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Brain Stem: Anatomy

The brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem is a stalk-like structure that connects the cerebrum with the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy and consists of the midbrain, pons, and medulla oblongata. The brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem contains many nerves, pathways, reflex centers, and nuclei and serves as a major relay station for sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology, motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology, and autonomic information. All cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions, except I and II, originate from the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem. The brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep–wake cycle.

Last updated: Dec 5, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

General Features

The brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem is located in the posterior cranial fossa Cranial fossa The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface. Skull: Anatomy on the dorsal aspect of the clivus. There should be CSF space between the clivus and the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem in normal patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship, and the 4th ventricle is posterior to the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem between it and the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy. The midbrain is most superior, followed by the pons, and the medulla oblongata, which is most inferior. 

Divisions (from rostral to caudal)

  • Midbrain
  • Pons
  • Medulla oblongata
The brainstem

Location of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem:
Note the ascending order from the medulla at the base through the pons in the middle, ending with the midbrain at the most rostral portion of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem.

Image: “The Brainstem” by Blausen.com staff (2014). License: CC BY 3.0

Midbrain

  • Connects to the diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face above and the pons below
  • Divided into the ventral tegmentum and the dorsal tectum
  • Contains many vital structures:
    • Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions (CNs) III and IV nuclei
    • Reticular formation
    • Extrapyramidal structures
    • Cerebral aqueduct Cerebral aqueduct Narrow channel in the mesencephalon that connects the third and fourth cerebral ventricles. Ventricular System: Anatomy
  • Blood supply: branches of posterior cerebral artery Posterior cerebral artery Artery formed by the bifurcation of the basilar artery. Branches of the posterior cerebral artery supply portions of the occipital lobe; parietal lobe; inferior temporal gyrus, brainstem, and choroid plexus. Cerebrovascular System: Anatomy (PCA)

Pons

Medulla oblongata

  • Connects brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem with the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy, with the transition occurring at the level of the foramen magnum
  • 3 vital centers located in the medulla:
  • Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions: site of CNs IX, X, XI, and XII nuclei
  • Blood supply (branches of):

Internal structure of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem

3 laminae:

  • Tectum:
    • Consists of quadrigeminal plate and medullary velum 
    • Responsible for auditory and visual reflexes
  • Tegmentum:
    • Middle layer
    • Site of cranial nerve nuclei somatotopic organization 
  • Basis:

Cranial nerve origins

  • Midbrain:
    • Oculomotor (III)
    • Trochlear (IV)
  • Pons:
    • Trigeminal (V)
    • Abducens (VI)
    • Facial (VII)
    • Vestibulocochlear (VIII)
  • Medulla oblongata:
    • Glossopharyngeal (IX)
    • Vagus (X)
    • Spinal accessory (XI)
    • Hypoglossal (XII)
Division of cranial nerves that arise in brainstem

Division of cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions that arise in the brainstem:
Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions (CNs) III–IV in the midbrain, V–VIII in the pons, and IX–XII in the medulla

Image by Lecturio.

Midbrain

Overview

  • Connects diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face to the pons
  • Origin of 2 cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions:
    • III (oculomotor) 
    • IV (trochlear)
Key structures of the midbrain

Key structures of the midbrain, including the superior colliculus Superior Colliculus The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching. Cranial Nerve Palsies, red nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles, crus cerebri, substantia nigra Substantia nigra The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce dopamine, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored melanin is a by-product of dopamine synthesis. Basal Ganglia: Anatomy, cranial nerve (CN) III nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles and nerve, as well as the cerebral aqueduct Cerebral aqueduct Narrow channel in the mesencephalon that connects the third and fourth cerebral ventricles. Ventricular System: Anatomy

Image by Lecturio.

Internal organization

  • Crus cerebri:
    • Major pathway of motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology output from the cortex
    • Anterior portion of cerebral peduncle
  • Substantia nigra Substantia nigra The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce dopamine, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored melanin is a by-product of dopamine synthesis. Basal Ganglia: Anatomy:
    • Member of the basal ganglia Basal Ganglia Basal ganglia are a group of subcortical nuclear agglomerations involved in movement, and are located deep to the cerebral hemispheres. Basal ganglia include the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus. Basal Ganglia: Anatomy
    • Conveys dopaminergic fibers to the basal ganglia Basal Ganglia Basal ganglia are a group of subcortical nuclear agglomerations involved in movement, and are located deep to the cerebral hemispheres. Basal ganglia include the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus. Basal Ganglia: Anatomy
    • Involved in regulation of movement
    • Site of dopamine Dopamine One of the catecholamine neurotransmitters in the brain. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. Receptors and Neurotransmitters of the CNS production
  • Mesencephalic tegmentum:
    • Red nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
    • Oculomotor nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
    • Trochlear nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles
    • Medial longitudinal fasciculus Medial Longitudinal Fasciculus Internuclear Ophthalmoplegia
  • Tectum:
Transverse section of the midbrain

Transverse section of the midbrain at the superior colliculus Superior Colliculus The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching. Cranial Nerve Palsies level

Image: “An anatomical illustration from the 1908 edition of Sobotta’s Anatomy Atlas Atlas The first cervical vertebra. Vertebral Column: Anatomy” by Dr. Johannes Sobotta. License: Public Domain

Additional features

  • Cerebral aqueducts
  • Periaqueductal gray

Arterial supply of the midbrain

  • Various branches of the posterior cerebral artery Posterior cerebral artery Artery formed by the bifurcation of the basilar artery. Branches of the posterior cerebral artery supply portions of the occipital lobe; parietal lobe; inferior temporal gyrus, brainstem, and choroid plexus. Cerebrovascular System: Anatomy
  • Thalamoperforate arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • Medial posterior choroidal artery
Arterial supply of the midbrain

Arterial supply of the midbrain:
Note the perfusion territory of the arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology that supply the midbrain: the collicular artery in red, the thalamoperforate arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology in green, and the medial posterior choroidal artery in blue. All of these vessels are branches of the posterior cerebral artery Posterior cerebral artery Artery formed by the bifurcation of the basilar artery. Branches of the posterior cerebral artery supply portions of the occipital lobe; parietal lobe; inferior temporal gyrus, brainstem, and choroid plexus. Cerebrovascular System: Anatomy.

Image by Lecturio.

Related videos

Pons

Overview

  • Connects the midbrain above to the medulla oblongata below
  • Origin of 4 cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions:
    • V (trigeminal)
    • VI (abducens) 
    • VII (facial)
    • VIII (vestibulocochlear)
Cranial nerves throughout the brainstem

Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions throughout the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem:
Note the 4 cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions that originate from the pons: cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions (CNs) V, VI, VII, and VIII. All of these emerge from the pontine tegmentum.

Image by Lecturio.

Internal organization

  • Basilar pons contains motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers of the following tracts descending via the crus cerebri:
    • Corticopontine
    • Corticospinal
    • Corticobulbar
  • Pontine tegmentum: site of all cranial nerve nuclei associated with the pons

Arterial supply

Arterial supply of the pons

Arterial supply of the pons:
Note the perfusion territory of the arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology that supply the pons: Short circumferential branches of the basilar artery are in red, the long circumferential branches of the basilar artery as well as branches of the superior cerebellar artery Superior cerebellar artery Cerebrovascular System: Anatomy are in blue, and the paramedian branches of the basilar artery are in green.

Image: “ Coronal Coronal Computed Tomography (CT) section of the pons, at its upper part” by Henry Vandyke Carter. License: Public Domain, edited by Lecturio.

Anatomical localization

  • Anterior: prepontine cistern ( cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions (CNs) V and VI)
  • Posterior: 4th ventricle
  • Lateral: cerebellopontine angle Cerebellopontine angle Junction between the cerebellum and the pons. Acoustic Neuroma (CNs VII and VIII)
  • Superior: continuous with midbrain
  • Inferior: continuous with medulla oblongata

Mnemonic: pons rule of 4

  • Origin to 4 of the cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions:
    • V (trigeminal)
    • VI (abducens)
    • VII (facial) 
    • VIII (vestibulocochlear)
  • 4 medial structures with “M”:
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology pathway (corticospinal tract)
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (abducens)
    • Medial lemniscus (somatosensory fibers)
    • Medial longitudinal fasciculus Medial Longitudinal Fasciculus Internuclear Ophthalmoplegia (coordinating CNs III, VI, and VIII functions with the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy)
  • 4 lateral structures with “S”:
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology nuclei (trigeminal)
    • Spinothalamic tract ( pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and temperature)
    • Spinocerebellar pathway ( unconscious Unconscious Those forces and content of the mind which are not ordinarily available to conscious awareness or to immediate recall. Psychotherapy proprioception Proprioception Sensory functions that transduce stimuli received by proprioceptive receptors in joints, tendons, muscles, and the inner ear into neural impulses to be transmitted to the central nervous system. Proprioception provides sense of stationary positions and movements of one’s body parts, and is important in maintaining kinesthesia and postural balance. Neurological Examination
    • Sympathetic pathway

Medulla Oblongata

Overview

  • Extends from the 1st part of the cervical spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy (at the foramen magnum) → lower border of the pons
  • Origin for the lower cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions:
    • IX (glossopharyngeal)
    • X (vagus)
    • XI (accessory)
    • XII (hypoglossal)
  • 3 vital centers in the medulla:
    • Cardiac center: sets the rate of cardiac contractions
    • Medullary rhythmicity center: synchronizes with the pontine respiratory centers Respiratory Centers Part of the brain located in the medulla oblongata and pons. It receives neural, chemical and hormonal signals, and controls the rate and depth of respiratory movements of the diaphragm and other respiratory muscles. Respiratory Regulation to regulate the rhythm of breathing
    • Vasomotor center Vasomotor center ↓ preload and SVR when activated Arterial Pressure Regulation: controls vascular tone

Internal organization

  • Corticospinal tract:
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology pathway beginning in motor cortex Motor cortex Area of the frontal lobe concerned with primary motor control located in the dorsal precentral gyrus immediately anterior to the central sulcus. It is comprised of three areas: the primary motor cortex located on the anterior paracentral lobule on the medial surface of the brain; the premotor cortex located anterior to the primary motor cortex; and the supplementary motor area located on the midline surface of the hemisphere anterior to the primary motor cortex. Cerebral Cortex: Anatomy → lower motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology in the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy 
    • Controls motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology movements of limbs and trunk
  • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles of the trigeminal nerve Trigeminal nerve The 5th and largest cranial nerve. The trigeminal nerve is a mixed motor and sensory nerve. The larger sensory part forms the ophthalmic, mandibular, and maxillary nerves which carry afferents sensitive to external or internal stimuli from the skin, muscles, and joints of the face and mouth and from the teeth. Most of these fibers originate from cells of the trigeminal ganglion and project to the trigeminal nucleus of the brain stem. The smaller motor part arises from the brain stem trigeminal motor nucleus and innervates the muscles of mastication. The 12 Cranial Nerves: Overview and Functions:
    • Carries pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and temperature sensation through Aδ and C nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology from the ipsilateral face 
    • Project to the ventral posteromedial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (VPM) of the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
  • Dorsal column Dorsal column Spinal Cord: Anatomy nuclei:
    • Carries sensation of pressure, vibration Vibration A continuing periodic change in displacement with respect to a fixed reference. Neurological Examination, fine touch, and proprioception Proprioception Sensory functions that transduce stimuli received by proprioceptive receptors in joints, tendons, muscles, and the inner ear into neural impulses to be transmitted to the central nervous system. Proprioception provides sense of stationary positions and movements of one’s body parts, and is important in maintaining kinesthesia and postural balance. Neurological Examination from the ipsilateral body
    • Aɑ and Aß somatosensory fibers from gracile and cuneate nuclei of ipsilateral body
    • Decussate in medulla and continue contralaterally as medial lemniscus
    • Project to the ventral posterolateral nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (VPL) of the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
  • Spinothalamic tract:
    • Carries pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, temperature, and crude touch via Aδ and C nerve fiber from the contralateral body
    • Projects to VPL of the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy
  • Inferior olivary nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles:
    • Major source of input to the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy
    • Involved in motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology control
  • Nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles solitarius: gustatory information
  • Nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles ambiguus: associated with speech and swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility

Arterial supply

Arterial supply of the medulla oblongata

Arterial supply of the medulla oblongata:
Note the perfusion territory of the arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology that supply the medulla oblongata: The most medial portion, illustrated in red, is supplied by the anterior spinal artery Anterior Spinal Artery Anterior Cord Syndrome. Next, in blue, is the supply from the vertebral artery Vertebral artery The first branch of the subclavian artery with distribution to muscles of the neck; vertebrae; spinal cord; cerebellum; and interior of the cerebrum. Lateral Medullary Syndrome (Wallenberg Syndrome). Finally, most laterally, the medulla is supplied by the posterior inferior cerebellar artery Posterior inferior cerebellar artery Cerebrovascular System: Anatomy ( PICA Pica Pica is an eating disorder characterized by a desire or recurrent compulsion to eat substances that are nonnutritive and not food. These compulsions and ingested substances are inappropriate for age or culture. Pica), denoted in green.

Image: “Traverse section of the medulla oblongata at about the middle of the olive” by Henry Vandyke Carter. License: Public Domain, edited by Lecturio.

Brain Stem Reticular Formation

Overview

  • Set of interconnected nuclei:
    • Midbrain: dorsal tegmental nuclei
    • Pons: central tegmental nuclei
    • Medulla: inferior nuclei 
  • Composed of 2 components:
    • Ascending reticular formation (reticular activating system) 
    • Descending reticular formation

Internal organization

  • Median column of reticular nuclei:
  • Medial column of reticular nuclei:
    • Consists of medium and very large neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology, gigantocellular nuclei
    • Innervates CN XII nuclei and responses to glutamatergic stimuli
  • Lateral column Lateral column Spinal Cord: Anatomy of reticular nuclei:
    • Consists of 6 nuclear groups known as the parvocellular nuclei
    • Involved in inspiratory portion of respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose and Nasal Cavity: Anatomy

Clinical Relevance

  • Chiari malformation: Arnold-Chiari malformations Arnold-Chiari malformations A group of congenital malformations involving the brainstem, cerebellum, upper spinal cord, and surrounding bony structures. Type II is the most common, and features compression of the medulla and cerebellar tonsils into the upper cervical spinal canal and an associated meningomyelocele. Type I features similar, but less severe malformations and is without an associated meningomyelocele. Type III has the features of type II with an additional herniation of the entire cerebellum through the bony defect involving the foramen magnum, forming an encephalocele. Type IV is a form a cerebellar hypoplasia. Clinical manifestations of types i-iii include torticollis; opisthotonus; headache; vertigo; vocal cord paralysis; apnea; nystagmus, congenital; swallowing difficulties; and ataxia. Development of the Nervous System and Face are a group of congenital Congenital Chorioretinitis abnormalities that are associated with a bony base of the cranium Cranium The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull: Anatomy causing limitation of space in the posterior fossa affecting the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy, brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem, and upper spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy.
  • Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions: emerge directly via the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification stem through the bony skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull: Anatomy. Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions supply cranial structures and fulfill specific functions. There are 12 cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions that transmit sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology, motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology, and autonomic information to and from the intracranial and pericranial structures, with some interconnection to the rest of the body. 
  • Embryologic development: before the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification reaches the phase at which it looks like the organ, there are several complex processes that occur to achieve this goal. Beginning with neurulation Neurulation An early embryonic developmental process of chordates that is characterized by morphogenic movements of ectoderm resulting in the formation of the neural plate; the neural crest; and the neural tube. Improper closure of the neural groove results in congenital neural tube defects. Gastrulation and Neurulation, the neural tube Neural tube A tube of ectodermal tissue in an embryo that will give rise to the central nervous system, including the spinal cord and the brain. Lumen within the neural tube is called neural canal which gives rise to the central canal of the spinal cord and the ventricles of the brain. Gastrulation and Neurulation and neural crest cells Neural crest cells Gastrulation and Neurulation allow the developing embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week to form a central and peripheral nervous system Peripheral nervous system The nervous system outside of the brain and spinal cord. The peripheral nervous system has autonomic and somatic divisions. The autonomic nervous system includes the enteric, parasympathetic, and sympathetic subdivisions. The somatic nervous system includes the cranial and spinal nerves and their ganglia and the peripheral sensory receptors. Nervous System: Anatomy, Structure, and Classification
  • Diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face: The diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification consists of 4 components: the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy, the epithalamus, the hypothalamus Hypothalamus The hypothalamus is a collection of various nuclei within the diencephalon in the center of the brain. The hypothalamus plays a vital role in endocrine regulation as the primary regulator of the pituitary gland, and it is the major point of integration between the central nervous and endocrine systems. Hypothalamus, and the subthalamus. Overall, the diencephalon Diencephalon The paired caudal parts of the prosencephalon from which the thalamus; hypothalamus; epithalamus; and subthalamus are derived. Development of the Nervous System and Face coordinates unconscious Unconscious Those forces and content of the mind which are not ordinarily available to conscious awareness or to immediate recall. Psychotherapy vegetative and sensorimotor functions.
  • Hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage: disorder of CSF disequilibrium of formation, flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure, and/or absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption, resulting in an increase in the volume of fluid within the cranial cavity. 
  • Parkinson disease Parkinson disease Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson’s Disease: a movement disorder that is characterized by degeneration of dopaminergic neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology of the substantia nigra Substantia nigra The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce dopamine, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored melanin is a by-product of dopamine synthesis. Basal Ganglia: Anatomy, which is a part of the basal ganglia Basal Ganglia Basal ganglia are a group of subcortical nuclear agglomerations involved in movement, and are located deep to the cerebral hemispheres. Basal ganglia include the striatum (caudate nucleus and putamen), globus pallidus, substantia nigra, and subthalamic nucleus. Basal Ganglia: Anatomy.

References

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