3C - Regulation of Arterial BP Flashcards
Describe short term regulation for MAP.
- How quickly does it occur?
- Via what pathways?
- Main targets?
Occurs within seconds to minutes
Via the neuronal pathways
Mainly targets heart and blood vessels
Describe long term regulation for MAP
- How quickly does it occur?
- Via what pathways?
- Main targets?
Occurs within hours to days
Via endocrine pathways
Mainly targets kidneys and blood vessels
What receptor is key for short term regulation of MAP?
Baroreceptors - participating in baroreceptor reflexes
Where are significant baroreceptors located?
Carotid sinus and Aortic arch
- Positioned right near the initial release of blood
What nerves do the baroreceptors use to carry signals?
Glossopharyngeal (IX) and Vagus (X)
To what part of the brain do baroreceptors carry signals to?
The medullary cardiovascular center of the Brainstem
What does the medullary cardiovascular center do?
Makes decisions about how to respond to hypertension or hypotension
- Effects changes via SNS and ParaNS
A highly complex center consisting of “mini-centers”
What can alter the sensitivity of baroreceptors?
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.
When BP increases, how will the cardioregulatory center respond?
- ParaNS, SNS, and vasoconstrictor nerves?
- HR and SV?
- Dilate or constrict?
- CO and TPR?
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
When BP decreases, how will the cardioregulatory center respond?
- ParaNS, SNS, and vasoconstrictor nerves?
- HR and SV?
- Dilate or constrict?
- CO and TPR?
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
What are the three hormones critical for long-term regulation of MAP?
RAA (The RAA Pathway)
Renin, angiotensinogen, and angiotensin I
Will an increase or decrease in blood pressure trigger the secretion of renin?
Decrease in blood pressure (decrease in renal perfusion pressure)
What does renin do?
Catalyzes the conversion of angiotensinogen to angiotensin I
What organ releases angiotensinogen?
The liver
What is ACE?
Where does it function?
Angiotensin converting enzyme
Converts Angiotensin I into Angiotensin II
In the lungs
What are Angiotensin II’s four primary effects?
- Increase aldosterone release from adrenal glands
- Vasoconstriction of arterioles (Increase BP)
- Increase Na reabsorption of kidneys (Na-H exchange)
- Increase ADH secretion (pituitary gland) - Increase Na reabsorption
What is the most important physiologic stimulus for increasing ADH secretion?
Increased plasma osmolarity (solute level)
Essentially, decreases in extracellular fluid will cause a decrease in arterial bp that is sensed by baroreceptors
Besides plasma osmolarity, what is another potent stimulus for ADH secretion?
Hypovolemia (volume contraction) - ex. due to hemorrhage
What are the two effects of ADH?
- Increase water reabsorption via the kidneys by activating V2 receptors
- Act as a potent vasoconstrictor that increases TPR by activating V1 receptors on the arterioles (remember, MAP = CO X TPR)
What is ANP?
When is ANP released?
Atrial natriuretic peptide
High atrial pressure
What does ANP do?
- Causes relaxation of vascular smooth muscle, which results in vasodilation and decreased TPR
- The resulting vasodilation leads to increased Na+ and water excretion - reducing Na, ECF, and Blood volume
What can cause the formation of tortuous/varicose veins?
Inefficient leaflet valves on venuous valves leading to pooled fluid in the veins
Can occur in individuals who stand for long durations of time
Venous thrombo embolism - what is it?
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
