Chapter 13 - The Spinal Cord and Spinal Nerves Flashcards
spinal meninges/meninx
connective tissue coverings that encircle the spinal cord and brain, continuous with the cranial meninges, surround spinal cord
epidural space
The spinal cord is also protected by a cushion of fat and connective tissue located in the epidural space. a space between the dura mater and the wall of the vertebral canal.
dura mater
Thick, strong layer composed of dense irregular connective tissue.
arachnoid mater
Middle, thin, avascular, loosely arranged collagen and elastic fibers. spider web.
subdural space
between dura mater and arachnoid mater, contains interstitial fluid
pia mater
Thin, transparent connective tissue layer, adheres to the surface of the spinal cord and brain. Squamous to cuboidal cells within interlacing bundles of collagen fibers and some fine elastic fibers. many blood vessels.
subarachnoid space
Between the arachnoid mater and pia mate, contains shock-absorbing cerebrospinal fluid.
cervical and lumbar enlargements
the cervical enlargement, extends from the fourth cervical vertebra (C4) to the first thoracic vertebra (T1). Nerves to and from the upper limbs arise from the cervical enlargement. The inferior enlarge- ment, called the lumbar enlargement, extends from the ninth to the twelfth thoracic vertebra. Nerves to and from the lower limbs arise from the lumbar enlargement.
conus medullaris
tapering, conical structure ends at the level of the intervertebral disc between the first and second lumbar vertebrae (L1–L2) in adults.
filum terminale
Arising from the conus medullaris an extension of the pia mater that extends inferiorly, fuses with the arachnoid mater and dura mater, anchors the spinal cord to the coccyx.
spinal nerves
paths of communication between the spinal cord and specific regions of the body. 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
cauda equina
the lumbar, sacral, and coccygeal regions of the spinal cord do not leave the vertebral column at the same level they exit the cord. The roots of these lower spinal nerves angle inferiorly alongside the filum terminale in the vertebral canal like wisps of hair.
anterior median fissue
wide groove on the anterior (ventral) side.
posterior median sulcus
a narrow furrow on the posterior (dorsal) side.
gray commissure
forms the crossbar of the H.
central canal
center of the gray commissure is a small space , extends the entire length of the spinal cord and is filled with cerebrospinal fluid. , continuous with the fourth ventricle
anterior or ventral white commissure
connects the white matter of the right and left sides of the spinal cord.
nuclei
clusters of neuronal cell bodies form functional groups
posterior (dorsal) gray horn
contain cell bodies and axons of interneurons as well as axons of incoming sensory neurons
anterior (ventral) gray horn
contain somatic motor nuclei, which are clusters of cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles.
lateral gray horn
Between the posterior and anterior gray horns
columns
The anterior and posterior gray horns divide the white matter on each side into three broad areas called columns: (1) anterior (ventral) white columns, (2) posterior (dorsal) white columns, and (3) lateral white columns
tract
bundles of axons having a common origin or destination and carrying similar information.
sensory (ascending) tract
consist of axons that conduct nerve impulses toward the brain.
motor (descending) tract
axons that carry nerve impulses from the brain
spinal nerves
associated with the spinal cord and, like all nerves of the peripheral nervous system (PNS), are parallel bundles of axons and their associated neuroglial cells wrapped in several layers of connective tissue. Spinal nerves connect the CNS to sensory receptors, muscles, and glands in all parts of the body. The 31 pairs of spinal nerves are named and numbered according to the region and level of the vertebral column from which they emerge
mixed nerve
Because the posterior root contains sensory axons and the anterior root contains motor axons, a spinal nerve is classified as a mixed nerve.
endoneurium
a mesh of collagen fibers, fibroblasts, and macrophages wraps individual axons within a nerve
perineurium
wraps fascicles, thicker layer of connective tissue, 15+ layers of fibroblasts within a network of collagen fibers.
epineurium
fibroblasts and thick collagen fibers, fills spaces between fascicles.
ramus
A short distance after passing through its intervertebral foramen, a spinal nerve divides into several branches called rami,
Posterior dorsal = deep muscles and skin of the posterior surface of the trunk
Anterior ventral = muscles and structures of upper and lower limbs and skin of the lateral and anterior surfaces of trunk
meningeal branch
spinal nerves give off this branch, which reenters the vertebral cavity, supplies
plexus
network of axons
cervical plexus
C1-C4, contributions from C5. supplies the skin and muscles of the head, neck, and superior part of the shoulders and chest. nerves arise from the cervical plexuses and supply motor fibers to the diaphragm. Branches of the cervical plexus also run parallel to two cranial nerves, the accessory (XI) nerve and hypoglossal (XII) nerve.
brachial plexus
C5-C8 and T1,extends inferiorly and laterally on either side of the last four cervical and first thoracic vertebrae, Complex, roots, trunks, divisions, cord, branches.
shoulders and upper limbs.
(1) The axillary nerve supplies the deltoid and teres minor muscles. (2) The musculocutaneous nerve supplies the anterior muscles of the arm. (3) The radial nerve supplies the muscles on the posterior aspect of the arm and forearm.(4)The median nerve supplies most of the muscles of the anterior forearm and some of the muscles of the hand. (5) The ulnar nerve supplies the anteromedial muscles of the forearm and most of the muscles of the hand.
lumbar plexus
L1-L4, passes obliquely outward, between the superficial and deep heads of the psoas major muscle and anterior to the quadratus lumbo- rum muscle. Between the heads of the psoa major, the roots of the lumbar plexuses split into anterior and posterior divisions, which then give rise to the peripheral branches of the plexas.
The lumbar plexus supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs.
sacral plexus
L4–L5 and S1–S4, buttocks, perineum, and lower limbs. The largest nerve in the body—the sciatic nerve—arises from the sacral plexus.
coccygeal plexus
S4–S5, anococcygeal nerves supply a small area of skin in the coccygeal region.
dermatome
The area of the skin that provides sensory input to nerve the CNS via one pair of spinal nerves or the trigeminal (V) nerve
spinothalamic tracts
conveys nerve impulses for sensing pain, warmth, coolness, itching, tickling, deep pressure, and crude touch.
posterior column
consists of two tracts: the gracile fasciculus and the cuneate fasciculus. convey nerve impulses for discriminative touch, light pressure, vibration, and conscious proprioception (the awareness of the positions and movements of muscles, tendons, and joints).
direct motor pathways
convey nerve impulses that originate in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles.
indirect motor pathways
convey nerve impulses from the brain stem to cause automatic movements and help coordinate body movements with visual stimuli. Indirect pathways also maintain skeletal muscle tone, sustain contraction of postural muscles, and play a major role in equilibrium by regulating muscle tone in response to movements of the head.
reflex
fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus. Some reflexes are inborn, such as pulling your hand away from a hot surface before you even feel that it is hot. Other reflexes are learned or acquired
spinal reflex
When integration takes place in the spinal cord gray matter, the reflex is a spinal reflex. An example is the familiar patellar reflex (knee jerk)
cranial reflex
If integration occurs in the brain stem rather than the spinal cord, the reflex is called a cranial reflex. An example is the tracking movements of your eyes as you read this sentence.
somatic reflex
contraction of skeletal muscles.
autonomic or visceral reflex
responses of smooth muscle, cardiac muscle, and glands. heart rate, digestion, urination, defecation, ANS through autonomic reflexes
reflex arc
Nerve impulses propagating into, through, and out of the CNS follow specific pathways, depending on the kind of information, its origin, and its destination.
1) sensory receptor
2) sensory neuron
3) integrating center
4) motor neuron
5) effector
monosynaptic reflex arc
one synapse in CNS
polysynaptic reflex arc
Two types of neurons and more than one CNS synapse
stretch reflex
causes contraction of a skeletal muscle (the effector) in response to stretching of the muscle. This type of reflex occurs via a monosynaptic reflex arc.
muscle spindle
spindles monitor changes in the length of the muscle.
ipsilateral reflex arc
sensory nerve impulses enter the spinal cord on the same side from which motor nerve im- pulses leave it.
muscle tone
small degree of contraction present while the muscle is at rest
reciprocal innervation
components of a neural circuit simultaneously cause contraction of one muscle and relaxation of its antagonists,
tendon reflex
operates as a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force be- comes so great that tendons might be torn, less sensitive but can override stretch.
tendon organ or golgi tendon organ
sensory receptors for tendon reflex, detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction.
flexor or withdrawal reflex
response to pain
intersegmental reflex arc
nerve impulses from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord,
crossed extensor reflex
helps maintain balance
contralateral reflex arc
Sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side.
shingles
acute infection of the peripheral nervous system caused by herpes zoster
poliomyelitis
polio, fever, severe headache, a stiff neck and back, deep muscle pain and weak- ness, and loss of certain somatic reflexes. In its most serious form, the virus produces paralysis by destroying cell bodies of motor neurons, specifically those in the anterior horns of the spinal cord and in the nuclei of the cranial nerves. Polio can cause death from respiratory or heart failure if the virus invades neurons in vital centers that control breathing and heart functions in the brain stem.
