Blood-Brain Barrier and Cerebral Perfusion Practice Test

Low adrenergic signaling allows the glymphatic system to work more efficiently, because reduced norepinephrine during sleep expands the brain’s interstitial space and enhances convective CSF-ISF exchange along perivascular pathways. This means waste clearance, including metabolites like beta-amyloid, is increased during sleep when adrenergic tone is low. During wakefulness, higher adrenergic signaling constricts these spaces and dampens glymphatic flow, so clearance is reduced. Therefore, the statement that the glymphatic system is more active during sleep best fits what adrenergic signaling does to this clearance pathway.