Often used as a synonym for natural medicine, naturopathy is a philosophy rather than a treatment modality. Practitioners trained in colleges of naturopathy work on the basis that the body is a self-healing organism given the right conditions. They use diet and other therapies such as hydrotherapy (the external application of hot and cold water), herbalism and osteopathy to help obtain these conditions.

Neuron

A nerve cell. Neurons have a cell body fringed with outgrowths known as dendrites and containing a nucleus. Extending from the cell body sometimes several feet in length are one or more axons insulated by a myelin sheath and ending in axon terminals. Grey in colour, large clusters of neuronal cell bodies in the brain are sometimes known as 'grey matter' and the axons, due to the white colour of myelin, as 'white matter'. Motor neurons are those which transmit nerve impulses from the brain and spinal cord to the muscles and glandular tissue.

Nerve impulses are passed in accordance with electrochemical processes involving sodium, calcium and potassium ions and neurotransmitters (see next entry).

Neurotransmitter

A substance which modifies or helps to transmit impulses between neurons (nerve cells). Up to 10,000 neurotransmitters can be stored in a neuron's 'synaptic knobs'. When a nerve impulse reaches a nerve terminal, voltage-sensitive calcium channels open, allowing calcium to diffuse into the terminal. This stimulates the release of neurotransmitter molecules into the space (synapse) between this neuron and the next connecting neuron. The neurotransmitters then bind to specific receptors.

Neurotransmitters can have 'excitatory' or 'inhibitory' effects which in turn depend on the type of receptor to which the neurotransmitter attaches. An excitatory neurotransmitter-receptor combination causes membrane channels to open, which are permeable to sodium, potassium and other small, positively charged ions. This slightly depolarizes the neuron, bringing it closer to to the threshold at which it will 'fire', or send impulses to further neurons.

An inhibitory neurotransmitter-receptor effect opens potassium or chloride channels, and this lessens the likelihood of the cell firing.

Some substances which act as neurotransmitters include: acetylcholine, GABA, dopamine, adrenaline, noradrenaline, serotonin, histamine, the amino acids glycine, glutamate and aspartate, and the opioid substances known as endorphins and encephalins.

Niacinamide (see Vitamin B3)