Chapter Twelve: Spinal Cord and Spinal Nerves Flashcards
The spinal cord extends from the foramen magnum to the second…vertebra
lumbar
What are the four parts of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
The spinal cord gives rise to…pairs of spinal nerves
31
What part of the spinal cord?
- supplies upper limbs
Cervical Enlargement
What part of the spinal cord?
- supplies lower limbs
Lumbar (lumbosacral) enlargement
What part of the spinal cord?
- tapered inferior end; extends to level of 2nd lumbar vertebrae
Condus Medullaris
What part of the spinal cord?
- origins of spinal nerves extending inferiorly from lumbosacral enlargement and conus medullaris
Cauda Equina
Meninges of the spinal cord are…membranes surrounding the spinal cord and brain
connective tissue
What are the three parts of meninges of the spinal cord?
- Dura Mater
- Arachnoid Mater
- Pia Mater
What part of the meninges of the spinal cord?
- continuous with epineurium of the spinal nerves; forms thecal sac
Dura Mater
What part of the Dura Mater is this?
- surrounds spinal cord; extends from foramen magnum to 2nd sacral vertebrae
Thecal Sac
What part of the meninges of the spinal cord?
- thin and wispy
Arachnoid Mater
What part of the meninges of the spinal cord?
- bound tightly to surface of brain and spinal cord
Pia Mater
What are the two parts of Pia Mater?
- Filum Terminale
- Denticulate Ligaments
What part of the Pia Mater?
- anchors spinal cord to coccyx
Filum Terminale
What part of the Pia Mater?
- attach the spinal cord to the dura mater
Denticulate Ligaments
What are the three spaces of the meninges of the spinal cord?
- Epidural
- Subdural
- Subarachnoid
What space of the meninges of the spinal cord?
- contains blood vessels, areolar connective tissue and fat
Epidural
What space of the meninges of the spinal cord?
- serous fluid
Subdural
What space of the meninges of the spinal cord?
- CSF and blood vessels within web-like strands of arachnoid tissue
Subarachnoid
What type of anesthesia?
- injected into epidural space; often used during childbirth
- drugs must diffuse into CSF before they take effect
- advantage: drugs can be re-administered via catheter to maintain longer anesthesia
Epidural Anesthesia
What type of anesthesia?
- injected into subarachnoid space at L3/L4 or L4/L5
- drugs administered directly into CSF
Spinal Anesthesia
What type of Ligament of the spinal cord?
- extensions of the pia mater that attach to the dura mater
- limit lateral movement of the spinal cord
Denticulate Ligaments
What type of terminale?
- connective tissue strand that anchors conus medullaris and thecal sac to the first coccygeal vertebra
- about 20cm in length
- limits superior movement
Filum Terminale
What type of matter?
- myelinated axons organized into columns
White Matter
What are the three columns of the white matter?
- Ventral
- Dorsal
- Lateral
What type of matter?
- neuron, cell, cell bodies, dendrites, unmyelinated axons
Gray Matter
What are the three horns of the gray matter?
- Anterior
- Posterior
- Lateral
What part of the cross-section of the spinal cord?
- spinal nerves arise as rootlets then combine to form roots
Roots
What are the two types of roots?
Dorsal and Ventral
Two roots merge laterally and form what nerve?
Spinal Nerve
What is this?
- collections of cell bodies of pseudo-unipolar sensory neurons forming dorsal roots
Dorsal Root Ganglion
Motor neuron cell bodies are in anterior and lateral horns of spinal cord…matter
Gray
What kind of neurons are found within the anterior motor horn?
Mulipolar Somatic Motor Neurons
What kind of neurons are found within the lateral horn?
Autonomic Neurons
Axons of motor neurons form…and pass into spinal nerves
ventral roots
A…is the basic functional unit of nervous system and simplest portion capable of receiving a stimulus and producing a response
Reflex Arc
An automatic response to a stimulus that occurs without conscious thought is considered to be…
Homeostatic
What are the five components of reflexes?
- Sensory Receptors
- Sensory Neuron
- Interneurons
- Motor Neuron
- Effector Organ
What are the two types of reflexes?
Monosynaptic and Polysynaptic
What type of reflex?
- sensory neurons synapse directly with motor neurons
Monosynaptic
What type of reflex?
- multiple synapses with interneurons
Polysynaptic
Some reflexes involve excitatory neurons yielding a response; some involve…neurons that prevent an action
inhibitory
Higher brain centers can influence, suppress, or exaggerate…responses
reflex
Muscles contract in response to a…force applied to them
- no interneuron
stretching
What kind of spindle?
- specialized muscle cells that respond to stretch
Muscle Spindle
Muscle spindle is innervated by motor neurons called…
gamma motor neurons
Gamma motor neurons control sensitivity of…
muscle spindle
…neurons innervate the non-contractile centers of the muscle spindle fibers
Sensory
Sensory neurons synapse with motor neurons of the spinal cord called…which in turn innervate the muscle in which the muscle spindle is embedded
alpha motor neurons
The…tendon reflex prevents contracting muscles from applying excessive tension to tendons
Golgi
Where is the Golgi Tendon Organ located?
tendon near muscle
The Golgi Tendon prevents damage to tendons that could be caused by excessive…
tension
The Golgi Tendon Reflex produces a sudden…of the muscles through secretion of inhibitory neurotransmitters by interneurons onto alpha motor neurons
relaxation
The function of the withdrawal reflex is to…a body limb or other part from painful stimulus
remove
What is this?
- causes relaxation of extensor muscle when flexor muscle contracts
- also involved in stretch reflex
Reciprocal Innervation
What is this?
- when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb
Crossed Extensor Reflex
What are the three parts of spinal nerves?
- Axon Bundles
- Schwann Cells
- Connective Tissue
What are the three parts of spinal nerve connective tissue?
- Endoneurium
- Perineurium
- Epineurium
What type of connective tissue of the spinal nerve?
- surrounds individual neurons
Endoneurium
What type of connective tissue of the spinal nerve?
- surrounds axon groups to form fascicles
Perineurium
What type of connective tissue of the spinal nerve?
- surrounds the entire nerve or funiculus
Epineurium
How many pairs of spinal nerves?
31
How many cervical pairs of spinal nerves?
8
How many thoracic pairs of spinal nerves?
12
How many lumbar pairs of spinal nerves?
5
How many sacral pairs of spinal nerves?
5
How many coccygeal pairs of spinal nerves?
1
What pair of spinal nerves exits vertebral column between skull and atlas?
the first pair
What pair of spinal nerves exits via the sacral foramina?
the last pair
Other spinal nerves exit through…
intervertebral foramina
What is this?
- area of skin supplied with sensory innervation by a pair of spinal nerves
- may provide valuable information regarding the location of nerve damage
Dermatome
What are the three branches of spinal nerves?
- Dorsal Ramus
- Ventral Ramus
- Communicating Rami
What branch of the spinal nerve?
- innervate deep muscles of the trunk responsible for movements of the vertebral column and the connective tissue and skin near the midline of the back
Dorsal Ramus
What branch of the spinal nerve?
- innervation dependent on region
Ventral Ramus
What branch of the spinal nerve?
- communicate with sympathetic chain ganglia (associated with sympathetic nervous system)
Communicating Rami
Ventral Ramus Thoracic Region:
form…that innervate the intercostal muscles and the skin over the thorax
intercostal nerves
Ventral Ramus Remaining spinal nerve ventral rami form what five plexuses?
- Cervical Plexus
- Brachial Plexus
- Lumbar Plexus
- Sacral Plexus
- Coccygeal Plexus
What does the Cervical Plexus consist of?
C1-C4
What does the Brachial Plexus consist of?
C5-T1
What does the Lumbar Plexus consist of?
L1-L4
What does the Sacral Plexus consist of?
L4-S4
What does the Coccygeal Plexus consist of?
S4, S5, C0
…loops between C1 and C3
- nerves to the infrahyoid muscles branch from this
Ansa Cervicalis
What nerve?
- From C3-C5 (cervical and brachial plexuses)
- innervates diaphragm
Phrenic Nerve
What are the five branches/nerves of the brachial plexus?
- Axillary
- Radial
- Musculocutaneous
- Ulnar
- Median
The axillary nerve provides sensory innervation to the…
shoulder
The radial nerve provides sensory innervation to the posterior upper limb and…
hand
What is this?
- Damage to radial nerve can occur when nerve is compressed between the top of the crutch and the humerus
- Symptom: Wrist Drop
- Wrist remains permanently flexed because extensors fail to function
Crutch Paralysis
Musculocutaneous Nerve provides sensory innervation to lateral surface of…
forearm
The ulnar nerve provides sensory innervation to the…side of the hand
medial (ulnar)
What is this that relates to the ulnar nerve?
- passes by medial epicondyle of humerus close to skin
Funny Bone
What is this that relates to the ulnar nerve?
- loss of ulnar nerve innervation - loss of wrist flexion and finger extension
Claw Hand
The median nerve provides sensory innervation to the…side of the hand (palm)
lateral (radial)
What two plexuses are considered together because of their close relationship?
Lumbar and Sacral Plexuses
What four major nerves exit and enter the lower limb within the Lumbar and Sacral Plexuses?
- Obturator
- Femoral
- Tibial
- Common Fibular (Peroneal)
The obturator nerve provides sensory innervation to medial aspect of…
thigh
The femoral nerve provides sensory innervation to anterior and lateral…leg and foot
thigh/medial
The tibial and fibular nerves are bound together within a…sheath for the length of the thigh
Connective Tissue
What nerve?
- tibial and fibular nerves plus their sheath
Sciatic Nerve
What is this called?
- sciatic nerve may be compressed against the ischial bone causing the limb to “fall asleep”
Pins and Needles
The tibial nerve provides sensory innervation to posterior leg and…surface of the foot
plantar
The common fibular (peroneal) nerve provides sensory innervation to anterior and lateral leg and…of the foot
dorsum
