Symbiosis – a mutually beneficial inter-relationship between two organisms, for example between bees and flowers (pollen carrying in return for nectar).
Sympathetic nerves – the sympathetic nervous system is one of he two main pisions of the autonomic nervous system. Sympathetic nerves make synapses at ganglia close to the spinal cord and have long post -ganglionic axons which, in general place the body on a state of alert. Always acts as a balance to activity of the parasympathetic nervous system.
Synapse – the point at which one nerve cell connects with another. The nerve impulse is transmitted by the release of chemical neurotransmitter substances from the pre-synaptic cell membrane. The neurotransmitter substance diffuses across the synaptic cleft to the post-synaptic membrane which it depolarises. When the post-synaptic cell is sufficiently excited by a number of incoming impulses and enough neurotransmitter substance, it discharges an electrical impulse along its axon membrane to the next neurone.
Synovial fluid – the lubricating fluid containing glycosplayaminoglycans which is held in the capsule of a synovial joint.