Passage
At the blood-brain barrier, the cerebral spinal fluid (CSF) is separated from lymphatic circulation by epithelial cells bound by tight junctions. Within the central nervous system (CNS) , CSF surrounds and protects the brain and spinal cord and is believed to function in waste clearance for the CNS analogous to the role of the lymphatic system within the body.This waste clearance system has been dubbed the "glymphatic system." Although the mechanism of clearance is largely unknown, specialized glial cells known as astrocytes appear to modify the interstitial volume between neurons. This increase in interstitial volume allows for greater CSF flow, which increases the efficiency of neurotoxic clearance. Waste products removed from the brain include metabolic products such as ammonia and harmful compounds such as amyloid proteins.Recent advances in imaging technology suggest that interstitial clearance may be modified during sleep. To test this hypothesis, researchers indirectly studied changes in interstitial volume by measuring the percentage of CSF coverage in animal models during the first hour of sleep and again during the first hour of wakefulness (Figure 1) .
Figure 1. Percentage of CSF coverage of interstitial space during sleep and wakefulness
-Given the role of the glymphatic system outlined in the passage, chronic sleep deprivation might contribute to the development of which of the following disease states?

Question

Passage
At the blood-brain barrier, the cerebral spinal fluid (CSF) is separated from lymphatic circulation by epithelial cells bound by tight junctions. Within the central nervous system (CNS) , CSF surrounds and protects the brain and spinal cord and is believed to function in waste clearance for the CNS analogous to the role of the lymphatic system within the body.This waste clearance system has been dubbed the "glymphatic system." Although the mechanism of clearance is largely unknown, specialized glial cells known as astrocytes appear to modify the interstitial volume between neurons. This increase in interstitial volume allows for greater CSF flow, which increases the efficiency of neurotoxic clearance. Waste products removed from the brain include metabolic products such as ammonia and harmful compounds such as amyloid proteins.Recent advances in imaging technology suggest that interstitial clearance may be modified during sleep. To test this hypothesis, researchers indirectly studied changes in interstitial volume by measuring the percentage of CSF coverage in animal models during the first hour of sleep and again during the first hour of wakefulness (Figure 1) .

Figure 1. Percentage of CSF coverage of interstitial space during sleep and wakefulness
-Given the role of the glymphatic system outlined in the passage, chronic sleep deprivation might contribute to the development of which of the following disease states?

Quizplus · Accepted Answer

11ecba2d_0f33_087a_a3bf_a504abcc0e8d_MD0008_00 Alzheimer's disease is a progressive neurodegenerative brain disease characterized by the presence of plaques composed of beta amyloid proteins and neurofibrillary tangles composed of tau proteins. The presence of these amyloid beta plaques and neurofibrillary tangles are toxic to neurons and lead to cell death. Because beta amyloid and tau proteins are cleared by the glymphatic system during sleep, chronic sleep deprivation could lead to a buildup of these proteins and contribute to the development of Alzheimer's disease. Amyloid proteins and tau proteins build up over time, and so the risk of developing Alzheimer's disease increases with age, with nearly 50% of those over age 85 developing late-onset Alzheimer's disease. Amyloid beta plaques and tau tangles are believed to develop due to a complex combination of genetic and environmental factors. In individuals with early-onset disease, the genetic component is stronger. (Choice B) Multiple sclerosis is a neurodegenerative disease in which immune cells attack the myelin sheaths surrounding axons in the CNS. (Choice C) Huntington's disease is an autosomal dominant genetic neurodegenerative disease in which neuronal loss occurs in extensive regions of the brain including the basal ganglia. (Choice D) Parkinson's disease is a neurodegenerative disease in which neurons that produce the neurotransmitter dopamine in the substantia nigra of the basal ganglia are progressively lost. Educational objective: Alzheimer disease is a progressive neurodegenerative brain disease characterized by the presence of plaques composed largely of amyloid beta proteins and neurofibrillary tangles composed of tau proteins.

Passage At the Blood-Brain Barrier, the Cerebral Spinal Fluid (CSF) Is