Question

The ischemic stroke leads to blood-brain barrier disruption, inflammation, and oxidative stress. BBB disruption leads to edema and leukocyte infiltration, which enhances the inflammation. Then, protein, lipids, and DNA are attacked by reactive oxidative species (ROS) and reactive nitrogen species (RNS). Also, oxygen and glucose deprivation lead to ATP depletion, resulting in glutamate release and mitochondrial dysfunction. Oxidative stress activates apoptosis, necrosis, and autophagy pathways (cell death by self-eating), which determines the final infarct size; resulting in a lesion due to inadequate blood supply. Furthermore, ATP depletion leads to decreased activity of ATP-dependent transport systems, such as the Na+/K+ pump that usually transports K+ into the cells and Na+ out of the cell. Without this pump, excessive K+ accumulates outside the cells and causes membrane depolarization. More glutamate is then released by glutamatergic cells and astrocytes causing glutamate-mediated neurotoxicity.

a) Ischemic stroke does not affect mitochondrial function.

b) ATP depletion leads to increased activity of ATP-dependent transport systems.

c) Excessive K+ accumulation outside cells causes membrane hyperpolarization.

d) Glutamate release is not associated with oxidative stress.

Answer 1

The given statements about ischemic stroke are all incorrect: ischemic stroke does impact mitochondrial function, ATP depletion reduces the activity of ATP-dependent transport systems, excessive K+ outside of cells leads to depolarization, and glutamate release is indeed associated with oxidative stress.

Step-by-step explanation:

In the context of ischemic stroke, the statement a) Ischemic stroke does not affect mitochondrial function is incorrect because the lack of oxygen and glucose during a stroke impairs ATP production by mitochondria, leading to energy failure and affecting ionic gradients and neurotransmitter release. The statement b) ATP depletion leads to increased activity of ATP-dependent transport systems is also incorrect; ATP depletion actually causes these systems, such as the Na+/K+ pump, to fail, which disrupts ionic balance. The statement c) Excessive K+ accumulation outside cells causes membrane hyperpolarization is incorrect; it actually causes depolarization. Finally, d) Glutamate release is not associated with oxidative stress is incorrect, as glutamate release occurs due to membrane depolarization during ischemia, and it is associated with excitotoxic neuronal damage triggered by oxidative stress.