The brainstem (or brain stem ) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord . In the human brain the brainstem is composed of the midbrain , the pons , and the medulla oblongata . The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch , and sometimes the diencephalon is included in the brainstem.
41-438: The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem . It is anterior and partially inferior to the cerebellum . It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing . The medulla contains the cardiovascular center , the respiratory center , vomiting and vasomotor centers, responsible for
82-412: A range of impairments including locked-in syndrome . Duret haemorrhages are areas of bleeding in the midbrain and upper pons due to a downward traumatic displacement of the brainstem. Cysts known as syrinxes can affect the brainstem, in a condition, called syringobulbia . These fluid-filled cavities can be congenital, acquired or the result of a tumor. Criteria for claiming brainstem death in
123-416: Is a disease that attacks the nerves supplying the bulbar muscles. Infantile progressive bulbar palsy is progressive bulbar palsy in children. Both lampreys and hagfish possess a fully developed medulla oblongata. Since these are both very similar to early agnathans , it has been suggested that the medulla evolved in these early fish, approximately 505 million years ago. The status of the medulla as part of
164-402: Is bounded on either side by the inferior cerebellar peduncle , which connects the medulla to the cerebellum . The lower part of the medulla, immediately lateral to the cuneate fasciculus, is marked by another longitudinal elevation known as the tuberculum cinereum . It is caused by an underlying collection of gray matter known as the spinal trigeminal nucleus . The gray matter of this nucleus
205-451: Is composed of paired cerebral peduncles . These transmit axons of upper motor neurons . The midbrain consists of: The pons lies between the midbrain and the medulla oblongata . It is separated from the midbrain by the superior pontine sulcus , and from the medulla by the inferior pontine sulcus . It contains tracts that carry signals from the cerebrum to the medulla and to the cerebellum and also tracts that carry sensory signals to
246-411: Is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve . The base of the medulla is defined by the commissural fibers , crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord. Blood to the medulla is supplied by a number of arteries . The medulla oblongata forms in fetal development from
287-428: 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. Middle cerebellar peduncle
328-404: Is located inferior and lateral to the superior cerebellar peduncle, connecting pons to the cerebellum. Likewise, inferior cerebellar peduncle is found connecting the medulla oblongata to the cerebellum. The main supply of blood to the brainstem is provided by the basilar arteries and the vertebral arteries . The human brainstem emerges from two of the three primary brain vesicles formed of
369-420: Is positioned above the inferior colliculus, and 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 tegmentum which forms the floor of the midbrain, is ventral to the cerebral aqueduct . Several nuclei , tracts , and the reticular formation are contained here. The ventral tegmental area (VTA)
410-488: Is unnecessary. The absence of the cough and gag reflexes , of the corneal reflex and the vestibulo–ocular reflex need to be established; the pupils of the eyes must be fixed and dilated; there must be an absence of motor response to stimulation and an absence of breathing marked by concentrations of carbon dioxide in the arterial blood. All of these tests must be repeated after a certain time before death can be declared. Internal arcuate fibers In neuroanatomy ,
451-457: The anterior external arcuate fibers . The region between the anterolateral and posterolateral sulcus in the upper part of the medulla is marked by a pair of swellings known as olivary bodies (also called olives ). They are caused by the largest nuclei of the olivary bodies, the inferior olivary nuclei . The posterior part of the medulla between the posterior median sulcus and the posterolateral sulcus contains tracts that enter it from
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#1732858176130492-420: The autonomous nervous system which include: A blood vessel blockage (such as in a stroke ) will injure the pyramidal tract , medial lemniscus , and the hypoglossal nucleus . This causes a syndrome called medial medullary syndrome . Lateral medullary syndrome can be caused by the blockage of either the posterior inferior cerebellar artery or of the vertebral arteries. Progressive bulbar palsy (PBP)
533-423: The internal arcuate fibers or internal arcuate tract are the axons of second-order sensory neurons that compose the gracile and cuneate nuclei of the medulla oblongata . These second-order neurons begin in the gracile and cuneate nuclei in the medulla. They receive input from first-order sensory neurons, which provide sensation to many areas of the body and have cell bodies in the dorsal root ganglia of
574-506: The medullary 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 anterior grey column 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
615-413: The myelencephalon . The final differentiation of the medulla is seen at week 20 gestation. Neuroblasts from the alar plate of the neural tube at this level will produce the sensory nuclei of the medulla. The basal plate neuroblasts will give rise to the motor nuclei. The medulla oblongata connects the higher levels of the brain to the spinal cord , and is responsible for several functions of
656-401: The neural tube . The mesencephalon is the second of the three primary vesicles, and does not further differentiate into a secondary brain vesicle . This will become the midbrain. The third primary vesicle, the rhombencephalon (hindbrain) will further differentiate into two secondary vesicles, the metencephalon and the myelencephalon . The metencephalon will become the cerebellum and
697-400: The posterior funiculus of the spinal cord. These are the gracile fasciculus , lying medially next to the midline, and the cuneate fasciculus , lying laterally. These fasciculi end in rounded elevations known as the gracile and the cuneate tubercles. They are caused by masses of gray matter known as the gracile nucleus and the cuneate nucleus . The soma (cell bodies) in these nuclei are
738-400: The pyramidal tracts –the corticospinal tract , and the corticobulbar tract of the nervous system. At the caudal part of the medulla these tracts cross over in the decussation of the pyramids obscuring the fissure at this point. Some other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as
779-451: The thalamus . The pons is connected to the cerebellum by the cerebellar peduncles . The pons houses the respiratory pneumotaxic center and apneustic center that make up the pontine respiratory group in the respiratory center . The pons co-ordinates activities of the cerebellar hemispheres . The pons and medulla oblongata are parts of the hindbrain that form much of the brainstem. The medulla oblongata , often just referred to as
820-409: The tongue , pharynx and larynx . The medulla can be thought of as being in two parts: The anterior median fissure contains a fold of pia mater , and extends along the length of the medulla oblongata. It ends at the lower border of the pons in a small triangular area, termed the foramen cecum . On either side of this fissure are raised areas termed the medullary pyramids . The pyramids house
861-544: The UK have developed in order to make the decision of when to stop ventilation of somebody who could not otherwise sustain life. These determining factors are that the patient is irreversibly unconscious and incapable of breathing unaided. All other possible causes must be ruled out that might otherwise indicate a temporary condition. The state of irreversible brain damage has to be unequivocal. There are brainstem reflexes that are checked for by two senior doctors so that imaging technology
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#1732858176130902-538: The anterolateral sulci are the olives . The olives are swellings in the medulla containing underlying inferior nucleary nuclei (containing various nuclei and afferent fibers). Lateral (and dorsal) to the olives are the rootlets for CN IX ( glossopharyngeal ), CN X ( vagus ) and CN XI ( accessory nerve ). The pyramids end at the pontine medulla 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
943-440: The autonomic functions of breathing , heart rate and blood pressure as well as the sleep–wake cycle . "Medulla" is from Latin, ‘pith or marrow’. And "oblongata" is from Latin, ‘lengthened or longish or elongated'. During embryonic development, the medulla oblongata develops from the myelencephalon . The myelencephalon is a secondary brain vesicle which forms during the maturation of the rhombencephalon , also referred to as
984-432: The beginning of the central canal . The posterior intermediate sulcus separates the gracile fasciculus from the cuneate fasciculus. Lateral to the cuneate fasciculus is the lateral funiculus . Superior to the obex is the floor of the fourth ventricle . In the floor of the fourth ventricle, various nuclei can be visualized by the small bumps that they make in the overlying tissue. In the midline and directly superior to
1025-407: The conveyance of motor and sensory pathways from the rest of the brain to the body, and from the body back to the brain. These pathways include the corticospinal tract (motor function), the dorsal column-medial lemniscus pathway ( fine touch , vibration sensation , and proprioception ), and the spinothalamic tract ( pain , temperature, itch, and crude touch ). The parts of the brainstem are
1066-417: The critical roles of regulating heart and respiratory function, helping to control heart rate and breathing rate . It also provides the main motor and sensory nerve supply to the face and neck via the cranial nerves . Ten pairs of cranial nerves come from the brainstem. Other roles include the regulation of the central nervous system and the body's sleep cycle . It is also of prime importance in
1107-406: The dorsal root of the spinal nerves . Upon decussation (crossing over) from one side of the medulla to the other, also known as the sensory decussation , they are then called the medial lemniscus . The internal arcuate fibers are part of the second-order neurons of the posterior column-medial lemniscus system , and are important for relaying the sensation of fine touch and proprioception to
1148-420: 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 of the vestibular system , which
1189-459: The function of cranial nerves that 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. Brainstem stroke syndrome can cause
1230-442: The hindbrain. The bulb is an archaic term for the medulla oblongata. In modern clinical usage, the word bulbar (as in bulbar palsy ) is retained for terms that relate to the medulla oblongata, particularly in reference to medical conditions . The word bulbar can refer to the nerves and tracts connected to the medulla such as the corticobulbar tract , and also by association to those muscles innervated , including those of
1271-455: The level of the midpons, CN V (the trigeminal nerve ) emerges. Cranial nerve III (the oculomotor nerve ) emerges ventrally from the midbrain, while the CN IV (the trochlear nerve ) emerges out from the dorsal aspect of the midbrain. Between the two pyramids can be seen a decussation of fibers which marks the transition from the medulla to the spinal cord. The medulla is above the decussation and
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1312-436: The medulla at the pontomedullary junction. This region is supplied by the joining of the basilar , vertebral arteries . The posterior inferior cerebellar artery also joins from which a large number of perforating arteries arise. Lateral spinal arteries also emerge to supply the posterior surface of the medulla oblongata. In the medial part of the medulla is the anterior median fissure . Moving laterally on each side are
1353-418: The medulla, is the lower half of the brainstem continuous with the spinal cord. Its upper part is continuous with the pons. The medulla contains the cardiac , dorsal and ventral respiratory groups , and vasomotor centres, dealing with heart rate , breathing and blood pressure . Another important medullary structure is the area postrema whose functions include the control of vomiting . The pons meets
1394-429: The midbrain, the pons, and the medulla oblongata; the diencephalon is sometimes considered part of the brainstem. The brainstem extends from just above the tentorial notch superiorly to the first cervical vertebra below the foramen magnum inferiorly. The midbrain is further subdivided into three parts: tectum , tegmentum , and the ventral tegmental area . The tectum forms the ceiling. The tectum comprises
1435-427: The midbrain. The nuclei of the trigeminal nerve (V), abducens nerve (VI), facial nerve (VII) and vestibulocochlear nerve (VIII) are located in the pons. The nuclei of the glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI) and hypoglossal nerve (XII) are located in the medulla. The fibers of these cranial nerves exit the brainstem from these nuclei. Diseases of the brainstem can result in abnormalities in
1476-456: 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
1517-439: The paired structure of the superior and inferior colliculi and is the dorsal covering of the cerebral aqueduct . The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei, as well as inputs from the auditory cortex. Its inferior brachium (arm-like process) reaches to the medial geniculate nucleus of the diencephalon . The superior colliculus
1558-464: The pons. The more caudal myelencephalon will become the medulla . The brainstem plays important functions in breathing , heart rate , arousal / consciousness , sleep / wake functions and attention / concentration. There are three main functions of the brainstem: Ten of the twelve pairs of cranial nerves either target or are sourced from the brainstem nuclei. The nuclei of the oculomotor nerve (III) and trochlear nerve (IV) are located in
1599-422: The primordial reptilian brain is confirmed by its disproportionate size in modern reptiles such as the crocodile , alligator , and monitor lizard . [REDACTED] This article incorporates text in the public domain from page 767 of the 20th edition of Gray's Anatomy (1918) Brainstem The brainstem is very small, making up around only 2.6 percent of the brain's total weight. It has
1640-404: The second-order neurons of the posterior column-medial lemniscus pathway , and their axons, called the internal arcuate fibers or fasciculi, decussate from one side of the medulla to the other to form the medial lemniscus . Just above the tubercles, the posterior aspect of the medulla is occupied by a triangular fossa, which forms the lower part of the floor of the fourth ventricle . The fossa
1681-424: The spinal cord below. The most medial part of the medulla is the posterior median sulcus . Moving laterally on each side is the gracile fasciculus , and lateral to that is the cuneate fasciculus . 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 fourth ventricle and