Chapter 13 Spinal Cord

70 terms by amclloyd

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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

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