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spinal cord - Gral. Characteristics
Cylindrical & slightly flattened struct.Cont.of the brainstem. Extend form the medulla oblangata to the. superior border.L2. Approximately 42-45 cm in length
Surrounded and protected by 3 layers of membrane: CSF, fatty tissue in the epidural space, vertebral column
butterfly shaped (cross section) cons.of neuron cell bodies
density of the neurons give it its gray appearances
receives and integrates incoming & outgoing information
highly organized - Rexed's Laminae
-consists of myelinated Nerve.Fibers that.carry impulse up and down the SC (i.e. tracts)
- a highway for nerve impulse propagation. (sensory going up, motor going down.- Fatty material in myelin give it its appearance
. 8 cervical
. 12 thoracic
. 5 lumbar
. 5 sacral
. 1 coccygeal
*spinal nerve carry all sensory & motor axon of corresponding spinal segment; exit above the vertebra with the exception of C8 which emerges below C7 and above T1
other characteristcs of the spinal cord
1. length: 17 inches
2. cervical enlargement C4-T1; ass.w. emergenc UE.nerve
3.lumbar enlargement T9-T12;ass.w.emergen of L.E.nerve
4.conus medullaris: located at L1; tapered end of the SC
5.filum terminale:L1-S2; thread of non nervous tissue extending from the tip of the SC to end of dural sac
6.cauda equina: lumbar & sacral nerves that fill the dural sac on either side of the ft; horse tail shaped
7.diameter and shape: 1 inch & cylindrical in shape
-membranes that surround the brain and spinal cord
3 layers: a. Dura mater: outer membrane extending fm the foramen magnum to S2 where it fuses the filum terminale. b. Arachanoid: middle membrane; consist of two componts:.second layer next to the dura mater
c. Inner membrane containing many vessels providing nutrition to the SC .Meningitis affect.pia m. & arachanoid.
.a bundle of myelinated N. fibers located in the brain & SC
.Sensory: carry impulse up the SC to the brain
.Motor: carry impulses down the SC
"Crossing over" or decussation of pyramids
- Fibers of most tracts cross over at the medulla and SC
. Sensory nerve information from the left side of the body end in the right side of the brain
. Motor nerve impulses originating on the right side of the brain,control mm. on the left side of the body.
Anterior spinothalamic tract -
-crude touch and pressure, tickle and itch; anterior white column; crosses in spinal cord
Dorsal column pathway
-proprioception, vibration, kinesthesia, stereognosis, discriminative touch, barognosis; posterior white column; crossres in medulla
Anterior and posterior spinocerebellar tracts
-unconscious proprioception ant/lat & post/white columns; Info from trunk & LEs travels to the cerebellum to help w. balance & coordination; posterior tract is ipsilateral/anter. tract crosses in the SC, then most fibers recross before reaching the cerebellum (each side of cerebellum receives
infomation from both sides of the body)
Lateral corticospinal tract
-precise contraction of muscles in distal extremities (fine movement or fractionation); lateral white column; crosses in medulla
Anterior (medial) corticospinal tract
-coordinates movements of axial skeleton with contraction of mscles in the neck, trunk and shoulders; anterior white column; most ipsilateral (no crossing)
controls UE flexor muscles; lateral white column; originate
in the red nucleus of the midbrain; crosse in the midbrain.
-control movement of the head in response to visual and auditory stimulation; originates in the superior colliculi of the midbrain; crosses in midbrain
Medial vestibulospinal tract
-control muscles of the neck and upper back; originates in the medulla; info received from the vestibular apparatus of the inner ear regarding head movement; crosses in medulla; helps with balance.
Lateral vestibulospinal tract
-control extensors & inhibits flexors; originates in the medulla; info received from the vestibular apparatus of the inner ear regarding gravity; ipsilateral; active when upright to maintain COG over BOS
-control muscles of the face, tongue, pharynx,larynx, trapezius and SCM; originates in the cerebral cortex and synapses on cranial nerve nuclei in the brainstem; crosses in brainstem
Medial reticulospinal tract
-control postural muscles and limb extensors; originates in the reticular formation in the pons; ipsilateral
Lateral reticulospinal tract
-control extensor muscles during walking; originates in the reticular formation of the medulla; ipsilateral
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