Long Term Control of Blood Pressure Flashcards
What does long term control of blood pressure revolve around?
Control of plasma volume by the kidneys
What are the 3 main hormonal systems involved in long term control of blood pressure?
Renin-angiotensin-aldosterone system
Antidiuretic factor (ADH, vasopressin)
Atrial natriuretic peptide
What is antidiuretic factor also known as?
ADH or vasopressin
What are some examples of the functions of the kidneys?
Excretion of waste products
Maintenance of ion balance
Regulation of pH
Regulation of osmolarity
Regulation of plasma volume
What is controlled to regulate mean arterial pressure in the long term?
Plasma volume
How do the kidneys regulate plasma volume?
1) Renal counter-current system creates a very high osmolarity outside the collecting duct
2) Control over Na+ transport determines how big that osmotic gradient is
3) Control over the permeability of the collecting duct to water determines if water follows that osmotic gradient or not
4) Hence you can control how much water is lost in the urine, and how much is retained

What determines how big the osmotic gradient between the collecting duct and outside it is?
Control over Na+ transport
What determines whether water follows the osmotic gradient of the collecting duct or not?
Control over the permeability of the collecting duct
What are the 2 things the collecting duct can be made to be?
Very permeable to water
Very impermeable to water
What does the kidney duct being very permeable to water result in?
Lots of water reabsorption, little urine and conserve plasma volume

What does the kidney’s collecting duct being very impermeable to water result in?
Little reabsorption, lots of urine and a reduction in plasma volume

What is diuresis?
Increased or excessive production of urine
What is increased or excessive production of urine called?
Diuresis
What are the 3 distinct hormonal processes that regulate the permeability of the collecting ducts, and in turn plasma colume?
Renin-angiotensin-aldosterone system
Antidiuretic factor
Atrial natriuretic peptide
What is renin produced by?
Juxtaglomerular (granule cells) of the kidneys
What is production of renin triggered by?
Activation of sympathetic nerves to juxtaglomerular apparatus
Decreased distension of afferent arterioles (known as the renal baroreflex)
Decreased delivery of Na+/Cl- through the tubule
What does renin do?
Converts inactive angiotensinogen to angiotensin I, which in turn is converted by angiotensin converting enzyme to angiotensin II

What catalyses the reaction of angiotensinogen to angiotensin I?
Renin
What catalyses the reaction of angiotensin I to angiotensis II?
Angiotensis converting enzyme
What are all of the things that production of renin is triggered by a sign of?
Low arteriolar pressure
What does angiotensin II do?
Stimulates release of aldosterone from the adrenal cortex
Increases release of vasopressin from the pituitary
Acts as a vasocontrictor
Where is aldosterone released from?
Adrenal cortex
Where is vasopressin released from?
Pituitary
What does aldosterone do?
Increases Na+ reabsorption in the loop of Henle
Therefore reduces diuresis and increases plasma volume
What does vasopressin do?
Increases water permeability of the collecting duct
Therefore reduces diuresis and increases plasma volume
Increases sense of thirst
What does aldosterone being a vasocontrictor allow it to do?
Increase total peripheral resistance
What do all of the things that angiontensin II does cause?
Increase in mean arteriolar pressure
What kind of system is the renin-angiotensin-aldosterone system?
Negative feedback
Why is the renin-angiotensin-aldosterone system a negative feedback system?
1) Multiple mechanisms detect any decrease in mean arteriolar pressure
2) Stimulates release of renin
3) Evokes multiple mechanisms to increase mean arteriolar pressure
What is antidiuretic hormone produced and released from?
Produced from hypothalamus
Released from posterior pituitary
What triggers the release of antidiuretic hormone?
Decrease in blood volume
Increase in osmolarity of interstitial fluid
Circulating angiotensin II
What is a decrease in blood volume detected by?
Cardiopulmonary baroreceptors
What is an increase in interstitial fluid osmolarity detected by?
Osmoreceptors in the hypothalamus
What are all of the things that trigger the release of antidiuretic hormone a sign of?
Low plasma volume and/or low mean arteriolar pressure
What does antidiuretic hormone do?
Increases permeability of collecting duct to water, therefore reducing diuresis and increases plasma volume
Causes vasocontriction (increases mean arteriolar pressure)
What kind of system is the release of antidiuretic hormone?
Negative feedback
How is the release of antidiuretic hormone a negative feedback system?
1) Multiple mechanisms detect any increase in mean arteriolar pressure
2) Stimulates release of vasopressin
3) Evokes multiple mechanisms that increase mean arteriolar pressure
What does ANP stand for?
Atrial natriuretic peptide
Where is atrial natriuretic peptide produced?
Produced in and released from myocardial cells in the atria
What triggers the release of atrial natriuretic peptide?
Increase distension of atrium, which is a sign of increased mean arteriolar pressure
What does the atrial natriuretic peptide do?
Increases excretion of Na+ (natriuresis)
Inhibits release of renin
Acts on medullary cardiovascular centres to reduced mean arteriolar pressure
What kind of system is the release of atrial natriuretic peptide?
Negative feedback system
How is the release of atrial natriuretic peptide a negative feedback system?
1) A mechanism that detects any increase in mean arteriolar pressure
2) Stimulates release of atrial natiuretic peptide (ANP)
3) Evokes multiple mechanisms which reduce mean arteriolar pressure
What is hypertension?
Persistant elevation of blood pressure
What is persistant elevation of blood pressure called?
Hypertension
What percentage of hypertension is classed as secondary?
5-10%
What is secondary hypertension?
Due to a known cause
What is primary hypertension?
Due to an unknown cause
What are examples of drugs used to treat hypertension?
Ca2+ channel antagonists
B-adrenoceptor antagonist
Thiazide diuretics
Angiontensin converting enzyme inhibitors