Brain Stem and Cranial Nerves

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GRADUATE NEUROSCIENCE LSUHSC-S J BEAL

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BRAINSTEM OVERVIEW OBJECTIVES: -List the divisions of the brainstem -Describe the three layered longitudinal arrangement of the brainstem -Indicate the location and functions of the reticular formation, monoamine centers, and cranial nerve nuclei J. BEAL LSUHSC-S

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BRAIN & SPINAL CORD (Coronal Section) CEREBRUM THALAMUS BRAINSTEM (Midbrain-Pons-Medulla)SPINAL CORD 2

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TECTUM Pyramid Basilar Pons Cerebral Peduncle PYRAMIDAL TRACT Pyramid-Basilar Pons-Cerebral Peduncle CEREBELLUM BRAINSTEM(THREE TIER LONGITUDINAL ARRANGEMENT) TEGMENTUM: Reticular Formation Cranial Nerve Nuclei Sensory Pathways Motor Pathways (Except Pyramidal Tract)

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RETICULAR FORMATION The Reticular Formation is the oldest part of the brain. It forms a diffuse, multisynaptic, net-like meshwork (reticulum) of widely interconnected neurons in the Tegmentum. The RF is involved in nearly every aspect of brain function including the following: -Homeostasis -Consciousness -Arousal -Pain -Primitive motor control -Muscle tone -Behavioral mechanisms RETICULARFORMATION

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RETICULAR FORMATION MID MEDULLA Pyramid Pyramid

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RETICULAR FORMATION MID PONS BASILAR PONS

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RETICULAR FORMATION MIDBRAIN Cerebral Peduncle Cerebral Peduncle Tectum

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RETICULAR FORMATION Vital Centers are located in the medulla and pons and control cardiovascular respiratory, and other homeostatic mechanisms. Lesions in these centers are fatal. Examples of RF mediated reflexes are: -Aortic Body -Carotid Body -Aortic Sinus -Carotid Sinus -Respiratory -Cough -Swallowing -Salivary -Vomiting

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RETICULAR FORMATION The midbrain RF gives rise to a tonic ascending barrage of diffuse, non-specific sensory data called the ARAS. Acting like a battery, the ARAS stimulates the cerebral cortex and maintains the conscious state. Midbrain lesions of ARAS result in Coma. Incomplete lesions may result in Stupor.

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MONOAMINE BRAINSTEM CENTERS Monoamine Centers each have specific monoamine neurotransmitters which modulate (Enhance or Diminish) a broad spectrum of activities including: Arousal, Mood, Behavior Sleep Muscle Tone and Responsiveness Learning Pain, Pleasure, Motivation

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MID MEDULLA MONOAMINE CENTERS

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MID PONS MONOAMINE CENTERS

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MIDBRAIN MONOAMINE CENTERS

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Transverse Section CRANIAL NERVE NUCLEI Sagittal View MEDULLA PONS MIDBRAIN Nuclei are arranged in longitudinal columns and located in the tegmentum

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MID MEDULLA Anterior Posterior CRANIAL NERVENUCLEI Pyramid Nuclei are arranged in longitudinal columns and located in posterior Tegmentum Motor nuclei are medial, sensory nuclei lateral IMPORTANT CONCEPTS:

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MID MEDULLA Anterior Posterior CRANIAL NERVENUCLEI Pyramid MOTOR SENSORY Nuclei are arranged in longitudinal columns and located in posterior Tegmentum Motor nuclei are medial, sensory nuclei lateral

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MID MEDULLA Anterior Posterior CRANIAL NERVENUCLEI Pyramid MOTOR SENSORY Nuclei are arranged in longitudinal columns and located in posterior Tegmentum Motor nuclei are medial, sensory nuclei lateral

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MID MEDULLA Anterior Posterior CRANIAL NERVENUCLEI Pyramid MOTOR SENSORY Cranial nerves pass through the tegmentum to exit anteriorly

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CRANIAL NERVE NUCLEI MOTOR NUCLEI SENSORYNUCLEI BRAINSTEM Posterior View

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INTRODUCTION TO CRANIAL NERVES LSUHSC-S J. Beal

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II III IV V VI VII VIII IX X XI XII II OPTIC (CNS Tract) CRANIALNERVES III OCULOMOTOR IV TROCHLEAR V TRIGEMINAL VI ABDUCENS VII FACIAL VIII VESTIBULO- COCHLEAR IX GLOSSOPHARYNGEAL X VAGUS XI SPINAL ACCESSORY XII HYPOGLOSSAL I I OLFACTORY

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– Somatic structures, e.g., Skin, Skeletal Muscle, Joints (V, VII, IX, X) – Visceral Organs, e.g., Heart, Lungs, Liver, Gut etc. (IX, X) – Lower Motor Neurons to Skeletal Muscle (III, IV, V, VI, VII, IX, X,XI, XII) – Autonomics to Smooth & Cardiac Muscle, & Glands (III, VII, IX, X) - Vision (II) - Hearing & Balance (VIII) - Smell (I) - Taste (VII, IX, X) GENERAL SPECIAL CRANIAL NERVE COMPONENTS SENSORY MOTOR

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CN I OLFACTORY NERVE Sensory - OLFACTION (Smell) Nasal Cavity Olfactory Nerve Olfactory Bulb I

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CN II OPTIC NERVE EYE Sensory - VISION Retina Retina II

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Motor - ALL Extrinsic Eye Muscles - Intrinsic Eye Muscles (III) EXTRINSICEYE MUSCLES III INTRINSICEYE MUSCLES III IV VI

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CN V TRIGEMINAL Sensory - Sensory to Face, Scalp, Oral & Nasal Cavities, Teeth, Sinuses, Meninges, & Anterior 2/3 of Tongue Motor - Muscles of Mastication MUSCLESOFMASTICATION GENERALSENSATION FACE, SCALP, TEETH, ORAL & NASALCAVITIES, SINUSES,MENINGES,& ANT. 2/3 TONGUE MASSETER TEMPORALIS Anterior 2/3 Tongue Nasal & Oral Cavities V

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CN VII FACIAL Motor - Muscles of Facial Expression - Lacrimal Gland Submandibular & Sublingual Glands Sensory - Taste -Anterior 2/3 of Tongue MUSCLES OF FACE GLANDS: Lacrimal, Submandibular, & Sublingual TASTE –Tongue & Soft Palate VII Anterior 2/3

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CN VIII VESTIBULOCOCHLEAR Sensory - Balance & Equilibrium - Hearing VIII

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CN IX GLOSSOPHARYNGEAL Motor - Parotid Gland TONGUE Taste & General Sensation PAROTID GLAND Sensory - Posterior 1/3 of Tongue, Pharynx, & Palate Pharynx , Soft Palate Posterior 1/3 IX

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X Muscles of Pharnyx, Larynx, & Soft Palate Motor - Muscles of Pharynx, Larynx, & Soft Palate Pharynx & Larynx Thoracic & Abdominal Viscera - Thoracic & Abdominal Organs and Gut to the Left Colic Flexure. Sensory - Lower Pharynx & entire Larynx + fibers from thoracic & abdominal viscera. CN X VAGUS

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XI Trapezius Sternocleidomastoid CN XI SPINAL ACCESSORY Motor - Sternocleidomastoid & Trapezius Muscles XI

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XII CN XII HYPOGLOSSAL Motor - Muscles of the Tongue Tongue Muscles