Global Regulation Mechanisms

Question 1

Why is the vascular resistance associated with resting sympathetic tone higher than basal arterial tone?

Answer 1

This is due to the presence of tonically-released NE. Basal tone is just a theoretical reference point that we don’t normally operate at.

Question 2

What is the difference between active and passive mechanisms of regulating vascular tone?

Answer 2

Passive mechanisms induce a change in vascular resistance back toward the basal arterial tone; active mechanisms induce a change away from it.

Question 3

The baroreceptor reflex is an example of which physiological process?

Answer 3

a negative feedback loop

Question 4

Which adrenergic receptor causes vasoconstriction and which causes vasodilation?

Answer 4

alpha receptors cause vasoconstriction; beta-2 receptors cause vasodilation

Question 5

What is the difference between adrenergic and cholinergic receptors?

Answer 5

• adrenergic: sympathetic, metabotropic, & stimulated by isoproterenol, epi, and norepi
• cholinergic: parasympathetic, muscarinic, & stimulated by acetylcholine

Question 6

True or false: parasympathetic fibers innervate a large number of blood vessels.

Answer 6

false; parasympathetics actually innervate only a limited number of blood vessels (cerebral and some visceral- splanchnic, genitalia, bladder, and large bowel)

Question 7

True or false: skeletal muscle and cutaneous vessels are NOT innervated by parasympathetic nerves.

Answer 7

true

Question 8

What is the sympathetic cholinergic pathway, and why does it exist?

Answer 8

• describes postganglionic sympathetic fibers that release ACh on effectors (ex: sweat glands of non-apical skin and salivary glands to indirectly induce vasodilation)
• exists because sometimes want to increase blood flow to areas that are not innervated by parasympathetic fibers, such as the skin during exercise

Question 9

What are the main locations of baroreceptors in the body?

Answer 9

in the aortic arch and carotid sinus

Question 10

Arterial baroreceptors play a key role in responding to short-term adjustments of blood pressure in response to relatively abrupt changes in what?

Answer 10

blood volume (ie, hemorrhage), CO, peripheral resistance, and position

Question 11

What do baroreceptor nerve terminals respond to?

Answer 11

vascular stretch (mechanoreceptors)

Question 12

How do baroreceptors behave in response to increases and decreases in blood pressure?

Answer 12

• increase in BP=more firing

- decrease in BP=less firing

Question 13

What is the blood pressure threshold for activation of sinus nerve impulses?

Answer 13

~50 mmHg (at or below 50 mmHg, there are no sinus nerve impulses that happen throughout systole)

Question 14

Are baroreceptors more responsive to pulsatile (phasic) pressures or constant (static) pressures?

Answer 14

pulsatile pressures because they are rapid and noticeable

Question 15

What is our most powerful vasoconstrictor in the body?

Answer 15

angiotensin II

Question 16

Hormonal control mitigates things like_________.

Answer 16

dehydration, fluid loss, hypovolemia, and congestive heart failure

Question 17

Is the renin-angiotensin-aldosterone system effective for hemorrhage patients?

Answer 17

no, since the system takes a while (days) to kick in; hemorrhage patients need an immediate increase in blood volume and blood pressure

Question 18

What are chemoreceptors activated by?

Answer 18

primarily low arterial PO2 but also may be affected by high arterial PCO2 and low arterial pH (acidosis conditions)

Question 19

Do chemoreceptors have a more pronounced effect on the cardiovascular or respiratory system?

Answer 19

respiratory system!

Question 20

When do chemoreceptors become relevant in the cardiovascular system?

Answer 20

peripheral chemoreceptors only play a role during severe hypoxia

Question 21

Does hypoxia induce tachycardia or bradycardia? Why?

Answer 21

It induces tachycardia because the increase in ventilation acts via stretch receptors in the lung to inhibit efferent vagal nerve activity, resulting in an increase in HR to delivery oxygen