1. Cervical Enlargement 2. Thoracic Region 3. Lumbar Enlargement 4. Medullaris – blunt cone at inferior end of spinal cord. (L1/L2) 5. Filum Terminale – thin filament of pia mater and arachnoid mater extending from the spinal cord to the upper portion of the coccyx 6. Cauda Equina Horse’s Tail Spinal Nerves extending downward from the lower lumbar and sacral areas of the vertebral canal. C. Spinal Nerves (31 Pairs Total) 1. 8 Pairs of Cervical Nerves (C1 – C8) *Note….there are 7 cervical vertebrae but 8 pairs of cervical nerves 2. 12 Pairs of Thoracic Nerves (T1 – T12) 3. 5 Pairs of Lumbar Nerves (L1 – L5) 4. 5 Pairs of Sacral Nerves (S1 – S5) 5. 1 Pair of Coccygeal Nerves (Co) D. Cross Section of the Spinal Cord 1. Grooves – divides spinal cord into left and right halves a. Anterior Median Fissure b. Posterior Median Sulcus 2. Gray Matter – unmyelinated tissue a. Anterior Horn – contains cell bodies of motor neurons. b. Posterior Horn c. Lateral Horn – present between T1 – L2 regions of the spinal cord d. Gray Commissure – common site for decussation (crossing over) of sensory neurons. 3. White Matter – myelinated axons a. Anterior Funiculus (column) b. Posterior Funiculus (column) c. Lateral Funiculus (column)
b. Light inhibits the secretion of melatonin. G. Cerebrum (Telencephalon) 1. Structure of the Cerebrum a. Longitudinal Fissure –separates the two cerebral hemispheres Falx Cerebrum – of dura mater between the cerebral hemispheres. Corpus Callosum – bundle of axons that connects the cerebral hemispheres. b. Transverse Fissure – separates the occipital lobe from the cerebellum Tentorium Cerebelli – layer of dura matter between the cerebrum and cerebellum. c. Gyri (Gyrus, sing.) – convolutions or ridges of the cerebrum. Precentral Gyrus – primary motor cortex of cerebrum Postcentral Gyrus – somatosensory cortex of cerebrum d. Sulci (Sulcus, sing) – shallow grooves separating the gyri. Central Sulcus – separates the precentral and postcentral gyri Lateral Sulcus – separates the temporal lobe from the frontal/parietal e. Gray Matter – unmyelinated tissue in the central nervous system Cerebral Cortex – Thin outer layer of cerebrum. Cerebral cortex contains 75% of neurons in the nervous system. Nucleus – group of cell bodies within CNS e. White Matter – myelinated tissue in the central nervous system 2. Basal Nuclei – gray matter deep within the cerebrum a. Nuclei Include: Caudate Nucleus Putamen Globus pallidus b. Basal Nuclei secrete dopamine which inhibits skeletal muscle contractions c. Portions of the basal nuclei extend into the midbrain as substantia nigra
1. Nerves are bundles of Axons wrapped in layers of connective tissue. a. Nerve – bundle of fascicles b. Fascicles – bundle of axons 2. Connective Tissue Coverings a. Epineurium – covers entire nerve b. Perineurium – surrounds each fascicle Epineurium & Perineurium as passages for blood vessels c. Endoneurium – surrounds each axon Endoneurium contains capillaries – provides gas/nutrient/waste exchange. D. Classification of Peripheral Nerves 1. Definitions a. Sensory Nerves = Afferent b. Motor Nerves = Efferent c. Mixed Nerves = contain both Sensory and Motor Nerve Fibers d. Efferent = e. Somatic = Voluntary (skeletal muscles and cutaneous sensory) f. Visceral = Autonomic (visceral sensory, smooth muscles, cardiac muscles, and glands) g. General = distributed throughout the body: touch, temperature, pressure, h. Special = Localized in the head: vision, olfaction, hearing, balance, taste 2. Classifications of General Fibers a. General Somatic Efferent Fibers – conduct motor impulses from brain or spinal cord to skeletal muscles b. General Visceral Efferent Fibers – conduct motor impulses from brain or spinal cord to smooth muscles or glands associated with internal organs
Innervate lacrimal glands and Some Salivary Glands b. Sensory Fibers – innervates receptors for taste on anterior 2/3 tongue. 8. CN VIII – Vestibulocochlear Nerve a. Vestibular Branch – balance and equilibrium b. Cochlear Branch – hearing 9. CN IX – Glossopharyngeal a. Sensory Fibers – sensory of tongue, pharynx, and tonsils b. Fibers – muscles for swallowing and some salivary glands. 10. CN X – Nerve a. Somatic Fibers - Muscles for speech and swallowing b. Autonomic Fibers – Regulates Heart Rate, Digestion, The Vagus nerve contains about 75% of all parasympathetic nerve fibers in the body 11. CN XI – Accessory Nerve a. Supplies (along with vagus nerve) muscles of the pharynx and larynx b. Supplies muscles of the neck and shoulder: trapezius & sternocleidomastoid 12. CN XII – Hypoglossal Nerve a. Muscles that move the tongue for speech, chewing, and swallowing. Pneumonic: I. Oh Olfactory II. Once Optic III. One Oculomotor IV. Trochlear V. The Trigeminal VI. Anatomy Abducens