USMLE Step 1 Renal Physiology 1 Review 58 15 Renal Autoregulation

USMLE Step 1 Renal Physiology 1 Review 58 15 Renal Autoregulation

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Play USMLE Audio MP3 58 15 Renal Autoregulation Below

Begin 58 15 Renal Autoregulation Transcription

Within what range of mean arterial blood pressures do the glomerular filtration rate and renal plasma flow remain constant?

  • The glomerular filtration rate and renal plasma flow remain constant within a mean arterial pressure range of about 80 to 180 mmHg.

What kidney system functions to maintain a constant glomerular filtration rate? It starts with RA.

  • Renal autoregulation functions to maintain a constant glomerular filtration rate.

What does renal autoregulation adjust in order to counteract events such as an increased blood pressure that would tend to cause the GFR to change?

  • Resistance in the afferent arteriole is adjusted.

When blood pressure increases what change does the autoregulatory system make in afferent arteriolar resistance?

  • Afferent arteriolar resistance is increased by the autoregulatory system when blood pressure increases.

What are the two mechanisms thought to be responsible for renal autoregulation? They start with MM and TGFM.

  • The myogenic mechanism and the tubuloglomerular feedback mechanism are thought to be responsible for renal autoregulation.

What muscle is stimulated by the myogenic mechanism as blood pressure increases?

  • Arteriolar smooth muscle.

What does this counteract?

  • The tendency for flow to increase.

An increase in sodium chloride delivery at what nephron structure causes the tubuloglomerular feedback mechanism to send a signal to the afferent arteriole of the same nephron? It starts with MD.

  • Increased sodium chloride delivery at the macula densa causes the tubuloglomerular feedback mechanism to send a signal to the afferent arteriole of the same nephron.

And what is the result of this signal?

  • Vasoconstriction of the afferent arteriole.

And what is reduced by the vasoconstriction?

  • The signal nephron GFR.

Student doctor, please pause the tape and summarize what we’ve discussed about renal autoregulation, the myogenic mechanism, and the tubuloglomerular feedback mechanism.

The glomerular filtration rate and renal plasma flow remain constant within a mean arterial pressure range of about 80 to 180 mmHg. The renal autoregulatory system functions to maintain a constant glomerular filtration rate. Renal autoregulation adjusts the resistance in the afferent arterioles in order to counteract events, such as increased blood pressure, that would tend to cause the GFR to change. When blood pressure increases, afferent arteriolar resistance is increased. The myogenic mechanism and the tubuloglomerular feedback mechanism are though to be responsible for renal autoregulation. As blood pressure increases the myogenic mechanism stimulates the arteriolar smooth muscle thereby counteracting the tendency for flow to increase. Increased sodium chloride delivery at the macula densa causes the tubuloglomerular feedback mechanism to send a signal to the afferent arteriole of the same nephron. This results in vasoconstriction of the afferent arteriole which reduces the single nephron GFR.

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