Control of Peripheral Circulation

Question 1

What values can be used as preload?

Answer 1

EDV, EDP, LAP, RAP, pulmonary capillary pressure

Question 2

What is the little sharp blip in the curve of aortic pressure? What causes this?

Answer 2

Dicrotic notch; result of aortic valve closure where a small volume of aortic blood flows backward to fill the space behind the aortic valve leaflets as they close

Question 3

How can mean arterial blood pressure be calculated using Pulse pressure?

Answer 3

MABP= Diastolic pressure + (1/3) x pulse pressure

Question 4

Why is MABP not simply the average of diastolic and systolic blood pressures?

Answer 4

We spend more time in diastole

Question 5

Why is it important to have sufficient pressure in the aorta?

Answer 5

To provide sufficient blood flow to the systemic organs

Question 6

What serves as local (intrinsic) control for peripheral circulation?

Answer 6

Tissue cells, endothelium, vascular smooth muscle

Question 7

What exerts extrinsic control of peripheral circulation?

Answer 7

SNS and PSNS

Question 8

What ANS system has more influence over peripheral circulation?

Answer 8

SNS

Question 9

What is the capacity for cardiac output to increase?

Answer 9

CO can increase 4-fold overall

Question 10

What kind of vascular smooth muscle cells respond more to central (extrinsic) control?

Answer 10

Multiunit cells

Question 11

What type of peripheral circulation control is unitary vascular smooth muscle more sensitive to?

Answer 11

Local control

Question 12

What is the effect of Rho kinase phosphorylating MLC phosphatase?

Answer 12

It is inactivated, which leads to maintained smooth muscle contraction

Question 13

What does tone refer to in vessels?

Answer 13

The contractile state of the vessel

Question 14

How is myosin light chain kinase inhibited? What is the physiologic effect of this in blood vessels?

Answer 14

Phosphorylation by PKA, leading to vasodilation

Question 15

How does the sympathetic nervous system mediate vasodilation?

Answer 15

SNS activates PKA, which phophorylates MLCK and inhibits it

Question 16

In what type of cell are mechanical coupling-stretch activated Ca2+ channels found?

Answer 16

Unitary type smooth muscle cells

Question 17

How is membrane potential linked to force development?

Answer 17

Via a relationship between K+ channels and Ca++ channels: Opening K+ channels allows K+ efflux, decreasing the membrane potential, which closes the L-type voltage-gated Ca+ channels –> less Ca++ influx and less smooth muscle contraction

Question 18

How is smooth muscle contraction affected by ATP/ADP?

Answer 18

ADP opens K+ channels so that less contraction will occur to conserve energy

Question 19

How does the SNS mediate both vasoconstriction and vasodilation?

Answer 19

NE is released from nerves with binds to alpha adrenergic receptors, resulting in calcium inflex and contraction; Epinephrine released from the adrenal medula via SNS stimulation binds to beta 2 adrenergic receptors, causing phosphorylation of MLCK, relaxing smooth muscle tone

Question 20

What is the afferent limb of the baroreceptor reflex?

Answer 20

CN IX and CN X

Question 21

Where is the control center for the baroreceptor reflex?

Answer 21

Medulla

Question 22

How is vasodilation mediated by the PSNS? What vasodilations are under PNS control?

Answer 22

Vasodilation is mediated by NO and in the PSNS it controls coronary and cerebral vessels and erection

Question 23

How do local mechanisms affect blood flow?

Answer 23

Changing the radius of vessels

Question 24

What local factors mediate vasocontriction as a response to increased work of the tissue?

Answer 24

CO2, H+, K+, Lactic acid, adenosine

Question 25

What is reactive hyperemia?

Answer 25

A higher than normal blood flow that occurs transiently after the removal of any restriction that has caused a period of lower than normal blood flow

Question 26

What is active hyperemia?

Answer 26

Occurs in organs with a highly variable metabolic rate and results from local metabolic vasodilator feedback on arteriolar smooth muscle

Question 27

What caues reactive hyperemia?

Answer 27

Increased concentration of vasodilators in the interstitial space surrounding the vessel bc they are not being washed out with bf

Question 28

How is blood flow to a particular organ maintained during a sharp increase in blood pressure?

Answer 28

Increased vascular resistance via myogenic response and decreased vasodilator concentration

Question 29

What is the myogenic response of vascular smooth muscle?

Answer 29

When unitary smooth muscle is stretched, it wants to contract. As blood flow increases in a vessel, it stretches and opens Ca++ channels allowing for contraction, bringing blood flow back down

Question 30

How much blood flow does the brain receive?

Answer 30

750 mL/min

Question 31

What formula can be used to calculate a person's exact cardiac output?

Answer 31

CO= (MABP-RAP)/ SVR

Question 32

Unless explicitly stated what should the assumed value of RAP be?

Answer 32

0 mmHg

Question 33

What region/ oragn system receives the most blood flow during rest?

Answer 33

GI tract

Question 34

In what state are the kidneys most active?

Answer 34

Resting

Question 35

What is the best organ at local control? The 2nd best?

Answer 35

The brain; heart

Question 36

What is the impact on the exercise state on HR, CO, SV, EF, SVR, and MABP?

Answer 36

Increase in HR, CO, SV, EF; slight increase in MABP; decreased SVR

Question 37

How is stroke volume increased in the exercise state?

Answer 37

Increased contractility and the Frank-Starling mechanism

Question 38

How is GI blood flow affected in the exercise state? How is this response mediated?

Answer 38

GI blood flow is significantly decreased in the exercise state. SNS releases NE which binds to large amount of alpha receptors in vsm, increasing Ca++, leading to stonger contraction and vasoconstriction

Question 39

How does blood flow to the heart change in going from a resting state to an exercise state?

Answer 39

It increases in the exercise state

Question 40

Which organ system has the greatest capacity to increase its blood flow?

Answer 40

Skeletal muscle

Question 41

How does blood flow to the skin change in going from a resting state to an exercise state? What is the importance of this?

Answer 41

During exercise there is an increase in blood flow to the skin because the heat produced during exercise is dissapated through the skin

Question 42

What is the relative degree of SNS activation during the hemorrhage state compared to the exercise state?

Answer 42

Approximately the same

Question 43

What is the effect of hemorrhage on HR, CO, SV, pulse pressure, contractility, SVR, and MABP?

Answer 43

Decrease in CO, massive decrease in SV, weakened pulse pressure, increased contractility (compensatory), tremendous increase in SVR, slight decrease in MABP

Question 44

What can the tremendous increase in SVR during the hemorrhage state be attributed to?

Answer 44

Massive vasoconstriction occuring in the GI and renal systems and in skeletal muscle

Question 45

What is the blood flow to skin in the hemorrhage state relative to other states?

Answer 45

Decreased