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Neuron Internals

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Membrane | In the nucleus | See also

Membrane

The neuron is bounded by a membrane with a double layer of fat-like (lipid) molecules.

Within the membrane are assorted proteins that have various functions including:

• Detecting external substances such as hormones and pass information through the membrane about these.
• Controlling access to the interior or the cell, acting as 'gatekeeper'.
• Transporting molecules into and out of the cell.

In the nucleus

Within the nucleus are the nucleolus and chromosomes. The nucleolus produces ribosomes, which are small substances that get used in protein synthesis.

Chromosomes

Chromosomes are long strands of DNA (deoxyribonucleic acid) which contain genetic information. When active, they produce messenger ribonucleic acid (mRNA). The mRNA leaves the nucleus and attaches to ribosomes to produce protein.

The genome is the sequence of nucleotide bases on the chromosomes that provides information on how to synthesize the proteins for the organism. Humans have about 25000 genes.

Proteins and enzymes

Proteins provide structure in cells and act as enzymes in controlling chemical processes. Enzymes act as catalysts in various reactions and can act to both combine and break apart molecules (and thus act as 'factory machines').

Only about 1.5% of the human genome codes for proteins and the rest has been classified as 'junk', although recent research shows this seems not to be the case. Non-coding RNA (ncRNA) have individual function, for example ncRNA molecules attach to and modify proteins that regulate gene expression.

The structure of the neuron is created from a set of non-soluble proteins called the cytoskeleton, the thickest of which are bundles of 13 protein filaments called microtubules. Tau proteins are microtubule components that provide a transport mechanism for the cell. Deformation of these in dying neutrons are a key factor in Alzheimer's disease.

Cytoplasm

The majority of the cell is made up of cytoplasm, a viscous, semi-liquid substance that contains small specialized substances called organelle. These are like organs in that they have specific functions.

Mitochondria are oval bead-shaped organelle, that contain their own DNA and help break down nutrients to create energy in the form of adenosine triphosphate (ATP).

Endoplasmic reticulum

Endoplasmic reticulum is a storage reservoir and transportation channel through cytoplasm. Rough endoplasmic reticulum contains ribosomes that will be transported out of the cell or used in the membrane. Smooth endoplasmic reticulum provides channels for segregation of molecules. Lipid molecules are produced here.

The Golgi apparatus is a special form of smooth endoplasmic reticulum which is used to assemble synaptic vesicules and some complex modules and also produces a wrapping using a process called exocytosis. The Golgi apparaus also produces lysosomes, which are small sacs that contain enzymes that break down waste substances.

See also

Neurons