Brain Stem: Anatomy

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 Posterior cranial fossa The infratentorial compartment that contains the cerebellum and brain stem. It is formed by the posterior third of the superior surface of the body of the sphenoid (sphenoid bone), by the occipital, the petrous, and mastoid portions of the temporal bone, and the posterior inferior angle of the parietal bone. 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

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

• Connects the midbrain above to the medulla oblongata below
• 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 V, VI, VII, and VIII nuclei
• Blood supply: branches of the basilar artery and anterior inferior cerebellar artery Anterior inferior cerebellar artery Cerebrovascular System: Anatomy

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:
  • Cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) center
  • Medullary rhythmicity center
  • Vasomotor center Vasomotor center ↓ preload and SVR when activated Arterial Pressure Regulation
• 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 anterior spinal artery Anterior Spinal Artery Anterior Cord Syndrome, 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), and posterior inferior cerebellar artery Posterior inferior cerebellar artery Cerebrovascular System: Anatomy

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:
  • Most anterior part
  • Route of motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology pathways

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)

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)

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:
  • Inferior colliculus
  • 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
  • Pretectal nucleus Pretectal Nucleus Pupil: Physiology and Abnormalities

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

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)

Internal organization

• Basilar pons: motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers of the corticopontine, corticospinal, and corticobulbar descending via the crus cerebri
• Pontine tegmentum: site of all cranial nerve nuclei associated with the pons

Arterial supply

• Blood supply to the pons is primarily derived from branches of the basilar artery.
• Additional supply comes from branches of anterior inferior cerebellar artery Anterior inferior cerebellar artery Cerebrovascular System: Anatomy.

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 Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) center: sets the rate of cardiac Cardiac Total Anomalous Pulmonary Venous Return (TAPVR) 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 Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology cortex → 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

• Lateral: 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)
• Medial: anterior spinal artery Anterior Spinal Artery Anterior Cord Syndrome/ 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) ( ASA ASA Anterior Cord Syndrome/ VA VA Ventilation: Mechanics of Breathing)

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 Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion column of reticular nuclei:
  • Extends through medulla, pons, and midbrain
  • Collectively, these constitute raphe Raphe Testicles: Anatomy 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 abnormalities Congenital Abnormalities Malformations of organs or body parts during development in utero. Omphalocele 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 Neural crest The two longitudinal ridges along the primitive streak appearing near the end of gastrulation during development of nervous system (neurulation). The ridges are formed by folding of neural plate. Between the ridges is a neural groove which deepens as the fold become elevated. When the folds meet at midline, the groove becomes a closed tube, the neural tube. Hirschsprung Disease cells 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 Nervous system The nervous system is a small and complex system that consists of an intricate network of neural cells (or neurons) and even more glial cells (for support and insulation). It is divided according to its anatomical components as well as its functional characteristics. The brain and spinal cord are referred to as the central nervous system, and the branches of nerves from these structures are referred to as the peripheral nervous system. 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.