Unit 2: Circulation Pt2 Flashcards
T/F. The Vasoactive role of endothelium tends to be more vasoconstriction.
False– it tends to be more dilation in natures–> unless it is damaged, then vasoconstrictive
What does endothelium release that inhibits platelet aggregation and relaxes vascular smooth muscle (vasodilation)?
Prostacyclin (PGI2)
What three things does the endothelium release that will play its vasoactive role on the vessels?
Release:
- Prostacyclin (PGI2)
- Nitric Oxide (NO)–> when healthy
- Endothelin –> when damaged
What does endothelium release when it is healthy that is a vasodilator? What stimulates the release?
Nitric oxide
Release Stimulated by:
- shear stress ass. with increase flow
- ACh binding to endothelium
What does endothelium release when it is damaged that causes vasoconstriction and may be contribute to vasoconstriction when endothelium is damaged by hypertension?
Endothelin
- constricts vascular smooth muscle
What is the functional unit of circulation?
capillaries
Where does bulk of exchange take place in circulation system?
capillaries
What is intermittent constriction of metarterioles and precapillary sphincters?
vasomotion
What are three mechanisms of capillary exchange?
- Passive Diffusion
- Ultrafiltration
- Vesicular Transport
What is the equation for oxygen uptake/utilization ?
= the product of flow (F) x arterial-venous oxygen difference
O2 = (F) (A-V O2 diff)
What type of flow is associated with increased oxygen uptake/utilization?
Functional or Nutritive flow
end of page 7
What type of flow is associated with shunting of blood through a capillary bed?*
Non nutritive flow
What type of capillary exchange involves permeability and concentration gradient?
Passive diffusion
What type of capillary exchange involves larger MW non lipid soluble substance?
vesicular transport
What type of capillary exchange involves bulk flow through a filter (capillary wall) and Starling Forces (Hydrostate P and Colloid Osmotic P)?
Ultrafiltration
What does Hydrostatic Pressure gradient favor?
ass. Ultrafiltration
filtration (high to low) Ex: - capillary HP averages 17 mmHg - Interstitial HP avers -3 mmHg
What does Colloid Osmotic Pressure favor? (ass. Ultrafiltration)
reabsorption
(low to high)
- Capillary COP averages 28 mmHg
- Interstitial COP average 9 mmHg
What does the Net Filtration Pressure = ?
= (Capillary Hydrostatic Pressure - Interstitial HP) - (Capillary Colloid Osmotic Pressure - Interstitial COP)
What is the most abundant plasma proteins?
Albumin (75%)
What is the colloid osmotic pressure a function of?
function of the protein concentration - like plasma proteins
What is the calculated Colloid Effect? What is the Actual Colloid Effect? What is the discrepancy b/w the two due to?
Calculated = 19 mmHg Actual = 28 mmHg
Discrepancy due to Donnan Effect
What is the Donnan Effect?
is increases the colloid osmotic effect; large MW plasma proteins carries neg. charges which attract pos. ions –> therefore increasing the osmotic effect by about 50%
T/F. Proteins that can and can’t cross capillary walls will exert osmotic pressure.
False– ONLY protein that CANNOT cross capillary wall can exert osmotic pressure
What effect can the capillary wall have on Colloid Osmotic pressure?
how tight/loose they are
What areas have capillary walls with tight junctions?
What areas have capillary walls that are discontinuous?
tight junctions–> BBB
discontinuous–> liver capillaries
Where is the body do capillaries have filtration slits (fenestrations)?
Glomerular Capillaries in kidney
What expresses how readily protein can cross the capillary wall?
Reflection Coefficient (ranges from 0-1)
What does it mean when the Reflection Coefficient = 0? What if it = 1? Where is body would be ass. with these number?
If = 0 –> all colloid proteins freely cross wall, none are reflected, and therefore NO colloid effect –> LIVER
If = 1 –> all colloid proteins are reflected, none cross capillary wall, therefore FULL colloid effect –> BRAIN
What drains excess fluid from interstitial space?
Lymph capillaries
Where are no true lymphatics found?
- superficial portions of skin
- CNS?–new finding ass.
- endomysium of muscle
- bones
What drains the lower body and left side of head, left arm, and part of chest(3/4)?
Thoracic duct
What does the right lymph duct drain?
right side of head, neck, right arm, and part of chest (1/4)
What is the discussion of the CNS having modified lymphatic function?
How are plasma filtrate and escaped substances in perivascular spaces returned to vascular system in CSF?
true lymphatic vessels just discovered in CNS near Dural Venous sinuses
via arachnoid villi which empties into Dural venous sinuses
Where is 2/3 of all lymph from?
liver and intestines
What will increase lymph formation?
any factor that increases filtration or any factor that decrease reabsoprtion
What is the total lymph flow per hour? per day?
120 ml/hr
2.9 L/day
What is the rate of lymph formation/flow in the Thoracic duct? Right Lymph duct?
Thoracic Duct = 11 ml/hr
Right Lymph Duct = 20 ml/hr
(therefore 120 ml/hr total)
T/F. Everyday the volume of lymph filtered is roughly equal to our entire plasma volume.
True
How is arterial blood pressure created?
by the interaction of blood with vascular wall
Arterial BP = vol of blood interacting with the wall
What does Arterial BP =?
CO x TPR (Total peripheral resistance)
Where is greater than 1/2 of TPR (total peripheral resistance) occur at?
at level of systemic arterioles
T/F. A change in pressure follows a change in volume. *
True
During systole the left ventricular output (SV) is ____ than peripheral runoff. What does this cause?
greater
therefore total blood volume rises and causes arterial BP to increase to a peak (=systolic BP)
T/F. During systole the veins are distended.
False– the arteries are distended during this time
When you see systole, think ________. When you see Diastole, think ______.
Systole –> stretch
Diastole –> recoil
What is occurring during diastolic BP?
total blood volume in arterial tree is decreasing, which causes arterial BP to fall to a minimum value
What serves to maintain perfusion to the tissue beds when the left ventricle is filling?
the arteries are now recoiling
diastole BP
What is the stretch (systole) and recoil (diastole) of the arterial tree that normally occurs during the cardiac cycle called?
Hydraulic Filtering
What phenomenon save the heart work?*
Hydraulic Filtering (through stretch and recoil)
– creates intermittent output by the heart to a stead delivery at the tissue beds
Describe what happens with age and Hydraulic Filtering.
increase in age causes a decrease in distensibility of the arterial tree–> therefore hydraulic filtering is reduced–> and work load on the heart is increased
What is the maximum pressure in the systemic arteries?
systolic blood pressure
When does blood pressure peak?
as blood is ejected from left ventricle into aorta (systolic BP)
What occurs during systole that causes arterial pressure to increase?
inflow volume from LV typically occurs at a faster rate than peripheral runoff out the arterial tree
What is the minimum pressure in the systemic arteries called?
Diastolic Blood pressure
How low the systemic artery BP falls is dependent on what 2 factors?*
- Cycle Length–> inversely proportional to DBP
2. Total Peripheral Resistance (TPR) –> proportional to DBP
What affect will an increase in cycle length have on DBP?*
decreases DBP
What affect with an increase in TPR (total peripheral resistance) have on DBP?*
will increase DBP
Will DBP change much during exercise? why or why not?
during exercise DBP may not change much due to:
- decrease in cycle length being offset by decrease in total peripheral resistance (TPR)
What is the Mean Arterial Blood Pressure?
= 1/3 Pulse Pressure + DBP
(approximation)
(it is NOT the arithmetical mean b/w systole and diastole)
Example: What is the Mean Arterial Blood Pressure if BP = 120/80
120(systole)-80(diastole) = 40(pulse pressure)
1/3 of 40 = ~13
80(diastole)+13 = 93
MAP = 93
What do most post-ganglionic SNS terminal release? What is the predominant receptor type?
NE; alpha receptor
SNS stimulation causes widespread vasoconstriction causing a decrease in blood flow, EXCEPT in what three places?
- Brain (arterioles weakly innervated by SNS)
- Lungs (arterioles weakly innervated by SNS)
- Heart (overrides SNS vasoconstriction by local vasodilators, like adenosine)
As the arterial pressure falls, what is the critical pressure in which flow ceases due to closure of the arterioles called?
Critical Closing Pressure
What critical luminal pressure is required to keep arterioles from closing completely?
critical closing pressure
What is proportional to Critical Closing Pressure?
vascular tone
Ex: SNS stimulation of arterioles increases tone and therefore increases CCP
What do we call the equilibrium pressure where arterial BP = venous BP?
Mean Circulatory Filling Pressure
How could Mean Circulatory Filling Pressure occur?
if cardiac output is stopped, arterial pressure falls and venous pressure will rise
MCFP –> arterial BP = venous BP
NOT GOOD
How do we prevent Mean Circulatory Filling Pressure?
by closure of arterioles (critical closing pressure)
What occurs if Mean Circulatory Filling Pressure = Central Venous Pressure?
venous return goes to 0 –> which = DEATH
At a give Mean Circulatory Filling Pressure, as Central Venous Pressure increases, what happens to venous return?
venous return decreases
What can we gather from a Vascular Function Curve?
Venous return on Y axis and Central Venous Pressure of X axis
–where the Vascular Function curve intersects with x-axis–> will be where Venous return = Central venous pressure –> and is called the Mean Circulatory Filling Pressure
As Central Venous Pressure increases, what happens to cardiac output? What is this due to?
CO will increase; due to intrinsic and extrinsic effects
What is the Cardiac Function Curve?
CO on Y-axis and Central Venous Return on X-axis
–as CVP increases so does CO
What is the pressure in the central veins (superior and inferior vena cava) at the entry into the right atrium called?
Central Venous Pressure
T/F. Central Venous Pressure = right atrial pressure
True
T/F. Walking and laying down = more similar physiologically in a cardiovascular sense.
True (b/c when just standing, blood pools, but when talking you pump it back to heart and it is more even throughout body, just like how it is when you are lying down)