ANAT 7. Spinal Cord & Peripheral Nerves.docx

Learning objectives: (VERY IMPORTANT VIDEOS IN POWERPOINT TO WATCH) - - - - - - - - - Spinal nerves: motor & sensory innervation of body below the head. - - - - Cervical spinal nerves: C1-7 emerge above the associated vertebra, C8 below C7 & above T1. All the rest:...

Learning objectives: (VERY IMPORTANT VIDEOS IN POWERPOINT TO WATCH) - - - - - - - - - Spinal nerves: motor & sensory innervation of body below the head. - - - - Cervical spinal nerves: C1-7 emerge above the associated vertebra, C8 below C7 & above T1. All the rest: follow the rule of emerging [inferior] to same-numbered vertebra. \*Spinal nerves are named according to the vertebrae between which they emerge, NOT by the vertebra where the segment is. Conus medullaris: cone-shaped end of spinal cord(at \~L1). - Cauda equina(horsetail): spinal nerve roots from lumbar(L2-5), sacral, & coccygeal cord. - Spinal cord Intumescences: areas where cord widens due to increased demand by limbs. - - - - Spinal cords have same protective meningeal coverings as brain. From Inside → Out. - - - - Filum terminale: modified extension of pia mater from end of cord helps stabilize cord within canal. After cord ends below L1, it extends & attaches to coccygeal segments, Gray Matter: cell bodies; dorsal-sensory, ventral-motor, lateral-visceral sensory+motor neurons. White Matter: myelinated axons; ascending sensory, descending motor. Peripheral nerve components: dorsal/ventral rootlets & roots & ramus, DRG, spinal nerve. \*\*Know the difference btw dorsal/ventral roots & dorsal/ventral rami !!! Posterior(Dorsal) ramus- innervates intrinsic or epaxial(deep back muscles). Anterior(Ventral) ramus- innervates hypaxial muscles of anterolateral trunk. \*\*Anterior Rami: merges to form [plexuses] everywhere, except at thoracic segments. Muscle stretch reflexes: tests spinal segments & associated spinal nerves. - Dermatomes & Myotomes: Embryonic [Myotome]: cells migrate into body to form skeletal muscle. Embryonic [Dermatome]: cells migrate out to form dermis. Each segmental pair of spinal nerves innervates specific muscles/areas of skin & this association between segment/nerves and skin/muscles established during development. Adult level: Dermatomes: area of skin innervated by spinal nerves mainly belonging to 1 spinal-cord Level. Myotome: muscle(testable w/ an action) are innervated by a single spinal cord Level. \*\*Clinical takeaway: you can test specific spinal nerves/segments by testing reflexes, or sensory areas of skin & motor actions. EQ: \*Cells of dermomyotome that migrate Posteriorly, give rise to epaxial (deep) back muscles & overlying dermis. Innervated by S&M fibers of [Posterior ramus] of that segment. \*Cells that migrate Anteriorly, give rise to the hypaxial muscles of the anterolateral trunk(+ limbs) & associated dermis. Innervated by S&M fibers of [Anterior ramus] of that segment. \*Where are the soma of Peripheral nerves? DRG. So the gray matter of spinal cord is what? It's sensory neurons, where the peripheral nerves synapse onto.