Long term control of blood pressure Flashcards
What is long term control of blood pressure regulated by?
Control of plasma volume by the kidney
NOT baroreflex
How many hormone systems regulate long term control?
3
- Renin-angiotension-aldosterone system
- Antidiuretic factor (ADH, vasopressin)
- Atrial natriuretic peptide
What are the functions of the kidney system? (gwan for the craic)
- Excretion of waste products
- Maintenance of ion balance
- Regulation of pH
- Regulation of osmolarity
- Regulation of plasma volume
How does kidney regulate plasma volume?
-Making collecting duct very permeable to water will result in lots of water reabsorption, little urine, and conserve plasma volume
Where is renin produced?
From the juxtaglomerular (granule cells) of the kidney
What triggers renin production?
- Activation of sympathetic nerves to the juxtaglomerular apparatus- decreased MAP
- Decreased distension of afferent arteioles (renal baroreflex)- Decreased MAP
- Decreased delivery of Na+/Cl- through the tubule- Decreased MAP
What does Renin do?
-Converts inactive angiotensinogen to angiotensin 1
What is angiotensin 1 converted to and how?
Converted to angiotensin 2 by angiotensin converting enzyme
What does angiotensin 2 do? (3 things)
- Stimulates release of aldosterone from adrenal cortex
- Increased release of ADH
- Vasocontriction
What does aldosterone do?
- Increases NA+ Reabsorption in the loop of Henle
- Reduces diuresis and increases plasma volume
What does ADH do?
- Increases water permeability of the collecting duct
- Therefore reduces diuresis and increase plasma volume
- Increases sense of thirst
Explain how renin-angiotensin -aldosterone system is a negative feedback system?
- Multiple mechansims detect decrease in MAP
- Stimulates release of renin
- Evokes multiple mechanisms which increase MAP
Where is ADH made?
-Synthesised in hypothalamus
Where is ADH Released from?
Posterior pituitary
What triggers ADH release?
- A decrease in blood volume (as sensed by cardiopulmonary baroreceptors and relayed via medullary cardiovascular centres)
- An increase in osmolarity of interstitial fluid (as sensed by osmoreceptors in the hypothalamus)
- Circulating angiotensin 2 (triggered by the renin angiotensisn- aldosterone system)
What does ADH do?
- Increases permeability of collecting duct
- Causes vasoconstriction
What is an alternative name foe ADH?
-Vasoopressin
What is ANP?
Artrial natriuretic peptide
Where is ANP produced?
-Produced in, and released from myocardial cells in the atria
What triggers release of ANP?
Increased distension of the atrium
What does ANP do?
- Increase excretion of Na+
- Inhibits the release of renin
- Acts on medullary CV centres to reduce MAP
What is hypertension?
Increased blood pressure
What percentage of cases are secondary hypertension?
-5-10%
How is hypertension treatment?
- Ca2+ channel antagonists
- B-adrenoreceptor antagonists
- Thiazide diuretics
- Angiotensin converting enzyme inhibitors
Why are Ca2+ channels blocked to treat hypertension?
-Stops hard contraction of heart and contraction of smooth muscle
Why are B1 receptors blocked to treat hypertension?
Beta-1 is activated by symp system to increase heart rate and CO
What does thiazide diuretics do to treat hypertension?
Acts on sodium transporter increases rate - more wee
How do angiotensin converting enzyme inhibitors work to treat hypertension?
Stops angiotensin 2 ever being created
And blocks angiotensin 2 receptors are also blocked (just incase)
