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Flashcards in Introduction to the Nervous System Deck (41):

nervous system is structurally divided into ___ & ___

central nervous system (CNS) - brain (encased in skull) & spinal cord (encased within vertebral column)

peripheral nervous system (PNS) - cranial nerves (12) & spinal nerves (31)


nervous system is functionally divided into ___ & ___ & is found throughout the ___ & ___ nervous systems

somatic nervous system (body wall) - innervates structures derived from embryonic somites or branchial arches (ex. skin & body wall, skeletal muscles, skeletal system, joints, etc.)

visceral nervous system (internal organs) - innervates visceral structures of body (ex. heart & blood vessels, digestive systems, respiratory system, urinary system, reproductive system, glands, smooth muscle, etc.)

central & peripheral


somatic & visceral nervous systems are both divided into ___ & ___, & further into ___

motor (efferent)

sensory (afferent)

visceral motor: autonomic nervous system --> sympathetic & parasympathetic


neuron (definition)

structural & functional unit of nervous system that's specialized for rapid communication


neuron (components)

cell body

dendrites - carry impulses toward cell body (often, not always)

axon (fiber) - carries impulses away from cell body, neurons always have one and only one axon


neuron (communication)

neurons communicate w/ each other at synapses

communication occurs by means of chemical agents called neurotransmitters secreted by one of the neurons

neurotransmitter may either excite or inhibit another neuron


multipolar cell

contains many processes (dendrites & axons)


peripheral nervous system

consists of nerve fibers & cell bodies outside central nervous system


peripheral nerve

bundle of nerve fibers (axons) in PNS



collection of nerve cell bodies in PNS


cranial nerves

originate from brain & exit cranial cavity through foramina (openings in skull bones)

12 sets of cranial nerves


spinal nerves

arise from spinal cord & exit through intervertebral foramina in vertebral column

31 sets of spinal nerves


typical spinal nerve

two roots: ___ & ___

arises from spinal cord by rootlets which converge to form two nerve roots

dorsal (sensory) root

ventral (motor) root


dorsal root:

carries ___ (___) impulses ___

sensory neuron cell bodies located in ___ located in ___

sensory neurons have a ___ process that ___, & these cells are termed ___

sensory, afferent, toward CNS

a swelling on the dorsal root called the dorsal root ganglion, intervertebral foramen

single, emanates from the cell body which splits in a t-like fashion into a peripheral & a central process, pseudounipolar neurons


central root:

carries ___ (___) impulses ___

motor neuron cell bodies located in ___

motor neurons have ___ processes & these cells are termed ___

motor, efferent, away from CNS toward some peripheral structure (muscle, gland, etc.)

central horn of spinal cord

many (numerous dendrites & one axon), multipolar neurons


immediately after the dorsal & ventral roots join forming the ___, it splits into a ___ & ___

both of these have ___ components

mixed (sensory & motor) spinal nerve

dorsal ramus - supplies skin & muscles of back

ventral ramus - supplies skin & muscles of anterior side of body & limbs

sensory & motor


somatic sensory fibers:

general somatic ___

reach ___ level

they may be ___ or ___ sensations

afferent (GSA)


exteroceptive (touch, pressure, vibration, pain, & temperature) from skin

pain & proprioceptive from muscles, tendons, & joints - convey info on joint position & tension of tendons & muscles, providing info on how body & limbs are oriented in space


somatic motor fibers:

general somatic ___

sole target tissue of somatic motor fibers is ___ & their only effect is to ___ them & cause them to ___

efferent (GSE)

skeletal muscle fibers, stimulate, contract


visceral sensory fibers:

general visceral ___

fibers transmit ___

reach ___ level

afferent (GVA)

pain or subconscious visceral reflex sensations (e.g. info concerning organ distension, blood gas & blood pressure levels, etc.)

not conscious (internal bodily functions)


visceral motor fibers:

general visceral ___

aka ___

fibers innervate ___

fibers may have a ___effect on target tissue

efferent (GVE)

autonomic nervous system (ANS)

a wide variety of visceral structures (e.g. smooth muscle, glands, blood vessels, the heart, etc.)

stimulatory or inhibitory


spinal cord

cylindrical structure extending from foramen magnum to intervertebral disc b/n L1 & L2 (not all the way to tip of coccyx)


ordered segmented pattern throughout spinal cord's length gives rise to 31 pairs of spinal nerves

8 cervical - 7 vertebrae, 1st nerve b/n skull & C1 (b/n occipital bone & atlas), 2nd-7th exit above vertebra, 8th nerve exits under vertebra

all following nerves exit under vertebra

12 thoracic

5 lumbar

5 sacral

1 coccygeal


spinal cord & vertebral column grow at ___ rate until ___, after which the ___ grows much more ___ than the ___


end of 3rd month of fetal development

vertebral canal


spinal cord


at six months of fetal development, spinal cord ___

terminates at S1


at birth, spinal cord ___

terminates at L3


in adults, spinal cord terminates at ___

intervertebral disc b/n L1 & L2


in adults, the coccygeal spinal cord segment is located at the level of the intervertebral disc b/n ___ & ___ vertebrae

dorsal & ventral roots of lower ___, ___, & ___ spinal nerves must descend ___

collection of spinal nerve roots forms ___

L1, L2

lumbar, sacral, coccygeal, a considerable distance within the vertebral canal to reach their respective intervertebral foramina

cauda equina


two fusiform enlargements of spinal cord

below the lower enlargement, the spinal cord tapers off into the ___

cervical enlargement (C4/C5 - T1) - reflects large number of neurons serving brachial plexus (upper limbs)

lumbar enlargement (L1 - S3) - reflects large number of neurons serving lumbosacral plexus (lower limbs)

conus medullaris (termination of cord)

*refers to nerves, not vertebrae



protective barrier (membrane) b/n bone & soft tissue of CNS


dura mater:


spinal dura is separated from vertebrae by ___ which contains ___

the dura forms the ___ which continues down to the ___ vertebrae

outermost tough, dense, fibrous layer of meninges

epidural space, adipose tissue & a venous blood plexus (veins)

dural sac (a long tubular sheath within the vertebral canal that houses both brain & spinal cord), S2


arachnoid mater:


held against the___ of the dura by the pressure of ___

the subarachnoid space lies between the ___ & the ___ and contains ___

delicate strands of connective tissue called ___ span the ___

delicate membrane of meninges

inner surface, cerebrospinal fluid

arachnoid, pia mater, cerebrospinal fluid

arachnoid trabeculae, subarachnoid space


pia mater:


closely adherent to ___

spinal cord suspended in dural sac by ___

at apex of cord, a continuation of pia mater continues as ___ which continues to end of dural sac at ___, pierces the dural sac & receives an investment of arachnoid & dura mater & is now referred to as the ___ which attaches to the tip of the coccyx

delicate, highly vascular, innermost layers of meninges

neural tissue

saw-toothed denticulate ligaments - lateral extensions of pia mater midway b/n dorsal & ventral nerve roots, attach to inner surface of dura mater, anchor spinal cord within sac

filum terminal interum (after conus medullaris), S2, filum terminale externum or coccygeal ligament


subarachnoid space:

lies below ___

encloses ___

enlargement caudal to conus medullaris containing cauda equina is ___ which extends from ___ to ___

arachnoid mater

spinal cord & spinal nerve roots

lumbar cistern, L2, S2


lumbar puncture (spinal tap)

performed to withdraw a sample of cerebrospinal fluid for examination

spinal cord terminates at level of L1/L2, while lumbar cistern of subarachnoid space extends down to lower border of S2

a needle introduced into lumbar cistern below L4 pushes nerve roots of cauda equina aside w/o causing damage


herniation of nucleus pulposes:

herniation/protrusion of gelatinous nucleus pulposus into/through anulus fibrosus is a well-recognized cause of ___

flexion of the vertebral column produces ___ & ___, squeezing the nucleus pulposus further ___ toward the thinnest part of the annulus fibrosus

if the annulus fibrosus has degenerated, the nucleus pulposus may ___ into the vertebral canal & ___ the spinal cord or the nerve roots of the cauda equina

herniations of the nucleus pulposus usually extend ___, where the anulus fibrosus is relatively ___ & doesn't receive support from either the anterior or posterior longitudinal ___

a posterolateral herniated IV disc is more likely to be ___ b/c of the proximity of ___

lower back pain & lower limb pain

compression anteriorly, stretching/tension posteriorly, posteriorly

herniate, compress

posterolaterally, thin, ligaments

symptomatic, spinal nerve roots


spinal cord segment

region of spinal cord to which a spinal nerve is attached



area of skin supplied by dorsal (sensory) root of spinal nerve



muscle mass innervated by ventral (motor) root of spinal nerve


nerve plexus

network of nerve fibers


somatic nerve plexus

nerve plexus formed by ventral rami of certain spinal nerves

ex. cervical plexus, brachial plexus, lumbar plexus, sacral plexus

does have autonomic components, but principally sensory


autonomic nerve plexus

network of sympathetic & parasympathetic nerve fibers

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