Regulation of Peripheral and Coronary Circulation

Question 1

What is compliance? Is the aorta compliant?

Answer 1

Compliance is how easily a structure can stretch to accomodate an increase in volume. Yeah the aorta is compliant.

Question 2

The aorta expands during ventricular systole, storing _______ _______ in its elastic walls. During diastole the aorta’s elastic recoil continues pushing blood forward into the circulatory system.

Answer 2

pressure energy

Question 3

The aorta’s compliance ________ the upswings and downswings of pressure and helps maintain continuous flow in the capillaries.

Answer 3

dampens

Question 4

What vascular disease would greatly reduce the compliance of a great artery such as the aorta?

Answer 4

atherosclerosis

Question 5

Is neural control the fastest acting of all the mechanisms that control BP?

Answer 5

Yeah

Question 6

In which vessel layer do baroreceptors mainly run through?

Answer 6

adventitia

Question 7

How do baroreceptors detect pressure changes?

Answer 7

Indirectly by sensing stretch of the cell membrane.

Question 8

In which two vessels are baroreceptors mainly localized?

Answer 8

The aortic arch and in the carotid bifurcation

Question 9

How does baroreceptor cell membrane stretch affect AP frequency?

Answer 9

Increased stretch = increased AP frequency

Question 10

Are baroreceptors multipolar, unipolar, or bipolar?

Answer 10

bipolar

Question 11

Carotid baroreceptors’ cell bodies are located in the ______ ______ outside the brainstem and they travel in the ___________ nerve to the carotid artery. The other end of the nerve projects to the ________.

Answer 11

cell bodies are located in the petrosal ganglion outside the brainstem and they travel in the glossopharyngeal nerve to the carotid artery. The other end of the nerve projects to the medulla.

Question 12

Aortic baroreceptors’ cell bodies are located in the ______ ______ near the brainstem and they travel in the ______ nerve to the aorta. The other end of the nerve projects to the ________ where they synapse in the ______ ______ ______ which modulates cardiovascular activity via ANS connections with the heart and vessels.

Answer 12

cell bodies located in the nodose ganglion. Travel in the vagus nerve. Other end projects to the medulla where they synapse in the nucleus tractus solitaries.

Question 13

Describe baroreceptor AP frequency with each heart beat.

Answer 13

AP frequency is high at the beginning of each ventricular systole and adaptation occurs quickly, lowering AP frequency.

Question 14

Baroreceptor AP firing is most sensitive to changes in blood pressure between ____mmHg and ____mmHg. Therefore this is the BP range in which the system is most effective.

Answer 14

75 and 150

Question 15

Name four physiologic changes that occur when baroreceptors tell the medulla that BP is too high.

Answer 15

1. Decreased B1 receptor activation at the SA node and myocardial cells.
2. Increased muscarinic Ach receptor activation in the SA node.
3. Decreased alpha1 receptor activation of vessels.
4. Increased venous capacitance –> decreased venous return –> decreased filling pressure of the heart –> decreased stroke volume and contractility (Starling law).

Question 16

Low pressure baroreceptors exist in which three structures?

Answer 16

atria, ventricles, and pulmonary vessels.

Question 17

A constant low-level background of sympathetic outflow from the spinal cord generates ________ _____ in vascular smooth muscle and cardiac tissue that maintains normal BP.

Answer 17

sympathetic tone

Question 18

Arteriolar constriction/dilation is under _____ control (not ANS control).

Answer 18

local

Question 19

What two structures assist arterioles in distributing flow between different areas of the same capillary bed?

Answer 19

precapillary sphincters and metarterioles

Question 20

What are the two systems of autoregulation of the arterioles and precapillary sphincters?

Answer 20

1. Myogenic mechanism

2. Dilator metabolite mechanism

Question 21

Describe the myogenic mechanism of autoregulation at the arteriolar level.

Answer 21

Increased venous smooth muscle stretch –> opening of stretch-sensitive channels –> Na+ and Ca2+ influx –> depolarization –> more Ca2+ influx (through L-type) –> vasoconstriction

Question 22

Describe the dilator metabolite mechanism of autoregulation at the arteriolar level.

Answer 22

Increased blood flow –> dilution of vasodilating metabolites –> inhibition of tonic dilating effect –> vasoconstriction

Question 23

How does a decrease in p02 cause smooth muscle relaxation in systemic arteries and arterioles? Does the same thing happen in pulmonary vessels?

Answer 23

Intracellular Ca2+ regulators are very sensitive to changes in O2 levels such that when O2 drops, so does intracellular [Ca2+] –> no muscle contraction (vasodilation).

Pulmonary vessels CONSTRICT in response to hypoxia.

Question 24

Adenosine, a byproduct of metabolism, is a potent _______ that acts through purinergic receptors.

Answer 24

vasodilator

Question 25

Which four major forces determine capillary blood flow? (In/out of capillary)

Answer 25

1. Capillary BP (Pc) 2. Blood oncotic pressure (pp) 3. Interstitial hydrostatic pressure (Pi) 4. Interstitial oncotic pressure (pi)

Question 26

At the arterial end of the capillary, _________ pressure contributes to a net outward force of ~9mmHg and at the venous end of the capillary, _______ pressure contributes to a net inward force of ~9mmHg.

Answer 26

hydrostatic at the arterial end, osmotic at the venous end.

Question 27

Imbalances in Starling forces can lead to ______ or a decrease in extracellular fluid (dehydration).

Answer 27

edema

Question 28

Is there a large pressure drop from the capillaries to the vena cavae?

Answer 28

No, only about 15mmHg

Question 29

Venous smooth muscle is arranged _______ and has compliant connective tissue to allow veins to function as variable _______ that can store large volumes of blood.

Answer 29

muscle is arranged helically, veins are variable capacitors.

Question 30

How does venous smooth muscle affect the heart's stroke volume and contractility?

Answer 30

Contraction of venous smooth muscle leads to an increase of blood volume return to the heart, increasing filling pressure, and increasing stroke volume and contractility.

Question 31

Pain from coronary ischemia is called ______.

Answer 31

angina

Question 32

What are the three major determinants of myocardial work (and thus its O2 requirement)?

Answer 32

1. Afterload (arterial pressure) 2. Stroke volume 3. Heart rate

Question 33

What is the only way to increase O2 delivery to the heart muscle?

Answer 33

Vasodilation of the coronary arterioles and small arteries increases coronary blood flow.

Question 34

How are are the effects of sympathetic stimulation of a-1 receptors on coronary arteries overridden when an increase in cardiac output is needed?

Answer 34

The effect of adenosine (as a byproduct of increased myocardial metabolism) acting on purinergic receptors on the coronary arteries (autoregulatory control) greatly overrides the a-1 stimulation to cause dilation of the arteries.

Question 35

Does perfusion of the heart muscle happen largely during systole, or diastole? How does the heart cope with increased heart rates?

Answer 35

It happens during diastole because contraction pinches off the coronary arteries. Aortic pressure during diastole is crucial to perfusing the coronary arteries and anything that lowers aortic pressure (such as aortic regurgitation or atherosclerosis) will compromise coronary blood flow.