Circulation 5

Question 1

Basal tone

Answer 1

Theoretical reference point. Amount of vascular contraction found under resting conditions without neural or hormonal influences

Question 2

Resting sympathetic tone

Answer 2

Amount of vascular constriction found under resting conditions as a result of tonic sympathetic nerve activity

Question 3

Resistance during sympathetic resting tone vs. basal tone

Answer 3

Higher due to presence of tonically- released norepinephrine

Question 4

Active vs. passive mechanisms

Answer 4

Active move it away from basal tone, whereas passive mechanisms move it toward basal tone

Question 5

Alpha receptors

Answer 5

Located on vascular smooth muscle; causes vasoconstriction. (Heart and brain have very few of these)

Question 6

Beta-1 receptors

Answer 6

Primary adrenergic receptor on cardiac muscle; stimulates heart rate and contractility

Question 7

Beta-2 receptors

Answer 7

Secondary adrenergic receptors on cardiac muscle that stimulates heart rate and contractility
Also located on vascular smooth muscle and causes vasodilation

Question 8

Cholinergic receptors

Answer 8

Muscarininc receptors stimulated by acetylcholine

Question 9

Parasympathetic fibers on blood vessels

Answer 9

Limited number of blood vessels; cerebral, viscera, genitalia, bladder, and large bowel
Causes vasodilation
NOT on skeletal muscle or cutaneous vessels

Question 10

Sympathetic cholinergic pathway

Answer 10

Postganglionic sympathetic fibers that release acetylcholine on effectors
Example: sweat glands of nonapical skin to indirectly induce vasodilation

Question 11

Baroreceptor reflex

Answer 11

A negative feedback loop to control arterial pressure

Question 12

Arterial baroreceptors play a key role in what?

Answer 12

Short-term adjustments of blood pressure in response to relatively abrupt changes in blood volume, cardiac output, or peripheral resistance

Question 13

Where are baroreceptors located?

Answer 13

In nerve terminals located in the walls of carotid sinus and aortic arch

Question 14

What is special about the tissue where baroreceptors are located?

Answer 14

The walls are relatively thinner, making them more sensitive to the changes in blood pressure

Question 15

Instead of “baroreceptors,” what are they actually?

Answer 15

Mechanoreceptors that sense the change in stretch of the vascular walls

Question 16

Where do the nerve fibers of the baroreceptors connect?

Answer 16

Join the glossopharygeal (carotid) and vagus (aortic) nerves to vasomotor centers in the medulla

Question 17

What happens with a decrease in arterial pressure as sensed by the baroreceptors?

Answer 17

Increased sympathetic activity (increased peripheral resistance, increased heart rate, and increased ventricular contractility) and decrease in parasympathetic activity (cessation of inhibition of heart rate)

Question 18

What happens with an increase in arterial pressure as sensed by baroreceptors?

Answer 18

The exact opposite of what happens during and increase in blood pressure (increased parasympathetic and decreased sympathethic)

Question 19

What are baroreceptors most responsive to?

Answer 19

More responsive to pulsatile (phasic) pressures, but still somewhat responsive to constant (static) pressures

Question 20

What happens in hypertension with baroreceptors?

Answer 20

Sensitivity decreases, so threshold is increased and receptors are less sensitive to changes in transmural pressure

Question 21

Peripheral chemoreceptors

Answer 21

Small, highly vascular bodies located in the region of the aortic arch and just medial to the carotid sinus at the bifurcation of the internal and external carotid arteries

Question 22

What activates peripheral chemoreceptors?

Answer 22

Low arterial PO2 and high arterial PCO2 as well as low pH

Question 23

Chemoreceptors are involved with which autonomic process?

Answer 23

Respiration

Also involved with the heart during severe hypoxia

Question 24

When the chemoreceptor signals go through the ninth and tenth cranial nerves to the medulla, what do they do?

Answer 24

Simulate efferent sympathetic or parasympathetic nerves to cause vasoconstriction or bradycardia

Question 25

What effect on the heart does hypoxia have, and why?

Answer 25

Induces tachycardia; increase in ventilation acts via stretch receptors to centrally inhibit efferent vagal nerve activity

Question 26

Hormonal control of the circulatory system

Answer 26

Renin-angiotensin-aldosterone (primary mechanism responsible for long-term regulation of blood pressure)

Question 27

What three effects does angiotensin II have?

Answer 27

1. Vasoconsriction of renal/systemic vessels
2. Increase in sodium resorption by release of aldosterone
3. Stimulates hypothalamus to release ADH and increase thirst

Question 28

Sympathetic stimulation from baroreceptors causes release of what substance from the kidneys?

Answer 28

Renin in the juxtaglomerular apparatus

Question 29

Renin has what effect in the kidneys?

Answer 29

Stimulates ACE to convert angiotensin I to angiotensin II