Brain stem

Brain: Brain stem

Latin	truncus encephali
Gray's	subject #187
Part of	Brain
Components	Medulla, Pons, Midbrain
NeuroNames	ancil-218
MeSH	Brain+Stem
Dorlands/Elsevier	b_21/12195821

The brain stem is the lower part of the brain, adjoining and structurally continuous with the spinal cord. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This is a list of the subjects in Gray's Anatomy: IX Neurology The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the Brain stem. In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" NeuroNames is a system of nomenclature for the human and/or macaque Brain. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected Some taxonomies describe the brain stem as the medulla and mesencephalon, where as others include diencephalic regions. The diencephalon (or interbrain is the region of the Brain that includes the Thalamus, Hypothalamus, Epithalamus, Prethalamus or

1 General anatomy
2 Embryology
3 Physiology
4 Physical signs of brainstem disease
5 See also
6 References

General anatomy

Ventral view/medulla and pons

The most medial part of the medulla is the anterior median fissure. The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure Moving laterally on each side are the pyramids. The pyramids contain the fibers of the corticospinal 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 corticospinal or pyramidal tract is a massive collection of Axons that travel between the Cerebral cortex of the Brain and the Spinal
The anterolateral sulcus is lateral to the pyramids. Emerging from the anterolateral sulci are the hypoglossal nerve (CN XII) rootlets. The hypoglossal nerve is the twelfth Cranial nerve (XII leading to the tongue Lateral to these rootlets and the anterolateral sulci are the olives. In Anatomy, the olivary bodies or simply olives (Latin oliva and olivae, singular and plural respectively are a pair of prominent oval structures 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 and X (glossopharyngeal and vagus, respectively). The glossopharyngeal nerve is the ninth of twelve pairs of Cranial nerves. The vagus nerve (ˈveɪˌgəs (VĀ-gəs (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired Cranial nerves, and is the The pyramids end at the pontomedullary junction, noted most obviously by the large basal pons. Between the basal pons, cranial nerve 6, 7 and 8 emerge (medial to lateral). These cranial nerves are the abducens nerve, facial nerve and the vestibulocochlear nerve, respectively. The abducens nerve (the sixth cranial nerve, also called the sixth nerve or simply VI) is a “somatic efferent” nerve that controls the movement of a The facial nerve is the seventh (VII of twelve paired Cranial nerves. The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve Cranial nerves, and is responsible for transmitting sound At the level of the midpons, the large trigeminal nerve, CN V, emerges. The trigeminal nerve (the fifth Cranial nerve, also called the fifth nerve or simply V) is responsible for sensation in the face At the rostral pons, the occulomotor nerve emerges at the midline. The oculomotor nerve is the third of twelve paired Cranial nerves. Laterally, the trochlear nerve has emerged after emerging out of the dorsal rostral pons and wrapping around to the anterior. The trochlear nerve (the fourth cranial nerve, also called the fourth nerve or simply IV) is a motor nerve (a “somatic efferent” nerve that innervates

Dorsal view/medulla and pons

The most medial part of the medulla is the posterior median fissure. The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure Moving laterally on each side is the fasciculus gracilis, and lateral to that is the fasciculus cuneatus. The fasciculus gracilis ( tract of Goll) is a bundle of Axon fibres in the dorsomedial Spinal cord that carries information about fine touch vibrations The fasciculus cuneatus ( tract of Burdach, named for Karl Friedrich Burdach) is a bundle of nerves in the spinal cord which primarily transmits information from the Superior to each of these, and directly inferior to the obex, are the gracile tubercles and cuteanus tubercles, respectively. OBEX (abbreviation of OBject EXchange, also termed IrOBEX) is a communications protocol that facilitates the exchange of binary objects between devices Underlying these are their respective nuclei. The obex marks the end of the 4th ventricle and the beginning of the central canal. For the engineering project see Indiana Central Canal. The central canal is the Cerebrospinal fluid -filled space that runs longitudinally through the The posterior intermediate sulci separates the fasciculi gracilis from the fasciculi cuneatus. Lateral to the fasciculi cuneatus is the lateral funiculus. The most lateral of the bundles of the anterior nerve roots is generally taken as a dividing line which separates the Antero-lateral region into two parts viz
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. 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 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 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. The facial colliculus is an elevated area located on the dorsal pons 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. In the Fourth ventricle, the sulcus limitans forms the lateral boundary of the Medial eminence. 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. The inferior colliculi ( Latin, lower hills) together with the superior colliculi form the eminences of the Corpora quadrigemina, and also part

Spinal Cord to Medulla Transitional Landmark: From a ventral view, there can be seen a decussation of fibers between the two pyramids. Decussation (or decussatio) is used in biological contexts to describe a crossing A pyramid is a Building where the upper surfaces are triangular and converge on one point 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

Main article: Midbrain

The midbrain is divided into three parts. In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" The first is the tectum, which is "roof" in Latin. The tectum (Latin roof) is a region of the Brain, specifically the dorsal part of the Mesencephalon (midbrain Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. The tectum includes the superior and inferior colliculi and is the dorsal covering of the cerebral aqueduct. The inferior colliculus, involved in the special sense of hearing sends its inferior brachium to the medial geniculate body of the diencephalon. The inferior colliculi ( Latin, lower hills) together with the superior colliculi form the eminences of the Corpora quadrigemina, and also part The Medial Geniculate Nucleus or Medial Geniculate Body (MGB is part of the auditory Thalamus and represents the thalamic relay between the Inferior colliculus The diencephalon (or interbrain is the region of the Brain that includes the Thalamus, Hypothalamus, Epithalamus, Prethalamus or Superior to the inferior colliculus, the superior colliculus marks the rostral midbrain. The superior colliculus ( Latin, higher hill) is a paired structure that is part of the Brain 's tectal area. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon. The lateral geniculate nucleus ( LGN) of the Thalamus is a part of the Brain, which is the primary processor of visual information received from the The second part is the tegmentum and is ventral to the cerebral aqueduct. The tegmentum (from Latin for "covering" is a general area within the Brainstem. Several nuclei, tracts and the reticular formation is contained here. Last, the ventral side is comprised of paired cerebral peduncles. The cerebral peduncle, by most classifications is everything in the Mesencephalon except the Tectum. These transmit axons of upper motor neurons.

Midbrain internal structures

Periaqueductal Gray: 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 raphe nucleus 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. The red nucleus is a structure in the Rostral Midbrain involved in Motor coordination.
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. The substantia nigra ( Latin for "black substance" Sömmering) or locus niger is a heterogeneous portion of the midbrain, separating Dopamine is a Hormone and Neurotransmitter occurring in a wide variety of animals including both vertebrates and invertebrates Its dysfunction is implicated in Parkinson's Disease. Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's
Reticular formation: This is a large area in the midbrain that is involved in various important functions of the midbrain. In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" 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.

Embryology

The adult human brainstem emerges from two of the three primary vesicles formed of the neural 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 is the second of the three primary vesicles, and does not further differentiate into a secondary vesicle. In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" This will become the midbrain. The third primary vesicle, the rhombencephalon, will further differentiate into two secondary vesicles, the metencephalon and the myelencephalon. The rhombencephalon (or hindbrain) is a developmental categorization of portions of the Central nervous system in Vertebrates. The metencephalon is a developmental categorization of portions of the Central nervous system. The myelencephalon is a developmental categorization of a portion of the Central nervous system. The metencephalon will become the cerebellum and the pons. The cerebellum ( Latin: "little brain" is a region of the Brain that plays an important role in the integration of sensory perception The myelencephalon will become the medulla.

Physiology

There are three main functions of the brainstem. The first is its role in conduit functions. That is, all information related 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 spinothalamic tract is a sensory pathway originating in the spinal cord Proprioception (ˌproʊpriːəˈsɛpʃən PRO -pree-o-SEP-shun from Latin proprius, meaning "one's own" and perception is the Sense (The facial sensations have similar pathways, and will travel in the spinothalamic tract and the medial lemniscus also). 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 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 brainstem's vestibular, red, tactile, and reticular nuclei, which also descend and synapse in the spinal cord. Second, the cranial nerves 3-12 emerge from the brain stem. Third, the brain stem has integrative functions (it is involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, and consciousness). Thus, brain stem damage is a very serious and often life-threatening problem.

Physical signs of brainstem disease

Diseases of the brainstem 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 brainstem may be very precise, although it relies on a clear understanding on the functions of brainstem anatomical structures and how to test them. ^[1]

References

^ brainstem examination

A cranial nerve nucleus is a collection of Neurons ( Gray matter) in the Brain stem that is associated with one or more Cranial nerves. Reptilian complex or R-complex is a part of the triune brain model ('tri' as in 3 part proposed by Paul D

Dictionary

-noun

(anatomy) The part of the brain that connects the spinal cord to the forebrain and cerebrum.

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