5_Neuroanatomy and Physiology of the Spinal Cord Flashcards
The spinal cord is approximately ___ in length in males - _____ in females with a diameter of approximately _____.
45 cm
42 cm
1.0 - 1.5 cm
In the adult, this means that the spinal cord ends at the vertebral level of _____.
L1-L2
This disparity in length is due to a differential growth of the spinal cord versus ____________________.
the vertebral column
Along the length of the cord are two observable enlargements. These occur in which two regions?
These occur in the cervical region and in the lumbar/sacral regions.
Their occurrence marks the areas of the spinal cord that contain the neurons concerned with the ______________, respectfully.
Upper and lower extremities (brachial and lumbar plexi)
Rostrally, the cord is continuous with the ______, caudally it tapers into a structure referred to as ___________.
medulla
conus medullaris
The dorsal and ventral roots of the lower lumbar and sacral segments continue caudally to exit their appropriate ____________. Due to the differential growth of the cord versus the spine, this makes these roots very long. The collection of these long roots is the ______________.
intervertebral foramina
cauda equina
The three layers of meninges:__________________________________ .
dura mater, arachnoid and pia cover the spinal cord.
The dura consists only of a ____________. (the _____________ layer ended at _____________).
meningeal layer
the periosteal layer ended at foramen magnum
What is the epidural space is an actual space filled with?
fat
The organization of the arachnoid, acting as the limiting component for:
CSF containment
The CSF gets into the subarachnoid space of the spinal canal after leaving the ___________________________.
foramina of Luschka and Magendie
Since the cord ends at vertebral levels______, that leaves a large pocket of subarachnoid space below the caudal tip of the cord, known as the ________.
L1 - L2
lumbar cistern
In what region are lumbar punctures (spinal taps) are routinely made? (It is safe in this region. )
lumbar cistern
The pia has two components: 1) a_______ that is adhered directly to the ______, much the same as with the brain. The 2) the ___________.
1) pia intima
spinal cord
2) denticulate ligaments
The denticulate ligaments are extension that _____________________ and _______________ to attach the dura.
extensions that PROTRUDE from the lateral sides of the cord and PIERCE THE ARACHNOID to attach to the dura.
The purpose of the denticulate ligaments is to help _______ and ________ the cord in the vertebral canal.
anchor
stablize
At the caudal end of conus medullaris, the ligament that extends to anchor the cord is called:
filum terminale
The filum terminale is made up of:
pia, glial elements and maybe some remnants of coccygeal neuronal elements.
AS the filum terminale extends through/and is encased with the dura to attach to the coccyx; it is termed the _________________.
coccygeal (sacral) ligament
The coccygeal (sacral) ligament anchors the:
end of the cord in the spinal canal.
There are ____ pairs of spinal nerves: ___ cervical, ___ thoracic, ___ lumbar, ___ sacral, and ___ coccygeal.
31(32) 8 12 5 5 1(2)
During development of the cord, the segmental arrangement is obscured; with the only evidence remaining being the:
rootlets of the spinal nerves.
The segmental arrangement, however, is still represented to an extent as evidenced by:
dermatomal maps and the multisegmental innervation of muscles
Why is this organization clinically important in discerning the extent and/or location of a deficit? by documenting the loss of certain sensations or changes in motor activity, following damage to the central nervous system.
By documenting the loss of certain sensations or changes in motor activity (following damage to the central nervous system).
The spinal cord has two main subdivisions: (as does the entire CNS): gray matter and white matter.
1) gray matter
2) white matter
Gray matter of the spinal cord is:
the central “butterfly” shaped area
Gray matter consists of______________ and _________________.
neuron cell bodies and glial cells.
What is white matter that is made up?
myelinated axons.
The white matter contains both:
ascending and descending fiber tracts or pathways.
The ascending and descending fiber tracts or pathways can be divided into three general locations named ______
funiculi
Name the 3 funiculi:
1) dorsal (posterior) funiculus
2) lateral funiculus
3) ventral (anterior) funiculus
Funiculus is a general term for an:
area of white matter
Each funiculus is composed of a number of specific named _____, pathways or ____.
tracts
fasciculi
The naming of each specific pathway can be descriptive of ________ within the transverse section of the spinal cord and may also give an indication of what __________________________.
location
areas within the CNS the pathway is connecting
For example, the lateral corticospinal tract is located in the _____________ and originates in the ___________________ ending in the ___________
lateral funiculus
cortex of the cerebral hemisphere
spinal cord.
The gray matter is composed of what 3 structures:
1) nerve cell bodies
2) their dendritic processes
3) glial cells.
True or False: the organization within the gray matter of the spinal cord was not setup developmentally.
False: There is an organization within the gray matter of the spinal cord that was set up developmentally.
The alar plate is ______ located and is concerned with ___________ sensory information from the ________.
dorsally
afferent
periphery
The basal plate is ________ located and is concerned with _______ components of the cord.
ventrally
motor
The butterfly shaped gray area is then divided into a:
dorsal horn (sensory) and a ventral horn (motor).
There is a lateral horn (intermediolateral cell column) present from spinal cord segment ____.
T1-L2
The lateral horn is the location of the _________________________, a component of the Autonomic Nervous System (ANS).
preganglionic sympathetic neurons
The sacral segments (S1 -S3) also have a lateral horn that contains the ___________________________ for the lower parts of the body, the other part of the ANS
preganglionic PARAsympathetic neurons
Where are other parasympathetic neurons located?
cranial nerves
The gray matter has been divided into various nuclei or divisions as a result of:
cellular (cytoarchitecture) and connectional studies.
One terminology uses Roman Numerals referred to as ________________. Another system names ______________________.
Lamina of Rexed
regions of the gray matter
Name 6 regions of the gray matter:
1) Lissauer’s Tract (dorsolateral tract of Lissauer)
2) substantia gelatinosa
3) nucleus proprius
4) Dorsal nucleus of Clarke
5) intermediolateral cell column or lateral horn
6) ventral horn; location of the lower motor neurons
The dorsal horn contains which two regions of gray matter?
substantia gelatinosa and nucleus proprius (among others)
The substantia gelatinosa is in lamina _____.
II
The nucleus proprius is in lamina _____.
III and IV
the dorsal nucleus of Clarke is located in lamina _____ and segmental levels __________.
VII
T2-T12
The intermediolateral cell column or lateral horn is in lamina ____ (in part) and segmental levels ______________________________.
IX
C8/T1-L2 and S1-3
the ventral horn is locate in part in lamina ___
IX
There is a ___________ organization of the fibers that enter the cord via the dorsal root.
medial to lateral
When viewed from a transverse (horizontal) perspective, the more medially situated fibers are the __________________________________.
large diameter, heavily myelinated (Ia/b, A-α, ΙΙ) fibers
The more laterally placed fibers are the __________________________ .
small diameter, non-myelinated C fibers.
Fibers of intermediate caliber that are _____________________________.
finely myelinated lie intermediate in this organization (A-delta; A-δ).
Which fiber types are the fibers that enter the cord at Lissauers tract.
A-delta
The ventral horn contains the _______________ that will leave the spinal cord and____________. These are the ___________.
cell bodies with axons
innervate muscles
lower motor neurons
What is the “Final Common Pathway” for information that is needed to make a muscle do its thing.
synapsing from ventral horn
There are two types of lower motor neurons (LMN) within the ventral horn:
1) α motor neurons and
2) γ-motor neurons
The cell bodies of these neurons are arranged within the ventral horn so that those situated most medially are concerned with :
axial musculature, i.e. trunk, neck, etc
*This cell column extends throughout the entire length of the cord
The LMNs situated more laterally innervate:
The muscles of the extremities.
Where would the largest ventral horns be located?
at cervical and lumbar regions, associated with brachial and lumbar plexuses ????
LMNs situated posteriorly in the ventral horn are concerned with__________________, and those located anteriorly are concerned with ________________.
muscles of flexion
muscles of extension
The merging of the dorsal and ventral roots away from the spinal cord forms the _________.
spinal nerve
Prior to them merging, the dorsal root is _______ sensory and the ventral root is ______ motor.
entirely
entirely
Once they have combined, the spinal nerve is a _____ nerve, i.e., has both motor and sensory components.
mixed
**This spinal nerve is a component of the peripheral nervous system.
After the dorsal and ventral roots have combined, each spinal nerve then branches into a number of branches to :
reach its specific dermatomal segment or muscle of innervation
Associated with the spinal nerves at spinal cord levels T1-L2 is a series of ___________________.
autonomic ganglia
These autonomic ganglia are the location of the ___________________________________________.
postganglionic cell bodies for the sympathetic nervous system.
The preganglionic cell bodies (of the autonomic ganglia?) are located in the :
lateral horn in the spinal cord (intermediolateral cell column).
Reflexes are _____, ________________ responses to an adequate (appropriate) stimulus.
specific
stereotyped motor
Reflexes require a series of structures consisting of a minimum of what 4 components:
1) receptor
2) afferent limb
3) efferent limb
4) effector organ
(**complex reflexes may contain more connections in the CNS):
Examples of a receptor:
muscle spindles, golgi tendon organs, encapsulated and free nerve endings.
An afferent limb carries the impulse (stimulus) into the:
CNS; i.e., dorsal root fibers.
An efferent limb carries the impulse for the response:
out of the CNS; i.e., lower motor neuron (α-motor neuron).
lower motor neurons are:
a-motor neurons
An example of an effector organ would be:
skeletal muscle, glands.
Stretch Reflex or Deep Tendon Reflex (DTR) used to be classified:
Myotatic or monosynaptic
The patellar ligament or knee jerk is an example of what?
stretch reflex
This stetch reflex demonstrates the principle of:
Autogenic Facilitation
Autogenic Facilitation and can be thought to include a small amount of __________________.
Reciprocal Inhibition
Any external force stretching the muscle excites the Type Ia axons, which excite the motor neuron pool, which oppose the external force by activating the muscle, this process is termed:
autogenic facilitation
Whenever antagonist muscles are inhibited during the activation of agonist muscles, the process is called:
reciprocal inhibiton
The Golgi Tendon Organ (GTO), is sensitive to tension when the associated muscle is _______.
contracting
At a certain point of increased tension, during the GTO, the stimulus generates an inhibitory influence to the α motor neurons that are driving the contracting muscle, demonstrating the principle of:
Autogenic Inhibition
During the GTO, autogenic inhibition, the muscle now can relax which ___________.
releases the tension
Through the interneuronal pool, the antagonistic muscle can be activated to facilitate the release of tension, which is a process called:
Reciprocal Facilitation
What reflex if more complex compared to the stretch reflex and GTO?
Flexor Withdrawal Reflex and Crossed Extension Reflex.
Why are the Flexor Withdrawal Reflex and Crossed Extension Reflexes more complex?
more than just two neurons are involved.
When more than just 2 neurons are involved, what must happen?
Reciprocal inhibition of antagonist or opposing muscle masses must occur.
Reciprocal inhibition = ___________ muscle
antagonistic
Recurrent inhibition = (Renshaw cells) =
same muscle and synergists
Non- reciprocal inhibition =
inhibits agonists, synergists and antagonists (coordination of various movements)
Segmental loss involves the structures that are:
present at the specific segmental level.
Segmental loss includes the gray matter areas of the cord and to some extent the _________________________ that are bringing in sensory information and/or sending out motor information.
dorsal and ventral root components
What segmental loss generally does not refer to is the additional:
involvement of ascending or descending white matter pathways that are also involved.
In the real world, segmental losses will most likely include
some involvement of the white matter.
