Long Term control of Blood Pressure Flashcards
Why dont people think baroreceptors are the main thing regulating long term BP?
They took them out of dogs and they stayed regulated around a normal value, even if theyre BP graphs did get a lot messier now they couldnt control short term BP
Basically, how do the kidneys regulate plasma volume?
They control how much water is lost in the urine and how much you reabsorb
In what way do the kidneys control water reabsorption?
By altering the osmotic gradient between the collecting duct and the arterioles. And the ducts permeability to water
How is the osmotic gradient controlled?
By altering the amount of Na+ pumped out the duct into the arterioles
What do we call the system by which the kidneys regulate plasma volume?
The renal counter-current system
What do we call it when very little water is reabsorped and you have loads of dilute urine?
Diuresis
What 3 hormone systems regulate the renal counter-current system?
- The renin-angiotensin-aldosterone system
- Antidiuretic factor (ADH, vasopressin)
- Atrial/Brain Natriuretic Peptide (ANP/BNP)
What cells produce renin?
juxtaglomerular (granule) cells of the kidney
Where are juxtaglomerular cells found?
Around the afferent & efferent arteriole clsoe to the glomerulus
What do we call the capsule of the glomerulus?
Bowman’s Capsule
What 3 things signal the juxtaglomerular cells to release renin?
Symp. innervation signals a lower MAP
Decreased distension in the afferent arteriole signals lower MAP
The macula densa signal a reduced MAP
How do the macula densa detect a lower MAP, and what the fuck are they?
Macula Densa is/are a set of eithelial cells in the ascending loop of henle that border on the juxtaglomerular cells on the outside.
They detect a lower flow of Na+ and Cl- ions through the ascending loop of henle.
What does renin do?
Converts angiotensinogen to angiotensin I
How does angiotensin I become angiotensin II?
By Angiotensin converting enzyme
What does angiotensin II do?
Increases ADH release from the pituitary gland
Causes vasconstriction -> TPR increase -> MAP increase
Increases aldosterone release form adrenal cortex
Whats the function of Anti-diuretic hormone?
Increases the water permeability of the collecting duct so more is reabsorped and plasma volume increases
It also increases thirst
What does aldosterone do to increase MAP?
Increases Na+ reabsorption in the loop of Henle.
- > increased osmotic gradient
- > increased water reabsorption
- > increased plasma volume
Summarize the renin-angiotensin-aldosterone system:
A negative Feedback System
Multiple mechanisms detect MAP dropping
-> Stimulates Relase of Renin
-> Multiple mechanisms increase MAP
Where is ADH produced?
ADH is made in the hypothalalmus but released from the posterior pituitary
When is ADH released?
- Circulating angiotensin II
- Blood volume decreases
(detected by cardiopulmoanry baroreceptors & relayed by medullary baroreceptors…
…also detected by osmoreceptors in hypothalamus which sense increase ISF osmolarity.)
What does ADH do?
Increases water permeability of the collecting duct so more is reabsorped and blood volume increases.
Where are atrial & brain natriuretic peptide produced?
The myocardial cells of the atria and ventricles respectively
When are ANP/BNP released?
When theres increased distension of atria & ventricles, a sign of abnormally high MAP
What do ANP & BNP do?
- decrease Na+ reabsorption leading to deceased water reabsorption (natriuresis)
- Inhibits renin release (inhibiting the renin-angiotensin-aldosterone system)
- Acts on the medullary CV centres to reduce MAP
Summarize the ANP/BNP function:
A negative feedback system
- > 2 mechanisms detect a MAP drop
- > ANP & BNP released
- > 3 mechanisms act to decrease MAP
How many cases of hypertension are secondary (i.e. explained)?
5-10%
What do we call unexplained cases of hypertension?
Primary or essential
Name 5 treatments for hypertension?
- Ca2+ channel antagonists
- B-adrenoceptor antagonists
- Thiazide diuretics
- angiotensin converting enzyme inhibitors
- angiotensin II antagonists
How do B-adrenoceptor antagonists work?
They block B1 receptors in the heart causing a lowered HR & contractility -> lowers CO -> lowers MAP
How do thiazide diuretics work?
They increase water excretion to lower MAP
What do angiotensin converting enzyme inhibitors and angiotensin II antagonists do?
They both block the production or function of angiotensin II, lowering MAP
How do Ca2+ channel antagonists treat hypertension?
They block calcium channels in the cardiac muscle, reducing the force of contraction and so SV, therefore CO and MAP are reduced.
In summary what three hormones act on the kidney to control blood pressure?
- Renin-Angiotensin-Aldosterone system
- Antidiuretic Hormone (ADH, vasopressin)
- Atrial/Brain Natriuretic Peptide (ANP/BNP, Atriopeptin)
