Vascular Resistance

Question 1

Vascular resistance eqn

Answer 1

R=8Ln/(pi)r^4

Question 2

Factors affecting vascular resistance (R)

Answer 2

-length of the artery
-viscosity of blood
-radius of the artery

Question 3

Affect of length on vascular resistance

Answer 3

-can change over lifetime with growth
-greater resistance with greater length

Question 4

Affect of viscosity on vascular resistance

Answer 4

-increased viscosity results in increased resistance

Question 5

Affect of radius on vascular resistance

Answer 5

-decrease radius will result in increased resistance

Question 6

Vascular tone

Answer 6

-the amount of vasoconstriction experienced by a blood vessel relative to its maximally relaxed or dilated state

Question 7

Why does radius have a greater impact on resistance than the other factors?

Answer 7

-radius is exponential to power of 4 (not 1:1)
-on a beat to beat basis, viscosity and length does not change however radius/diameter does change a lot

Question 8

Vascular tone and diameter

Answer 8

-high vascular tone, more constricted vessel (high pressure)
-low vascular tone, more dilated vessel (low pressure)

Question 9

Smooth muscle of arteries

Answer 9

-smooth muscle wraps intima/endothelium and contracts to decrease lumen diameter
-vascular smooth muscle will exhibit some tone (constriction) during a relaxed state so that dilation possible

Question 10

Degree of vasculature tone depends on the organ

Answer 10

-tone, resistance, and blood flow are organ dependent
-arteries supplying heart or skeletal muscle have huge capacity to dilate
-arteries to kidney and brain don’t necessarily have huge capacity to dilate. Don’t want to increase blood volume in the brain much because it is encased and cannot handle extra pressure

Question 11

Vasoconstrictors and vasodilators

Answer 11

-there are extrinsic and intrinsic factors which help regulate blood pressure
-Extrinsic factors (ex.neurohumoral factors) help serve to maintain systemic blood pressure
-Intrinsic factors (myogenic, endothelial, local substances, metabolic byproducts, hypoxia, etc.) are important for blood flow regulation within an organ

Question 12

Exercise, vasoconstriction, and blood supply to organs (skeletal muscle vs. kidney)

Answer 12

-during exercise, CO increases (sympathetic increasing), SV increasing, preload and venous return increases.
-During renal circulation, constriction occurs during exercise (sympathetic) which reduces blood flow
-during skeletal circulation, also receiving constriction but it is being outcompeted by other aspects (hypoxia, CO2, shear, Ach spill over, H+, ATP, etc.) that cause dilation of arteries, reducing resistance and increasing blood flow

Question 13

Cerebral circulation and exercise

Answer 13

-does not change with exercise. Cerebral circulation is kept constant
-highly regulated to keep it the same. but there are different neurons firing and blood will be shifted towards areas of the brain that are more active (motor regions) during exercise
Ex. hard to do math while exercising because different parts of brain