Question

what is atrophy and apoptosis? why is the brain vulnerable to them?

Answer 1

Atrophy and apoptosis are cellular processes that are interconnected.

Cellular atrophy is an adaptation of the cells in response to drastical changes in function demands, trophic influences or mutations.In this process, a decrease in cell size is a consequence of loss of subcellular substances and organelles.

Apoptosis or programmed cell death, is a natural process that allows the control of the number of cells and it happens according its condition such as aging.

In neural system, apoptosis plays a main role in the development.It is known that more than 50% of neurons are lost during development as result of limiting trophic support from the target tissue to be inervate.

In the brain, the remotion of an important number of inmature neurons , helps to ensure that maduration and homeostatic function of neuronal networks in brain procceed correctly.

Cell death is trigger by external and brain microenvironment signals.

Different types of neurons have a variety of neuron type specific pro survival constituents that might help them to survival in certain brain regions.

The effect of brain maduration on neuronal survival is seen in the decrease in survival of embryonic small axonless neurons.

Brain environment also determines apoptosis through the availability of prosurvival factors in the region that can be variable in brain and other cortical layers.

Any process that desregulates apoptosis of neural cells may lead to brain atrophy and the development of many and different kinds of brain diseases.

For example in neurodegenerative process such as spinal muscular atrophy, a condition associated with a mutation in a gene that encodes for a protein NAIP, that is a survival motor neuron factor because functions as a neuronal apoptosis inhibitory protein.

Or in familial amyotrophic lateral sclerosis associated with a mutation in the gene of a superoxide dismutase ,that results in the synthesis of a mutated protein with a dominant proapoptotic signal.