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122 Cards in this Set
- Front
- Back
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what are two considerations in hemodynamics?
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-reltnshp btwn pressure and flow
-reltnshp btwn resistnc and flow |
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how does flow change with pressure gradient change?
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flow increases as change in P increases assuming resistance is the same throughout.
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how does resistance cause flow to change?
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as R increases, F decreases.
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what 3 things determine resistance?
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-viscosity
-radius of tube -length of tube |
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how do we physiologically change resistance?
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by changing tube radius.
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what does increasing radius do to resistance and flow?
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decreases resistance and increases flow.
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what is viscosity defined as?
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measure of resistance between molecules of a fluid - could increase by incr. RBCs
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how does changing length alter resistance?
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make tube longer increases resistance.
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numerically how is resistance related to radius?
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1
R = ----- r^4 |
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What is Poiseuille's Law?
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Flow = Pressure gradient/R
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what is the equation for resistance?
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8vl
R = --- pi r^4 |
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using the R equation what does Flow = ?
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P pi r^4
F = -------- 8vl |
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What are the 2 main functions of arteries?
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1. To act as low resistance pathway to bloodflow.
2. To convert distcontinuous output to continuous blood flow. |
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what are the terms for the high and low ends of blood pressure?
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HIGH = systole
LOW = diastole |
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how is bp reported?
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Systole/diastole.
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what is pulse pressure?
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the difference between systolic and diastolic blood pressure. Felt as a pressure point when the aortic valve slams shut after systole.
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what is MAP?
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Mean arterial pressure.
MAP = DP + DP + SP / 3 |
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what determines mean artial pressure?
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blood volume in the arteries.
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what are the 2 determinants of arterial blood volume?
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1. Cardiac output
2. Total peripheral resistance to bloodflow. |
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what happens to the arterial blood volume if you increase total periph. resistance?
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it increases. think about it; blood is in the arteries, resistance is in front of it; more will be in arteries.
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what type of vessel provides th most resistance in the periphery?
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arterioles
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what is the fundamental equation for MAP?
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MAP = CO X TPR
MAP therefore, CO = ----- TPR |
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what is arterial compliance, and why is it important?
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compliance = stretchiness of arteries.
The stretchier they are, the more volume can hold. |
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if the arteries are noncompliant, how does this affect blood pressure?
-why? |
systolic increases and diastolic decreases.
ummmm |
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based on compliance, how does kinetic energy convert to potential?
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During systole, KE is converted to PE as artery walls stretch.
During diastole, PE of stretched walls converts to KE as it drives blood out of arteries. |
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what does compliance really determine?
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peripheral pressure.
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as stroke volume increases what happens to periph. pressure?
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it increases.
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Does compliance have any affect on mean arterial pressure?
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no - only on peripheral pressure.
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what are resistance vessels?
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arterioles
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why are arterioles resistance vessels (2 reasons)?
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1. beause most resistance is here.
2. because they can be changed. |
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why can we change artos?
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because they have lots of smooth muscle. when smooth muscle contracts, it changes the radius of the tube.
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what 2 changes occur when we constrict artos?
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1. Global resistance increases
2. Cardiac output distribution changes - local changes. |
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what are 5 methods of changing resistance in arterioles?
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1. sympathetic vasoconstrictor nerves
2. other nerves 3. hormones 4. local control 5. endothelial factors. |
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how do sympathetic nerves alter arteriole resistance?
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-Release norepinephrine.
-Norepi binds alpha-adrenergic receptors on arterioles. -artos constrict and TPR and MAP both increase. |
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how do arterioles vasodilate in opposition to sympathetic nerves causing constriction?
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just decrease sympathetic output - here is no parasympathetic equivalent, no dual-innervation.
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What other nerves control arterioles?
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non-adrenergic, non-cholinergic autonomic nerves release NO and cause vasodilation
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what types of arterioles recieve NO vasodilation commonly?
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-genitalia
-GI tract |
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what three hormones alter resistance in arterioles?
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-epinephrine
-angiotensin II -Vasopressin |
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what 2 ways can epinephrine alter arterioles?
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-If binds alpha receptor, vasoconstriction of SKIN vessels
-If binds beta receptor, causes dilation of vessels supplying skeletal muscle. |
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what do Angiotensin II and Vasopressin do to arterioles?
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cause increase in blood volume by inducing vasoconstriction.
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what are 2 ways of locally controlling arteriole resistance?
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1. Active hyperemia
2. Flow autoregulation |
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What is active hyperemia?
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blood flow adjustment to meet metabolic needs of tissue
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how does active hyperemia control arteriole resistance?
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arteriole smooth muscles sense changes in interstitial fluid and vasodilate/relax
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what interstit. fluid changes occur in active hyperemia?
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Decreased O2, pH
Increased CO2, K+, Adenosine, Bradykinin |
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What is flow autoregulation?
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a change in flow to an organ causing a change in resistance to compensate and keep flow nearly the same.
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what is an example of flow autoregulation?
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Kidneys - dilate when blood pressure is increased so that resistance is decr and same amt of blood will flow through.
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what interstit. fluid changes occur when flow is decreased?
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same as in active hyperemia -
Decreased O2, pH Increased CO2, K+, Adenosine, Bradykinin |
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how does flow autoreg cause
-Dilation -Constriction |
Dilation - sense changes in interstit. fluid
Constrict - sense Stretch |
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what's an example of flow autoreg to cause constriction?
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1. Incr b. pressure
2. smooth muscle in vessels senses stretching. 3. Ca2+ channels open and cause stronger contractions |
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How do endothelial cells control arteriole resistance?
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Secrete paracrine agents - diffuse to adjacent vascular smooth muscle, induce vasodil or constriction
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what are 2 factors produced by endothelial cells?
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-Nitric oxide
-Endothelin-1 |
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what does nitric oxide do?
-Endothelin-1? |
Vasodilates
Vasoconstricts |
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What 6 things cause arteriole vasoconstriction?
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Sympath. vasoconst. nerves
Epineph on alpha receptors Angiotensin II/Vasopressin Vessel stretch Endothelin-1 |
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what are the units for flow and pressure gradient?
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Flow = vol/time
Pressure = mm of Hg |
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what two factors are secreted by endothelial cells?
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-nitric oxide
-endothelin 1 |
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what is the effect of
-NO -endothelin 1 |
no is a vasodilator
endothelin-1 is a constrictor |
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what type of vessel is a capillary?
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EXCHANGE vessel
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what are some characteristics of capillaries?
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-tiny cells, about 1mm long and 5 microns in diameter.
-most cells w/in .1 mm of a capillary. -composed of only ENDOTHELIAL cells |
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what is resistance in capillaries like?
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fairly high, but all-together the capillaries have low R
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what is the PURPOSE of capillaries?
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to exchange blood nutrients and wastes
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what are the 2 ways nutrient exchange takes place across capillaries?
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1. diffusion
2. filtration |
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what exchanges across capillaries by diffusion?
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CO2, O2, wastes, and nutrients.
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how does water go through capillaries?
how does fat? |
by pores.
fat crosses the lipid membrane. |
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what is filtration by capillaries for?
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maintaining the distribution of extracellular fluid between plasma and interstitial fluid.
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What is interstitial fluid really?
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ultrafiltrate of plasma, without the plasma proteins.
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What is Starling's Hypothesis?
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-direction/magnitude of fluid movement across capillary walls is determined by Hydrostatic + Osmotic pressure.
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What favors fluid movemnt from
-vessel->interstitial space? -interstit. space -> vessels? |
Increasing intracapillary hydrostatic pressure.
Increasing osmotic pressure. |
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how do you increase osmotic pressure in a capillary?
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increase osmotically active particles (plasma proteins) inside it.
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What direction is fluid move in
-filtration? -absorption? |
Filtration = movement of fluid out of capillaries.
Absorption = movemnt of fluid into capillaries from tissue. |
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what four pressures make up net filtration pressure?
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-Capillary blood pressure
-Capillary osmotic pressure -Tissue hydrostatic pressure -Tissue osmotic pressure. |
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what does capillary hydrostatic pressure increase do to filt/absorp?
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Filtration will increase, absorption will decrease.
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what does capillary osmotic pressure increase do to filt and absorption?
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Filtration will decrase
ABsorption will incrase |
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what is another name for capillary osmotic pressure?
what mostly causes this pressure? |
colloid osmotic pressure.
-plasma proteins. |
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What is affect on filt/absoptn when tissue hdrostatic pressure increases?
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filtration decreases, absorption increases.
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what is affect on filt/absoptn when tissue osmotic pressure increases?
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filtration increases, absorption decreases.
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What causes filtration?
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Filtration is caused by Hydrostatic capillary pressure and tissue osmotic pressure.
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What causes absorption?
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Absorpn is caused by capillary osmotic prssure and tissue hydrostatic pressure.
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What is net filtration pressure?
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(Causes of filtration) minus (Causes of absorption)
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what four things can disturb hydrostatic-oncotic balance?
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1. Arteriole costriction
2. Arteriole dilation 3. Low plasma proteins 4. Lymphatic damage |
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What effect does arteriole constriction have on:
-MAP and capillary pressure? -Filtration? -Absorption? -Blood volume? |
-Increases MAP
-Decreases Capillary pressure -Decreases filtration -Increases absorption -Increases blood volume |
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How does arteriole dilation effect filtration/absorption?
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-Increases capillary pressure
-Increases filtration -Decreases absorption -Decreases blood volume -Decreased MAP |
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If plasma proteins are low how is NFP affected?
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Lower capillary osmotic pressure and higher NFP.
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What do we see in starving children with lower plasma protein?
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Pitting edema - fluid in the interstitial space due to increased NFP
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what 4 things cause decreased plasma proteins?
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-chronic liver disease
-protein defic. diet -kidney disease -severe burns |
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how does lymphatic damage affect NFP?
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-Normally lymphatics take up proteins and fluid leaked from capillaries and return to CVS.
-If defic, stay in ISF and swell |
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How does wearing an elastic cuff alter NFP?
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Increases tissue hydrostatic pressure, increases absorption and decreases filtration.
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what are veins?
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the psgway from tissues to the heart.
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what is the function of veins
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to act as a reservoir - most - 2/3 of the blood at any given time is in the veins.
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How do you increase Arterial blood?
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By CONSTRICTING THE VEINS.
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Why does vein constriction increase arterial blood?
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because it increases venous return to the heart, which increases EDV, thus increasing stroke volume and arterial volume.
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what is the difference between constricting arterioles versus veins?
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Arteriolar constriction will cause big increase in resistance, less in blood vol.
Veinous constrictn will cause little affect on R, but big increase in blood volume. |
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what are 4 ways you can control venous return?
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1. Sympathetic vasoconstrictor nerves to those veins.
2. Changes in blood volume 3. Skeletal muscle pumps 4. Respiratory movements |
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How do symp vasoconst. nerves control veinous return?
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By releasing norepinephrine, which acts on smooth muscle to contract and constrict veins.
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How does blood volume alter venous return?
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If increased, it will cause more blood to go to heart, and thus increase EDV.
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How does skeletal muscle alter venous return?
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Long veins have valves; normally muscle movement pushes on the veins and blood moves toward heart.
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How does respiratory movement alter venous blood return?
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When inspire, venous return increases because diaphragm presses on veins.
Expiring decreases venous return. |
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What is the function of the lymphatics?
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To return excess fluid and plasma to the CVS and dump it back into veins.
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Why is MAP regulation important?
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because it is the driving force for blood circulation through the body.
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What happens if MAP is
-too low -too high |
Low = faint; inadequete perfusion.
High = heart overworked, damaaged arterial walls. |
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How is MAP regulated?
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-Baroreceptors
-Hormones -Capillary fluid shift -Longterm regulation |
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What regulates MAP in the
-longterm? -short-term? |
longterm is done by kidneys.
shorterm is done by baroreceptors - elicitis an immediate change if necessary. |
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For example, what would baroreceptors respond to?
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If you stand and your blood pressure decreases, these would immediately respond.
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What are the Sensors in baroreceptor control?
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Baroreceptors in the
-carotid artery -aortic arch. |
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how do baroreceptors work?
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when bp increases, vessel walls stretch; generates an action potential and signal is sent.
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What is the integrating center in barorecp. control?
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the Medulla of the brain.
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What are the 3 effectors in barorecp. regulation?
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1. Mean Arterial Pressure MAP
2. the HEART 3. vasculature |
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what 3 things about the heart can the brain change to alter MAP?
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-Cardiac Output
-Nervous Control -Hormone control |
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How does the brain alter cardiac output in the heart?
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by altering
-Stroke volume -Heart rate b/c CO = SVxHR |
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what 3 types of nerves are changed to alter the heart to regulate MAP?
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1. Cardiac Parasymp nerves
2. Cardiac Sympathetic nerves 3. Sympathetic vasoconstrictor nerves to the veins. |
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What is the effect of stimul:
-Cardiac Parasymp nerves -Cardiac Sympathetic nerves -Sympathetic vasoconstrictor nerves to the veins |
Parasymp = decrease heartrate
Symp = increase heartrate Symp vasoconsrictors constrict veins, to increase EDV and SV. |
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Specifically how do cardiac nerves alter heartrate?
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Parasymp decrease slope of pacemaker potential.
Sympathetic increase slope. |
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How do hormones control the heart?
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Epinephrine stimulates the SA node and ventricles to increase heart rate. Increases SV.
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what two vasculature components does the medulla control to alter MAP?
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-Arterioles
-Veins |
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wHAT IS THE AFFECT ON Mean arterial pressure when the medulla acts on arterioles to constrict?
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Their vasoconstriction increases total peripheral resistance. This decreases venous return and SV.
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Why does the medulla's control of veins alter MAP?
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If veins constrict, it increases venous return to the heart, increasing EDV and Stroke volume.
Increasd SV alters cardiac output, which directly affects MAP. |
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If blood pressure decreases, what is response of
-Sympathetic nerves -Parasympath nerves |
Symp will stimulate constriction to increase bp
Parasymps will decrease. |
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Other than changing CO, TPR, and heartrate, how does the medulla control MAP?
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-Capillary fluid shift
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what is capillary fluid shift?
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Negative feedback response to decreased MAP.
-arterioles constrict, causing capillary press to decrease, and NFP decreases. -Absorption increases and causes increase in Blood vol. |
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What does increased RBC production do?
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increases blood viscosity, increasing total peripheral resistance to blood flow.
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what is primary polycythemia?
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increased blood production due to tumor cells
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what is secondary polycythemia?
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increased RBC production in response to altitude, or a non-bmarrow problem.
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what is erythropoeisis in response to hypoxia an example of?
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negative feedback.
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