure - Answer Transmural pressure = pressure across the wall, i.e
pressure inside vessel - pressure outside
Since outside pressure is zero, the transmural pressure is the pressure inside the
vessels.
stiffening of ventricles with age - Answer the heart itself has a compliance so as you get
older your ventricles tend to lose their compliance, they get to be stiffer. So when the
blood comes in to fill the ventricle, They will not stretch as much. the ventricle will not fill
up as much as it did when you were younger. And so if the ventricle pumps out less and
your cardiac output will fall and your ventricle simply cannot provide the flow that your
body needs. This is the main cause of one of two types of heart failure right, and if the
heart failure is significant enough, it will kill you. And that's due to a stiffening in the
ventricles.
where are the valves located in heart? - Answer 4 valves- between ventricles & blood
vessels; & between atria & ventricles. Prevent backflow, made of fibrous tissues. All
except mitral valve have 3 leaflets. There are no valves at the inlets of the ventricles,
there's only valves at the outlets.
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