3C - Regulation of Arterial BP

Question 1

Describe short term regulation for MAP.

• How quickly does it occur?
• Via what pathways?
• Main targets?

Answer 1

Occurs within seconds to minutes
Via the neuronal pathways
Mainly targets heart and blood vessels

Question 2

Describe long term regulation for MAP

• How quickly does it occur?
• Via what pathways?
• Main targets?

Answer 2

Occurs within hours to days
Via endocrine pathways
Mainly targets kidneys and blood vessels

Question 3

What receptor is key for short term regulation of MAP?

Answer 3

Baroreceptors - participating in baroreceptor reflexes

Question 4

Where are significant baroreceptors located?

Answer 4

Carotid sinus and Aortic arch

- Positioned right near the initial release of blood

Question 5

What nerves do the baroreceptors use to carry signals?

Answer 5

Glossopharyngeal (IX) and Vagus (X)

Question 6

To what part of the brain do baroreceptors carry signals to?

Answer 6

The medullary cardiovascular center of the Brainstem

Question 7

What does the medullary cardiovascular center do?

Answer 7

Makes decisions about how to respond to hypertension or hypotension
- Effects changes via SNS and ParaNS

A highly complex center consisting of “mini-centers”

Question 8

What can alter the sensitivity of baroreceptors?

Answer 8

Disease

Chronic hypertension can make it so that “abnormal” elevated blood pressure is seen as normal over time and the baroreceptors will act to maintain the higher bp.

Question 9

When BP increases, how will the cardioregulatory center respond?

• ParaNS, SNS, and vasoconstrictor nerves?
• HR and SV?
• Dilate or constrict?
• CO and TPR?

Answer 9

Increase ParaNS cardiac nerve activity
Decrease SNS cardiac nerve and vasoconstrictor nerve activity

Decreases HR and SV
Vasodilation

Decrease CO and TPR

Decreases BP back to normal

Question 10

When BP decreases, how will the cardioregulatory center respond?

• ParaNS, SNS, and vasoconstrictor nerves?
• HR and SV?
• Dilate or constrict?
• CO and TPR?

Answer 10

Increase SNS cardiac nerve and vasoconstrictor nerve activity
Decrease ParaNS cardiac nerve activity

Increase HR and SV
Vasoconstriction

Increase CO and TPR

Increases BP back to normal

Question 11

What are the three hormones critical for long-term regulation of MAP?

Answer 11

RAA (The RAA Pathway)

Renin, angiotensinogen, and angiotensin I

Question 12

Will an increase or decrease in blood pressure trigger the secretion of renin?

Answer 12

Decrease in blood pressure (decrease in renal perfusion pressure)

Question 13

What does renin do?

Answer 13

Catalyzes the conversion of angiotensinogen to angiotensin I

Question 14

What organ releases angiotensinogen?

Answer 14

The liver

Question 15

What is ACE?

Where does it function?

Answer 15

Angiotensin converting enzyme

Converts Angiotensin I into Angiotensin II

In the lungs

Question 16

What are Angiotensin II’s four primary effects?

Answer 16

1. Increase aldosterone release from adrenal glands
2. Vasoconstriction of arterioles (Increase BP)
3. Increase Na reabsorption of kidneys (Na-H exchange)
4. Increase ADH secretion (pituitary gland) - Increase Na reabsorption

Question 17

What is the most important physiologic stimulus for increasing ADH secretion?

Answer 17

Increased plasma osmolarity (solute level)

Essentially, decreases in extracellular fluid will cause a decrease in arterial bp that is sensed by baroreceptors

Question 18

Besides plasma osmolarity, what is another potent stimulus for ADH secretion?

Answer 18

Hypovolemia (volume contraction) - ex. due to hemorrhage

Question 19

What are the two effects of ADH?

Answer 19

1. Increase water reabsorption via the kidneys by activating V2 receptors
2. Act as a potent vasoconstrictor that increases TPR by activating V1 receptors on the arterioles (remember, MAP = CO X TPR)

Question 20

What is ANP?

When is ANP released?

Answer 20

Atrial natriuretic peptide

High atrial pressure

Question 21

What does ANP do?

Answer 21

1. Causes relaxation of vascular smooth muscle, which results in vasodilation and decreased TPR
2. The resulting vasodilation leads to increased Na+ and water excretion - reducing Na, ECF, and Blood volume

Question 22

What can cause the formation of tortuous/varicose veins?

Answer 22

Inefficient leaflet valves on venuous valves leading to pooled fluid in the veins

Can occur in individuals who stand for long durations of time

Question 23

Venous thrombo embolism - what is it?

Answer 23

Development of a thrombus in a vein, which can break away, becoming an embolus.

If it is in a vein, it can travel to the right side of the heart, which can go to the lungs - as a pulmonary embolis - and become trapped