Final answer:
Constriction of the efferent arteriole increases glomerular blood pressure and GFR, which is the opposite effect of afferent arteriole constriction. The myogenic response and tubuloglomerular feedback are mechanisms that help maintain a stable GFR despite fluctuations in blood pressure.
Step-by-step explanation:
The question asks about the effect of efferent arteriole constriction on glomerular blood pressure and glomerular filtration rate (GFR). Constriction of the efferent arteriole does indeed increase pressure in the glomerulus because it restricts the outflow of blood, which in turn, raises GFR. Conversely, constriction of the afferent arteriole would decrease the blood flow into the glomerulus and lower GFR. The fine-tuning of GFR is also facilitated by mechanisms like the myogenic response and tubuloglomerular feedback. For example, when blood pressure rises, the myogenic mechanism causes smooth muscle cells in the afferent arteriole to contract, mitigating the rise in glomerular pressure. Additionally, the tubuloglomerular feedback involves macula densa cells of the distal tubule monitoring Na+ concentration; changes here can signal the afferent arteriole to alter its tone to maintain a stable GFR.