The
terminal nerve, or
cranial nerve zero, was discovered by German scientist
Gustav FritschGustav Theodor Fritsch was a German anatomist and physiologist from Cottbus, best known for his work with neuropsychiatrist Eduard Hitzig on the electric localization of the motor areas of the brain...
in 1878 in the
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
s of
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s. It was first found in
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s in 1913, although its presence in humans remains controversial. However, a study has indicated that the terminal nerve is a common finding in the adult human brain. It projects from the
nasal cavityThe nasal cavity is a large fluid filled space above and behind the nose in the middle of the face.- Function :The nasal cavities conditions the air to be received by the areas of the respiratory tract and noses...
, enters the brain just a little bit ahead of the other
cranial nervesCranial nerves are nerves that emerge directly from the brain stem in contrast to spinal nerves which emerge from segments of the spinal cord.-Origin and function:...
as a microscopic
plexusA plexus is a network. In biology the term plexus has multiple meanings:-Nervous system:In many animals the processes of neurons join together to form a plexus or nerve net.-In vertebrates:...
of unmyelinated peripheral
nerve fascicleA small bundle of nerve fibers, enclosed by the perineurium, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or nerve fascicles, which are bound together in a common membranous...
s.
The nerve is often overlooked in autopsies because it is unusually thin for a cranial nerve, and is often torn out upon exposing the brain.
The
terminal nerve, or
cranial nerve zero, was discovered by German scientist
Gustav FritschGustav Theodor Fritsch was a German anatomist and physiologist from Cottbus, best known for his work with neuropsychiatrist Eduard Hitzig on the electric localization of the motor areas of the brain...
in 1878 in the
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
s of
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s. It was first found in
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s in 1913, although its presence in humans remains controversial. However, a study has indicated that the terminal nerve is a common finding in the adult human brain. It projects from the
nasal cavityThe nasal cavity is a large fluid filled space above and behind the nose in the middle of the face.- Function :The nasal cavities conditions the air to be received by the areas of the respiratory tract and noses...
, enters the brain just a little bit ahead of the other
cranial nervesCranial nerves are nerves that emerge directly from the brain stem in contrast to spinal nerves which emerge from segments of the spinal cord.-Origin and function:...
as a microscopic
plexusA plexus is a network. In biology the term plexus has multiple meanings:-Nervous system:In many animals the processes of neurons join together to form a plexus or nerve net.-In vertebrates:...
of unmyelinated peripheral
nerve fascicleA small bundle of nerve fibers, enclosed by the perineurium, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or nerve fascicles, which are bound together in a common membranous...
s.
The nerve is often overlooked in autopsies because it is unusually thin for a cranial nerve, and is often torn out upon exposing the brain. Careful
dissectionDissection is usually the process of disassembling and observing something to determine its internal structure and as an aid to discerning the functions and relationships of its components...
is necessary to visualize the nerve. Its purpose and mechanism of function is still open to debate; consequently, nerve zero is often not mentioned in
anatomyAnatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy and plant anatomy...
textbooks.
Although very close to (and often confused for a branch of) the
olfactory nerveThe olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity...
, nerve zero is not connected to the
olfactory bulbThe olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...
, where smells are analyzed. This fact suggests that the nerve is either vestigial or may be related to the sensing of pheromones. This hypothesis is further supported by the fact that nerve zero projects to the medial and lateral septal nuclei, and the
preoptic areaThe preoptic area is a region of the hypothalamus. According to the MeSH classification, it is considered part of the anterior hypothalamus.-Functions:...
s, all of which are involved in regulating sexual behavior in
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
s.
The zebrafish has been used as a model in recent research.
External links
- Diagram at kent.edu ("nervus terminalis", #4)