How does autoregulation occur by the myogenic mechanism?
Increased blood pressure increases stretch in afferent arteriole, this opens non-specific cation channels leading to depolarisation. Calcium channels open causing afferent arterioles to contract.
What is the tubuloglomerular feedback mechanism of autoregulation?
Increased blood pressure causes increased filtration which results in increase NaCl deliver to Macula densa cells which release ATP that has a local paracrine affect resulting in vasoconstriction of afferent arterioles.
Where are macula densa cells present?
What is the metabolic hypothesis of autoregulation?
Renal tissue metabolites maintain a degree of vasodilation, increased perfusion pressure results in increased blood flow and leaching of these metabolites. Hence, there is a decrease in vasodilation (vasoconstriction).
Other than renal tissue metabolites, what else may act as vasodilators?
Humoral factors derived from vascular endothelium e.g. NO.
What things can override autoregulation of renal blood flow?
Nerves Hormones e.g. angiotensin II
What affect does sympathetic nerve activity have on renal blood flow?
It causes afferent and (to some degree) efferent arteriolar constriction.
What affect affect does adrenaline have on renal blood flow?
Similar affect to sympathetic nerves - afferent arteriolar constriction.
What affect does the hormone angiotensin II have on renal blood flow?
It causes vasoconstriction, particularly of efferent arterioles.
Which locally produced substances cause vasodilation when released under conditions such as haemorrhage?
Prostaglandins and nitric oxide.
What do prostaglandins and nitric oxide protect kidneys from?