Chapter 13: The Spinal, Spinal Nerves, and Somatic Reflexes Flashcards by Hannah Thompson

nerve fibers conduct sensory and motor information up and down the spinal cord

conduction

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spinal neurons receive input from multiple sources integrate and execute appropriate output

neural integration

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spinal cord contains central pattern generators group of neurons that coordinate repetitive sequences of contractions for walking

locomotion

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involuntary responses to stimuli that are vital to posture coordination and protection

reflexes

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cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull

spinal

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where does the spinal cord’s inferior margin end?

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what segments is the spinal cord divided into?

cervical, thoracic, lumbar, and sacral

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nerves to upper thigh

cervical enlargement

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nerves to pelvic region and lower limbs

lumbar enlargement

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cord tapers to a point inferior to lumbar enlargement

conus medullaris

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bundle of nerve roots that occupy the vertebral canal from L2 to S5

cauda equina

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three fibrous membranes that enclose the brain and spinal cord

meninges

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what are the meninges from superficial to deep?

dura mater, arachnoid mater, and pia mater

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what separates the vertebrae from dura mater?

epidural space

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delicate membrane that follows contours of spinal cord?

pia mater

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pia mater continues inferiorly as the

filum terminale

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what is the subarachnoid space filled with?

cerebrospinal fluid (CSF)

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congenital defect in which one of more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord

spina bifida

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what is the most serious form of spina bifida?

spina bifida cystica

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what reduces the risk of spina bifida

folic acid

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when does spina bifida occur?

defect occurs within the first 4 weeks of development

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contains neuron cell bodies with little myelin; site of information processing, synaptic integration

gray matter

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contains myelinated axons; carries signals from one part of the CNS to another

white matter

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contains interneuron cell bodies

dorsal (posterior) horns

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made up of only sensory fibers

dorsal (posterior) root

contains motor neuron cell bodies

ventral (anterior) horns

made up only of motor fibers

ventral anterior root

connects right and left sides; central canal lined with ependymal cells filled with CSF

gray commissure

T2 through L1; contains neurons of sympathetic nervous system

lateral horn

columns of funiculi

posterior (dorsal), lateral, and anterior (ventral) columns

subdivisions of columns or funiculi

tracts or fasciculi

spinal tract; carry sensory information up

ascending tracts

spinal tracts; carry motor information down

descending tracts

crossing of the midline that occurs so that the brain senses and controls the contralateral side of body

decussation

spinal tracts; origin and destination on opposite sides of the body

contralateral tracts

spinal tract; have an origin and destination on the same side of the body

ipsilateral tract

detect stimulus and transmit signal to spinal cord or brainstem

first order neurons

continue to the thalamus at the upper end of the brainstem

second order neurons

carry the signal the rest of the way to the sensory region of the cerebral cortex

third order neurons

ascending tracts: carries signals from midthoracic and lower parts of body

gracile fasciculus

nonvisual sense of the position and movements of the body

proprioception

ascending tract: passes up the anterior and lateral columns of the spinal cord from the spinal cord to the thalamus; carries signals for pain pressure temperature light touch, tickle and itch

spinothalamic tract

what tract travels up the anterolateral system

spinoreticular tract

what tracts travel through lateral column

anterior and posterior spinocerebellar tracts

two motor neurons involved with descending tracts

upper motor neurons and lower motor neurons

originate in the cerebral cortex or brainstem and terminate on a lower motor neuron

upper motor neuron

somata are in the brainstem or spinal cord; axons lead to muscle or other target organs

lower motor neuron

carry signals from the cerebral cortex for precise finely coordinated movements of the limbs

corticospinal tracts

begins at midbrain region; reflex turning of head in response to sights and sounds

tectospinal tract

cord like organ composed of numerous nerve fibers bound together by connective tissue

nerve

contain both afferent and efferent fibers

mixed nerves

loose connective tissue external to neurilemma

endoneurium

layers of overlapping squamous cells that wrap fascicles: bundles of nerve fibers

perineurium

dense irregular connective tissue that wraps entire nerve

epineurium

caused by poliovirus; destroys motor neurons in brainstem and anterior horn of spinal cord; signs of polio include muscle pain, weakness, and loss of some reflexes; spreads by fecal contamination of water

poliomyelitis

destruction of motor neurons and muscular atrophy; also sclerosis (scarring) of lateral regions of the spinal cord; astrocytes fail to reabsorb the neurotransmitter glutamate from the tissue fluid

amyotrophic lateral sclerosis (ALS)

skin, skeletal, muscles, bones, joints

somatic

blood vessels, glands, and viscera

visceral

widespread innervation

general

localized innervation

special

cluster of cell bodies outside the CNS

ganglion

sensory ganglion associated with spinal nerves

dorsal (posterior) root ganglion

carries sensory input to the spinal cord

posterior dorsal root

carries motor output from the spinal cord

anterior ventral root

formed from the roots arising from L2 to Co1

cauda equina

innervates the muscles and joints in that region of the spine and the skin of the back

posterior ramus

reenters the vertebral canal and innervates the meninges, vertebrae, and spinal ligaments

meningeal branch

supplies neck and phrenic nerve to the diaphragm

cervical plexus

supplies upper limb and some of shoulder and neck; median nerve carpal tunnel syndrome

brachial plexus

supplies remainder of lower trunk and lower limb

sacral plexus

carry sensory signals from bones joints muscles and skin

somatosensory function

common disease of early childhood; caused by varicella zoster virus; produces itchy rash that clears up without complication

chickenpox

localized disease caused by the virus traveling down the sensory nerves by fast axonal transport when immune system is compromised

shingles (herpes zoster)

major motor and sensory nerve diaphragm; phrenic nerve receives fibers from C3 to C5

phrenic nerve

5 nerves of brachial plexus

axillary, musculocutaenous, median, ulnar, radial

skin of anterolateral forearm upper arm flexors

musculocutaenous nerve

skin of lateral shoulder and arm; deltoid muscle

axillary nerve

skin of posterior arm and forearm; extensor muscles of posterior arm and forearm

radial nerve

skin of lateral 2/3 of hand; forearm flexor and lateral palm

median nerve

skin of palmar and medial hand forearm flexors and hand muscles

ulnar nerve

longest and thickest nerve of body; innervates hamstring muscles, adductor magnus, and most muscles in leg and foot

sciatic nerve

sharp pain that travels from gluteal region along the posterior side of the thigh and leg to ankle

sciatica

specific area of skin that conveys sensory input to a spinal nerve

dermatome

a diagram of the cutaneous regions innervated by each spinal nerve

dermatome map

quick involuntary stereotyped reactions of glands or muscles to stimulation

reflexes

involve the somatic nervous system innervating skeletal muscle

somatic reflexes

stretch receptor embedded in skeletal muscle that informs the brain of muscle length and body movements

muscle spindle

innervates the intrafusal fiber to maintain tension and sensitivity

gamma motor neuron

when a muscle is stretched it responds by contracting

stretch myotatic reflex

monosynaptic reflex example

knee jerk patellar reflex

reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist when the agonist is excited

reciprocal inhibition

quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus

flexor reflex

involves the contraction of extensor muscles in limb opposite of the one that is withdrawn

crossed extension reflex

stimulus and response on same side

ipsilateral reflex arc

input and output are on opposite sides

contralateral reflex arc

one in which the input and output occur at different levels

intersegmental reflex

proprioceptors in a tendon near its junction with a muscle

tendon organs

a response to excessive tension on the tendon

tendon reflex

complete severance of cord

complete transection

paralysis of both lower limbs

paraplegia

paralysis of all four limbs

quadriplegia

paralysis on one side of the body

hemiplegia

partial paralysis or weakness of the limbs

paresis