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1H06 Anatomy & Physiology: CNS Brainstem, Cerebellum, Eye.docx

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Health Sciences
Alexander Ball

CNS Brainstem, Cerebellum and Eye Brain Stem  Consists of medulla oblongata, pons, midbrain  Interspersed gray and white matter Medulla Oblongata  Begins at foramen magnum, extends to inferior border of pons  White matter – sensory (ascending) and motor (descending) tracts extend between spinal cord and brain  “Pyramid” protrusions (white matter bulges)  Corticospinal tracts control voluntary movements of limbs and trunk  Medulla contains nuclei – includes cardiovascular center and medullary rhythmicity area  Nuclei also control heartbeat, blood vessel diameter, breathing rhythm, vomiting, swallowing, sneezing, etc.  Olive – lateral to each pyramid o Inferior olivary nucleus receives input from cerebral cortex, red nucleus of midbrain, and spinal cord  Nuclei that influence touch, pressure, vibration are in posterior medulla Five pairs of cranial nerves: 1. Vestibulocochlear – hearing 2. Glossopharyngeal – taste, swallowing, salivation 3. Vagus – pharynx, larynx control 4. Accessory – swallowing 5. Hypoglossal – tongue movement Pons  Contains nuclei and tracts  Connects parts of brain with one another by axons  Ventral and dorsal regions  Ventral region is relay station of gray centers (pontine nuclei) o Coordinate and maximize voluntary motor output  Dorsal region – ascending and descending tracts along with nuclei of cranial nerves Nuclei associated with 4 pairs of cranial nerves: 1. Trigeminal – chewing 2. Abducens – eyeball movement 3. Facial – taste, saliva, tears (facial nerves) 4. Vestibulocochlear – balance and equilibrium Midbrain  Aqueduct passes through midbrain  Connects third ventricle with fourth ventricle  Contains both nuclei and tracts  Cerebral peduncles – bundles of axons in anterior section o Axons conduct nerve impulses from cerebral cortex to spinal cord, medulla, pons  Posterior midbrain (tectum) contains four elevations o Superior colliculi (superior elevations) control visual activities o Inferior colliculi (inferior elevations) control auditory  Substantia nigra and red nuclei are other nuclei Nuclei associated with two pairs of cranial nerves: 1. Oculomotor – eyeball movement 2. Trochlear – eyeball movement via trochlear nerves Reticular Formation  White and gray matter form netlike arrangement  Extends from superior spinal cord, throughout brain stem, into inferior diencephalon  Neurons contain both ascending (sensory) and descending (motor) functions  Reticular activating system (ascending portion) have sensory axons projecting to cerebral cortex o Stimuli include visual and auditory, mental activities Cerebellum  Main function – evaluate how well movements initiated by motor areas of cerebrum are carried out o Senses discrepancies, sends feedback to motor cerebral cortex (via thalamus connections)  Regulates balance and posture  Occupies inferior and posterior aspects of cranial cavity  Highly folded surface for more SA of outer gray matter cortex, allowing for more neurons  Transverse fissue and tentorium cerebelli separate cerebellum from cerebrum  Anterior and posterior lobes govern subconscious skeletal muscle movement  Cerebellar cortex – superficial layer of gray matter in parallel folds (folia)  Cerebellar peduncles attach cerebellum to brain stem o This white batter contain axons that conduct impulses between
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