Chapter 13: The Spinal Cord and Nerves

The spinal cord begins at....and ends at.. In adults

Begins at the medulla oblongata and ends at the second lumbar vertebrae

Subarachnoid space

Between arachnoid mater and pia mater

Subdural space

Between dura mater and arachnoid mater

Epidural space

Between dura mater and vertebral column

Posterior (dorsal) rami

Branch of each spinal nerve that innervates deep muscles and skin of the posterior surface of the trunk

Anterior (ventral) rami

Branch of each spinal nerve that innervates the ventral and lateral body surfaces; structures in the body wall and limbs

Roots

Bundles of axons which connect each spinal nerve to segments of the spinal cord by even smaller bundles of axons called rootlets

Gray matter consists primarily of

Cell bodies (with their dendrites) of association and motor neurons; Unmyelinated axons

A nerve is a bundle of fascicles within an..

Epineurium

Injuries to the brachial plexus

Erb-Duchenne palsy, median nerve injury (carpal tunnel syndrome), ulnar nerve

Central canal

Extends entire length of spinal cord and is filled with cerebral spinal fluid

Filum terminale

Extension of Pia mater that extends inferiorly and blends with the arachnoid and dura to anchor the spinal cord to the coccyx

The tendon reflex operates as

Feedback mechanism to control tension by causing muscles relaxation when muscle fleece becomes too extreme

Cauda equina "horse's tail"

Roots of lower spinal nerves that angle down along side the filum terminale

Coccygeal plexus (numbers and what do they supply)

S4-S5 Supplies small area of the skin in the coccygeal region

Ipsilateral

Same side of the body

Dermatomes

Skin over the entire body is supplied by somatic sensory neurons that carry impulses from the skin into the spinal cord and up to the brain

Pathways are

Specific neuronal circuits and thus include at least one synapse

Cervical-Thoracic, superior to inferior

Spinal cord becomes progressively smaller

How does the spinal cord compare to the vertebral column?

Spinal cord is much shorter because during growth the vertebral column grows faster

Two types of reflexes

Stretch reflex and tendon reflex

Spinal neeves

Structure of the PNS which connect the CNS to sensory receptors, muscles, and glands in all parts of the body

Dorsal root ganglion

Swelling which contains the cell bodies of sensory neurons from the periphery

Conus medullaris

Tampered portion

All tracts are located in the

White matter

Transaction of spinal cord means that

Ascending and descending tracts are completely severed - paralysis

Sensory neuron

Axon conducts impulses from receptor to integrating center

Median nerve injury

(Also known as carpal tunnel syndrome) Seen in people who perform repetitive motions of the hand and wrist

How many pairs of spinal nerves does coccygeal have?

1

How many pairs of spinal nerves does thoracic have?

12

How many left-right pairs of spinal nerves are there?

31

How many pairs of spinal nerves are there?

31

How many pairs of spinal nerves does lumbar have?

5

How many pairs of spinal nerves does sacral have?

5

How many pairs of spinal nerves does cervical have?

8

Tracts

A bundle of nerve axons in the CNS

Reflex

A fast, involuntary response to a stimulus

Stretch reflex, in response to the muscle being stretched..

A muscle spindle initiates a somatic spinal reflex that causes contraction of the agonist and relaxation of the antagonist muscles Important in maintaining muscle tone and muscle coordination during exercise Is ipsilateral

Tendon reflex, in response to a tendon being stretched excessively..

A tendon organ initiates a somatic spinal reflex that causes contraction of the antagonist and relaxation of the agonist muscles

Shingles (Herpes Zoster Virus)

After you get better from chicken pox, the "virus" sleeps (dormant) in your nerve roots

The spinal cord serves as

An integrating center for spinal reflexes, occurs in the gray matter

Cervical plexus (numbers and what do they supply)

C1-C5 Supplies skin, muscles of head, neck, upper part of shoulders and diaphragm

Brachial plexus (numbers and what do they supply)

C5-C8 and T1 Supplies neck, shoulders, and upper limb

Contains two enlargements

Cervical enlargement, Lumbar enlargement

5 types of plexuses

Cervical, brachial, lumbar, sacral, coccygeal

5 parts of the spinal cord

Cervical, thoracic, lumbar, sacral, coccygeal

Sensory (ascending) tracts

Conduct nerve impulse up the spinal cord toward the brain

Motor (descending) tracts

Conduct nerve impulses down the spinal cord from the brain

Spinal nerve axons are grouped within..

Connective tissue sheaths

Posterior gray horns

Consists of axons of sensory neurons and cell bodies of interneuron

Lateral gray horns

Consists of cell bodies of autonomic (visceral) motor neurons

Anterior gray horns

Consists of cell bodies of somatic motor neurons

White matter

Consists primarily of bundles of myelinated axons of motor and sensory neurons; Anterior white commissure; Divided into columns called funiculi

The anterior or ventral (motor) root

Contains axons of motor neurons-conducts nerve impulses from the CNS to effectors (muscles and glands) in the periphery

White matter

Contains major sensory and motor tracts ("highways") to and from the brain

The posterior or dorsal (sensory) root

Contains only sensory axons-conducts nerve impulses from sensory receptors in the skin, muscles, and internal organs in the CNS

Thoracic

Control sensory and motor activity of hands, fingers, chest, and abdominal muscles

Cervical

Control sensory and motor activity of head, neck, upper body, arms, and hands

Lumbar

Control sensory and motor activity of hips, knees, ankles and toe muscles

Sacral

Control sensory and motor activity of legs, toes, bladder and anal muscles

Lateral corticospinal tract

Conveys nerve impulses from cerebral cortex of brain to spinal cord for voluntary movement of skeletal muscles

Reflex circuits

Coordinate and control rapid reactions to environmental changes

Anterior fissure and the posterior median sulcus

Divide spinal cord into right and left sides

Meninges

Dura mater, Arachnoid mater, Pia mater

A fiber is a single axon within an..

Endoneurium

Damage to the femoral nerve

Inability to extend leg and loss of sensation

Pia mater

Inner layer

Gray matter

Integrates inhibitory postsynaptic potentials (IPSPs) and exhibitory postsynaptic potentials (EPSPs) triggered by nerve impulses from brain (motor) and peripheral nerves (sensory)

Spinal reflex

Integration takes places in the spinal cord, not the brain

The anterior rami of spinal nerves T2-T12 do not enter into the formation of plexuses and are known as..

Intercostal or thoracic nerves

The tendon reflex is

Ipsilateral and prevents damages to muscles and tendons as a result of stretching

Lumbar plexus (numbers and what do they supply)

L1-L4 Supplies anterolateral abdominal wall, external genitalia, and part of the lower limbs

Sacral plexus (numbers and what do they supply and what nerve)

L4-L5 & S1-S4 Supplies buttocks, perineum, and part of lower limbs Sciatic nerve

Femoral nerve

Largest nerve of the lumbar plexus

Ulnar nerve

Largest unprotected nerve in the human body - Emerges from brachial plexus to supply the medial half of the hand

Lumbar-Sacral, superiors to inferior

Less white matter, fewer sensory tracts ascending and fewer motor tracts ascending

Posterior columns (gracile fasciculus & cuneate fasciculus)

Light touch, pressure

The spinal cord is protected by two connective tissue coverings

Meninges and vertebrae... With a cushion of cerebrospinal fluid

Arachnoid mater

Middle layer

5 types of damages to the spinal cord

Monoplegia, diplegia, paraplegia, hemiplegia, quadraplegia

Polysynaptic

Multiple synapses between two or more neurons

Anterior white commissure

Narrow band of white matter that connects thee anterior columns together

Epidural injection

Needle inserted into the epidural space

Pinched nerve

Occurs when too much pressure is applied to a nerve by surrounding tissues, such as bones, cartilage, muscles, or tendons

Monosynaptic

One synapse between two neurons

Dura mater

Outer layer

Spinothalamic tract

Pain and temperature sensory information is carried by these tracts to the brain

Quadraplegia

Paralysis of all four limbs

Paraplegia

Paralysis of both lower limbs

Diplegia

Paralysis of both upper limbs and both lower limbs

Monoplegia

Paralysis of one limb

Erb-Duchenne palsy

Paralysis of the arm that most often occurs during child birth as an infants head and neck are pulled toward the side

Hemiplegia

Paralysis of upper limb, trunk, and lower limb on one side of the body

Example of stretch reflex

Patellar reflex- operates as a feedback mechanism to control muscle length by causing muscle contraction

Spinal tap

Performed to withdraw CSF from SAS for diagnostic purposes of meningitis or some other disease

A fascicle is a bundle of fibers within a..

Perineurium

The anterior rami of spinal nerves, except for T2-T12, form networks of nerves called..

Plexuses

Five functional components of a reflex arc

Receptor, sensory neuron, motor neuron, integrating center neuron, and effector

The spinal cord contains

Reflex circuits, gray matter, white matter

The internal organization of the spinal cord allows..

Reflexes to be processed and to inform the brain of the results of those reflexes

Receptor

Responds to a stimulus by producing a generator or receptor potential

Numerous blood vessels are within..

The coverings

Reflex arc

The simplest type of pathway

Denticulate ligaments

Thickenings of pia mater which suspend spinal cord in its dural sheath