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1. General Characteristics

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

Gray Matter

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
Very specialized

White matter

-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

spinal nerve

. 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

Meninges

-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.

Tracts

.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.

ascending tracts

- sensory pathway; conveys information from the SC to
the brain

descending tracts

- motor pathway; conveys information from the brain to
the SC

Anterior spinothalamic tract -

-crude touch and pressure, tickle and itch; anterior white column; crosses in spinal cord

Lateral spinothalamic tract

-pain & temperature; lateral white column; crosses in SC

Dorsal column pathway

-proprioception, vibration, kinesthesia, stereognosis, discriminative touch, barognosis; posterior white column; crossres in medulla

Fasciculus cuneatus

(brings above information from upper trunk & UEs;lateral)

Fasciculus gracilis .

(brings above information from lower trunk & LEs;medial)

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)

Rubrospinal tract

controls UE flexor muscles; lateral white column; originate
in the red nucleus of the midbrain; crosse in the midbrain.

Tectospinal tract

-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

Coticobulbar tract

-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

Naming of spinal nerves

. First seven cervical nerves emerge above the vertebra
of the same number
. eighth spinal nerve emerges between the 7th cervical
vertebrae and the 1st thoracic

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