Excitotoxicity begins with:
A. Excessive production of lactic acid.
B. Destruction of cellular proteins.
C. Cellular edema.
D. Persistent binding of glutamate to N-methyl-D-aspartate (NMDA)–type receptors in the postsynaptic cell membrane.
E. Interference of mitochondria functions.
ANS: D
Rationale: First, glutamate binds persistently to the NMDA-type glutamate receptor in the cell membrane. Stimulation of this receptor results in an influx of calcium ions (Ca+2) into the cell, and indirectly facilitates the release of internal Ca+2 stores. An influx of sodium ions (Na+) into the cell results in further stimulation of NMDA receptors and an additional influx of Ca+2 into the cell. Channels that are permeable to Ca+2 open because of the injury. With the increase in Ca+2 inside the cell, more potassium ions (K+) diffuse out of the cell, requiring increased glycolysis that provides energy for the Na+/K+ pump to actively transport K+ into the cell. Together, the increased glycolysis and the increased Ca+2 lead to several destructive consequences for neurons.
You might also like to view...
Which cell-surface glycoprotein distinguishes professional antigen-presenting cells from other cells and is involved in the co-stimulation of T cells?
What will be an ideal response?
Explain why an organ transplant made between a donor of blood group AB and a recipient of blood group O will always be rejected, even if it is perfectly HLA-matched and the recipient has been given immunosuppressant drugs
What is this type of rejection called? What will be an ideal response?
Ischemia and other toxic injuries increase the accumulation of intracellular calcium as a result of:
A) Release of stored calcium from the mitochondria B) Improved intracellular volume regulation C) Decreased influx across the cell membrane D) Attraction of calcium to fatty infiltrates
Mila plans to retire at age 62. Which of the following is likely TRUE about the consequences of this decision?
A. She will receive lower Social Security monthly payments. B. She will receive Medicare benefits as soon as she retires. C. She may need to borrow against her Social Security benefits to make ends meet. D. She will pay more income taxes for a longer amount of time.