Vascular System

Question 1

Major functions of the vascular system

Answer 1

Regulating BP and distributing blood flow.

Question 2

Arteries

Answer 2

• Large radii, high elasticity
• low-resistance tubes
• “Pressure reservoirs”

Question 3

Systolic Pressure

Answer 3

max arterial pressure reached during the peak of ventricular contraction/ejection.

Question 4

Compliance

Answer 4

change in volume / change in pressure

Higher compliance = more stretch

Question 5

Diastolic Pressure

Answer 5

Min arterial pressure reached just prior to ventricular ejection.

Question 6

Arterial Blood Pressure

Answer 6

Systolic Pressure / diastolic pressure

Question 7

Pulse Pressure

Answer 7

systolic Pressure - diastolic pressure

Question 8

Mean arterial pressure (MAP)

Answer 8

average pressure driving blood to the tissues over cardiac cycle

Question 9

Factors affecting magnitude of the pulse pressure:

Answer 9

• SV
• Speed of ejection of the stroke volume
• Arterial compliance

Question 10

Arterioles Function

Answer 10

• Determine relative blood flow to organs at any given MAP
• Determine MAP

Question 11

Arteriole diameter is controlled by:

Answer 11

• Neural
• Hormonal
• Local chemicals

Question 12

Flow-Pressure Relationship

Answer 12

Flow = change in pressure / resistance

Question 13

Vasoconstriction of arterioles = increases resistance; if pressure remains constant what happens to blood flow to tissues/organs?

Answer 13

Decreased

Question 14

Active hyperemia

Answer 14

increase in blood flow due to increased metabolic activity.

Ex: blood flow to skeletal muscles increases while exercising due to vasodilation.

Question 15

Flow Autoregulation

Answer 15

the automatic adjustment of blood flow despite changes in pressures.

Ex: kidneys reacts to reduction in BF, due to diseased renal artery, by vasodilating its own arterioles.

Question 16

Reactive Hyperemia

Answer 16

a temporary, significant increase in blood flow to an organ, following release of complete blood flow occlusion.

Ex: increase in BF to the arm, during a BP reading, after a brachial artery has been squeezed shut by the BP cuff.

Question 17

Response to injury

Answer 17

chemicals released by injured cells or found in the blood cause vasodilation of blood vessels in injured area.

Ex: this occurs during the inflammatory repsonse to injury or infection.

Question 18

Nitric Oxide is an example of a paracrine hormone secreted by endothelial cells. What is the function?

Answer 18

Induces relaxation or contraction.

Question 19

Gas and nutrient exchange occurs at what level of vasculature?

Answer 19

Capillaries

Question 20

Venules

Answer 20

• large capacity for blood (capacitance vessel)
• some permeability to macromolecules
• Site of migration of leukocytes into tissues during inflammation and infection.

Question 21

Veins

Answer 21

Thin and compliant, blood reservoirs

Question 22

Mechanisms that aid in venous return

Answer 22

• Respiratory pump
• Muscular pump
• Smooth muscle

Question 23

Respiratory pump

Answer 23

increased venous pressure d/t diaphragm contraction = increased abdominal pressure which compressed abdominal veins to return blood to heart.

Question 24

Muscular Pump

Answer 24

muscles contract and squeeze veins resulting in movement of blood towards heart.

Ex: calf pumps

Question 25

Smooth Muscle

Answer 25

In veins is under Sympathetic NS control and contracts when stimulated = venous contraction which promotes venous return.

Question 26

How is MAP calculated?

Answer 26

Cardiac Output x Total Peripheral Resistance

Question 27

Where in the vascular system does the majority of resistance occur that effects MAP?

Answer 27

arterioles

Question 28

Baroreceptor reflex

Answer 28

a group of homeostatic responses to changes in arterial blood pressure (MAP) that provide short term regulation of BP

Question 29

How are baroreceptor reflexes initiated?

Answer 29

arterial stretch/pressure receptors

Question 30

Baroreceptor reflexes are under control of

Answer 30

autonomic regulation

Question 31

Arterial Baroreceptors are stretch/pressor receptors - where are they located?

Answer 31

carotid sinuses and aortic arch

Question 32

Where is sensory input from the arterial baroreceptors input?

Answer 32

In the medullary cardiovascular control center

Question 33

How does the action potential firiting frequency change with response to pressure?

Answer 33

- Increased firing of AP due to elevated MAP. - Decreased firing rate of AP due to reduced MAP

Question 34

How can PT help to challenge the strength of the baroreceptor reflexes?

Answer 34

slow positional changes

Question 35

What are some potential causes of hypotension?

Answer 35

- Hemorrhage - Decreased cardiac contractility - Strong emotion - Massive release of endogenous substances (allergic reaction)

Question 36

Why is the skeletal muscle pump in the LE's important?

Answer 36

It reduces the effects of gravity (pressure) and aids in return of blood to heart.