pressure gradients and blood flow

Question 1

what are arteries

Answer 1

low resistance vessels conducting blood to various organs with little loss in pressure

they act as pressure reservoirs for maintaining blood flow between ventricular contractions

Question 2

what are the arterioles responsible for

Answer 2

major site for resistance to blood flow and responsible for pattern of blood flow distribution
also regulation of arteriol blood pressure

Question 3

what are capillaries the site of

Answer 3

exchange between blood and tissue

Question 4

what are veins

Answer 4

low resistance vessels for blood to flow back to heart, their capacity for blood is adjusted to facilitate flow

Question 5

what is meant by the term “hydrostatic pressure”

Answer 5

the pressure exerted by a fluid

Question 6

in terms of pressure how does blood flow in vascular systme

Answer 6

from a region of higher pressure to lower pressure

Question 7

how can you determine the flow rate

Answer 7

you need to know the pressure difference between 2 points and also the resistance to flow

Question 8

what is meant by resistance

Answer 8

A measure of how difficult it is for blood to flow between two points at any given pressure difference.

a measure of the friction impeding flow.

Question 9

what is meant by driving force

Answer 9

the pressure generated by contractions of the heart

Question 10

how do we calculate the flow rate of blood through a vessel

Answer 10

F = delta P/R

F = flow rate of blood through a vessel (l/min)
deltaP = pressure gradient (mmHg)
R = resistance of blood vessels (mmHg·min/l)

Question 11

what does resistance to blood flow depend on

Answer 11

1) viscosity of the blood (designated )
2) vessel length (designated L)
3) vessel radius (designated r) MAJOR DETERMINANT (small change bring about noticeable change in flow)

Question 12

Poiseuille equation

Answer 12

flow rate = pie delta Pr*4 / 8nL

deltaP = pressure gradient
r = radius of vessel
n = viscosity
L = length of vessel

Question 13

• A two-fold change in radius will produce a 16-fold change in flow

Question 14

Why do arterioles create significant resistance to blood flow?

Answer 14

The small radius of arterioles offers considerable resistance to blood flow.

Question 15

How does arteriolar resistance affect blood pressure as it flows through arterioles?

Answer 15

The high resistance in arterioles causes a major drop in mean blood pressure, from 93 mmHg to 37 mmHg.

Question 16

Why is the pressure drop across arterioles physiologically important?

Answer 16

his pressure gradient helps drive blood from the heart to the tissue capillary beds.

Question 17

How does arteriolar resistance affect capillary pressure?

Answer 17

It converts the pulsatile arterial pressure into a steady, non-fluctuating pressure in the capillaries.

Question 18

what happens during vasoconstriction of the smooth muscle of the arteriole

Answer 18

decreased radius, increased resistance =
decreased local blood flow

Question 19

what happens during vasodilation of the smooth muscle of the arteriole

Answer 19

increased radius, decreased resistance =
increased local blood flow

Question 20

what is the smooth muscle sentistive too

Answer 20

local chemical changes and certain circulating hormones

Question 21

what is the structure of the arteriolar wall

Answer 21

thick layer of smooth muscle richly innervated by nerves of sympathetic nervous system

Question 22

What is vascular tone, and what causes it?

Answer 22

Vascular tone is the partial constriction of arteriolar smooth muscle. It is caused by:

Myogenic activity
Sympathetic activity

Question 23

Why is vascular tone important for blood flow?

Answer 23

Vascular tone allows for changes in arteriolar contraction:

Vasodilation (decrease in contraction)
Vasoconstriction (increase in contraction)
This ability to adjust contraction levels significantly affects resistance to blood flow (Poiseuille’s law).