SS2. Cardio vascular system - Resistance

Question 1

Is there more resistance in larger or smaller tubes?

Answer 1

In smaller tubes.

Question 2

What do you have to know to calculate the resistance?

Answer 2

Length (L), radius (r) and viscosity (eta).

Question 3

What is the equation of measuring resistance (R)?

Answer 3

R = (8x L x eta) / pi x r^4.

Question 4

What can be seen to the arterioles with low resistance?

Answer 4

Vaso dilation.

Question 5

What can be seen to the arterioles with high resistance?

Answer 5

Vaso-constriction

Question 6

How can resistance be increased?

Answer 6

1) keep radius but longer, doubles resistance (not feasible)
2) Change the radius with help of smooth muscles around vessels, so half of what it was, where the resistance is 16x higher.

Question 7

How are vessels in a series calculated?

Answer 7

The resistances are added up.

e.g: Resistance of 5, 8 and 2. Rtotal = 5+8+2 = 15

Question 8

What happens when, in a series of vessels, one is clotted and halved in radius?

Answer 8

It increases the clotted vessel resistance 16x times.
e.g. Resistance: 2, 2 and 2. Clot in vessel 2:
2 + (2x16) + 2 = 36

Question 9

How is resistance in parallel calculated?

Answer 9

Vessels lay parallel (beneath) one another.
Rt = 1/ ((1/R1) + (1/R2) + (1/R3)) etc.
E.g: 1/ ((1/6 + 1/10 + 1/5) –> 1 / (5/30 + 3/30 + 6/30) = 1 / (14/30) = 30/14 = 2.1

Question 10

Is the total resistance less or more than any component?

Answer 10

It is always less.