TGF Afferent Constriction — FRCA Primary MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: B — Constricting the afferent arteriole to reduce GFR (negative feedback)
TGF: increased NaCl delivery to the macula densa (indicating high GFR) triggers release of ATP and adenosine which cause afferent arteriolar constriction reducing GFR back towards normal. Conversely decreased NaCl delivery (low GFR) causes afferent vasodilation and renin release. This is a negative feedback mechanism maintaining stable single-nephron GFR.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist