test 2 cv phys

Question 1

describe the seven functions of the endothelium

Answer 1

1. Regulates blood-tissue exchange.
2. Paracrine secretions regulate vascular tone (nitric oxide (NO), endothelium-
   derived hyperpolarizing factor (EDHF), prostacyclin, and endothelin).
3. Endothelial surface enzymes modify vasoactive peptides in the blood (e.g., ACE
   converts angiotensin I into angiotensin II, a potent vasoconstrictor).
4. 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.
5. Endothelium participates in the inflammatory defense against pathogens.
6. Endothelium initiates new blood vessel formation (angiogenesis).
7. Endothelial dysfunction contributes to atheroma

Question 2

what could happen to going from supine to an upright position? Why could this happen?

Answer 2

A transitory hypotension might occur because blood is transferred to the veins in the
legs resulting in reduced venous return, SV and Q.

Question 3

what causes generalized edema in heart failure patients

Answer 3

Decreased Q increases venous pressure, which raises capillary pressure and thus capillary filtration

Question 4

after exercising, muscles may appear a bit larger due to swelling. what causes this?

Answer 4

Exercising muscle fiber release lactate and K+ ions into the interstitial fluid, which draws water form the plasma

Question 5

laminar flow characteristics

Answer 5

laminar flow has smooth parallel streamlines. the layer in contact with the wall has zero velocity due to cohesive forces.

Question 6

types of vessel laminar flow occurs in

Answer 6

occurs in normal arteries, arterioles, veins and venules

Question 7

turbulent flow where

Answer 7

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.

Question 8

what encourage and decourages turbulent flow

Answer 8

encourages: high fluid velocity, large tube diameter, and high fluid density,
Discouraged: high fluid viscosity.

Question 9

Identify the specific location of angiotensin converting enzyme (ACE) in the human
body. Given that location, what organ has the richest supply of ACE?

Answer 9

surface of the endothelium, lungs

Question 10

Calculate the ankle-brachial index (ABI)

Answer 10

ankle SBP/ brachial SBP

Question 11

Calculate SVR given the following parameters.

Answer 11

SVR=MAP/Q. MAP= DBP + 1/3(SBP-DBP)

Question 12

What structure essentially forms the small pore system?

Answer 12

glycocalyx

Question 13

Arteriovenous anastomoses

Answer 13

the are no capillaries between the arterioles and the venules.

Question 14

vasomotion

Answer 14

regular cycling of arterioles between dilation and constriction.

Question 15

veni arteriole response

Answer 15

local arteriolar vasoconstriction occur upon standing up

Question 16

List paracrine secretions of the endothelium that regulate vascular tone. Which
ones produce vasodilation? Vasoconstriction?

Answer 16

Vasodilation- NO, EDHF, prostacyclin
Vasoconstriction- endothelin

Question 17

Describe the arterial pressure pulse pattern in pulsus paradoxus and pulsus
alternans. What are they caused by or a sign of?

Answer 17

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

Question 18

continuous capillaries

Answer 18

occur in skeletal muscle, myocardium, skin, lung, connective tissue, and fat. least permeable to water

Question 19

fenestrated capillaries

Answer 19

specialized for rapid fluid filtration. Occur in kidneys, exocrine and endocrine glands

Question 20

discontinuous capillaries

Answer 20

allow blood cell turnover, highly permeable to plasma proteins. Occur in bone marrow, spleen and liver.

Question 21

What is the approximate O2 extraction in skeletal muscle and myocardium at rest?
At high intensity exercise?

Answer 21

At rest: skeletal muscle = 25% , myocardium = 67%
High intensity: both around 80%

Question 22

What factors affect diffusion of solutes and how do they affect it?

Answer 22

1. direction proportional to the concentration difference
2. inversely proportion to diffusion difference
3. directly proportional to surface area
4. directly proportional to solute diffusion coefficient
5. inversely proportional to solute size

Question 23

How does capillary recruitment occur (i.e., increased perfusion of capillaries)?

Answer 23

vasodilation fo arterioles

Question 24

How does increased capillary density benefit solute exchange in a tissue?

Answer 24

increased endothelial surface area and shorter diffusion distance.

Question 25

What is the veni-arteriolar response?

Answer 25

local arteriolar vasocontriction occurs, increased pre-capillary resistance, shifting capillary pressure to the venules, PREVENT EDEMA

Question 26

Describe the relationship between endothelial cells, NO and the development of atheromas.

Answer 26

endothelium produces NO, which is antiatherogenic. Reduced NO levels are thought to contribute to atheroma formation

Question 27

What could she try to terminate the SVT?

Answer 27

activate PSNS by carotid massage, hard coughs

Question 28

basic shape of arterial pulse pressure in central systemic arteries

Answer 28

assymetrical

Question 29

shear stress on the endothelium stimulates what vasoconstrictor.

Answer 29

oxygen and no

Question 30

what happens to blood velocity in stenosed narrowed arteries

Answer 30

blood velocity increases

Question 31

typical capillary transit time for gas exchange

Answer 31

.5-2 seconds

Question 32

vasoconstricting drugs will have what effect on the reflected wave

Answer 32

it will return faster

Question 33

the key change precipitating swelling

Answer 33

formation of gaps in the endothelium. filtration exceeds absorption

Question 34

capillary filtration rate

Answer 34

hydraulic push- osmotic suction

Question 35

vasoactive agent that causes vasoconstriction

Answer 35

endothelin

Question 36

large arteries account for what percentage of SVR

Answer 36

2%

Question 37

poiseuilles law

Answer 37

8nl/piR^4

Question 38

Discuss factors that affect solubility of molecules and how they affect it

Answer 38

-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.

Question 39

Discuss factors that affect central venous pressure (CVP) (venous return), how they affect it and mechanisms involved.

Answer 39

-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.

Question 40

How do these factors affect Q and why?

Answer 40

Anything that reduces venous return will reduce SV and, thus, Q and vice versa.

Question 41

Consider the physiological regulation of solute transfer. Identify and discuss numerous factors/mechanisms that contribute to the marked increase in solute transfer during exercise.

Answer 41

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.

Question 42

Also, explain how endurance training increases the rate of diffusion of solutes from blood to muscle.

Answer 42

Endurance training increases capillary density which shortens diffusion distance and increases surface area for diffusion