Chapter 13 - The Spinal Cord and Spinal Nerves

Question 1

spinal meninges/meninx

Answer 1

connective tissue coverings that encircle the spinal cord and brain, continuous with the cranial meninges, surround spinal cord

Question 2

epidural space

Answer 2

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.

Question 3

dura mater

Answer 3

Thick, strong layer composed of dense irregular connective tissue.

Question 4

arachnoid mater

Answer 4

Middle, thin, avascular, loosely arranged collagen and elastic fibers. spider web.

Question 5

subdural space

Answer 5

between dura mater and arachnoid mater, contains interstitial fluid

Question 6

pia mater

Answer 6

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.

Question 7

subarachnoid space

Answer 7

Between the arachnoid mater and pia mate, contains shock-absorbing cerebrospinal fluid.

Question 8

cervical and lumbar enlargements

Answer 8

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.

Question 9

conus medullaris

Answer 9

tapering, conical structure ends at the level of the intervertebral disc between the first and second lumbar vertebrae (L1–L2) in adults.

Question 10

filum terminale

Answer 10

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.

Question 11

spinal nerves

Answer 11

paths of communication between the spinal cord and specific regions of the body. 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

Question 12

cauda equina

Answer 12

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.

Question 13

anterior median fissue

Answer 13

wide groove on the anterior (ventral) side.

Question 14

posterior median sulcus

Answer 14

a narrow furrow on the posterior (dorsal) side.

Question 15

gray commissure

Answer 15

forms the crossbar of the H.

Question 16

central canal

Answer 16

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

Question 17

anterior or ventral white commissure

Answer 17

connects the white matter of the right and left sides of the spinal cord.

Question 18

nuclei

Answer 18

clusters of neuronal cell bodies form functional groups

Question 19

posterior (dorsal) gray horn

Answer 19

contain cell bodies and axons of interneurons as well as axons of incoming sensory neurons

Question 20

anterior (ventral) gray horn

Answer 20

contain somatic motor nuclei, which are clusters of cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles.

Question 21

lateral gray horn

Answer 21

Between the posterior and anterior gray horns

Question 22

columns

Answer 22

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

Question 23

tract

Answer 23

bundles of axons having a common origin or destination and carrying similar information.

Question 24

sensory (ascending) tract

Answer 24

consist of axons that conduct nerve impulses toward the brain.

Question 25

motor (descending) tract

Answer 25

axons that carry nerve impulses from the brain

Question 26

spinal nerves

Answer 26

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

Question 27

mixed nerve

Answer 27

Because the posterior root contains sensory axons and the anterior root contains motor axons, a spinal nerve is classified as a mixed nerve.

Question 28

endoneurium

Answer 28

a mesh of collagen fibers, fibroblasts, and macrophages wraps individual axons within a nerve

Question 29

perineurium

Answer 29

wraps fascicles, thicker layer of connective tissue, 15+ layers of fibroblasts within a network of collagen fibers.

Question 30

epineurium

Answer 30

fibroblasts and thick collagen fibers, fills spaces between fascicles.

Question 31

ramus

Answer 31

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

Question 32

meningeal branch

Answer 32

spinal nerves give off this branch, which reenters the vertebral cavity, supplies

Question 33

plexus

Answer 33

network of axons

Question 34

cervical plexus

Answer 34

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.

Question 35

brachial plexus

Answer 35

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.

Question 36

lumbar plexus

Answer 36

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.

Question 37

sacral plexus

Answer 37

L4–L5 and S1–S4, buttocks, perineum, and lower limbs. The largest nerve in the body—the sciatic nerve—arises from the sacral plexus.

Question 38

coccygeal plexus

Answer 38

S4–S5, anococcygeal nerves supply a small area of skin in the coccygeal region.

Question 39

dermatome

Answer 39

The area of the skin that provides sensory input to nerve the CNS via one pair of spinal nerves or the trigeminal (V) nerve

Question 40

spinothalamic tracts

Answer 40

conveys nerve impulses for sensing pain, warmth, coolness, itching, tickling, deep pressure, and crude touch.

Question 41

posterior column

Answer 41

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).

Question 42

direct motor pathways

Answer 42

convey nerve impulses that originate in the cerebral cortex and are destined to cause voluntary movements of skeletal muscles.

Question 43

indirect motor pathways

Answer 43

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.

Question 44

reflex

Answer 44

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

Question 45

spinal reflex

Answer 45

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)

Question 46

cranial reflex

Answer 46

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.

Question 47

somatic reflex

Answer 47

contraction of skeletal muscles.

Question 48

autonomic or visceral reflex

Answer 48

responses of smooth muscle, cardiac muscle, and glands. heart rate, digestion, urination, defecation, ANS through autonomic reflexes

Question 49

reflex arc

Answer 49

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

Question 50

monosynaptic reflex arc

Answer 50

one synapse in CNS

Question 51

polysynaptic reflex arc

Answer 51

Two types of neurons and more than one CNS synapse

Question 52

stretch reflex

Answer 52

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.

Question 53

muscle spindle

Answer 53

spindles monitor changes in the length of the muscle.

Question 54

ipsilateral reflex arc

Answer 54

sensory nerve impulses enter the spinal cord on the same side from which motor nerve im- pulses leave it.

Question 55

muscle tone

Answer 55

small degree of contraction present while the muscle is at rest

Question 56

reciprocal innervation

Answer 56

components of a neural circuit simultaneously cause contraction of one muscle and relaxation of its antagonists,

Question 57

tendon reflex

Answer 57

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.

Question 58

tendon organ or golgi tendon organ

Answer 58

sensory receptors for tendon reflex, detect and respond to changes in muscle tension that are caused by passive stretch or muscular contraction.

Question 59

flexor or withdrawal reflex

Answer 59

response to pain

Question 60

intersegmental reflex arc

Answer 60

nerve impulses from one sensory neuron ascend and descend in the spinal cord and activate interneurons in several segments of the spinal cord,

Question 61

crossed extensor reflex

Answer 61

helps maintain balance

Question 62

contralateral reflex arc

Answer 62

Sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side.

Question 63

shingles

Answer 63

acute infection of the peripheral nervous system caused by herpes zoster

Question 64

poliomyelitis

Answer 64

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.