test 2 cv phys Flashcards
describe the seven functions of the endothelium
- Regulates blood-tissue exchange.
- Paracrine secretions regulate vascular tone (nitric oxide (NO), endothelium-
derived hyperpolarizing factor (EDHF), prostacyclin, and endothelin). - Endothelial surface enzymes modify vasoactive peptides in the blood (e.g., ACE
converts angiotensin I into angiotensin II, a potent vasoconstrictor). - Endothelium secretes antithrombotic and pro-thrombotic factors.
a. NO and prostacyclin are vasodilators and also inhibit platelet aggregation.
b. It also secretes von Willebrand factor which participates in clotting. - Endothelium participates in the inflammatory defense against pathogens.
- Endothelium initiates new blood vessel formation (angiogenesis).
- Endothelial dysfunction contributes to atheroma
what could happen to going from supine to an upright position? Why could this happen?
A transitory hypotension might occur because blood is transferred to the veins in the
legs resulting in reduced venous return, SV and Q.
what causes generalized edema in heart failure patients
Decreased Q increases venous pressure, which raises capillary pressure and thus capillary filtration
after exercising, muscles may appear a bit larger due to swelling. what causes this?
Exercising muscle fiber release lactate and K+ ions into the interstitial fluid, which draws water form the plasma
laminar flow characteristics
laminar flow has smooth parallel streamlines. the layer in contact with the wall has zero velocity due to cohesive forces.
types of vessel laminar flow occurs in
occurs in normal arteries, arterioles, veins and venules
turbulent flow where
normally in aorta and pulmonary artery during peak flow.
turbulent flow also occurs in the ventricles and stenosed arteries.
can also occur in leg arteries due to plaque.
what encourage and decourages turbulent flow
encourages: high fluid velocity, large tube diameter, and high fluid density,
Discouraged: high fluid viscosity.
Identify the specific location of angiotensin converting enzyme (ACE) in the human
body. Given that location, what organ has the richest supply of ACE?
surface of the endothelium, lungs
Calculate the ankle-brachial index (ABI)
ankle SBP/ brachial SBP
Calculate SVR given the following parameters.
SVR=MAP/Q. MAP= DBP + 1/3(SBP-DBP)
What structure essentially forms the small pore system?
glycocalyx
Arteriovenous anastomoses
the are no capillaries between the arterioles and the venules.
vasomotion
regular cycling of arterioles between dilation and constriction.
veni arteriole response
local arteriolar vasoconstriction occur upon standing up
List paracrine secretions of the endothelium that regulate vascular tone. Which
ones produce vasodilation? Vasoconstriction?
Vasodilation- NO, EDHF, prostacyclin
Vasoconstriction- endothelin
Describe the arterial pressure pulse pattern in pulsus paradoxus and pulsus
alternans. What are they caused by or a sign of?
pulsus paradoxus- condition where pulse pressure falls by 10 during inspiration. caused by cardiac tamponade
pulsus alternans- condition where pulse alternates between strong and weak. sign of severe LV failure
continuous capillaries
occur in skeletal muscle, myocardium, skin, lung, connective tissue, and fat. least permeable to water
fenestrated capillaries
specialized for rapid fluid filtration. Occur in kidneys, exocrine and endocrine glands
discontinuous capillaries
allow blood cell turnover, highly permeable to plasma proteins. Occur in bone marrow, spleen and liver.
What is the approximate O2 extraction in skeletal muscle and myocardium at rest?
At high intensity exercise?
At rest: skeletal muscle = 25% , myocardium = 67%
High intensity: both around 80%
What factors affect diffusion of solutes and how do they affect it?
- direction proportional to the concentration difference
- inversely proportion to diffusion difference
- directly proportional to surface area
- directly proportional to solute diffusion coefficient
- inversely proportional to solute size
How does capillary recruitment occur (i.e., increased perfusion of capillaries)?
vasodilation fo arterioles
How does increased capillary density benefit solute exchange in a tissue?
increased endothelial surface area and shorter diffusion distance.
What is the veni-arteriolar response?
local arteriolar vasocontriction occurs, increased pre-capillary resistance, shifting capillary pressure to the venules, PREVENT EDEMA
Describe the relationship between endothelial cells, NO and the development of
atheromas.
endothelium produces NO, which is antiatherogenic. Reduced NO levels are thought to contribute to atheroma formation
What could she try to terminate the SVT?
activate PSNS by carotid massage, hard coughs
basic shape of arterial pulse pressure in central systemic arteries
assymetrical
shear stress on the endothelium stimulates what vasoconstrictor.
oxygen and no
what happens to blood velocity in stenosed narrowed arteries
blood velocity increases
typical capillary transit time for gas exchange
.5-2 seconds
vasoconstricting drugs will have what effect on the reflected wave
it will return faster
the key change precipitating swelling
formation of gaps in the endothelium. filtration exceeds absorption
capillary filtration rate
hydraulic push- osmotic suction
vasoactive agent that causes vasoconstriction
endothelin
large arteries account for what percentage of SVR
2%
poiseuilles law
8nl/piR^4
Discuss factors that affect solubility of molecules and how they affect it
-Factors that affect solubility include molecular size, chemical nature of the molecule (lipid or nonlipid), and net charge of the molecule.
-Lipid-soluble solutes (e.g., O2) diffuse through the entire lipid cell membrane, givingthem a much greater area for diffusion compared to lipid-insoluble solutes.
-Hydrophilic solutes are restricted to water-filled pathways through intercellular
junctions and fenestrae.
Large lipid-insoluble molecules (e.g., proteins) pass through a large pore system.
-Capillaries are many thousand times more permeable to lipid-soluble O2 than to lipid-insoluble glucose; 1000 times more permeable to glucose than albumin. -Negatively charged molecules are repulsed by the negatively charged glycocalyx.
Discuss factors that affect central venous pressure (CVP) (venous return), how they affect it and mechanisms involved.
-Gravity – orthostasis shifts blood to the veins in the legs, reducing venous return. -Immersion in water up the chest or neck increases venous return since gravity acts
on the water as well as blood, transmural venous pressure barely changes.
-The skeletal muscle pump (rhythmic exercise) increases venous return.
-Inspiration increases venous return as intrathoracic pressure decreases and
abdominal venous pressure increases (diaphragm compresses abdominen).
- Valsalva maneuver or coughing increase intrathoracic pressure - ↓ venous return.
How do these factors affect Q and why?
Anything that reduces venous return will reduce SV and, thus, Q and vice versa.
Consider the physiological regulation of solute transfer. Identify and discuss numerous factors/mechanisms that contribute to the marked increase in solute transfer during exercise.
A. More uniform perfusion of the capillary bed due to capillary recruitment.
b. Blood flow increases with increased metabolic activity due to increased Q and
vasodilation, which increases the rate of delivery of glucose and O2.
c. Capillary recruitment (vasodilation) increases the surface area of endothelium
available for exchange and reduces the diffusion distance.
d. Increased metabolic consumption steepens the concentration gradient.
e. Endothelial permeability increases in response to flow – mediated by NO.
f. Partially deoxygenated myoglobin greatly speeds up the rate of O2 diffusion.
Also, explain how endurance training increases the rate of diffusion of solutes from blood to muscle.
Endurance training increases capillary density which shortens diffusion distance
and increases surface area for diffusion
