chapter 14 the spinal cord and spinal nerves

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spinal cord

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

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