Neuroanatomy Part 2 PDF (UCC)

Neuroanatomy – Part 2 Maria Hill Acknowledgements: Niamh Brady PP6012 Learning Outcomes To understand the structure and role of the thalamus in relaying information throughout the CNS To understand the anatomy of the brainstem, including external and internal topography To appreciate the role of the...

Neuroanatomy – Part 2 Maria Hill Acknowledgements: Niamh Brady PP6012 Learning Outcomes To understand the structure and role of the thalamus in relaying information throughout the CNS To understand the anatomy of the brainstem, including external and internal topography To appreciate the role of the brainstem and its various connections To become familiar with the Cranial Nerves, where they are found, their function and where they exit the brain and cranium To understand the structure and function of the cerebellum Divisions of the brain Forebrain Telencephalon & Diencephalon Midbrain Mesencephalon Hindbrain Metencephalon & Myelencephalon The Diencephalon Thalamus Sensory relay station Process sensory info Nuclei Hypothalamus Link to Immune System Autonomic Control Pituitary Gland Endocrine Function Pineal Gland Circadian Rhythm - Melatonin Thalamus - External features Similar in size and shape to a small hen’s egg Superior to the brainstem Posterosuperior to the Hypothalamus Forms the lateral wall of the 3rd ventricle and part of the floor of the lateral ventricle Thalamus – Internal features Divided into several nuclei, each with their own connections All nuclei (except reticular nucleus) project to ipsilateral cerebral cortex All of the cortex receives input from thalamus Lateral nuclear group Connections Ventral posterior → Primary Somatosensory Cortex (Spinothalamic, Trigeminothalamic, Medial Leminiscus) Ventral anterior → Premotor, Supplementary motor Cortices (Basal ganglia) Ventral lateral → Primary motor Cortex (Basal ganglia & cerebellum) Lateral geniculate → Primary Visual Cortex Medial geniculate → Primary Auditory Cortex Other Thalamic Connections Anterior nuclear group → Limbic system Anteroventral, Anteromedial, Anterodorsal Medial nuclear group → Prefrontal cortex Dorsomedial Intralaminar nuclei → Cerebral cortex, basal ganglia Reticular nucleus → Reticular formation (receives input from fibres passing between thalamus and cortex) Divisions of the brain Forebrain Telencephalon & Diencephalon Midbrain Mesencephalon Hindbrain Metencephalon & Myelencephalon The Brainstem The stem of the brain Located anterior to cerebellum Referred to as “Bulb” Continues as the spinal cord Function Houses Cranial Nerves (CNIII – CNXII) Contains important Nuclei Contains neural pathways (tracts) Integrates input/output for respiration, cardiovascular function, complex motor patterns The Brainstem Midbrain Connects brainstem to diencephalon & cerebrum Pons Connection to cerebellum Medulla Continues as Spinal Cord Brainstem External features Midbrain Interpeduncular fossa (mamillary bodies, CNIII, Infundibulum) Colliculi Pons Medulla Oblongata Pyramids Olives Brainstem External View Emergence of Cranial Nerves Anterior View Posterior View Brainstem Internal features Throughout the brainstem you will find: Tracts (ascending/descending pathways) – represented by white matter Nuclei (Brainstem nuclei, cranial nerve nuclei), represented by grey matter Reticular formation – A network of nuclei that form the oldest part of the brain and are responsible for control of the cardiovascular system, breathing, sleep-wake cycle, attention, arousal) Midbrain Superior Colliculi – Visual Inferior Colliculi – Auditory Anterior to cerebral aqueduct – tegmentum Posterior to cerebral aqueduct – tectum Tracts: Spinothalamic & Trigeminothalamic, Medial Leminiscus, Corticospinal, Corticopontine Midbrain Nuclei: Red Nucleus, Cranial Nerve Nuclei (III, IV, V) Substantia Nigra (Basal Ganglia) Periaqueductal grey – Pain modulation Pons Identified by cerebellar peduncles Tracts: Ascending (medial leminiscus, Spinothalamic), Descending (Corticospinal) Nuclei: Cranial Nerve Nuclei (V, VI, VII, VIII), Reticular formation 4th Ventricle Pons Medulla Oblongata Identified by pyramids (Corticospinal tracts) Inferior cerebellar peduncles Tracts: Dorsal Column Medial Leminiscus, Spinothalamic, Spinocerebellar, Corticospinal Nuclei: Reticular formation, Olivary Nucleus, Cranial Nerve Nuclei (IX, X, XI, XII) Medulla Oblongata Cranial Nerves 12 pairs of peripheral nerves Carry afferent and efferent fibers to/from structures in the head & neck Cranial Nerves may be motor, sensory or mixed Cranial Nerves CN CN CN CN CN CN CN CN CN CN CN CN I – Olfactory (Cerebrum) II – Optic (Cerebrum) III – Oculomotor (Midbrain) IV – Trochlear (Midbrain) V – Trigeminal (Pons) VI – Abducens (Pons) VII – Facial (Pons) VIII – Vestibulocochlear (Pons) IX – Glossopharyngeal (Medulla) X – Vagus (Medulla) XI – Accessory (Medulla) XII – Hypoglossal (Medulla) Cranial Nerves CN I – Olfactory – Smell CN II – Optic – Sight (visual information) CN III – Oculomotor – Eye movement (upper eyelid, extraocular, pupillary muscles) CN IV – Trochlear – Eye movement (Extraocular muscle/superior oblique) CN V – Trigeminal – Sensation head, muscles of mastication) CN VI – Abducens – Eye movement (lateral rectus) CN VII – Facial – Muscles of facial expression, taste CN VIII – Vestibulocochlear Hearing, balance CN IX – Glossopharyngeal – Swallowing, taste CN X – Vagus – GI tract, heart, larynx CN XI – Accessory – Trapezius, Sternocleidomastoid CN XII – Hypoglossal – Tongue movement Cranial Nerves III, IV, VI Cranial Nerve Foramina Cranial Nerves Foramina Olfactory Cribiform plate Optic Optic Canal Occulomotor, Trochlear, Abducens, Ophthalmic (VI) Superior Orbital Fissure Maxillary (VII) Foramen Rotundum Mandibular (VII) Foramen Ovale Facial Vestibulocochlear Internal Acoustic Meatus Glossopharyngeal, Vagus, Accessory Jugular Foramen Hypoglossal Hypoglossal Canal Cranial Nerve Foramina Cranial Nerve V - Trigeminal VI – Ophthalmic Sensory VII – Maxillary Sensory VIII – Mandibular Mixed (Supplies muscles of mastication) Cranial Nerve Nuclei Cranial nerves III-XII have their nuclei in the brainstem Cranial Nerve Nuclei Receive afferent fibres from periphery Contain cell bodies that send efferent fibres to periphery Sensory/afferent = yellow Motor/efferent = blue Level of emergence vs location of Nuclei Cranial Nerve Summary Clinical Conditions Vascular/Stroke Tumours Medulloblastoma Chiari Malformation The Cerebellum Latin for “Little Brain” Important role in motor control and movementrelated functions Co-ordination of movement – the cerebellum controls the timing and pattern of muscle activation during movement The primary function is to detect motor error The Cerebellum If there is a difference between an intended movement and the actual movement that takes place, the cerebellum should pick this up. When this feedback loop is damaged, the individual in question will make persistent movement errors Cerebellar Anatomy 2 hemispheres united by a midline vermis Attached to the bottom of the brain (cerebral cortex on top and pons in front) Fissures and Folia Lobes - Anterior, Posterior, Flocculonodular Peduncles x 3 Cerebellar Anatomy Anterior lobe Bounded by the primary fissure Posterior lobe Youngest Includes tonsil Flocculonodular lobe Oldest Consists of the nodule of the vermis and the flocculus Cerebellar Anatomy Functional Divisions Vestibulocerebellum Flocculonodular lobe Maintains equilibrium, balance, posture Spinocerebellum Vermis & Intermediate zone Receives info on limb position, touch, pressure Responsible for muscle tone and coordination Pontocerebellum/ Cerebrocerebellum Inferior & lateral cerebellum Communicates with cerebral cortex Involved in planning & initiating movement Functional Divisions & Nuclei Fastigal Nucleus (Vestibulocerebellum) Interposed Nucleus (Spinocerebellum) Dentate Nucleus (Ponto/Cerebrocerebellum) Output from cerebellum originates from these nuclei Vestibulospinal Tract Oldest tract in the animal kingdom Controls posture & head, neck, eye stability Vestibular Apparatus → Vestibular Nerve (CNVIII) →Vestibular Nuclei → Vestibulocerebellum (Flocculonodular lobe) → Fastigal Nucleus →Vestibular Nuclei → Vestibulospinal Tract Rubrospinal Tract Responsible for the control of distal muscles involved in posture and gait Spinocerebellum →Interposed nucleus → Red Nucleus → Rubrospinal tract Cerebellarthalamic tract Communicates with cerebral cortex Involved in planning & initiating movement Dentate Nucleus → Ventralateral nucleus thalamus → Primary motor and Premotor cortices Cerebellar Peduncles Connections between the cerebellum and other parts of the Nervous System Cerebellar Peduncles Superior cerebellar Mostly efferent/motor Output: Red nucleus, superior colliculus, reticular formation Middle cerebellar Only afferent/Sensory Input: Cortex, superior colliculus Inferior cerebellar Afferent/efferent Input: Spinocerebellar tract, vestibular nuclei, reticular formation Output: Vestibular nuclei/reticular formation Cerebellar dysfunction Conditions affecting the cerebellum disrupt motor coordination and timing, and are usually accompanied by a loss of muscle tone Ataxia Dysmetria Dysdiadochokinesia Coarse Tremor Ataxic Dysarthria Causes Vascular/Stroke (PICA) Tumour