Cell Death

In order to best understand neuron survival it is a good idea to understand what it is that they are avoiding!

Cell death can be divided into two types;

• Apoptosis, or programmed cell death (PCD).
• Necrosis, which follows a traumatic injury to the cell.

Apoptosis

Cells will willingly destroy themselves if they receive intructions to do so, instructions for apoptosis can arrive by an extrinsic route where a signal comes from outside the cell, or an intrinsic route where the signal comes from the inside, normally from damaged mitochondria.

Apoptosis requires gene transcription and protein synthesis by the cell.

The chromatin condenses and aggregates at the nuclear membrane, this is known as pyknosis.  The cell shrinks and small pieces of it, called apoptotic bodies, break off.

The apoptotic bodies are engulfed and destroyed by macrophages.  Enzymes break down the DNA.

Necrosis

This form of cell death follows cell injury, its is a far more violent process and can damage the cells in the vicinity.

• Mitochondria stop producing energy.
• Because of this the neuron is unable to regulate the movement of ions and water leading to changes in hydrostatic pressure.
• The cell and its organelles swell up.
• Lysosomal enzymes are activated.
• Cytoplasmic components are broken down.
• The cell bursts open.

Image from Wikimedia Commons https://commons.wikimedia.org/wiki/File:Apoptosis.png, in public domain