Spinal Cord and Spinal nerves
Terms
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- General External Features of spinal cord
-
w/in spinal (vertrbral) canal
from brain stem to conus-ap. L2
foramen mag. is division between brain and sp. cord.
longitudinal view Flattened in dorsal - cervical enlargement
- origin for nerves supplying upper extremity
- lumbar enlargement
- origin for nerves supplying lower extremity
- conus medullaris
- cone shaped ending of sp. cord ap. T12-2
- filum terminal
- tissue from conus (pia mater) to coccyx
- causa equina
-
"horses tail" group of spinal nerves inside spinal canal
(hangs off conus) - spinal segments
- there are 31; one pair of spinal nerves arises from each segment
- R & L sides of spinal cord
-
anterior median fissure
posterior median sulcus - anterior median fissure
- deep, wide groove on the anterior(ventral)side groove penetrates whiter matter on spin. cord & divids the L&R side
- posterior median sulcus
- a shallow narrow furrous on the posterior dorsal side
- misnomer
- cord only appears segmented in early stages of development
- cross section of spinal cord
-
lateral white column &
posterior white column - white matter
- surrounds gray matter; consists of myelinated fibers
- anterior(ventral) white column
- is column shaped in longitudinal view
- anterior white commissure
- pronounced "kom" is sure; connects white colimns
- Gray matter
- unmyelinated fibers & cell bodies (not myelinated); of multipolar neurons
- anterior(ventral) gray horn
-
term "horn" is used when cord seen in x.s.
frontal division of the lateral ventricle of the brain, extending forward from Monro's interventricular foramen. - Lateral (gray) horn
-
between the anterior & posterior gray horns
present only in the thoracic, upper lumbar, & sacral segments of spinal cord - Posterior (gray) horn
- contain somatic & autonomic sensory nuclei
- Gray commissure
- on either side (surrounds) central canal of sp. cord
- central canal of spinal cord
- continuous w/ ventricles (cavities) of brain; contains c.s.f. (cerebral spinal fluid)
- Tracts
- running inside the C.N.S.
- Ascending tracts
- is a sensory tract (consists of sensory or afferent neurons)
- Desending tracts
- is a motor tract (consists of motor or efferent neurons)
- Protective Coverings of spinal cord
-
vertebral column
meninges - vertebral column
- strongest of the protective coverings
- vertebral (spinal) canal
-
made up of indiv. vertebrae
stacked on top of one another - Meninges
-
Cranial
Spinal - Cranial meninges
- conn. tissue encircle the brain
- spinal meninges
- conn. tissue surrounding spinal cord
- dura mater
- outer layer of meninges or outer meninx
- epidural space
-
between dura & bone of vert. column
has fat, vessels
it is the injection site for anesthetics - subdural space
- contains interstitial fluid
- Arachnoid
-
middle layer of meninges or middle menix
(spiter webb like) - subarachnoid space
-
contains c.s.f.
(below arachnoid memebrane) - Pia mater
- inner layer or inner menix (part of the meninges)
- Denticulate ligament
- runs laterally between tracts from pia to dura mater; helps to anchor chord in vertebral canal
-
Meninges: 3 layers
protective cover:
P
A
D -
Pia
Arachnoid
Dura - Two major spinal cord functions
-
connect periphery & brain
Intergrate reflexes - connect periphery & brain
- away from c.n.s. is periphery
- integrate reflexes
- volentary or involentary
- impulse conduction
- function is carried out by ascending & desending tracts; names of the tracts indicate the white column or funculus in which the tracts travel
- reflex
- a fast involuntary response to a change (stimulus) helps maintain homeostasis
- conduction pathway
- the path an impulse travels from it's origin to it's point of termination
- posterior or dorsal (sensory) root ganglion
-
nerves outside c.n.s
ganglia contain unipolar neurons
(swelling on back root) - anterior or ventral (motor) root
- contain axons of motor neurons, which conduct nerve impulses from the CNS to effector and cells.
- Reflex arc & conduction pathway
- involuntary conduction pathway
- receptor
-
end of a dendrite either naked or associated w/ adjacent tissue
(picks up impulses all over body) - sensory neuron
-
conducts impulse from recptors to c.n.s.
(travels through out) - center (brain and/or spinal cord)
-
impulses translated, slowed, redirected
(can do anything)
association neuron may or may not be present
btwn. sensory and motor neurons - motor neuron
-
carries impulse from c.n.s. to effector
(directly stimulated) - effector
-
muscle or gland
(knee jerk reflex - spinal reflexes
- reflexes involving sp cord only
- somatic reflex
- reflexes inv. skeletal muscle
- cranial reflex
- reflexes inv. brain centers & cranial nerve
- visceral (autonomic) reflex
- reflex inv. involuntary effectors=smooth & cardiac muscles; glands
- cervial #
- C1-C8
- thoracic #
- T1-T12
- lumbar #
- L1-L5
- sacral #
- S1-S5
- coccygeal #
- 1 PAIR
- sensory (afferent)
- to c.n.s.
- motor (efferent)
- away c.n.s.
- mixed neurons
- includes all spinal nerves & all directions
- epineurium
- surrounds entire nerve
- fascicles (fasciculi)
- bundle of nerve fibers (axons)
- perineurum
- surrounds or difines fascicles
- endoneurum
- surrounds each nerve fiber
- branches (rami) of a spin. nerve
- branches close to cord
- ramus
- means branch
- dorsal ramus
-
sm. ramus of two
supplies deep muscle & skin of back of trunk - ventral ramus
-
supplies superfical back muscles, all extremities
lateral & ventral trunk - rami communicants
-
branches of sp. nerves
belongs to the a.n.s. - plexuses
-
network of vessels, nerves, lymphatics, ect.
These spinal plexuses are formed from the venral rami of all sp. nerves except T2-T12 - dermatomes
-
thin skin
skin segments
somatic sensory & motor system are involved in the regulation of ________ - What nerves DO NOT form plexuses?
- intercostal (thoracic) nerves
- Posterior or dorsal (sensory) root
- contains only sensory axons, which skin, muscles and internal organs into CNS