|Cell Death can occur by a number of processes, including necrosis and apoptosis.|
|Necrosis is the process where ischaemia, infection or toxins cause the death of many cells of different types in a particular location.|
|Excitotoxic cell death occurs when the cell fills with calcium ions as a result of overexcitation with glutamate, as occurs in neurological trauma or ischaemia. High intracellular concentrations of calcium ions activate various enzymes that may damage the cytoskeleton, cell membrane and DNA, and lead to necrosis|
|Apoptosis is the physiological process of programmed cell death that affects cells individually. It has a characteristic sequence of biochemical and anatomical changes resulting in cell death. Apoptosis is initated by a family of enzymes called caspases.|
|Apoptosis is common during neural development, when it removes roughly 50% of the neurones produced in the embryonic CNS.|
The anatomical characteristics of apoptosis include
Apoptosis is common during neural development, when it removes roughly 50% of the neurones produced in the embryonic CNS.
Apoptosis also plays a part in the pathology of neurodegenerative diseases and may affect all cell types within the CNS. Oligodendrocytes can undergo apoptosis in multiple sclerosis, but neurones appear to be relatively resistant to it.
Many neurones have long axons, e.g. fibre tracts connecting the brain and spinal cord or association fibres crossing the midline in the corpus callosum.
In some neurones the perilarya account for only a small fraction of the cytoplasm, with the majority being in the axon. Neurotrophic factors carried by axonal transport appear to be involved in maintaining the integrity the periphery of the nerve cell and its synapses.
The 'dying back' phenomenon is an important process that affects the function of neurones, and appears to be quite separate from apoptosis.
|Neuronal apoptosis can occur in a variety of neurological diseases, including AIDS and HIV, and trauma. Neuronal apoptosis can be induced by glutamate.|
|Many neurones appear to be relatively resistant to apoptosis, possibly because of the need to maintain their axons as long a they are functional. Trauma that interrupts axons is associated with apoptosis.|
Astrocytes are involved in neuronal nutrition and metabolism, particularly around the cell body and synapses, and oligodendrocytes provide myelination that supports the transmission of nerve impulses along the length of the axon. Both cell types can exhibit apoptosis.
|Trauma, such as spinal cord injury, results in degeneration of the peripheral sections of axons separated from their cell bodies, while the cell bodies that have lost functional contact with their projection neurones undergo changes including apoptosis.|
Similar apoptotic changes occur in the thalamus following traumatic lesions of the cortex.
Hypoglycaemia is also known to induce apoptosis in neurones; consequently it is important to ensure that hypgycaemia does not occur in patietns recovering from neurological trauma.