Neuroanatomy - Brainstem PDF

11/27/24 Encephalon Animal Body Function VII Luís Resende nov-24 Educational purposes. Egas Moniz School of Health and Sicence 0 Summary Know the...

11/27/24 Encephalon Animal Body Function VII Luís Resende nov-24 Educational purposes. Egas Moniz School of Health and Sicence 0 Summary Know the anatomy of the Brainstem: Medulla oblonga Pons Midbrain Nuclei grey matter White mater: association fibers, commissural fibers and projection fibers nov-24 Educational purposes. Egas Moniz School of Health and Sicence 1 1  11/27/24 https://regionalneurological.com/wp-content/uploads/2020/03/Regional-Neurological_Brain-Science.jpeg Brain (encephalon) Functions: control the organs of the body responsible for the regulation, co-ordination and integration of the rest of the nervous system. its abilities are resembled by its morphological features. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 2 (Konig, 2020) Localization: Housed in the neurocranium Frontal bones Brain Parietal bones (encephalon) Occipital bone Temporal bones Dyce, 2018) Ethmoid bone Sphenoid bone Cranial cavity nov-24 Educational purposes. Egas Moniz School of Health and Sicence 3 2  11/27/24 Brain (encephalon) Can be divided anatomically and functionally Anatomic division: Rhombencephalon (hindbrain) Myelencephalon – medulla oblongata Metencephalon – pons (ventral) and cerebellum (dorsal) Mesencephalon (midbrain) Prosencephalon (forebrain) Diencephalon Telencephalon Functional division: Brainstem Cerebrum Cerebellum nov-24 Educational purposes. Egas Moniz School of Health and Sicence 4 Brainstem Cerebrum Cerebellum Myelencephalon Diencephalon Dorsal Medulla oblongata Hipotalamus Metencephalon Subtlamus Talamencephalon Arquicerebellum Epitalamus Paleocerebellum Talamus ** Neocerebellum Metatalamus Ventral Metencephalon Telencephalon Arquipalium Pons Paleopalium Neopalium Mesencephalon (midbrain) Tectum corpora quadrigeminal, Tegmentum e Cerebellar pedunculus nov-24 Educational purposes. Egas Moniz School of Health and Sicence 5 3  11/27/24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 6 Brainstem nov-24 Educational purposes. Egas Moniz School of Health and Sicence 7 4  11/27/24 Brainstem Functions: Most basic and primitive portion of the brain Main contribution to regulate homeostatic functions Connects the cerebrum with the spinal cord Origin of cranial nerves (except the olfactory) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 8 Brainstem Localization: Occupies the fossae of the floor of the cranial cavity, caudal to the optic canals (Konig, 2020) Anatomic relations: Cranial: Cerebrum, connected by internal capsule and cerebral peduncles Caudal: Spinal cord Dorsal: Cerebellum, connected by three cerebellar peduncles nov-24 Educational purposes. Egas Moniz School of Health and Sicence 9 5  11/27/24 Brainstem Organization: mix of grey and withe matter Reticular formation Grey matter (organized in nuclei) White matter (organized in tracts) Lorenz, 2011 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 10 Brainstem Reticular formation An additional region distinct from the other regions formed by grey matter nuclei and white matter tracts - Grey and white matters are mixed together Extensive area occupying the entire length of the brainstem Lorenz, 2011 It exerts a facilitating or inhibitory action on the cerebral cortex and spinal cord. Neurons give rise to: Reticulospinal tracts Thalamic projections Cerebellar relay sites Visceral relay sites Premotor nuclei nov-24 responsable respiratory and pattern generator Educational purposes. Egas Moniz School of Health and Sicence 11 6  11/27/24 Brainstem Reticular formation Anatomically individual reticular formation nuclei organized in three longitudinal zones: start in reticular and finsih in spinal cord Lateral and medial zones (bilateral) Lateral nuclei (parvocellular neurons) received spinal input and activate reticulospinal neurons. Medial nuclei gives (magnocellular neurons) rise to reticulospinal tracts Project to the cerebellum. Involved in the forebrain arousal and processing visceral information. Raphe nuclei (Unpaired and located along the midline) Neurons release serotonin that affect mood and sensitivity to noxious stimuli Send axons rostrally that affects limbic system and affective behaviours nov-24 Educational purposes. Egas Moniz School of Health and Sicence 12 Brainstem Reticular formation Gray substance organized in nuclei: Cranial nerves nuclei Gracilis and cuneiform nuclei important Pre-cerebellar nuclei Pre-cerebellar system: Nuclei responsible for receiving information from cerebral cortex and spinal cord and send it to cerebellum Essential for motor coordination Tectal nuclei Red nucleus and substantia nigra Hypothalamus nuclei dont have to know where they are nov-24 Educational purposes. Egas Moniz School of Health and Sicence 13 7  11/27/24 Brainstem Cranial nerves nuclei - overview Neurons associated with cranial nerves are found at all levels of the brainstem. Individual cranial nerve nuclei form interrupted longitudinal columns that extend from the midbrain caudally, even entering the spinal cord nov-24 Educational purposes. Egas Moniz School of Health and Sicence 14 Brainstem Cranial nerves nuclei - overview + fibres of cranial nerve General Somatic afferent column - red General Visceral afferent column - orange Special somatic afferente column Special visceral afferent column General Somatic efferent column – dark blue and light blue Visceral efferent (parasympathetic) column - green Special visceral efferent nov-24 Educational purposes. Egas Moniz School of Health and Sicence 15 8  11/27/24 Cranial nerves - Organized according to their function: Sensory nerves with receptors in head, body and limbs General Somatic Afferent Attention à connaitre Pathways (GSA) CN V (and spinal nerves) Sensory neurons from visceral Motor neurons that innervate skeletal structures – head, body cavities striated muscle of the head (and and blood vessels skeleton) General Visceral Afferent General Somatic Efferent Pathways Pathways (GVA) Efferent pathways (GSE) CN VII, IX, X (and spinal nerves) Cranial Nerve (CN) III, IV, VI, XII (and Afferent pathways spinal nerves) Vision and hearing Motor neurons that innervate skeletal striated muscle of the head with Special Somatic Afferent different embryonic origin of the GSE. Pathways (SSA) Special Visceral Efferent Pathways CN II, VIII (SVE) CN V, VII, IX, X, XI Associated with the vestibular system Motor neurons of the autonomic Special Proprioception (SP) nervous system CN VIII General Visceral Efferent Pathways (GVE) CN III, VII, IX, X (and spinal nerves) General Proprioception (GP) CN V (and spinal nerves) Recommendation: Do not memorize fiber type content per cranial nerve or Taste and Smell nucleus. Rather, learn what a nerve/nucleus innervates and then you can Special Visceral Afferent deduce its fiber type content! Fiber type understanding provides a useful Pathways (SVA) overview of a nerve's innervation role CN I, VII, IX, X nov-24 Educational purposes. Egas Moniz School of Health and Sicence 16 Brainstem Efferent nuclei of the cranial nerves General Somatic efferent column motor nucleus of the hypoglossal nerve (XII) Langue motor nucleus of the abducente nerve (VI) motor nucleus of the trochlear nerve (IV) motor nucleus of the oculomotor nerve (III) General Visceral efferent (parasympathetic) column parasympathetic nucleus of the vagus nerve (X) parasympathetic nucleus of the glossopharyngeal nerve (IX) parasympathetic nucleus of the facial nerve (VII) parasympathetic nucleus of the oculomotor nerve (III) Special visceral eferente column motor nucleus of the trigeminal nerve (V) motor nucleus of the facial nerve (VII) for facial muscle nucleus ambigus (motor nucleus of vagal nerve and and facial glossopharyngeal nerves) motor nucleus of the accessory nerve (XI) expressions nov-24 Educational purposes. Egas Moniz School of Health and Sicence 17 9  11/27/24 Brainstem optic nerve move the eye muscle Efferent nuclei of the cranial nerves General Somatic efferent column motor nucleus of the hypoglossal nerve (XII) muscles of the tongue motor nucleus of the abducente nerve (VI) rectus lateral and eyeball retractor muscles motor nucleus of the trochlear nerve (IV) dorsal oblique muscle motor nucleus of the oculomotor nerve (III) dorsal, medial and ventral rectus muscle, levator palpebrae superioris muscle, and ventral oblique muscles nov-24 Educational purposes. Egas Moniz School of Health and Sicence 18 Brainstem Efferent nuclei of the cranial nerves General Visceral efferent (parasympathetic) column parasympathetic nucleus of the vagus nerve (X) abdominal and thoracic organs parasympathetic nucleus of the glossopharyngeal nerve (IX) parotid and zigomatic salivary glands parasympathetic nucleus of the facial nerve (VII) nasal, lacrimal,mandibular, and sublingual glands parasympathetic nucleus of the oculomotor nerve (III) Constrictor muscles of the pupil and ciliary muscles of the eye nov-24 Educational purposes. Egas Moniz School of Health and Sicence 19 10  11/27/24 Brainstem Efferent nuclei of the cranial nerves Special visceral efferente column motor nucleus of the trigeminal nerve (V) motor nucleus of the facial nerve (VII) nucleus ambiguous (motor nucleus of vagal nerve and glossopharyngeal nerves) 1st visceral arch - muscles of mastication motor nucleus of the accessory nerve (XI) 2nd visceral arch – muscles of the face or facial expression 3rd, 4th, and 6th visceral arches – striated muscles of the larynx and pharynx (vocalization and swallowing), and some of the neck nov-24 Educational purposes. Egas Moniz School of Health and Sicence 20 Brainstem Afferent nuclei of the cranial nerves General Somatic afferent column mesencephalic nucleus of the trigeminal nerve (V) Propioceptive sensation of the teeth, mouth, temporomandibular joint, eye muscles, and mastication. principal (pontine) sensory nucleus of the trigeminal nerve (V) Tactile sensations or detailed pressure of the ipsilateral side of the head. nucleus of the descending (spinal) tract of the trigeminal nerve (V) Pain and temperature of the head by the 3 branches of the trigeminal N. They receive fibers from the glossopharyngeal and vagus N. (sensitivity of the skin of the inner surface of the pinna, internal acoustic meatus, tympanic membrane and meninges). nov-24 Educational purposes. Egas Moniz School of Health and Sicence 21 11  11/27/24 Brainstem Afferent nuclei of the cranial nerves General Visceral afferent column (general and special) nucleus of the solitary tract (vagus nerve (X), glossopharyngeal nerve (IX), and facial nerve (VII)) rostral part- related to taste. It receives the fibers with taste sensitivity from the facial and glossopharyngeal nerves. caudal part - receives the intraceptive information collected by the vagus and glossopharyngeal nerves at the level of the carotid body, lungs and bronchi. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 22 Brainstem Afferent nuclei of the cranial nerves Special somatic afferente column vestibular and cochlear nuclei of the vestibulocochlear nerve (VIII) Vestibular nuclei - maintain head position, coordinate eye movements, maintain balance and trunk posture. Cochlear nuclei - receive acoustic stimuli. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 23 12  11/27/24 Brainstem Other nuclei Gracillis nucleus Medial cuneate nucleus Nucleus Z Olivary nucleus Lateral cuneate nucleus Caudal colliculus Rostral colliculus Red nucleus Substantia nigra nov-24 Educational purposes. Egas Moniz School of Health and Sicence 24 Brainstem Anatomic parts: A. Diencephalon or interbrain Thalamus, hypothalamus, epithalamus and subthalamus B. Mesencephalon or midbrain Tectum, cerebral aqueduct, tegmentum and cerebral peduncles C. Metencephalon (ventral) Pons D. Myelencephalon or afterbrain Medulla oblongata and caudal part of IV ventricle nov-24 Educational purposes. Egas Moniz School of Health and Sicence 25 13  11/27/24 Diencephalon http://www.cvmbs.colostate.edu/ nov-24 Educational purposes. Egas Moniz School of Health and Sicence 26 Diencephalon Functions: Provides sensorial information to cerebral cortex Control of hypophysis Influence behavior and autonomic nervous system Regulate sexual activity and the circadian cycle Associated with the limbic system nov-24 Educational purposes. Egas Moniz School of Health and Sicence 27 14  11/27/24 Diencephalon Rostral extent of the brainstem Internal capsule: mass of corticopedal and corticofugal projection axons connecting the diencephalon bilaterally to each cerebral hemisphere Third Ventricle Divided in 5 regions: Epithalamus Thalamus Metathalamus Hypothalamus Subthalamus Hypophyse nov-24 Educational purposes. Egas Moniz School of Health and Sicence 28 Diencephalon Epithlamus Thalamus Hipothalamus http://www.cvmbs.colostate.edu/ nov-24 Educational purposes. Egas Moniz School of Health and Sicence 29 15  11/27/24 Diencephalon Epithalamus – dorsal view The most dorsal part of the diencephalon, forming a film over the thalamus. The smallest and oldest portion of the diencephalon. Formed by: pineal gland, habenular nuclei and caudal commissure (conects the rostral colliculus) Function: functionally and anatomically related to the limbic system. It is a reflex area of smell. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 30 Diencephalon A savoir Epithalamus – dorsal view tout ca Pineal gland (25) et que Habenular commissure (3) c'et Habenula relier avec le 3rd ventricle systeme Habenular striat limbic Habenula Habenular comissure Pineal gland nov-24 Educational purposes. Egas Moniz School of Health and Sicence 31 16  11/27/24 Diencephalon Epithalamus – dorsal view Pineal gland (17) Endocrine gland situated between the habenular nuclei and the caudal commissure Composed of pinealocytes and glial cells contained within connective tissue trabeculae derived from meninges. Lacks a blood-brain barrier. Pinealocytes secrete melatonin and its production is inhibited by daylight (circadian rhythm) Habenula: Receives information from the limbic system and basal nuclei Formed by habenular nuclei (25) and habenular commissure (16). It connects the forebrain and midbrain within the epithalamus. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 32 Diencephalon Thalamus – medial view Largest part of the diencephalon and can be divided in dorsal thalamus and subthalamus The thalamus is bilateral, both parts fuse to each other across the thirth ventricule. Closely linked to the cerebral cortex, via reciprocal connections – is the major relay station that integrates sensory and motor signals before projecting to the cerebral córtex. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 33 17  11/27/24 Diencephalon Thalamus – medial view Dorsal thalamus Several nucleus divided in groups: Rostral, lateral, medial and reticular thalamic nuclei Afferent and efferent pathways Provide information to brain, including sense organs (taste, vision, acoustic, vestibular) Part of the limbic system Thalamocortical circuits are essential for movement. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 34 Diencephalon Thalamus – medial view Thalamus - bilateral Interthalamic adhesion (33) 3rd ventricle (32) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 35 18  11/27/24 Diencephalon Thalamus – medial view Interthalamic adhesion (33) Connects both parts of the thalamus at their medial surfaces contains thalamic nuclei but not commissural axons. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 36 Diencephalon Thalamus – medial view 3rd ventricle (3) Narrow chamber separating right and left halves of the diencephalon, except where the interthalamic adhesion occupies the center of the ventricle Bilaterally a dorsolateral interventricular foramen allows the third ventricle to communicate with the lateral ventricle on each side. The rostral wall of the third ventricle is formed by lamina terminalis Combined ependyma and pia mater, constituting tela choroidea forms the roof of the third ventricle and gives rise to paired choroid plexuses. Ventrally, the third ventricle exhibits an optic recess (5) between the optic chiasm and the lamina terminalis, a neurohypophyseal (infundibular) recess (4) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 37 19  11/27/24 Diencephalon Metathalamus or dorsal caudal thalamus – dorsal view The metathalamus consists of lateral (4) and medial (4) geniculate bodies (nuclei), which function like thalamus but are specialized for vision and audition, respectively nov-24 Educational purposes. Egas Moniz School of Health and Sicence 38 Diencephalon Methathalamus or caudal dorsal thalamus lateral geniculate nucleus located dorsal, rostral, and slightly lateral to the medial geniculate body receives fibers of the optic tract, then projects visual signals to the visual cortex and to the rostral colliculus (visual reflex center of the midbrain) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 39 20  11/27/24 Diencephalon Methathalamus or caudal dorsal thalamus medial geniculate nucleus comprises the caudal extent of the diencephalon. It is attached to the lateral surface of the midbrain. mediate the auditory signals to the auditory cortex. Connected to the caudal colliculus (auditory reflex center of the midbrain) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 40 Diencephalon Hypothalamus Functions: Maintenance of homeostasis, body temperature, eating and drinking habits, circadian cycles and sleep-wake cycle. Important in affective behaviors, contributing to behaviors related to anger, escape, pleasure, reproductive behavior and stress response - Limbic System. Controls the autonomic nervous system: Stimulation of the rostral region of the hypothalamus –parasympathetic stimulation Stimulation of the caudal region of the hypothalamus – sympathetic stimulation nov-24 Educational purposes. Egas Moniz School of Health and Sicence 43 21  11/27/24 Diencephalon Hypothalamus Ventral to the thalamus and medial to the subthalamus; occupies the floor and the wall of the third ventricle Ventral surface of the diencephalon shows only hypothalamic regions: Rostral end – dorsal to the optic chiasm (rostral) (34) Tuber cinereum (level of the hypophysis) (31) Infunfibulum (neurohypophysis) (30) Hypophysis = neurohypophysis (26) + adenohypophysis (28) Bilateral mamillary bodies (caudally) (27) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 44 Diencephalon Hypothalamus rostral end is above the optic chiasm – Optic nerve (II) - 75% (dogs and cats) of optic nerve axons cross in the optic chiasm and travel through the optic tracts to the lateral geniculate nucleus (thalamus) tuber cinereum - is the swollen region of the ventral hypothalamic surface. It gives rise to an infundibulum with an attached neural lobe. Together these constitute the neurohypophysis. hypophysis – controls endocrine activity neurohypophysis - includes the infundibulum and neural lobe of the pituitary paraventricular nucleus and supraotic nucleus (neurohypophysis) – produced vasopressin and oxytocin adenohypophysis – glandular epithelial tissue nov-24 Educational purposes. Egas Moniz School of Health and Sicence 45 22  11/27/24 Diencephalon Hypothalamus Infundibulum – a funnel-shaped, ventral extension of the hypothalamus connecting the hypophysis with the hypothalamus Mammillary bodies – mammillary nuclei: Caudal and ventral hypothalamus Receive axons from the hippocampus and thalamus. They are associated with memory and the Limbic System. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 46 Diencephalon Hypothalamus Subdivisions: rostral (supraquiasmatic) region that is dorsal to the optic chiasm and bounded rostrally by lamina terminalis. intermediate (tuberal) region at the level of the tuber cinereum caudal (mammilary) region that includes the mamillary body nov-24 Educational purposes. Egas Moniz School of Health and Sicence 47 23  11/27/24 Diencephalon Hypothalamus – rostral transverse region - suprachiasmatic Dorsal to the Optic chiasm – Optic nerve (II): Nuclei: Preotic nucleus: more rostral - parasympathetic activity Rostral hypothalamic nucleus: body temperature reduction (panting, sweating) Suprachiasmatic nucleus: receives retinal input and controls circadian rhythms (e.g., body temperature, sleep and wakefulness, hormone levels) Paraventricular nucleus and supraotic nucleus: form tracts ending in the neurohypophysis - Neurons of both nuclei produce vasopressin (antidi- uretic hormone) and oxytocin hormones. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 48 Diencephalon Hypothalamus – intermediate transverse region - tuberal Region at the level of the tuber cinereum Nuclei: Dorsomedial hypothalamic nucleus Ventromedial hypothalamic nucleus: Satiety center Lesion: voracious appetite Lateral hypothalamic nucleus: Feeding center Lesion: anorexia and weight loss nov-24 Educational purposes. Egas Moniz School of Health and Sicence 49 24  11/27/24 Diencephalon Hypothalamus – caudal transverse region - mammilary Mammillary bodies Nucleus: Caudal hypothalamic nucleus - controls sympathetic activity nov-24 Educational purposes. Egas Moniz School of Health and Sicence 50 Diencephalon Subtathalamus Ventral to the thalamus and lateral to the hypothalamus - continuation of the midbrain tegmentum. It features multiple nucleus. It contains the zona incerta, subthalamic nucleus, and white matter fields that border these nuclei. Part of the Limbic system and motor control nov-24 Educational purposes. Egas Moniz School of Health and Sicence 51 25  11/27/24 Diencephalon Form the optic nerve Nerve fibers originate in that passes through the CN II – Optic nerve the retina sclera and enters in the skull through the optic canal It is not a true nerve but a nervous tract (it is surrounded by cranial meninges and myelin is produced by oligodendrocytes): Pass the optic chiasm Then continues as optic (diencephalon) tracts to the (decussation) The optic tracts (fibers split and follow two paths): -Special somatic afferent pathway Conscious pathway: Lateral geniculate body to the Occipital lobe (visual cerebral cortex) Reflex pathway: pretectal region and rostral colliculi (mesencephalon) Ø The proportion of fibres that are exchanged with the opposing optic nerve is correlated with the Dyce, 2010 degree of binocular vision enjoyed by the species. Ø In most birds, vision essentially monocular, all fibres decussate. Ø In the dog and cat, binocular vision, approximately 75% of the optic nerve fibres decussate Ø In primates, binocular vision is best developed, approximately 50% of the fibres decussate. 2024 Instituto Universitário Egas Moniz - MIMV 52 52 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 53 26  11/27/24 CN II – Optic nerve Optic quiasma Optic tracts Counscious visual Reflex pupillary perception pathway pathway The optic tract synapses in Some fibres leave the optic the lateral geniculate tract to terminate in the nucleus (5) and in the optic rostral colliculi (7) of the thalamus. midbrain and pretectal nuclei From the thalamus second-stage neurons Synapse on neurons of the project, via the optic radiation (6) of the oculomotor nerve located in the internal capsule, on the visual cortex midbrain (pretectal region) that located within the occipital lobe of each are responsible for reducing hemisphere. pupillary diameter in response to http://www.cvmbs.colostate.edu/vetneuro/index.html light Information from the rostral colliculi pass through the middle cerebellar peduncle to the cerebellum) Neurologic exam (Menace response) Synapse on lower motor neurons https://vmerc.uga.edu/CranialNerves/mrp.html in the cervical spinal cord – 2024 Instituto Universitário Egas Moniz - MIMVtectospinal tract 54 54 Brainstem - Mesencephalon or midbrain Functions: Determined by cranial nerves III and IV, reflex center for audition (caudal colliculus) and vision (rostral colliculus) Coordination of voluntary motor function, locomotion, muscle tonus and body posture nov-24 Educational purposes. Egas Moniz School of Health and Sicence 55 27  11/27/24 Brainstem - Mesencephalon or midbrain Formed by: Tectum of the midbrain: Rostral colliculi (paired) Caudal colliculi (paired) Mesencephalic aqueduct Cerebral peduncles (paired): midbrain region located ventral to the tectum and aqueduct 3 regions: tegmentum, substantia nigra, crus cerebri. Cranial nerves: Trochlear (IV) and https://www.google.com/url?sa=i&url=http%3A%2F%2Fvanat.cvm.umn.edu%2FneurLab3%2Fpages%2FMidDgMed1074.html&psig=AOvVaw0HIZSD00VjthHAhg- oculomotor (III) qdKNo&ust=1699879016165000&source=images&cd=vfe&opi=89978449&ved=0CBIQjRxqFwoTCNjxrfy8voIDFQAAAAAdAAAAABBH Tegmentum the floor = TEG A savoir quelle nerf a pour origin the pons( trigeminal et abucens) ou la retine (optic nerve) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 56 Lateral view Dorsal view nov-24 Educational purposes. Egas Moniz School of Health and Sicence 57 28  11/27/24 Brainstem - Mesencephalon or midbrain Formed by – medial view Tectum of the midbrain: Rostral colliculi (paired) Caudal colliculi (paired) Comissure of rostral and caudal coliculli (14) Mesencephalic aqueduct (27´´) Cerebral peduncles (paired): midbrain region located ventral to the tectum and aqueduct 3 regions: tegmentum, substantia nigra, crus cerebri (19). Cranial nerves: Trochlear and oculomotor nov-24 Educational purposes. Egas Moniz School of Health and Sicence 58 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 59 29  11/27/24 Brainstem - Mesencephalon or midbrain Formed by – ventral view Crus cerebri (12) Interpeduncular fossa (13) Depression between the two peduncles Interpeduncular nucleus: associated with the limbic system Mesencephalic reflex center Cranial nerves: Trochlear (IV) and oculomotor (III) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 60 Brainstem - Mesencephalon or midbrain Mesencephalic aqueduct: Links the fourth ventricle (hindbrain) with the third ventricle (diencephalon) Surrounded by periaqueductal grey matter - important for endogenous analgesia system (high concentration of opiace receptors) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 61 30  11/27/24 Dorsal view Brainstem - Mesencephalon or midbrain Tectum of the midbrain: Rostral colliculi (paired), 3 layers: Conections with the lateral geniculate body (4) Superficial layer receive axons from both the optic tract and visual cortex via the brachium of the rostral colliculus Intermediate layer gives rise to the tectonuclear and medial tectospinal tracts that leave the colliculus for orientation reflexes and eye movements Deep layer receive auditory and spinal cord axons nov-24 Educational purposes. Egas Moniz School of Health and Sicence 62 Dorsal view Brainstem - Mesencephalon or midbrain Tectum of the midbrain: Caudal colliculi (8)(paired): Executes auditory reflex* via the medial tectospinal tract that leave the colliculus for orientation reflexes and eye movements * (e.g. turning the head in response to sound) Receives axons from the lateral lemniscus, commissure of the caudal colliculi (7), medial geniculate body (5), auditory area of the cerebral cortex, and the cerebellum nov-24 Educational purposes. Egas Moniz School of Health and Sicence 63 31  11/27/24 Brainstem - Mesencephalon or midbrain Tectum of the midbrain: Tectal nucleus: Any of nuclei residing in colliculus; relay functions for the visual and auditory systems and integrate reflex functions Pre-tectal nucleus: Between the colliculus and diencephalon; Controls the eye movement and pupillary light reflex. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 64 Brainstem - Mesencephalon or midbrain Cerebral peduncle (bellow the tectum) Formed by: 1. Tegmentum: Ventral to the mesencephalic aqueduct and dorsal to the substantia nigra Contains: gray matter (sensory and motor nuclei) Red nucleus and nuclei associated with reticular formation, cranial nerves white matter (ascending and descending tracts) interwoven gray and white matter – reticular formation Red nucleus receives input from the motor cortex to drive voluntary movement Reticular formation receives axonal input from spinoreticular and spinothalamic - responsible for maintaining awake status neuromodulation, and the mesencephalic locomotor region nov-24 Educational purposes. Egas Moniz School of Health and Sicence 65 32  11/27/24 Brainstem - Mesencephalon or midbrain Cerebral peduncle (bellow the tectum) Formed by: 1. Tegmentum: Red nucleus – in the rostral midbrain tegmentum, ventrolateral to the periaqueductal gray. Part of the motor system: receives input from the three motor centers (cerebral cortex, basal nuclei, and cerebellum) to drive voluntary movement gives rise to the rubrospinal tract and rubro- olivary fibers Motor and parasympathetic nucleus of the oculomotor nerve (III) Motor nucleus of the trochlear nerve (IV) Mesencephalic nucleus of trigeminal nerve (V) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 66 Brainstem - Mesencephalon or midbrain Cerebral peduncle (bellow the tectum) Formed by: 2. Substantia nigra: Grey matter immediately dorsal to the crus cerebri It participates in the control of movements – part of the motor system - but is not directly related to the spinal cord, exercising its function through connections with the basal nuclei of th cerebral cortex. Reticular (dorsal) and compact (ventral) Human brain neurons in the substantia nigra contain portion black pigments, and degeneration of this neurons results in Parkinson´s disease. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 67 33  11/27/24 Brainstem - Mesencephalon or midbrain Cerebral peduncle (bellow the tectum) Formed by: 3. Crus cerebri (12): covers the ventral surface of the midbrain. Massive bundle of motor fibers of corticonuclear, corticopontine, and corticospinal tracts. motor fibers that arise from neuron cell bodies in the motor cerebral cortex and descend in the internal capsule that runs lateral to the to the thalamus and caudate nucleus and go to the brainsteam and spinal cord. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 68 Brainstem - Mesencephalon or midbrain * pyramidal tract 3. Crus cerebri: corticonuclear tracts* – terminates in all cranial motor nuclei of the brainsteam and some fibers terminates in the spinal cord; - control of voluntary motor functions: eye movement, mastication, blinking, and swallowing. corticopontine tracts* – terminates in the pons and projects to the contralateral cerebellum; - mediate the motor information to the cerebellum. corticospinal tracts – reaches the contralateral side of the spinal cord to terminate in the spinal motor nuclei. - voluntary control of the skeletal muscles. 69 34  11/27/24 70 Brainstem - Mesencephalon – Midbrain Cranial nerves nuclei Mesencephalic nucleus of trigeminal nerve (V) Motor nucleus of the trochlear nerve (IV) Motor and parasympathetic nuclei of the oculomotor nerve (III) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 71 35  11/27/24 CN III – Oculomotor nerve General somatic efferent pathways (A) and general visceral efferent pathways (B) A. Somatic efferent axons – innervate skeletal muscle of extraocular muscles - Oculomotor nuclei of the rostral mesencephalon B. Parasympathetic efferent axons – innervate ciliary smooth muscle - Parasympathetic nucleus of the oculomotor nerve (rostral to the motor nuclei) 2024 Instituto Universitário Egas Moniz - MIMV 72 72 CN III – Oculomotor nerve Oculomotor nerve emerge from the mesencephalon in the Pass through the orbital fissure interpedencular fossa A. Somatic efferent axons – innervate skeletal muscle of extraocular muscles – Origin: Oculomotor nuclei of the rostral mesencephalon Entering in the orbita the nerve is divided into *The ventral branch also present the Dorsal branch – Dorsal rectus muscle, levator parasympathetic efferent axons palpebrae superioris muscle Ventral branch* – medial and ventral rectus muscles and ventral oblique muscle http://www.cvmbs.colostate.edu/vetneuro/index.html Dyce, 2010 2024 Instituto Universitário Egas Moniz - MIMV 73 73 36  11/27/24 CN III – Oculomotor nerve B. Parasympathetic efferent axons – innervate ciliary smooth muscle - Parasympathetic nucleus of the oculomotor nerve (rostral to the motor nuclei) Parasympathetic (PS) innervation of the eye Origin PS nucleus of oculomotor nerve (CN III) in midbrain Preganglionic pathway Oculomotor nerve Ganglion and location Ciliary ganglion (1) just caudal to the eye Postganglionic pathway With somatic motor fibers of the oculomotor nerve - de Lahunta, 2015 short ciliary nerves - innervate the ciliary m. (in the eye) Sympathetic Nervous System: Postganglionic fibers of the sympathetic system will also form the short Target organ and function Iris and ciliary body ciliary nerves:. Pupillary light reflex and accommodation Postganglionic fibres of the cranial cervical ganglion (sympathetic): Innervation: contracts the sphincter pupillary m - contracts the di l at or pupi l l ar y muscle - dilate the pupil Constrict the pupil Neurologic exam (Pupillary reflex) 2024 Instituto Universitário Egas Moniz - MIMV https://vmerc.uga.edu/CranialNerves/plrp.html 74 74 CN IV – Trochlear Cell bodies of neurons are in the Trochlear nucleus of midbrain nerve (mesencephalon) Pass through the orbital fissure Single cranial nerve with a dorsal origin (emerge caudally to the contralateral caudal colliculus General somatic efferent pathway The only cranial nerve that innervates only the contralateral side from which it originates Single cranial nerve with a dorsal origin Somatic motor nerve: (emerge caudally to the contralateral caudal colliculus innerve dorsal oblique muscle of the eye on the contralateral side Dyce, 2010 2024 Instituto Universitário Egas Moniz - MIMV 75 75 37  11/27/24 Brainstem - Metencephalon (ventral)– Pons Ventral portion of the metencephalon: Pons and cranial part of the IV ventricle Pons: between the midbrain (mesencephalon) rostrally and medulla oblongata caudally distinguished by transverse fibers along its ventral surface Dorsal part: Tegmentum Ventral part: Transverse pontine fibers Dyce, 2018 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 76 Brainstem - Metencephalon (ventral)– Pons Dorsal part: cerebellar peduncles and rostral portion of the fourth ventricule Tegmentum: ventral to the fourth ventricule and dorsal to the base of the pons gray matter (sensory and motor nuclei), White matter (ascending and descendig tracts) and reticular formation Ventral part: between the crus cerebri and the trapezoid body covered by transverse pontine fibers nov-24 Educational purposes. Egas Moniz School of Health and Sicence 77 A apprendre jusque la pour le deuxième test 38  11/27/24 Brainstem - Metencephalon (ventral)– Pons External anatomy – Dorsal view Rostral cerebellar peduncle (11) Caudal cerebellar peduncle (10) Middle cerebellar peduncle (9) Median sulcus in fourth ventricle (17) - midline of the rhomboid fossa (floor of the 4th ventricle) 15´ Sulcus limitans (19) 22 23 24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 78 Brainstem - Metencephalon (ventral)– Pons Cerebellar peduncles Brainstem is connected to the cerebellum by axons within three cerebellar peduncles: Rostral cerebellar peduncle (11) Middle cerebellar peduncle (9) 22 15´ 23 Caudal cerebellar peduncle (10) 24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 79 39  11/27/24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 80 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 81 40  11/27/24 Brainstem - Metencephalon (ventral)– Pons Rostral cerebellar peduncle (11) Connects the cerebellum with the midbrain (mesencephalon) Undirectional bundle: it is largely composed of efferent fibers leaving the cerebellum to synapse in the midbrain, red nucleus, reticular 15´ 22 formation, and thalamus 23 cerebellum rapidly influence 24 the motor cortex nov-24 Educational purposes. Egas Moniz School of Health and Sicence 82 Brainstem - Metencephalon (ventral)– Pons Middle cerebellar peduncle (9) Connects the pons to the cerebellum Origin in the transverse pontine fibers Afferent fibers – only – from the pons (part of the corticopontocerebellar tract = corticopontine + pontocerebellar tracts). nov-24 Educational purposes. Egas Moniz School of Health and Sicence 83 41  11/27/24 Brainstem - Metencephalon (ventral)– Pons Caudal cerebellar peduncle (10) Connects the medulla oblongata to the cerebellum Bidirectional bundle: Afferent fibers (proprioceptive) from the brain steam and spinal cord ,as well as from the vestibular nuclei, the olivary nucleus, and the reticular formation. Efferent fibers from the 22 15´ flocculonodular nuclei to the 23 vestibular nuclei and reticular 24 formation nov-24 Educational purposes. Egas Moniz School of Health and Sicence 84 Brainstem - Metencephalon (ventral)– Pons External anatomy - Ventral view Basilar sulcus – (basilar artery) Pons (14) – transverse pontine fibers Dyce, 2018 Cranial nerves V nov-24 Educational purposes. Egas Moniz School of Health and Sicence 85 42  11/27/24 Brainstem - Metencephalon (ventral)– Pons Transverse pontine fibers (14) Arise from contralateral pontine nuclei Run along the ventral surface of the pons and form the Dyce, 2018 contralateral middle cerebellar peduncle Part of the pre-cerebellar system Receives input from cerebral cortex and sends to cerebellum nov-24 Educational purposes. Egas Moniz School of Health and Sicence 86 Brainstem - Metencephalon (ventral)– Pons Trigeminal nerve (CN V) Origin in the lateral region of the pons Afferent neurons: Spinal tract of the trigeminal nerve – nucleus of the spinal tract of V (medulla): nociception and temperature Somatic efferent neurons: from the head Motor nucleus of the trigeminal nerve (pons): Pontine sensory nucleus of the trigeminal nerve (pons): Axons form a motor root that joins the mandibular discriminative touch from the head nerve from the trigeminal nerve. Innervate muscles of mastication. Nucleus of the mesencephalic tract of V (mesencephalon): proprioception from the head nov-24 Educational purposes. Egas Moniz School of Health and Sicence 87 43  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Medulla oblongata Located in the fossa medullae oblongata, dorsal to the Dyce, 2018 basioccipital Dorsally contact with the cerebellum (metencephalon) Rostrally contact with the pons (metencephalon) Caudally continuous with the spinal cord the border between the two is arbitrarily defined as the transverse plane just rostral to the first cervical nerves. Its rostral part is widened as the result of an accumulation of nuclei; and the central canal of the spinal cord opens into the fourth ventricle Dyce, 2018 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 88 Brainstem - Myelencephalon – Medulla oblongata Functions: Coordinates respiration and circulation (together with higher centres of the córtex) Nuclei of cranial nerves (VI to XII) Nuclei for several reflexes: protection of the eye (palpebral reflex, lacrimal secretion) upper respiratory tract (sneezing and coughing) food intake (suckling, swallowing) Nerve fibres extending between the different nuclei form the basis of central reflex arcs. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 89 44  11/27/24 Brainstem - Myelencephalon – Medulla oblongata External anatomy - Ventral view Ventral median fissure Trapezoid body (15) Pyramids (pyramidal tract) (17) Dyce, 2018 Pyramidal decussation, level of (18) Cranial nerves VI to XII nov-24 Educational purposes. Egas Moniz School of Health and Sicence 90 Brainstem - Myelencephalon – Medulla oblongata Pyramids (17) – prominent longitudinal bulge on the midventral surface of the medulla oblongata. pair of descending motor tracts on the ventral medulla oblongata, with origin in the cerebral cortex. they descend as part of the internal capsule, form the crus cerebri ant the ventral midbrain, run through the pons, and reappear to form the pyramid. Axons within the pyramids go to: the medulla oblongata (corticonuclear and corticoreticular axons) the spinal cord (corticospinal axons) The axons synapse on interneurons that regulate both efferent neurons (motor units) and projection neurons (cranial projecting pathways) nov-24 Educational purposes. Egas Moniz School of Health and Sicence Dyce, 2018 91 45  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Trapezoid body (15) – large band of transverse fibers on the ventral surface of the rostral medulla oblongata, caudal to the ventral pons and lateral to the rostral end of the pyramids. Auditory fibers (axons) primarily from the ventral cochlear nucleus and the dorsal nucleus of the trapezoid body. is part of the pathway projecting auditory stimuli rostrally (both sides of the brain) and terminate in: Dorsal nucleus of the trapezoid body (majority): prominent immediately dorsal to the trapezoid body with encapsulated appearance. Important in sound localization and it triggers reflex contraction of middle ear muscles Ventral nuclei of the trapezoid body (minority): neuronal cell bodies scattered among the axons of the trapezoid body nov-24 Educational purposes. Egas Moniz School of Health and Sicence Dyce, 2018 92 Sensory receptors (spiral organ) exist in the cochlea (modiolus) in the inner ear afferent neurons ends in the Spiral ganglion (sensory ganglion). Axons of the cochlear component of the vestibulocochlear nerve synapse within the dorsal and ventral cochlear nuclei (2) located on the dorsal surface of the brainstem second-order axons from the ventral cochlear nucleus then proceed to synapse within either an ipsilateral or a group of axons travels to and caudal cerebellar peduncle (for the auditory reflexes – contralateral nucleus of the trapezoid (3) synapses within the caudal colliculus e.g. movements of the ears (6) - towards the sound) The pathway is then continued by axons of third-stage neurons carried within the group of axons, (conscious perception of lateral lemniscos (4) sound), synapse in the medial geniculate nucleus of the thalamus (7), which in turn sends axons to the auditory córtex (9), located within the temporal lobe. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 93 46  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Pyramidal decussation (18) – ventrocaudal medulla oblongata at the spinomedullar junction – where the pyramids become less prominent. Most corticospinal axons (75% in the Pyramidal decussation dog) turn dorsally and cross the midline (pyramidal decussation) to Lateral corticospinal tract reach the dorsal half of the contralateral lateral funiculus, where Ventral corticospinal tract they project caudally as the lateral corticospinal tract. Dyce, 2018 A minority of axons delay decussation until they terminate in spinal gray matter; these run in the ipsilateral The decussation of pyramidal axons and other lateral corticospinal tract or in the caudally projecting tracts explains why one side of the ventral funiculus as the ventral corticospinal tract. brain controls voluntary movement on the contralateral side of the body. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 94 95 47  11/27/24 Brainstem - Myelencephalon – Medulla oblongata External anatomy - Lateral view Cranial nerves VI to XII External anatomy – Medial view Caudal part of the fourth ventricle (27´´´) nov-24 Educational purposes. Egas Moniz School of Health and Sicence 96 Brainstem - Myelencephalon – Medulla oblongata External anatomy – Dorsal view Emergency of cranial nerve – VIII Fasciculus gracilis (15) e nucleus gracilis (15´) Fasciculus cuneatus (14) Cuneate tubercule (medial cuneate nucleus) (13) Spinal tract of trigeminal nerve (22) Superficial arcuate fibers (16) Median sulcus in fourth ventricule (17) Medial eminence (18) Cochlear nucleus (dorsal and ventral) (12) 15´ Sulcus limitans (19) 22 23 Obex (23) 24 Area postrema (24) Rhomboid fossa nov-24 Educational purposes. Egas Moniz School of Health and Sicence 97 48  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Fourth ventricle Belongs to the ventricular system; covers the rostral 2/3 of the medulla oblongata – open part; caudal to this we have the central canal – closed part Rhomboid fossa – floor Median sulcus – divides in two halfs Sulcus limitans – mark the transition between the floor and the walls Tela choroidea – roof Rostral medullary velum Caudal medullary velum Choroide plexus – produce cerebrospinal fluid nov-24 Educational purposes. Egas Moniz School of Health and Sicence 98 Brainstem - Myelencephalon – Medulla oblongata Obex (24) Region where the fourth ventricle narrows to a point to become the central canal of the spinal cord. Lesions at the location can result in obstructive hydrocephalus 15´ 22 23 24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 99 49  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Internal anatomy Grey matter nuclei Nuclei of the cranial nerves VI-XII Gracillis nuclei Medial cuneate nuclei Lateral cuneate nuclei Olivary nuclei Solitary tract nucleus Nucleus ambiguus White matter tracts Ascending and descending fiber tracts that The medullary reticular formation is crucial for life as it connect the spinal cord with higher regions of the brain contains the vital centers that regulate visceral functions: Cranial nerves axons. heart rate and blood pressure Axonal connections with the cerebellum. waking and sleeping Tract axons traversing or terminating in the medulla oblongata. breathing Mixed grey and white matter. swallowing Reticular formation Medulla oblongata also plays a role in coordinating locomotion and posture. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 100 Brainstem - Myelencephalon – Medulla oblongata Area postrema (23) Densely vascularized (fenestrated capillaries) grey matter immediatly adjacente to the obex. the CTZ is located in here and his function an emetic centerin the medulla oblongata (activated by 23 apomorphine). 22 15´ 24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 101 50  11/27/24 nov-24 Educational purposes. Egas Moniz School of Health and Sicence 102 Brainstem - Myelencephalon – Medulla oblongata Fasciculus gracilis (nucleus gracilis) (15´) narrow tract flanking the dorsal median sulcus of the caudal medulla oblongata the fasciculus ascend along the spinal cord in this position, carrying fiber from the sacral, lumbar, and lower thoracic (T6-T13) dorsal roots. terminates in the nucleus gracilis receives and relays information from specialized touch, pressure, vibration and joint receptors from the pelvic limbs and caudal trunk. axons from neurons in the nucleus gracilis decussate in the deep arcuate fibers and 15´ travel rostrally as part of the medial lemniscus to the contralateral thalamus and somatosensory cortex (conscious proprioception). nov-24 Educational purposes. Egas Moniz School of Health and Sicence 103 51  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Fasciculus cuneatus(14) On the dorsal aspect of the caudal medulla oblongata, lateral to the fasciculus gracilis. formed by long ascending fibers from upper thoracic (T1-T5) and the cervical spinal cord. terminates in the nucleus cuneatus (13) receives and relays information from specialized touch, pressure, vibration and joint receptors from the thoracic limbs and cranial trunk. Axons from neurons in this nucleus 15´ decussate in the deep arcuate fibers and travel rostrally as part of the medial lemniscus to the contralateral thalamus and somatosensory cortex (conscious proprioception). nov-24 Educational purposes. Egas Moniz School of Health and Sicence 104 Brainstem - Myelencephalon – Medulla oblongata Superficial arcuate fibers (16). On the dorsal medulla oblongata rostral to the rostral end of the spinal tract of the trigeminal nerve mediate proprioception from the thoracic limbs to the cerebellum origin from the lateral cuneate nucleus (12) receives and mediate proprioceptive input from the thoracic limb and neck via the fasciculus cuneatus. This fibers merge with the dorsal spinocerebellar tract (mediates proprioception from the trunk and pelvic limb) to form the caudal cerebellar peduncle (10) 15´ subconscious proprioception nov-24 Educational purposes. Egas Moniz School of Health and Sicence 105 52  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Dorsal spinocerebellar tract ventral to the spinal trigeminal tract ascending sensory tract for proprioception of the trunk and pelvic limbs to the cerebellum form the caudal cerebellar peduncle nov-24 Educational purposes. Egas Moniz School of Health and Sicence 106 Brainstem - Myelencephalon – Medulla oblongata Spinal tract of the trigeminal nerve groove on the lateral surface of the medulla oblongata, lateral to the fasciculus cuneatus proceeds caudally to end in the medulla oblongata part of the trigeminal system – sensory fibers for pain and temperature of the face nov-24 Educational purposes. Egas Moniz School of Health and Sicence 107 53  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Olivary nucleus On the caudal medulla oblongata. It is located dorsolateral to the pyramid and lateral to the medial lemniscus. Afferent fibers from the cerebellum, from the cerebral cortex via the pyramids, and from the red nucleus and periaqueductal grey matter (PAG) via the central tegmental tract, and from the spinal cord. Efferent axons from the olivary nuclei decussate and reach the cerebellum via the caudal cerebellar peduncle. It has an important function in the regulation of motor feedback nov-24 Educational purposes. Egas Moniz School of Health and Sicence 108 Brainstem - Myelencephalon – Medulla oblongata Nucleus of the solitary tract Dorsolateral to the parasympathetic nucleus of the vagus (X) Contains axons from vagus, glossopharyngeal and facial nerves Conveys afferent information from stretch receptors and chemoreceptors in the walls of the cardiovascular, respiratory, and intestinal tracts. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 109 54  11/27/24 Brainstem - Myelencephalon – Medulla oblongata Nucleus ambiguous Ventral to the nucleus of the spinal tract of the trigeminal nerve Some visceral efferent neurons innervate the heart Via vagus (CN X) and glossopharyngeal (CN IX) nerves, the neurons send axons to striated muscles of the pharynx, larynx, and esophagus. Lesions of nucleus ambiguous results in nasal speech, dysphagia, dysphonia, and deviation of the uvula toward the contralateral side. nov-24 Educational purposes. Egas Moniz School of Health and Sicence 110 Brainstem - Myelencephalon – Medulla oblongata Cranial nerves nuclei Nucleus of the spinal tract of the trigeminal nerve (V) Motor nucleus of