Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «N»:
Nerve block: A procedure in which an anesthetic agent is injected directly near a nerve to block pain. A nerve block is a form of regional anesthesia....
Nerve cell: See: Neuron....
Nerve compression: "Pinching" a nerve by putting
too much pressure on it. For example, the sciatic
nerve may be painfully compressed by a ruptured disc in the
lower spine causing sciatica.
In nerve compression there is pressure on a nerve root or a peripheral nerve leading to ischemia (not enough...
Nerve conduction study
Nerve conduction study: See: Nerve conduction velocity test....
Nerve conduction velocity test
Nerve conduction velocity
test: An electrical test used to detect nerve conditions. In the nerve
conduction velocity (NCV) test, the nerve is electrically stimulated by one electrode while other electrodes detect the electrical impulse "down stream" from the first electrode. The NCV test is usuall...
Nerve growth factor
Nerve growth factor: Abbreviated NGF. A naturally occurring molecule in the body which stimulates the growth and differentiation of the sympathetic and certain sensory nerves. NGF is a protein that consists of 3 types of polypeptide chains -- alpha, beta and gamma -- that interact to form the protei...
Nerve palsy, laryngeal
Nerve palsy, laryngeal: Paralysis of the recurrent laryngeal nerve, a branch of the vagus nerve (a long and important nerve that originates in the brainstem and runs down to the colon). After the recurrent laryngeal nerve leaves the vagus nerve, it goes down into the chest and then loops back up to...
Nerve pathways, visual
Nerve pathways, visual: The optic nerves serving the eyes join behind the eyes just in front of the pituitary gland to form a cross-shaped structure called the optic chiasma.
Within the optic chiasma some of the nerve fibers cross. The fibers from the nasal (inside) half of each retina cross over, b...
Nerve, abducent: A small motor nerve that has one task: to supply a muscle called the lateral rectus muscle that moves the eye outward.
Paralysis of the abducent nerve causes inward turning of the eye (internal strabismus) leading to double vision.
The abducent nerve is the sixth cranial nerve. All...
Nerve, accessory: See: Accessory nerve....
Nerve, afferent: A nerve that carries impulses toward the central nervous system (CNS). The opposite of an afferent nerve is an efferent nerve that carries impulses away from the CNS....
Nerve, efferent: A nerve that carries impulses away from the central nervous system (CNS). An efferent nerve is the opposite of an afferent nerves that carries impulses toward the CNS....
Nerve, eighth cranial
Nerve, eighth cranial: The eighth cranial nerve is the vestibulocochlear nerve.
The vestibulocochlear nerve is responsible for the sense of hearing and it is also pertinent to balance, to the body position sense.
Problems with the vestibulocochlear nerve may result in deafness, tinnitus (ringing ...
Nerve, eleventh cranial
Nerve, eleventh cranial: The eleventh cranial nerve is the accessory nerve. The twelve cranial nerves, the accessory nerve included, emerge from or enter the skull (the cranium) as opposed to the spinal nerves which emerge from the vertebral column. The accessory is so-called because, although it ...
Nerve, facial: The facial nerve is the seventh cranial
nerve. It is a mixed nerve that has fibers both going out and coming
in (both efferent and afferent fibers). It supplies the muscles of
Paralysis of the facial nerve causes a characteristic picture with
drooping of one sid...