estion. 1) In the myogenic mechanism of renal autoregulation: A) renin causes co
ID: 3512009 • Letter: E
Question
estion. 1) In the myogenic mechanism of renal autoregulation: A) renin causes contraction of macula densa cells to increase GFER B) smooth muscle in afferent arterioles triggers vasoconstriction to decrease GFR. C) norepinephrine causes vasoconstriction of afferent arterioles to decrease GFR D)atrial natriuretic peptide causes relaxation of mesangial cells to increase GFR. E) angiotensin causes dilation of the proximal and distal convoluted tubules. 2) The function of atrial natriuretic peptide in renal autoregulation of GFR is to stimulate: A) renin secretion. B) conversion of angiotensin I to angiotensin C) relaxation of glomerular mesangial cells. D) constriction in afferent and efferent arterioles. E) reabsorption of sodium ions. 3) ALL of the following are mechanisms of renal autoregulation of GFR EXCEPT: A) sympathetic stimulation of afferent arterioles. B) the action of angiotensin on afferent and efferent arterioles. C) the action of ANP on mesangial cells. D) vasoconstriction in response to stretching of afferent arteriole walls E) secretion of ADH in response to increased osmolarity of blood. 4) The surface of glomerular capillaries available for filtration is regulated by: A) mesangial cells. B) macula densa cells C) juxtaglomerular cells. D) renin. E) ADHExplanation / Answer
Myogenic mechanisms in the kidney are part of the autoregulation mechanism which maintains a constant renal blood flow at varying arterial pressure. Concomitant autoregulation of glomerular pressure and filtration indicates regulation of preglomerular resistance.
The myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow within the blood vessel constant.
The smooth muscle of the blood vessels reacts to the stretching of the muscle by opening ion channels, which cause the muscle to depolarize, leading to muscle contraction. This significantly reduces the volume of blood able to pass through the lumen, which reduces blood flow through the blood vessel. Alternatively when the smooth muscle in the blood vessel relaxes, the ion channels close, resulting in vasodilation of the blood vessel; this increases the rate of flow through the lumen.
This system is especially significant in the kidneys, where the glomerular filtration rate (the rate of blood filtration by the nephron) is particularly sensitive to changes in blood pressure. However, with the aid of the myogenic mechanism, the glomerular filtration rate remains very insensitive to changes in human blood pressure.
So, the option B is most prominent in question 1.
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