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Physiology > vascular system > Flashcards

vascular system Flashcards

1
Q

poiseuilles law

A

flow=change in pressure/resistance
flow=(change in pressure)(radius)^4pi/(length)(viscosity)8
-increasing vessel length increases resistance and decreases flow
-increasing blood viscosity increases resistance and decreases flow
-increasing blood vessel radius decreases resistance and increases flow

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2
Q

a change in blood vessel radius is known as what

A

constriction or dilation

-accomplished by adjusting the tension of vascular smooth muscle cells

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3
Q

continuous flow system, location of highest resistance?

A
  • location of highest resistance is where the greatest pressure drop is observed
  • pressure will be high upstream of this section and low downstream
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4
Q

importance of high resistance section

A

where the overall flow can be controlled

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5
Q

where is the high resistance section located

A

small arterioles

-where vasocontriction or vasodilation are effective at controlling blood flow and the upstream and downstream pressures

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6
Q

flow velocity

A

flow velocity=flow rate(cm^3/min)/cross sectional area(cm^2)
-faster through arteries and slower in capillaries and veins because the capillaries and veins are numerous and so have a large combined cross-sectional area

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7
Q

poiseuille’s law for the systemic circulation

A

CO=(MAP-CVP)/TPR

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8
Q

MAP

A

mean arterial pressure

  • systolic pressure-diastolic pressure=pulse pressure
  • diastolic pressure + 1/3 pulse pressure=MAP
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9
Q

CVP

A

central venous pressure

  • pressure in the right atrium
  • CVP is usually very close to zero
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10
Q

TPR

A

total peripheral resistance

  • resistance to blood flow throughout the whole system, and it depends on the resistance through each of the routes blood could take
    (e. g. the route supplying blood to the brain, to the muscles, to the gut, etc.)
  • TPR controlled by the arteries, which are known as resistance vessels
  • most of the blood at any given time is in the veins.
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11
Q

what are the veins also called

A

capacitance vessels

-because they contain most of the blood

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12
Q

blood flow to the tissues

A

each tissue has a set of arterioles delivering blood to it

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13
Q

blood flow to and individual tissue

A

depends on the resistance of its arterioles and on the perfusion pressure
-each set of arteriole can be independently controlled to adjust blood flow to tissues based on their individual demands

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14
Q

perfusion pressure

A

mean arterial pressure-venous pressure
PP=MAP-VP
-perfusion pressure (how much pressure pushes flow through tissue)

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15
Q

venous pressure

A
  • NOT central venous pressure, which is near zero

- has a value of about 15mmhg

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16
Q

TPR determined by..

A

all the individual resistances of the tissue arterioles

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17
Q

autoregulation

A

local control of blood flow to a tissue by control of tissue arteriole resistance

  • tissue arteriole smooth muscles respond to local conditions
  • conditions caused by tissue activity will cause vasodilation
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18
Q

how to change flow of blood

A

MAP=COxTPR

-MAP remains somewhat constant, change resistance to change flow

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19
Q

tissue blood flow (flow equation)

A

PP/R

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20
Q

list of factors that will cause vasodilation

A
  • decreased [O2}
  • increased [CO2]
  • decreased pH
  • increased temperature
  • increased [K+]
  • adenosine
  • nitric oxide
  • histamine
  • activity is indicated when these change
  • cause arterial smooth muscle to relax
  • this is a local negative feedback system to maintain these concentrations at their set points within the tissues
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21
Q

MAP remains constant no matter what, examples of changes

A

if TPR drops, MAP drops

-CO increases to increase MAP

22
Q

hyperemia

A

an increase in blood flow due to the local conditions and paracrines

23
Q

active hyperemia

A

tissue responds to its own increased metabolism

24
Q

reactive hyperemia

A

tissue responds to period of reduced blood flow

25
Q

sensors for negative feedback loop to keep MAP constant

A

aortic and carotid baroreceptors

  • these are stretch receptors in the walls of the carotid sinus and aortic sinus
  • their action potential frequency increases as the blood pressure increases
26
Q

afferent pathway of stretch receptors for pressure

A

visceral sensory nerves

27
Q

integrator

A

nuclei in the medulla oblongata, including the solitary nucleus

28
Q

efferent pathways

A
  • autonomic nerves
  • epinephrine
  • angiotensin
29
Q

effectors

A
  • heart controls cardiac output by adjusting rate and contractility
  • veins control cardiac output by influencing venous return and EDV
  • arterioles control TPR by vasocontriction and vasodilation
30
Q

venous return equation

A

=(VP-CVP)/R
-VP=15
CVP=0
R=constant in veins
-VP changes due to skeletal muscle pumps (constrict veins, increasing pressure)
-change in VP to CVP drives blood back to the heart (gradient)

31
Q

how does expiration and inspiration effect pressure

A

expiration=increases pressure in thoracic cavity

  • inspiration=decrease in pressure in thoracic cavity (leads to decreased (CVP and increased venous return)
  • affects CVP +/- 1
32
Q

what effect does VR have on cardiovascular system

A

change VR, changes CO (more VR=more CO)

-while arteries changing changes TPR

33
Q

what effect does norepinephrine have on veins

A

vasoconstricts veins, which increases venous pressure, increasing venous return, increasing CO

34
Q

why is central venous pressure lower than venous pressure and what does this do

A

because of the low pressure inside the thoracic cavity
(CVP is measured inside the atrium)
-causes blood to flow towards heart (lowest pressure)
-increased venous return (during inspiration) stretches the right atrium, which causes a reflex increase in HR during inspiration

35
Q

what do sympathetic nerves do in relation to venous dilation

A

=alpha adrenergic receptors

-cause venous vasocontriction

36
Q

how does Frank-starlings law of the heart apply to venous return

A

increased venous return increases cardiac output

  • increased EDV leads to increased SV (F-S law)
  • stretch of right atrium leads to increased HR
37
Q

orthostatis hypotension

A

the response to it is a baroreceptor reflex that involves the hear, veins, and arteries

38
Q

difference of diastole and diastolic pressure

A

diastolic pressure (and systolic pressure) occurs in systole

39
Q

velocity in capillaries

A

slow because of large combined cross-sectional area

40
Q

exchange of nutrients and wastes between blood and tissue fluid happens by..

A
  1. diffusion: through endothelial cells and between cells
  2. filtration/absorption: bulk flow of water and solutes between cells and through fenestrations
  3. transcytosis: pinocytosis from blood, exocytosis into tissue (transport of proteins, antibodies, etc through mysiums)
41
Q

filtration

A

water and solutes leaving the capillaries by bulk flow

42
Q

absorption

A

water and solutes entering capillaries by bulk flow

43
Q

balance btwn absorption/filtration maintained by?

A

by the balance between hydrostatic and osmotic pressures

44
Q

hydrostatic pressure in arteriole vs venule end of capillary

A

its 35mmhg at arteriole end of capillary and 15mmhg at the venule end of capillary
-this force is favoring filtration

45
Q

osmotic pressure in capillaries

A
  • always greater inside the capillary because plasma proteins contribute to oncotic pressure
  • favors absorption
46
Q

oncotic pressure

A

relatively constant down the length of the capillary at about 25mmhg

  • relatively constant down the length of the capillary at about 25mmhg
  • pressure difference between capillaries and tissue fluid due to plasma protein=albumin
47
Q

net filtration occurs where

A

in the arteriole end of the capillary where the outward hydrostatic force exceeds the inward osmotic force

48
Q

where are the two forces balanced

A

towards the middle of the capillary, no net filtration or absorption occurs

49
Q

net absorption occurs where

A

at the venule end of the capillary where the osmotic force exceeds the hydrostatic force

50
Q

net filtration occuring?

A

yes, even though filtration/absorption mostly balance each other out thoughout the capillary
-extra fluid that leaves the blood and accummulates in the tissue fluid is taken up into the lymph capillaries, and brought back into circulation by the lymphatic system

51
Q

edema

A

an imbalance in forces across the capillary

  • an accumulation of excess tissue fluid
  • excess hydrostatic pressure (high blood pressure)
  • decreased plasma oncotic pressure
  • increased tissue oncotic pressure
  • blockage of lymph vessels
52
Q

oncotic edema

A

not enough protein, therefore not enough plasma protein

-oncotic pressure decreases

Physiology (11 decks)

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