Cardiac Pharmacology

Question 1

Where are the high pressure baroreceptors located?

Answer 1

Carotid sinus

Aortic arch

Question 2

Where are the low pressure baroreceptors located?

Answer 2

Right atrium: at junction of SVC & IVC

Left atrium: junction of 4 pulmonary veins

Question 3

What does stimulation of Vagal C fibers cause?

Answer 3

Bradycardia, hypotension, brief apnea

Question 4

What is the Bezold-Jarisch reflex?

Answer 4

Fibers in endocardium touching each other (due to too much contraction) can increase vagal tone and try and decrease contractility

Question 5

Are baroreceptors more sensitive to rates of change or magnitude of change?

Answer 5

Rate of change

Question 6

What occurs when you have increased baroreceptor discharge?

Answer 6

Inhibit sympathetic discharge

Excite vagal innervation

Question 7

Sympathetic innervation to arterioles causes ______ and innervation to veins causes ______

Answer 7

Vasoconstriction, mild vasconstriction

Question 8

Sympathetic innervation to skeletal muscle arterioles causes ______

Answer 8

Cholinergic vasodilation

Question 9

Parasympathetic innervation to vasculature causes ______

Answer 9

Trick question! Nothing. There is no parasympathetic innervation to the vasculature

Question 10

How does vasodilation occur?

Answer 10

Withdrawal of sympathetic tone (dimmer switch)

Question 11

What are the clinical effects of increased baroreceptor discharge?

Answer 11

Vasodilation
Decreased blood pressure
Decreased heart rate
Decreased cardiac output

Question 12

What occurs to vessels with sympathetic withdrawal?

Answer 12

Decreased venous tone (Increased venous capacity)
Decreased arterial tone
Decrease in CO

Question 13

What occurs to vessels with increased sympathetic tone?

Answer 13

Increased mean arterial pressure
Increased venous tone
Increase in CO

Question 14

What occurs to the heart with sympathetic stimulation?

Answer 14

Chronotropy (heart rate increases)
Dromotropy (rate of conduction increases)
Inotropy (force of contraction increases)
Lusotropy (rate of relaxation increases)

Question 15

What occurs to the heart with parasympathetic stimulation?

Answer 15

Heart rate slowed

Decreased force of contraction

Question 16

Describe the pressor response?

Answer 16

Fall in MAP is sensed by arterial baroreceptors

Pressor response: sympathetic tone increases, causing increased CO and TPR and therefore increased MAP

Question 17

What is the effect of sympathetic increase in exercise on heart, veins, and arteries?

Answer 17

Heart - increased HR, increased SV
Veins - increased venous tone
Arteries - vasoconstriction except in muscle (vasodilation)

Question 18

What occurs in phase 1 of valsalva?

Answer 18

BP increase
HR decrease

Blood pressure rises at onset of straining due to increase in intrathoracic pressure
Baroreceptors fire, decreasing sympathetic tone and decreasing heart rate

Question 19

What occurs in phase 2 of valsalva?

Answer 19

BP decrease
HR increase

High intrathoracic pressure compresses veins, decreasing venous return to heart and decreasing cardiac output, causing blood pressure to drop
Decrease in pressure inhibits the baroreceptors, causing tachycardia and a rise in peripheral resistance

Question 20

What occurs in phase 3 of valsalva?

Answer 20

Glottis is opened
Transient decrease in BP

Intrathoracic pressure had decreased the amount of blood in peripheral vasculature
Once you release the strain, still have decreased amount of blood, therefore BP decreases transiently

Question 21

What occurs in phase 4 of valsalva?

Answer 21

BP increases
HR decreases

Intrathoracic pressure returns to normal and cardiac output is restored, but peripheral vessels are still constricted so BP rises above normal
BP increase stimulates baroreceptors, causing bradycardia
HR stays decreased for prolonged period

Question 22

Is syncope during physical activity benign?

Answer 22

NO

Question 23

What are the 3 presentations of neurocardiogenic syncope aka vasovagal syncope?

Answer 23

Cardioinhibitory - increased parasympathetic tone –> bradycardia
Vasodepresspr - decreased sympathetic tone –> hypotension
Mixed response of cardioinhibitory and vasodepressor

Question 24

What it the theory of how neurocardiogenic syncope occurs?

Answer 24

Sensory input via vagal afferents to Nucleus Tractus Solitarius
Causes sympathetic withdrawal - vasodepressor
Causes parasymapthetic tone - cardioinhibitory

Question 25

Describe a typical neurocardiogenic syncope episode?

Answer 25

Prolonged standing = venous pooling and decreased BP
Baroreceptors are inhibited by decreased BP and sympathetic tone increases
HR increases, contractility increases
Pressure receptors in heart are stimulated by excessive contractility, causing vagal efferent influence on heart and sympathetic withdrawal