Blood Flow and Blood Pressure

Question 1

Which blood vessels alter their diameter to adjust blood supply?

Answer 1

Arterioles - this is an example of variable resistance

Question 2

Where does the circulatory system pass from arterial to venous system?

Answer 2

Capillary beds

Question 3

Which part of the circulatory system acts as a pressure reservoir to maintain blood flow during ventricular relaxation?

Answer 3

Systemic arteries

Question 4

Which part of the circulatory system acts as a volume reservoir and holds most of the blood at any given time?

Answer 4

Systemic veins

Question 5

Which vessels are elastic and why?

Answer 5

Arteries and veins - to accommodate high pressure blood

Question 6

Which vessels have a layer of smooth muscle and why?

Answer 6

Arteries, arterioles, and veins

To allow for vasodilation and vasoconstriction

Question 7

Metarterioles

Answer 7

Bypass channels for blood passing from arterioles to venules when precapillary sphincters constrict blood flow to capillaries

Question 8

Precapillary sphincters

Answer 8

Close off capillaries in response to local signals

Question 9

By what mechanism is blood returned to the heart in the venous system?

Answer 9

Skeletal muscle pumps and valves that prevent the back flow of blood when the muscle releases

Respiratory pump - creation of negative thoracic cavity pressure upon inhalation decreases pressure in the large central vein which increases flow in the direction of the heart

Question 10

How do arteries & arterioles function as pressure reservoirs?

Answer 10

Expand upon ventricular contraction to store pressure in their elastic walls
Upon ventricular relaxation, elastic recoil of arteries propels blood to systemic circulation. Movement of arteries back o resting diameter increases the pressure in the arteries which pushes blood forward.

Question 11

Pulse pressure

Answer 11

Systolic - diastolic pressure

Question 12

Mean arterial pressure

Answer 12

Diastolic pressure - (1/3)pulse pressure

Question 13

How to measure BP

Answer 13

Inflate cuff until blood flow stops
Release pressure in cuff until korotkoff sounds = systolic pressure
Continue releasing pressure in cuff until sounds disappear = diastolic pressure

Question 14

How does blood volume affect mean arterial blood pressure?

Answer 14

Fluid intake increases blood volume which increases BP

Fluid loss may be passive or regulated by kidneys - lowers blood volume, decreases BP

Question 15

How do changes in cardiac output affect mean arterial blood pressure?

Answer 15

Cardiac output = heart rate x stroke volume

Increasing cardiac output increases BP

Question 16

Active hyperemia

Answer 16

Blood flow to capillary beds regulated by local signals such as metabolic vasodilator during exercise

Question 17

Reactive hyperemia

Answer 17

Hyperemia that follows a period of decreased blood flow usually due to an occlusion

Metabolic vasodilators accumulate in the ECF due to an occlusion

Question 18

Autonomic nervous system control of vasodilation/constriction

Answer 18

Arterioles have sympathetic (epi/norepi) and parasympathetic receptors (ACh)

In sympathetic signaling, the amount of epi/norepi determines whether vasoconstriction or dilation will occur. Signaling rate increases cause constriction while signaling rate decreases cause dilation.

Question 19

At rest, approx. how much blood goes to the kidneys and liver/digestive tract?

Answer 19

20% to kidneys

25% to digestive tract and liver

Question 20

How does constriction of one blood vessel affect flow in neighboring vessels?

Answer 20

Since total flow in a closed system must be equal, if one vessel is constricted, the other vessels compensate with higher flow rates.

Question 21

Baroreceptor reflex

Answer 21

Sensors in carotid and aortic arteries sense pressure changes via mechanoreceptors which balances parasympathetic and sympathetic NS

Standing up shifts to sympathetic signaling —> increase in HR

Question 22

Sympathetic neurons stimulate which parts of the circulatory system

Answer 22

SA node, ventricles, arterioles, veins

Question 23

Sympathetic stimulation of arteriolar smooth muscle affects what aspect of blood pressure?

Answer 23

Vasoconstriction/dilation and thus peripheral resistance

Question 24

Sympathetic stimulation of ventricular myocardium affects

Answer 24

Cardiac output

Question 25

How do materials enter and exist the capillary bed?

Answer 25

Leaky junctions where water and small dissolved solutes bass through the basement membrane of the capillary

Transcytosis where proteins and macromolecules cross the endothelium

Fence started pores that allow larger molecules to pass through the basement membrane - kidneys, intestines

Question 26

Filtration

Answer 26

Movement of fluid and solutes out of the blood plasma into the interstitial fluid

Question 27

Absorption

Answer 27

Movement of fluid and solutes out of the interstitial fluid into the blood plasma

Question 28

Net pressure in systemic capillaries is composed of what types of pressure?

Answer 28

Hydrostatic pressure - colloid osmotic pressure

Hydrostatic pressure is the pressure that forces fluid out of the capillary

Colloid osmotic pressure is the pressure of proteins within the capillary that fulls fluid into the capillary

Question 29

Positive net pressure (hydrostatic pressure > colloid osmotic pressure) indicates?

Answer 29

Net filtration

Question 30

Negative net pressure (hydrostatic pressure < colloid osmotic pressure) indicates?

Answer 30

Net absorption

Question 31

Function of the lymphatic system

Answer 31

Return excess filtered fluid and proteins to the circulatory system

Take fat front he small intestine to the circulatory system

Captures and destroys pathogens with the immune system