Brain stem
Encyclopedia
In vertebrate
anatomy
the brainstem (or brain stem) is the posterior part of the brain
, adjoining and structurally continuous with the spinal cord
. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves
. Though small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brain stem. This includes the corticospinal tract
(motor), the posterior column-medial lemniscus pathway
(fine touch, vibration sensation and proprioception
) and the spinothalamic tract
(pain, temperature, itch and crude touch). The brain stem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle.
It is usually described as including the medulla oblongata
(myelencephalon), pons
(part of metencephalon), and midbrain (mesencephalon). Less frequently, parts of the diencephalon
are included.
is the anterior median fissure. Moving laterally on each side are the pyramids
. The pyramids contain the fibers of the corticospinal tract (also called the pyramidal tract), or the upper motor neuronal axons as they head inferiorly to synapse on lower motor neuronal cell bodies within the ventral horn of the spinal cord.
The anterolateral sulcus is lateral to the pyramids. Emerging from the anterolateral sulci are the CN XII (hypoglossal nerve
) rootlets. Lateral to these rootlets and the anterolateral sulci are the olives
. The olives are swellings in the medulla containing underlying inferior olivary nuclei (containing various nuclei and afferent fibers). Lateral (and dorsal) to the olives are the rootlets for cranial nerves
IX (glossopharyngeal), CN X (vagus) and CN XI (accessory nerve
). The pyramids end at the pontomedullary junction, noted most obviously by the large basal pons. From this junction, CN VI (abducens nerve), CN VII (facial nerve
) and CN VIII (vestibulocochlear nerve
) emerge. At the level of the midpons, CN V (the trigeminal nerve
) emerges. At the rostral pons, CN III (the occulomotor nerve) emerges at the midline. Laterally, CN IV (the trochlear nerve
) emerges out of the dorsal rostral pons, wrapping around towards the ventral pons.
is the posterior median fissure. Moving laterally on each side is the fasciculus gracilis
, and lateral to that is the fasciculus cuneatus
. Superior to each of these, and directly inferior to the obex
, are the gracile and cuneate tubercles, respectively. Underlying these are their respective nuclei. The obex marks the end of the 4th ventricle and the beginning of the central canal
. The posterior intermediate sulci separates the fasciculi gracilis from the fasciculi cuneatus. Lateral to the fasciculi cuneatus is the lateral funiculus
.
Superior to the obex is the floor of the 4th ventricle. In the floor of the 4th ventricle, various nuclei can be visualized by the small bumps that they make in the overlying tissue. In the midline and directly superior to the obex is the vagal trigone
and superior to that it the hypoglossal trigone
. Underlying each of these are motor nuclei for the respective cranial nerves. Superior to these trigones are fibers running laterally in both directions. These fibers are known collectively as the striae medullares
. Continuing in a rostral direction, the large bumps are called the facial colliculi. Each facial colliculus
, contrary to their names, do not contain the facial nerve nuclei. Instead, they have facial nerve axons traversing superficial to underlying abducens (CN VI) nuclei. Lateral to all these bumps previously discussed is an indented line, or sulcus
that runs rostrally, and is known as the sulcus limitans
. This separates the medial motor neurons from the lateral sensory neurons. Lateral to the sulcus limitans is the area collectively known as the vestibular area, which is involved in special sensation. Moving rostrally, the inferior, middle, and superior cerebellar peduncles are found connecting the midbrain to the cerebellum. Directly rostral to the superior cerebellar peduncle, there is the superior medullary velum and then the two trochlear nerves. This marks the end of the pons as the inferior colliculus
is directly rostral and marks the caudal midbrain.
Spinal Cord to Medulla Transitional Landmark: From a ventral view, there can be seen a decussation
of fibers between the two pyramids. This decussation marks the transition from medulla to spinal cord. Superior to the decussation is the medulla and inferior to it is the spinal cord.
. The tectum includes the superior and inferior colliculi and is the dorsal covering of the cerebral aqueduct. The inferior colliculus
, involved in the sense of hearing sends its inferior brachium to the medial geniculate body of the diencephalon
. Superior to the inferior colliculus, the superior colliculus
marks the rostral midbrain. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon. The second part is the tegmentum
and is ventral to the cerebral aqueduct
. Several nuclei, tracts and the reticular formation are contained here. Last, the ventral side is composed of paired cerebral peduncles. These transmit axons of upper motor neurons.
: The area around the cerebral aqueduct, which contains various neurons involved in the pain
desensitization pathway. Neurons synapse here and, when stimulated, cause activation of neurons in the nucleus raphe magnus
, which then project down into the dorsal horn of the spinal cord and prevent pain sensation transmission.
Occulomotor nerve nucleus: This is the nucleus of CN III.
Trochlear nerve
nucleus: This is the nucleus of CN IV.
Red Nucleus
: This is a motor nucleus that sends a descending tract to the lower motor neurons.
Substantia nigra
: This is a concentration of neurons in the ventral portion of the midbrain that uses dopamine
as its neurotransmitter and is involved in both motor function and emotion. Its dysfunction is implicated in Parkinson's Disease
.
Reticular formation
: This is a large area in the midbrain that is involved in various important functions of the midbrain. In particular, it contains lower motor neurons, is involved in the pain desensitization pathway, is involved in the arousal and consciousness systems, and contains the locus ceruleus, which is involved in intensive alertness
modulation and in autonomic
reflexes.
Central tegmental tract
: Directly anterior to the floor of the 4th ventricle, this is a pathway by which many tracts project up to the cortex and down to the spinal cord.
. The mesencephalon
is the second of the three primary vesicles, and does not further differentiate into a secondary vesicle. This will become the midbrain. The third primary vesicle, the rhombencephalon
, will further differentiate into two secondary vesicles, the metencephalon
and the myelencephalon
. The metencephalon will become the cerebellum
and the pons. The myelencephalon will become the medulla.
1. The first is its role in conduction. That is, all information relayed from the body to the cerebrum and cerebellum and vice versa, must traverse the brain stem. The ascending pathways coming from the body to the brain are the sensory pathways, and include the spinothalamic tract
for pain and temperature sensation and the dorsal column, fasciculus gracilis, and cuneatus for touch, proprioception
, and pressure sensation (both of the body). (The facial sensations have simiar pathways, and will travel in the spinothalamic tract and the medial lemniscus
also). Descending tracts are upper motor neurons destined to synapse on lower motor neurons in the ventral horn and intermediate horn of the spinal cord. In addition, there are upper motor neurons that originate in the brain stem's vestibular, red, tectal, and reticular nuclei, which also descend and synapse in the spinal cord.
2. The cranial nerves 3-12 emerge from the brain stem.
3. The brain stem has integrative functions (it is involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, awareness, and consciousness). Thus, brain stem damage is a very serious and often life-threatening problem.
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
anatomy
Anatomy
Anatomy 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...
the brainstem (or brain stem) is the posterior part of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, adjoining and structurally continuous with the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
. Though small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brain stem. This includes the corticospinal tract
Corticospinal tract
The corticospinal or pyramidal tract is a collection of axons that travel between the cerebral cortex of the brain and the spinal cord....
(motor), the posterior column-medial lemniscus pathway
Posterior column-medial lemniscus pathway
The posterior column-medial lemniscus pathway is the sensory pathway responsible for transmitting fine touch, vibration and conscious proprioceptive information from the body to the cerebral cortex; as well as tactile pressure, barognosis, graphesthesia, stereognosis, recognition...
(fine touch, vibration sensation and proprioception
Proprioception
Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...
) and the spinothalamic tract
Spinothalamic tract
The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch...
(pain, temperature, itch and crude touch). The brain stem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle.
It is usually described as including the medulla oblongata
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
(myelencephalon), pons
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
(part of metencephalon), and midbrain (mesencephalon). Less frequently, parts of the diencephalon
Diencephalon
The diencephalon is the region of the vertebrate neural tube which gives rise to posterior forebrain structures. In development, the forebrain develops from the prosencephalon, the most anterior vesicle of the neural tube which later forms both the diencephalon and the...
are included.
Ventral view/medulla and pons
In the medial part of the medullaMedulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
is the anterior median fissure. Moving laterally on each side are the pyramids
Pyramid of medulla oblongata
The anterior or ventral portion of the medulla oblongata is named the pyramid and lies between the anterior median fissure and the antero-lateral sulcus....
. The pyramids contain the fibers of the corticospinal tract (also called the pyramidal tract), or the upper motor neuronal axons as they head inferiorly to synapse on lower motor neuronal cell bodies within the ventral horn of the spinal cord.
The anterolateral sulcus is lateral to the pyramids. Emerging from the anterolateral sulci are the CN XII (hypoglossal nerve
Hypoglossal nerve
The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal...
) rootlets. Lateral to these rootlets and the anterolateral sulci are the olives
Olivary body
In anatomy, the olivary bodies or simply olives are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem...
. The olives are swellings in the medulla containing underlying inferior olivary nuclei (containing various nuclei and afferent fibers). Lateral (and dorsal) to the olives are the rootlets for cranial nerves
Cn
- Places :* People's Republic of China, ISO 3166-1 alpha-2 country code; sometimes refers exclusively to Mainland China* Comoros, FIPS Pub 10-4 and obsolete NATO digram* CN Tower, Toronto* CN Centre - an arena in Prince George, British Columbia...
IX (glossopharyngeal), CN X (vagus) and CN XI (accessory nerve
Accessory nerve
In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...
). The pyramids end at the pontomedullary junction, noted most obviously by the large basal pons. From this junction, CN VI (abducens nerve), CN VII (facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
) and CN VIII (vestibulocochlear nerve
Vestibulocochlear nerve
The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...
) emerge. At the level of the midpons, CN V (the trigeminal nerve
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
) emerges. At the rostral pons, CN III (the occulomotor nerve) emerges at the midline. Laterally, CN IV (the trochlear nerve
Trochlear nerve
The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....
) emerges out of the dorsal rostral pons, wrapping around towards the ventral pons.
Dorsal view/medulla and pons
The most medial part of the medullaMedulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
is the posterior median fissure. Moving laterally on each side is the fasciculus gracilis
Fasciculus gracilis
The fasciculus gracilis is a bundle of axon fibres in the posterior column of the spinal cord and carries information from the middle thoracic and lower limbs of the body...
, and lateral to that is the fasciculus cuneatus
Fasciculus cuneatus
The fasciculus cuneatus is a tract of nerves in the spinal cord which primarily transmits information from the arms...
. Superior to each of these, and directly inferior to the obex
Obex
The obex is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord.The obex occurs in the caudal medulla.The decussating of sensory fibers happens at this point....
, are the gracile and cuneate tubercles, respectively. Underlying these are their respective nuclei. The obex marks the end of the 4th ventricle and the beginning of the central canal
Central canal
For the engineering project, see Indiana Central Canal.The central canal is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is contiguous with the ventricular system of the brain...
. The posterior intermediate sulci separates the fasciculi gracilis from the fasciculi cuneatus. Lateral to the fasciculi cuneatus is the lateral funiculus
Lateral funiculus
The most lateral of the bundles of the anterior nerve roots is generally taken as a dividing line that separates the antero-lateral region into two parts, viz., an anterior funiculus, between the anterior median fissure and the most lateral of the anterior nerve roots; and a lateral funiculus,...
.
Superior to the obex is the floor of the 4th ventricle. In the floor of the 4th ventricle, various nuclei can be visualized by the small bumps that they make in the overlying tissue. In the midline and directly superior to the obex is the vagal trigone
Vagal trigone
The cells of the dorsal nucleus are spindle-shaped, like those of the posterior column of the spinal cord, and the nucleus is usually considered as representing the base of the posterior column. It measures about 2 cm...
and superior to that it the hypoglossal trigone
Hypoglossal trigone
In the upper part of the medulla oblongata, the hypoglossal nucleus approaches the rhomboid fossa, where it lies close to the middle line, under an eminence named the hypoglossal trigone.-External links:...
. Underlying each of these are motor nuclei for the respective cranial nerves. Superior to these trigones are fibers running laterally in both directions. These fibers are known collectively as the striae medullares
Striae medullares
Winding around the inferior peduncle and crossing the area acustica and the medial eminence are a number of white strands, the striae medullares, which form a portion of the cochlear division of the vestibulocochlear nerve and disappear into the median sulcus....
. Continuing in a rostral direction, the large bumps are called the facial colliculi. Each facial colliculus
Facial colliculus
The facial colliculus is an elevated area located on the dorsal pons. In the floor of the 4th ventricle It is formed by motor fibers of the facial nerve as they loop over the abducens nucleus...
, contrary to their names, do not contain the facial nerve nuclei. Instead, they have facial nerve axons traversing superficial to underlying abducens (CN VI) nuclei. Lateral to all these bumps previously discussed is an indented line, or sulcus
Sulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
that runs rostrally, and is known as the sulcus limitans
Sulcus limitans
In the floor of the fourth ventricle, the sulcus limitans separates the cranial nerve motor nuclei from the sensory nuclei . In the superior part of the rhomboid fossa, it corresponds with the lateral limit of the fossa and presents a bluish-gray area, the locus ceruleus In the floor of the fourth...
. This separates the medial motor neurons from the lateral sensory neurons. Lateral to the sulcus limitans is the area collectively known as the vestibular area, which is involved in special sensation. Moving rostrally, the inferior, middle, and superior cerebellar peduncles are found connecting the midbrain to the cerebellum. Directly rostral to the superior cerebellar peduncle, there is the superior medullary velum and then the two trochlear nerves. This marks the end of the pons as the inferior colliculus
Inferior colliculus
The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex...
is directly rostral and marks the caudal midbrain.
Spinal Cord to Medulla Transitional Landmark: From a ventral view, there can be seen a decussation
Decussation
Decussation is used in biological contexts to describe a crossing.Examples include:* In the brain, where nerve fibers obliquely cross from one lateral part to the other, that is to say they cross at a level other than their origin...
of fibers between the two pyramids. This decussation marks the transition from medulla to spinal cord. Superior to the decussation is the medulla and inferior to it is the spinal cord.
Midbrain
The midbrain is divided into three parts. The first is the tectum, which is "roof" in LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
. The tectum includes the superior and inferior colliculi and is the dorsal covering of the cerebral aqueduct. The inferior colliculus
Inferior colliculus
The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex...
, involved in the sense of hearing sends its inferior brachium to the medial geniculate body of the diencephalon
Diencephalon
The diencephalon is the region of the vertebrate neural tube which gives rise to posterior forebrain structures. In development, the forebrain develops from the prosencephalon, the most anterior vesicle of the neural tube which later forms both the diencephalon and the...
. Superior to the inferior colliculus, the superior colliculus
Superior colliculus
The optic tectum or simply tectum is a paired structure that forms a major component of the vertebrate midbrain. In mammals this structure is more commonly called the superior colliculus , but, even in mammals, the adjective tectal is commonly used. The tectum is a layered structure, with a...
marks the rostral midbrain. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon. The second part is the tegmentum
Tegmentum
The tegmentum is a general area within the brainstem. It is located between the ventricular system and distinctive basal or ventral structures at each level...
and is ventral to the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
. Several nuclei, tracts and the reticular formation are contained here. Last, the ventral side is composed of paired cerebral peduncles. These transmit axons of upper motor neurons.
Midbrain internal structures
Periaqueductal grayPeriaqueductal gray
Periaqueductal gray is the gray matter located around the cerebral aqueduct within the tegmentum of the midbrain. It plays a role in the descending modulation of pain and in defensive behaviour...
: The area around the cerebral aqueduct, which contains various neurons involved in the pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
desensitization pathway. Neurons synapse here and, when stimulated, cause activation of neurons in the nucleus raphe magnus
Nucleus raphe magnus
The nucleus raphes magnus, located directly rostral to the nucleus raphes obscurus, is afferently stimulated from axons in the spinal cord and cerebellum....
, which then project down into the dorsal horn of the spinal cord and prevent pain sensation transmission.
Occulomotor nerve nucleus: This is the nucleus of CN III.
Trochlear nerve
Trochlear nerve
The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....
nucleus: This is the nucleus of CN IV.
Red Nucleus
Red nucleus
The red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
: This is a motor nucleus that sends a descending tract to the lower motor neurons.
Substantia nigra
Substantia nigra
The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...
: This is a concentration of neurons in the ventral portion of the midbrain that uses dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
as its neurotransmitter and is involved in both motor function and emotion. Its dysfunction is implicated in Parkinson's Disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
.
Reticular formation
Reticular formation
The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...
: This is a large area in the midbrain that is involved in various important functions of the midbrain. In particular, it contains lower motor neurons, is involved in the pain desensitization pathway, is involved in the arousal and consciousness systems, and contains the locus ceruleus, which is involved in intensive alertness
Alertness
Alertness is the state of paying close and continuous attention, being watchful and prompt to meet danger or emergency, or being quick to perceive and act. It is related to psychology as well as to physiology...
modulation and in autonomic
Autonomic nervous system
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
reflexes.
Central tegmental tract
Central tegmental tract
The central tegmental tract is a structure in the midbrain and pons.* The central tegmental tract includes ascending axonal fibers that arise from the caudal nucleus solitarius and terminate in the ventral posteromedial nucleus of thalamus...
: Directly anterior to the floor of the 4th ventricle, this is a pathway by which many tracts project up to the cortex and down to the spinal cord.
Embryology
The adult human brain stem emerges from two of the three primary vesicles formed of the neural tubeNeural tube
In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
. The mesencephalon
Mesencephalon
The midbrain or mesencephalon is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal , and temperature regulation....
is the second of the three primary vesicles, and does not further differentiate into a secondary vesicle. This will become the midbrain. The third primary vesicle, the rhombencephalon
Rhombencephalon
The rhombencephalon is a developmental categorization of portions of the central nervous system in vertebrates.The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres...
, will further differentiate into two secondary vesicles, the metencephalon
Metencephalon
The metencephalon is a developmental categorization of portions of the central nervous system. The metencephalon is composed of the pons and the cerebellum; contains a portion of the fourth ventricle; and the trigeminal nerve , abducens nerve , facial nerve , and a portion of the vestibulocochlear...
and the myelencephalon
Myelencephalon
The myelencephalon is categorized as a secondary vesicle in the development of the central nervous system. The prefix "myelen" is derived from Greek for medulla...
. The metencephalon will become the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
and the pons. The myelencephalon will become the medulla.
Functions
There are three main functions of the brain stem:1. The first is its role in conduction. That is, all information relayed from the body to the cerebrum and cerebellum and vice versa, must traverse the brain stem. The ascending pathways coming from the body to the brain are the sensory pathways, and include the spinothalamic tract
Spinothalamic tract
The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch...
for pain and temperature sensation and the dorsal column, fasciculus gracilis, and cuneatus for touch, proprioception
Proprioception
Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...
, and pressure sensation (both of the body). (The facial sensations have simiar pathways, and will travel in the spinothalamic tract and the medial lemniscus
Medial lemniscus
The medial lemniscus, also known as Reil's band or Reil's ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus.-Path:...
also). Descending tracts are upper motor neurons destined to synapse on lower motor neurons in the ventral horn and intermediate horn of the spinal cord. In addition, there are upper motor neurons that originate in the brain stem's vestibular, red, tectal, and reticular nuclei, which also descend and synapse in the spinal cord.
2. The cranial nerves 3-12 emerge from the brain stem.
3. The brain stem has integrative functions (it is involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, awareness, and consciousness). Thus, brain stem damage is a very serious and often life-threatening problem.
Physical signs of brain stem disease
Diseases of the brain stem can result to abnormalities in the function of cranial nerves which may lead to visual disturbances, pupil abnormalities, changes in sensation, muscle weakness, hearing problems, vertigo, swallowing and speech difficulty, voice change, and co-ordination problems. Localizing neurological lesions in the brain stem may be very precise, although it relies on a clear understanding on the functions of brain stem anatomical structures and how to test them.See also
- Brain stem tumorBrain stem tumorA brain stem tumor is a tumor in the part of the brain that connects to the spinal cord .-Symptoms:The symptoms of brain stem tumors vary greatly,and can include ataxia, cranial nerve palsy, headaches, problems with speech and swallowing, hearing loss,weakness, hemiparesis, vision abnormalities,...
- Cranial nerve nucleusCranial nerve nucleusA cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by...
- Reptilian brain
- Comparative Neuroscience at Wikiversity
External links
- http://www.cancerhelp.org.uk/help/default.asp?page=5019
- http://www.meddean.luc.edu/lumen/Meded/Neuro/frames/nlBSsL/nl40fr.htm
- http://biology.about.com/library/organs/brain/blbrainstem.htm
- http://www.waiting.com/brainanatomy.html
- http://www.martindalecenter.com/MedicalAnatomy_3_SAD.html
- NIF Search - Brainstem via the Neuroscience Information FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...