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Renal Physiology: Regulation of Glomerular Filtration quiz #1

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  • What are the main internal and external mechanisms that regulate glomerular filtration rate (GFR) in the kidneys?
    Internal mechanisms include the myogenic mechanism and tubuloglomerular feedback, which are forms of renal autoregulation. External mechanisms include neural regulation (sympathetic nervous system) and the renin-angiotensin-aldosterone system (RAAS).
  • How does the myogenic mechanism help maintain a stable glomerular filtration rate (GFR) during normal fluctuations in blood pressure?
    The myogenic mechanism responds to changes in blood pressure by causing the afferent arteriole to contract when stretched (high blood pressure) and relax when not stretched (low blood pressure), thereby maintaining a consistent GFR.
  • Describe the role of macula densa cells in the tubuloglomerular feedback mechanism for regulating GFR.
    Macula densa cells detect changes in sodium chloride concentration in the filtrate. If NaCl is high (due to increased GFR), they release vasoconstrictors to constrict the afferent arteriole and lower GFR. If NaCl is low, they reduce vasoconstrictor release, allowing afferent arteriole dilation and increasing GFR.
  • What effect does sympathetic nervous system activation have on glomerular filtration rate (GFR), and why is this response important?
    Sympathetic activation causes vasoconstriction of both afferent and efferent arterioles, reducing GFR. This response minimizes fluid loss and preserves blood volume and pressure for vital organs during stress or emergency situations.
  • Explain how the renin-angiotensin-aldosterone system (RAAS) increases blood pressure and affects GFR.
    RAAS is activated by low blood pressure or sympathetic activity. Renin leads to the formation of angiotensin II, which causes systemic vasoconstriction, stimulates aldosterone release (increasing sodium and water reabsorption), and constricts the efferent arteriole, all of which raise blood pressure and help maintain or increase GFR.
  • What are the main internal and external mechanisms that regulate glomerular filtration rate (GFR) in the kidneys?
    Internal mechanisms include the myogenic mechanism and tubuloglomerular feedback (renal autoregulation), while external mechanisms include neural regulation (sympathetic nervous system) and the renin-angiotensin-aldosterone system (RAAS).
  • How does the myogenic mechanism help maintain a stable glomerular filtration rate (GFR) during normal fluctuations in blood pressure?
    The myogenic mechanism causes the afferent arteriole to contract when stretched by high blood pressure and relax when not stretched by low blood pressure, keeping GFR consistent.
  • Describe the role of macula densa cells in the tubuloglomerular feedback mechanism for regulating GFR.
    Macula densa cells detect changes in sodium chloride concentration in the filtrate; if NaCl is high, they release vasoconstrictors to constrict the afferent arteriole and lower GFR, and if NaCl is low, they reduce vasoconstrictor release, allowing dilation and increasing GFR.
  • What effect does sympathetic nervous system activation have on glomerular filtration rate (GFR), and why is this response important?
    Sympathetic activation causes vasoconstriction of both afferent and efferent arterioles, reducing GFR to minimize fluid loss and preserve blood volume and pressure for vital organs during stress.
  • Explain how the renin-angiotensin-aldosterone system (RAAS) increases blood pressure and affects GFR.
    RAAS is activated by low blood pressure or sympathetic activity, leading to renin release, formation of angiotensin II (which causes vasoconstriction and aldosterone release), increasing sodium and water reabsorption, raising blood pressure, and constricting the efferent arteriole to help maintain or increase GFR.