Cardiovascular Receptors (Middlekauff)

Question 1

Where are arterial baroreceptors located?

Answer 1

Adventitial walls (outside) of aortic arch and carotid sinus

Question 2

How do arterial baroreceptors travel back to the brain?

Answer 2

Cranial nerves IX and X

Synapse in the brain in the NTS (nucleus of solitary tract)

Question 3

What do arterial baroreceptors sense?

Answer 3

Stretch, or CHANGES in BP (not BP itself)

Question 4

How do arterial baroreceptors affect the NTS?

Answer 4

BP increases –> stretch occurs –> baroreceptors fire –> inhibit NTS –> inhibit sympathetic nerve activity from CNS –> decrease in HR, etc

OR

BP decreases –> decreased stretch –> decrease in baroreceptor firing –> stimulate NTS –> stimulate sympathetic nerve activity from CNS –> increase HR, etc

Question 5

What exactly do arterial baroreceptors do?

Answer 5

Buffer ACUTE changes in BP

If they’re cut, you have same mean BP (because that’s determined by bigger things like kidneys’ RAAS, ADH, ANP, etc) but you have more fluctuation around that mean BP because you can’t buffer the changes when they occur

Question 6

Where are cardiopulmonary baroreceptors located?

Answer 6

They are unmyelinated and located in (posterior inferior) atria and left ventricle

Question 7

How do cardiopulmonary baroreceptors travel back to the brain?

Answer 7

Cranial nerve X

Synapse in the brain in the NTS (nucleus of solitary tract)

Question 8

What do cardiopulmonary baroreceptors sense?

Answer 8

Stretch induced by changes in left ventricular filling pressures (LVEDP = left ventricular end diastolic pressure) and ventricular contractility

Question 9

How do cardiopulmonary baroreceptors affect the NTS?

Answer 9

Pressure increases –> stretch occurs –> baroreceptors fire –> inhibit NTS –> inhibit sympathetic nerve activity from CNS –> decrease in HR, etc

OR

Pressure decreases –> decreased stretch –> decrease in baroreceptor firing –> stimulate NTS –> stimulate sympathetic nerve activity from CNS –> increase HR, etc

Question 10

Why are cardiopulmonary baroreceptors so important?

Answer 10

They are important regulators of renal blood flow and volume regulation

Question 11

Where are the arterial chemoreceptors located?

Answer 11

Small, highly vascularized nodules in carotid and aortic bodies

Question 12

How do arterial chemoreceptors travel back to the brain?

Answer 12

Cranial nerves IX and X

Synapse in the brain in the NTS (nucleus of solitary tract)

Question 13

What do the arterial chemoreceptors sense?

Answer 13

Changes in the blood: CO₂, O₂, pH

(Hypoxemia, hypercapnia, acidosis)

Question 14

How do arterial chemoreceptors affect the NTS?

Answer 14

O₂ decreases –> increased chemoreceptor firing –> stimulate NTS –> increased vagal actibity causes bradycardia –> increased sympathetic activity causes RAAS to be activated, respiratory center stimulated

Question 15

Arterial chemoreceptor effects on the body when low O₂

Answer 15

Decrease HR

Renal vasoconstriction

Increase RAAS

Vasoconstrict smooth muscle

Increase tidal volume

Vasoconstrict and venoconstrict in splanchnic circulation

Question 16

Lung inflation reflex

Answer 16

When tidal volume increases –> pulmonary stretch receptors activate lung inflation reflex –> withdrawal of vagal activity –> increase HR

WINS over arterial chemoreflex trying to decrease HR!

Question 17

Dive reflex

Answer 17

Initiated by ice cold water touching face –> vagal nerve activity increases –> HR decreased, increased sympathetic output (vasoconstriction) to renal, splanchnic and muscle tissues

1) Works with arterial chemoreceptors to let diving animals decrease metabolic/O₂ demands and stay underwater longer
2) Can be used in humans to terminate supraventricular tachycardia

Question 18

Where are muscle metaboreceptors located?

Answer 18

Lightly myelinated and unmyelinated type III and IV nerve endings located in skeletal muscle

Question 19

How do muscle metaboreceptors travel back to the brain?

Answer 19

Sympathetic afferent nerve fibers go to spinal column

From spinal column, first synapse is in NTS

Question 20

What do the muscle metaboreceptors sense?

Answer 20

Ischemic metabolides:

Interstitial K+

Acidosis

Hyperosmolarity

Hypoxia

Adenosine

(Overall sensitive to uner-perfusion of working muscle)

Question 21

How do muscle mechanoreceptors affect the NTS?

Answer 21

Ischemic metabolites generated –> muscle metaboreceptors increase firing –> sympathetic activity increases and vagal activity decreases –> increased HR, renal vasoconstriction and activation of RAAS, etc. –> BP maintained and directs blood flow to working muscle

Question 22

Systems affected by arterial baroreceptor induced sympathetic stimulation

Answer 22

Heart: HR up, contractility up, SV up

Kidney: Vasoconstriction, RAAS up

Muscle: Vasoconstriction

Splanchnic: Vasoconstriction, venoconstriction

Question 23

Systems affected by cardiopulmonary baroreceptor induced sympathetic stimulation

Answer 23

Muscle: Vasoconstriction

Kidney: Vasoconstriction, RAAS up

Skin: Vasoconstriction

Question 24

Systems affected by arterial chemoreceptor induced sympathetic stimulation

Answer 24

Heart: wants to decrease HR (however, Lung inflation reflex decreases vagal actvity and wins over and increases HR!)

Kidney: Vasoconstriction, RAAS up

Muscle: Vasoconstriction

Lungs: Increase tidal volume

Splanchnic: Vasoconstriction, venoconstriction

Question 25

Systems affected by muscle metaboreceptor induced sympathetic stimulation

Answer 25

Heart: HR up, contractility up

Kidney: Vasoconstriction, RAAS up

Muscle: Vasoconstriction

Splanchnic: Vasoconstriction, venoconstriction