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