Central nervous system
The central nervous system (CNS) represents the largest part of the nervous system,
including the brain and the spinal cord.
Cutaneous allodynia
Pain
resulting from an innocuous stimulus (not normally painful) to normal skin
or scalp.
Dura mater
Outermost, toughest, and most fibrous of the three membranes (meninges),
covering and protecting the brain and spinal cord.
Glial cell
These cells provide structure to the nervous system. There are three types:
astrocytes and oligodendrocytes (astroglia and oligodendroglia), which appear
to play a role in myelin formation, transport of material to neurons, and
maintenance of the ionic environment of neurons; and microcytes (microglia),
which phagocytize waste products of nerve tissue.
Limbic system
A group of brain structures common to all mammals (including the hippocampus
and dentate gyrus with their archaeocortex, the anterior cingulate cortex
and septal areas, and the amygdala), associated with olfaction but of greater
importance in other activities, such as autonomic functions and certain aspects
of emotion and behavior.
Mast cell
A connective tissue cell whose specific physiologic function remains unknown;
capable of elaborating basophilic, metachromatic cytoplasmic granules that
contain histamine, heparin, and, in certain species, such as the rat and
mouse, serotonin; called also mastocyte and labrocyte.
Neuron
Conducting cells of the nervous system. A typical neuron consists of
a cell body, containing the nucleus and the surrounding cytoplasm (perikaryon);
several short radiating processes (dendrites); and one long process (the
axon), which terminates in twiglike branches (telodendrons) and may have
branches (collaterals) projecting along its course. The axon together with
its covering or sheath forms the nerve fiber.
Neuropeptide
Any of several types of molecules found in brain tissue, composed of short
chains of amino acids; they include endorphins, enkephalins, vasopressin,
and calcitonin gene-related peptide. They are often localized in axon terminals
at synapses and are classified as putative neurotransmitters, although
some are also hormones.
Neurotransmitter
Any of a group of substances that are released on excitation from the axon
terminal of a presynaptic neuron of the central or peripheral nervous system
and travel across the synaptic cleft to either excite or inhibit the target
cell. Among the many substances that have the properties of a neurotransmitter
are acetylcholine, norepinephrine, epinephrine, dopamine, glycine, gamma-aminobutyrate,
glutamic acid, substance P, enkephalins, endorphins, and serotonin.
Primary sensory neuron
The first neuron comprising in an afferent pathway, beginning at the receptor
and ending at a synapse with a secondary sensory neuron, often within a nucleus
of the central nervous system. One common type is the pseudounipolar neuron.
Somatosensory cortex
A cortical projection area lateral and posterior to the primary somatosensory
area; it receives somatic sensations mainly from the skin, particularly sensations
of pain and of movement across the skin.
Synapse
The site of functional apposition between neurons, at which an impulse
is transmitted from one neuron to another, usually by a chemical neurotransmitter
(eg, acetylcholine, norepinephrine) released by the axon terminal
of the excited (presynaptic) cell. The neurotransmitter diffuses across the
synaptic cleft to bind with receptors on the postsynaptic cell membrane,
and thereby effects electrical changes in the postsynaptic cell, which result
in depolarization (excitation) or hyperpolarization (inhibition).
Thalamus
A large ovoid mass in the posterior part of the diencephalon forming most
of each lateral wall of the third ventricle, composed chiefly of gray substance
and associated laminae of white substance. It is divided into anterior, medial,
and lateral parts, each part containing groups of nuclei that function as
relay centers for sensory impulses and cerebellar and basal ganglia projections
to the cerebral cortex.
Trigeminovascular system
The trigeminal nerve consists of peripheral and central fibers (or
projections) of pseudounipolar neurons whose cell bodies reside in the trigeminal
ganglion. The peripherally projecting fibers of the trigeminal nerve synapse
near cerebral vessels and provide the sole innervation of the cerebral vessels
and dura mater. The centrally projecting fibers synapse in the brainstem. The
peripherally and centrally projecting fibers constitute the trigeminovascular
system, whose role is to transmit pain signals from cranial vessels to pain
centers involved in the perception of headache pain.
Vasodilation
Blood vessel dilation especially of arterioles leading to increased blood
flow.
