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chapter 14 the spinal cord and spinal nerves

spinal cord
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although spinal cord and brain connected they still have some
-functional independence
integrates and processes information on its own and relays info to and from the brain
-spinal cord
the adult spine has a
-posterior median sulcus and
-anterior median fissure
shallow
-posterior median sulcus
wide
-anterior median fissure
cervical and lumbar
-enlargements
expanded localized regions where there is increased gray matter to provide innervation of the limbs on the spinal cord
-enlargements
adult spinal cord extends from the
-foramen magnum to L1
the spinal cord tapers to a conical tip
-conus medullaris
strand of fibrous tissue that originates at the tip and extends through the vertebral canal to the second sacral vertebra, ultimately becoming part of the coccygeal ligament
-filum terminale
becomes part of coccygeal ligament
-filum terminale
how many segments in spinal cord
-31 segments
each segment of the spinal cord associated with a pair of a) ____ ___ _____ and pairs of b) _____ ____ and c)_____ ____
-dorsal root ganglia
-dorsal roots
-ventral roots
what represents exceptions in that the dorsal roots are absent in many individuals
-the first cervical and first coccygeal nerves
sensory and motor fibers unite as a single _____ _____ distal to each dorsal root ganglion
-spinal nerve
spinal nerves emerge from
-intervertebral foramina
spinal nerves are ____ ____
mixed nerves
mixed nerves since contain both
-sensory fibers and
-motor fibers
largest nerve in the body
-sciatic nerve
inferior extension of the ventral and dorsal roots and the filum terminale in the vertebral canal
-caudal equina
spinal meninges
-series of specialized membranes that provide physical stability and shock absorption for neural tissues of the spinal cord
membranes that surround the brain
-cranial meninges
3 spinal meningeal layers
-dura mater
-arachnoid mater
-pia mater
the tough, fibrous outermost layer that covers the spinal cord
-dura mater
caudally the dura mater forms the _____ ______ with the filum terminale
-coccygeal ligament
what separates the dura mater from the inner walls of the vertebral canal
-epidural space
internal to the inner surface of the dura mater
-subdural space
when present it separates the dura mater from the middle meningeal layer
-arachnoid mater
internal to the arachnoid mater
-subarachnoid space
space that contains cerebrospinal fluid (csf)
-subarachnoid space
acts as a shock absorber and used for spinal tap
-cerebrospinal fluid
innermost meningeal layer
-pia mater
layer bound firmly to the underlying neural tissue
-pia mater
paired supporting fibers extending laterally from the spinal cord surface
-dendiculate ligaments
paired supporting fibers binding the spinal pia mater and arachnoid mater to prevent side-to-side or inferior movement of the spinal cord
-dendiculate ligaments
surrounds the central canal and contains cell bodies of neurons and glial cells
-central gray mater
gray matter projections toward the outer suface of the spinal cord
-horns
contains myelinated and unmyelinated axons in tracts and columns
-peripheral white matter
neuron cell bodies in the the spinal cord gray matter are organized into groups termed,
-nuclei
sensory nuclei
-dorsal
-touch receptors
motor nuclei
-ventral
-issue motor commands to peripheral effectors,muscles
separates the sensory nuclei from the motor nuclei
-frontal section along the axis of the central canal
horn that contain somatic and visceral sensory nuclei
-posterior gray horn
horn that contain nuclei involved with somatic motor control
-anterior gray horn
horn that contain visceral motor neurons
-lateral gray horn
-found between t1 and l2
posterior and anterior to the central canal
-gray commissures
contain the axons of interneurons that cross from one side of the cord to the other
-gray commissures
white matter can be divided into six
-columns
columns aka
-funiculi
each column or funiculi contains
-tracts or fasiculi
tracts aka
-fasiculi
tract that relays information from the spinal cord to the brain
-ascending tracts
tract that carry information from the brain to the spinal cord
-descending tracts
how many pairs of spinal nerves?
-31 pairs
each spinal nerves is identified through its
-association with an adjacent vertebra
vertebra
-cervical, thoracic, lumbar, sacral
each spinal nerve is ensheated by a series of connective tissue layers
-epineurium
-perinuerium
-endoneurium
outermost layer of spinal nerve, dense network of collagen fibers
-epineurium
middle layer of spinal nerve that partitions the nerve into a series of bundles (fascicles) and conveys blood vessels into each individual fiber
-perineurium
inner layer of spinal nerve that is composed of delicate connective tissue fibers that surround individual axons
-endoneurium
first branch of spinal nerve in the thoracic and upper lumbar regions
-white ramus
contains myelinated axons going to an autonomic ganglion
-white ramus
what 2 groups of unmyelinated fibers exit the autonomic ganglion
-gray ramous
-autonomic nerve
gray ramous
-carry axons that innervate glands and smooth muscles in the body wall or limbs back to the spinal nerve
autonomic nerve
-carry fibers to internal organs
rami communicantes
-white and gray rami
each spinal nerves has both a ____ ____ and a ____ _____
-dorsal ramus
-ventral ramus
each pair of spinal nerves monitors a region of the body surface called
-dermatome
dorsal ramus
-provides sensory/motor innervation to the skin and muscles of the back
ventral ramus
-supplies ventrolateral body surface, body wall structures, and limbs
complex, interwoven network of nerves
-nerve plexus
four major nerve plexuses are the
-cervical plexus
-brachial plexus
-lumbar plexus
-sacral plexus
plexus that consists of the ventral rami of c1-c4 and some fibers from c5
-cervical plexus
plexus in which muscles of the neck are innervated, and some branches extend into the thoracic cavity to the diaphragm
-cervical plexus
which nerve is the major nerve in the cervical plexus
-phrenic nerve
plexus that innervates the pectoral girdle and upper limbs by the c5-t1.
-brachial plexus
nerves in this plexus originate from cords or trunks
-brachial plexus
superior, middle, and inferior trunks give rise to the
-lateral cord, medial cord, and posterior cord
what 2 plexuses collectively originate from the posterior abdominal wall and ventral rami of nerves supply the pelvic girdle and lower limb
-lumbar plexus
-sacral plexus
plexus that contains fibers from spinal segments t12-l4
-lumbar plexus
plexus that contains fibers from spinal segments l4-s4
-sacral plexus
rapid, automatic, involuntary motor response to stimuli
-neural reflex
help preserve homeostasis by rapidly adjusting the functions of organs or organ systems
-reflexes
the neural 'wiring' of a single reflex
-reflex arc
a ______ is a specialized cell that monitors condition in the body or external environment
-receptor
each receptor has a characteristic range of _________
-sensitivity
there are _ steps involved in the neural reflex
-5
neural reflex steps
-1) arrival of a stimulus and activation of a receptor
-2) relay of information to the cns
-3) information processing
-4) activation of a motor neuron
-5) response by a peripheral effectors
what step of neural reflex information processing
3
what step of neural reflex -4) activation of a motor neuron
4
what step of neural reflex response by a peripheral effectors
5
what step of neural reflex relay of information to the cns
2
what step of neural reflex arrival of a stimulus and activation of a receptor
1
reflexes classified by
1) their development (innate, acquired)
2) where information is processed (spinal, cranial)
3) motor response (somatic, visceral)
4) complexity of the neural circuit (monosynaptic, polysynaptic)
innate reflexes are determined _______
-genetically
acquired reflexes are
-learned following repeated exposure to a stimulus
reflexes processed in the brain
-cranial reflexes
reflex where the important interconnections and processing occur inside the spinal cord
-spinal reflex
reflex that control skeletal muscle contractions
-somatic reflex
visceral (autonomic) reflex
-control the activities of smooth and cardiac muscles and glands
simplest reflex arc
-monosynaptic reflex
which neuron synapses direct on a motor neuron that acts as the processing center
-sensory neuron
polysynaptic reflexes
-have at least one interneuron places between the sensory afferent and the motor efferent
which reflex have a longer delay between stimulus and response?
-polysynaptic reflexes
spinal reflexes range from simple a)______reflexes to more complex b)_______reflexes
a) monosynaptic
b) polysynaptic
simple monosynaptic reflexes
-involving only one segment of the cord
complex polysynaptic reflexes
-many segments of the cord interact to produce a coordinated motor response
stretch reflex
-a monosynaptic reflex that automatically regulates skeletal muscle length and muscle tone.
reflex that includes patellar, bicep, triceps, and ankle jerk reflex
-stretch reflex
reflex the familiar knee jerk, where in a rap on the patellar ligament stretches the muscle spindles in the quadriceps muscles.
-patellar reflex
stretch reflex that maintains normal upright posture
-postural reflex
what can enhance or inhibit reflex motor patterns based in the spinal cord
-higher centers in the brain
loss of sensation and motor control of the upper and lower limbs
-quadriplegia
ventral root
-motor neuron axons
epidural space
-loose connective tissue, adipose tissue
white matter
-tracts and columns
fascicle
-single bundle of axons
dermatome
-specific region of body surface
phrenic nerve
-cervical plexus
brachial plexus
-pectoral girdle/upper extremity
obturator nerve
-lumbar plexus
reflex
-involuntary motor response
pudendal nerve
-sacral plexus
the _____ ______ is a strand of fibrous tissue that provides longitudinal support as a component of the coccygeal ligament
-filum terminale
axons crossing from one side of the spinal cord to the other within the gray matter are found in the
-gray commissures
the paired structures that contain cell bodies of sensory neurons and are associated with each segment of the spinal cord are the
-dorsal root ganglia
the deep crease on the ventral surface of the spinal cord is the
-anterior median fissure
sensory and motor innervations of the skin of the lateral and ventral surfaces of the body are provided by the
-ventral ramus
brachial plexus
-innervates the shoulder girdle and the upper extremity, is formed from the ventral rami of spinal nerves c5-t1, and is the source of the musculocutaneous, radial, median, and ulnar nerves
the middle layer of connective tissue that surrounds each peripheral nerve is the
-perineurium
the expanded area of the spinal cord that supplies nerves to the pectoral girdle and upper limbs is the
-cervical enlargement
spinal nerves are called mixed nerves because
-they contain sensory and motor fibers
the gray matter of the spinal cord is dominated by
-cell bodies of neurons and glial cells