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70 terms

Chapter 13 Spinal Cord

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conduction
bundles of fibers passing information up and down spinal cord, connecting different levels of the trunk with each other and with the brain
locomotion
walking involves repetitive coordinated actions of several muscle groups.
reflex
involuntary stereotyped responses to stimuli. withdrawl of hand from pain
spinal cord
sylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull
segment
part of the spinal cord supplied by each pair of spinal nerves
cervical enlargement
nerves to upper limb
lumbar enlargement
nerves to pelvic region and lower limbs
medullary cone (conus medullaris)
cord tapers to a point inferior to lumbar enlargement
cauda equina
bundle of nerve roots that occupy the vertebral canal from L2 to S5
meninges
three fibrous connective tissue membranes that enclose the brain and spinal cord.
dura mater
formes loose fitting sleeve around spinal cord - dural sheath.
arachnoid membrane
layer of simple squamous epithelium lining dura mater and a loose mesh of collagen and elastic fibers spanning the gap between the arachnoid membrane and the pia mater.
subarachnoid space
gap between arachnoid membrane and pia mater.
lumbar cistern
subarachnoid space inferior to medullary cone that contains cauda equina and CSF
pia mater
delicate, translucent membrane that follows the contours of the spinal cord
terminal filum
fibrous strand of pia mater that extends beyond the medullary cone within the lumbar cistern
coccygeal ligament
formed from fusion of terminal filum and dura mater. anchors the cord and meninges to vertebra Co1
denticulate ligament
extend through the arachnoid to the dura. anchors spinal cord to limit side to side movement
spina bifida
congenital defect in which one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord.
gray matter
neuron cell bodies with little myelin. site of information processing
white matter
abundantly myelinated axons. carry signals from one part of the CNS to another.
lateral horn
visible from T2 through L1. contains neurons of sympathetic nervous system
columns (funiculi)
three pair of these white matter bundles
tracts (fasciculi)
subdivisions of each column
ascending tract
carry sensory information up the spinal cord
descending tract
carry motor information down the spinal cord
decussation
as the fibers pass up or down the brainstem and spinal cord they cross over from the left to the right and vise versa.
ipsilateral
when the origin and destination of a tract are on the same side of the body. does not decussate
first order neuron
detect stimulus and transmit signal to spinal cord or brainstem
second order neuron
continues to the thalamus at the upper end of the brainstem
third order neuron
carries the signal the rest of the way to the sensory region of the cerebral cortex
gracile fasciculus
carries signals from the midthoracic and lower parts of the body
proprioception
nonvisual sense of the position and movements of the body
cuneate fasciculus
joins the gracile fasciculus at the T6 level.
medial leminscus
formed from the second order neurons of gracile and cuneate sustems that decussate in the medulla
spinothalamic tract
one fo the smaller tracts of the anterolateral system. passes up the anterior and lateral columns of the spinal cord. carrys signals for pain, pressure, temp, light touch, tickle, and itch.
pyramid
ridges on anterior surface of the medulla oblongata formed from fibers of this system.
tectospinal tract
begins in midbrain region (tectum). reflex turning of head in response to sights and sounds.
amyotrophic lateral sclerosis
destruction of motor neurons and muscular atrophy.
nerve
cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue.
fascicle
nerve fibers gathered in bundles
perineurium
wraps fascicles
epineurium
bundles numerous fascicles that constitutes whole nerve
ganglion
cluster of neurosomas outside the CNS enveloped in an endoneurium continuous with that of the nerve
mixed nerve
consists of both afferent and efferent fibers and thus conducts signals in two directions.
anterior ramus
innervates the anterior and lateral skin and muscles of the trunk
posterior ramus
innervates the muscles and joints in that region of the spine and the skin of the back.
meningeal branch
reenters the vertebral canal and innervates the meninges vertebrae and spinal ligaments
somatosensory function
carry sensory signals from bones, joints muscles and the skin
motor funtion
primarily to stimulate muscle contraction
radial nerve injury
passes through axilla. crutch paralysis. wrist drop.
sciatica
sharp pain that travels from gluteal region along the posterior side of the thigh and leg to ankle
chickenpox
common disease of early childhood. caused by caricella zoster virus
shingles
localized disease caused by the virus traveling down the sensory nerves by fast axonal trasport when immune system is compromised.
dermatome
a specific area of the skin that receives sensory input from a pair of spinal nerves
dermatome map
a diagram of the cutaneous regions innervated by each spinal nerve
muscle spindle
stretch receptors embedded in skeletal system
proprioceptor
specialezed sense organs to monitor the position and movement of the body parts
intrafusal fiber
muscle fibers within spindle
stretch (myotatic) reflex
when a muscle is stretched, it fights back and contracts which maintains increased tonus making it stiffer than unstretched muscle.
tendon reflex
reflexive contraction of a muscle when its tendon is tapped. ex. knee jerk.
reciprocal inhibition
reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist.
flexor reflex
the quick contraction of flexor muscles resulting in the withdrawl of a limb from an injurious stimulus.
polysynaptic reflex arc
pathway in which signals travel over many synapses on their way back to the muscle
crossed extension reflex
the contraction of extensor muscles in the limb opposite of the one that is withdrawn
ipsilateral reflex arc
one in which the sensory input and the motor output are on the same sides of the spinal cord
contralateral reflex arc
one in which the input and output are on the opposite sides
intersegmental reflex
one in which the input and output occur at different levels (segments) of the spinal cord
tendon organ
proprioceptors in a tendon near its junction with a muscle
complete transection
complete severance of cord