Urinary: LTReg Flashcards
What is the short term regulation of blood pressure?
Baroreceptor reflex
- Adjust sympathetic and parasympathetic inputs to the heart to alter the cardiac output
- Adjust sympathetic input to peripheral resistance vessels to alter TPR
What are the hormonal responses to low renal perfusion?
- Renin-angiotensin aldosterone system
- Sympathetic nervous system
- Prostaglandins
- ADH
What is the long term regulation of blood pressure?
Neurohormonal resposes to affect salt and water balance
What factors stimulate the renin release?
- Reduced NaCl delivery to the macula densa of distal tube
- Reduced perfusion pressure in the kidney causes the release of renin
- Sympathetic stimulation (B1) of the juxtaglomerular increases release of renin
Where is renin released from?
Juxtagomerular cells of the afferent arteriole in response to reduced perfusion pressure and stimulation by the sympathetic nervous system
What are the direct actions of angiotensin 2 on the kidney?
- Vasoconstriciton of the efferent and to a lesser extent the afferent arteriole
- Enhanced sodium reabsorption at the proximal collecting tubule by stimulation of Na-H(NHE3) exchanger in the apical membrane
- Increase in mesangial matrix
- Increase in mesangial cell proliferation
- Glomerular permeability to proteins
What are some indirect effects of angiotensin 2 on the kidney to control blood pressure?
- Release of aldosterone
- Release of ADH
What are the actions of aldosterone on the kidney?
Acts on principal cells of distal convoluted tubule and collecting ducts to:
- Stimulate Na+ and therefore water reabsorption
- Activates apical Na+ channel and apical K+ channel
- Increases basolateral Na+ extrusion via Na/K/ATPase
What are the actions of the sympathetic nervous system in response to low blood pressure?
- Reduction of the renal blood flow by vasocontrcitin of arterioles and decrease in the GFR
- Activates apical Na/H exchanger and basolateral Na/K ATPase in proximal collecting tubule
- Stimulates renin release from JG cells
What are effects of prostaglandins in the kidney?
- Causes vasodilation of the afferent arteriole
- Enhances renin release
Which hormones trigger the release of prostaglandins in the kidney?
- Angiotensin 2
- Noradrenaline
- Anti diuretic hormone
What is the net effect of the interaction of prostaglandins and the RAAS system?
- Systematic vasoconstriction
- Vasoconstriction of the efferent artriole
- Vasodilation of the afferent arteriole
- The GFR is preserved as a result
What is action of ADH?
- Formation of concentrates urine by retaining water to control the plasma osmolarity. Reabsorption of water is increased at the distal nephron. AQ2
- Vasoconstriction
What stimulate release of ADH?
- Increase in plasma osmolarity stimulates release of ADH
- Severe hypovolaemia stimulates release of ADH
What are the 2 major actions for atrial natriuretic peptide?
- Causes vasodilation of afferent arteriole and constriction of efferent in order to increase excretion of sodium
- Inhibits Na+ reabsorption especially in the collecting duct causing natriuresis
What inhibits ANP release?
Low circulating volume in order to support blood pressure
What is hypertension?
-Persistent increase in blood pressure
What is pressure natriuresis?
- Increasing blood pressure gradually resets the kidneys for salt concentrations and water volume and this means the regulatory mechanisms aren’t working as well.
- It is thought to be one of the causes of hypertension
What is hypertension?
-Persistent increase in blood pressure
140/90
What are some causes of secondary hypertension?
- Reno-vascular hypertension
- Coarctation of the aorta
- Primary hyperaldosteronism (Conn’s syndrome)
- Cushing’s syndrome
What are the 2 main causes of renovascualr disease?
- Atheroma
- Fibromuscular dysplasia
What is the mechanism behind renovascular disease?
-Renal artery stenosis which is narrowing of the renal artery
Why does renovascular disease lead to hypertension?
- Lack of blood supply to the kidney causes the kidney to sense hypovolaemia in the body
- This means that it triggers changes in order to increase the blood pressure
- This causes hypertension because the mechanism are constantly trying to increase blood pressure even though the blood is normotensive
What happens with unilateral renal artery stenosis?
- One kidney triggers mechanism to increase blood pressure by activating the RAAS system because it senses hypovolaemia
- One kidney works normally and sense the increase in sodium so acts to excrete the sodium. It suppresses the RAAS system.
- Net effect is hypertension with no fluid overload and salt as the kidney that works normally excrete the extra salt and water
What happens with bilateral renal artery stenosis?
- RAAS system is activated
- Kidney does not get rid of the extra salt and water and hypertension persists
- Risk of acute pulmonary oedema
What is coarctation of aorta?
Stenosis in the aorta vessel
What is the mechanism that causes hypertension due coarctation of the aorta?
- Less renal blood flow
- Kidney triggers the RAAS system as it senses hypovolaemia wrongly
What is primary hyperaldosteronism and the causes?
Excess secretion of aldosterone
- Adrenal adenoma
- Adrenal hyperplasia
What are the clinical features of primary hyperaldosteronism?
- Hypertension
- Can cause hypokalemia
What is used in the diagnosis of the the primary hyperaldosteronism?
- Aldosterone:renin ratio is high
- Look for adenoma with a CT scan and remove if present
- If no adenoma treat by blockage of aldosterone
What is the effect of excess liquorice on the blood pressure?
- Blocks an enzyme
- Cortisol can’t be converted to cortisone
- Cortisol interacts with mineralocorticoid receptor triggering the same effect as aldosterone
- Blood pressure increase
- Similar mechanism as Cushing’s
What is chronic kidney disease?
Irreversible and sometime progressive loss of renal function over a period of months to years. Renal injury can cause renal tissue to be replaces by extracellular matrix in response to tissue damage
Leads to hypertension and fluid overload (oedema)
Which ion primarily affects the effective circulating volume?
- Sodium ions
- Water in the extracellular fluid compartment depends on the sodium ion content.
What would be the effect of changing the amount of sodium that is ingested (without kidney action)?
- Amount of water in the extra cellular fluid would change
- Effective circulating volume would also change
- Blood pressure also changes as a result
Why does the kidney Na+ excretory rates have to vary over a wide range?
- The kidney needs to match excretion of sodium to ingestion to remain sodium balance.
- Urinary water excretion can be varied physiologically
What can you do to increase the plasma volume?
-Add an isosmotic solution
Adding water alone affect plasma osmolarity
How can we add or remove an isosmotic solution?
- Movement of osmoles
- Water will follow
What can affect the proximal tubule Na+ reabsorption?
- Changes in osmotic pressure and hydrostatic pressure
- RAAS system can stimulate proximal tubule Na+ reabsorption
What causes pressure natriuresis and pressure diuresis when renal blood pressure increases?
- Increased renal artery blood pressure
- Reduced number of Na-H and reduced Na-K ATPase activity in proximal tubule
- Causes reduction in sodium and water reabsorption in proximal tubule
- Leads to pressure natriuresis and pressure diruresis together in order for the ECF volume to be decrease and diminish the BP rise.
