Low blood pressure cascade
- Low blood pressure cascade
When blood pressure falls many physiological cascades commence in order to return the blood pressure to a more appropriate level.
# The blood pressure fall is detected by a decrease in blood flow and thus a decrease in GFR.
# Decrease in GFR is sensed as a decrease in Na+ levels by the Macula Densa.
# The Macula Densa cause an increase in Na+ reabsorption, which causes water to follow in via osmosis and leads to an ultimate increase in plasma volume. Further, the macula densa releases adenosine which causes constriction of the afferent arterioles
# At the same time the Juxtaglomerular cells sense the decrease in blood pressure and thus release Renin.
# Renin acts on Angiotensinogen (inactive form) and converts it to Angiotensin I (active form)
# Angiotensin I flows in the bloodstream until it reaches the capillaries of the lungs where Angiotensin Converting Enzyme (ACE) acts on it to convert it intoAngiotensin II.
# Angiotensin II is a vasoconstrictor which will increase bloodflow to the heart and subsequently the preload, ultimately increasing the cardiac output.
# Angiotensin II also causes an increase in the release of Aldosterone from the Adrenal glands.
# Aldosterone further increases the Na+ and H2O reabsorption in the Distal Convoluted Tubule of the nephron.
References
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