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