Glossary

Organization terms

Central nervous system (CNS) – This consists of the brain and spinal cord. This is where integration occurs and where the majority of neuronal connections are found.

Peripheral nervous system (PNS) – This consists of all the nerves which are found exclusively outside the CNS. Nerves themselves are composed only of extensions from the body of the neuron. Nerves do not contain cell bodies.

Autonomic Nerves – These are motor nerves that control involuntary actions of the body generally involved in maintaining homeostasis. These nerves are connected to smooth muscle, cardiac muscle and glands. They are unique in having a synapse outside of the CNS.

Sympathetic Division – This division of the autonomic nervous system is responsible for the ability to respond to perceived danger. This is often called the “fight or flight” response.

Parasympathetic Division – This division of the autonomic nervous system opposes the sympathetic division, lowering heart rate, blood pressure and respiratory rate while increasing the motility of the digestive system. This is sometimes referred to as the “rest and repose” response.

Functional terms

Afferent – In reference to nerves this denotes a nerve carrying signals to the CNS from the periphery. These are also known as sensory nerves as the tissues are sending impulses containing information from sensing cells in the body. In the text sensory and afferent will be used interchangeably.

Efferent – In reference to nerves this denotes a nerve carrying signals from the CNS to the periphery. These are also known as motor nerves as the tissues stimulated perform an action and again motor and efferent will used as equivalent terms in this course.

Integration – This is the interface between the afferent and efferent system where incoming signals from sensory nerves are interpreted and responses generated by the CNS then sent to the organs and muscle in the periphery to respond to the stimulus.

Cellular terms

Neuron – The cell that forms all nervous tissue.

Fiber – An extension from the neuronal cell body that carries signals to or from the neuronal cell body.

Synapse – A gap between neurons where chemical mediators are released to affect the adjacent neuron. This is the primary means for neurons to communicate with each other.

Ganglion – This is an appendage to a peripheral nerve where neuronal cell bodies are found outside the central nervous system. These are found associated with all sensory and autonomic nerves.

Preganglionic fibers – These are the autonomic neuronal fibers that enter a ganglion.

Postganglionic fibers – These are the autonomic neuronal fibers that leave the ganglion after they synapse with the preganglionic fibers