Spinal Cord Anatomy Flashcards
Describe the following spinal segments:
cervical enlargement
lumbar enlargement
cervical enlargement - C5-T1 (why we have brachial plexus)
lumbar enlargement - L1-S2 (why we have lumbo sacral plexus
Describe the relationship between a given vertebral level and the corresponding spinal nerve.
Spinal nerves come out above the same named vertebrae, until nerve c8, which comes out of the cord below vertebra C7. The rest of the nerves come out below their corresponding vertebrae.—Thus vertebra C7 has 2 nerves associated with it—–c7 and c8
How far does the fetal cord extend? What is the significance of this?
to L3
Care must be taken during spinal tap
Describe the meninges.
Dura, Arachnoid, Pia
spinal dura continuous with meningeal layer of cranial dura
dura fuses with epineurium of peripheral nerves
delicate arachnoid trabeculae attach to pia
What is the denticulate ligament?
pial extension anchoring the cord to the dura
Describe motor/sensory, afferent/efferent nerves.
motor tend to be efferent (movement)
sensory tend to be afferent (pain)
Describe sympathetics and splanchnics.
For the most part sympathetics have short preganglionics and long postganglionics—exception: splanchnics, the greater splanchnic (t5-9) synapses in the celiac ganglion, the lesser (t10-11) in the superior mesenteric and aortico renal ganglia, and the least (t12) in the renal plexus.
WIGO. White/grey ramus myelinated?
White “in” grey “out”
grey are unmyelinated
white are myelinated
How does the pia extend?
What does it fuse with and form?
pia extends caudally as filum terminale
fuses with dura to form coccygeal ligament (filum terminale externa)
-attaches to coccyx
Describe the lumbar cistern.
subarachnoid space caudal to conus medullares (L1-S3)
What do cauda equina fibers surround?
sacral cord
Where doe spinal arteries come from?
Describe the spinal cord arteries.
All spinal arteries come from the vertebrals
one anterior, two posterior
anterior spinal artery sits in median anterior fissure. posterior is very tortuous
What do somites give?
dermis, muscle, skeleton
Review the diff between dermatomes and peripheral cutaneous nerves.
?
What are these important/common dermatomal references?
C2,C6
T4,T10
L3, S1
C2- back of head C6- thumb and index finger T4- nipples T-10 umbilicus L3- kneecap S1-lateral foot
Describe limb rotation of thumbs and big toes.
thumbs-laterally
big toes-medially rotate
In regards to the spinal cord/vertebral segment, where does the dorsal root enter?
posterior lateral sulcus (sensory info comes in, dorsal root comes in)
Describe posterior intermediate sulcus
Only above T6
Separation between gracilus and cuneatus
Label the spinal cord/vertebral segment soft chalk.
See powerpoint slide 37.
Describe the anterior median fissure.
Where the anterior spinal artery lives.
Describe the anterior lateral sulcus.
where the ventral root leaves. (motor fibers go out)
Describe the posterior funiculus.
axons forming bundle
White matter ascending axons mostly from the dorsal column pathway.
Describe the dorsolateral fasciculus (zone of Lissauer).
contains finely myelinated and unmyelinated axons originating in the substantia gelatinosa and involved in sensory modulation.
Area where axons ascend or desend several segments (fibers can go up/down cord before leaving or entering…pain)
Describe the anterior commissure.
A spot where fibers cross from one side to another
Describe the gray matter regions.
What is white matter full of?
anterior horn (motor) intermeidate gray posterior horn (sensory)
white matter full of myelin/oligodendrites
Describe all the functional components.
GSA—general somatic afferent—pain, vibration, touch, proprioception from skin, body wall, and skeletal muscle
GVA—general visceral afferent—pain, stretch from guts
GVE—general viscera efferent—–motor to viscera, glands, and blood vessels—autonomics
GSE—general somatic efferent—-motor to skeletal muscle
SSA—special sensory afferent—-vision, hearing, and balance
SVA—special visceral afferent—-taste and smell
SVE—special visceral efferent—innervates muscle of branchiomeric origin—”gills”—pharynx, larynx,mastication, and facial expression—5,7,9,10, and 11
Describe nucleus in regards to the neuroscience definition.
a group of neurons with a common function or modality. Example: hypoglossal nucleus –motor to the tongue (GSE)
(basal ganglia is a nuclei, CN use 1 or more nuclei depending on its functional units)
Describe the alar/basal plates functional components.
alar (dorsal, afferent/sensory) GSA, GVA
basal (ventral, efferent/motor) GVE, GSE
Describe substantia gelatinosa. What do the cells do? Where do axons ascend and descend? What is it homologous to? What does it receive?
“gelatinous substance”
small compact cells that modify sensory input by synapsing on dendrites in nucleus proprius. Axons ascend and descend in Lissauer’s tract.
Homologous to spinal trigeminal nucleus
receives mall diameter dorsal root afferents
all cord levels
Describe nucleus proprius.
What does it receive?
What does it contain?
"proper sensory nucleus" receives many sensory inputs contains many interneurons contains "tract cells" that project contralaterally as the spinothalamic tract all cord levels
Describe nucleus dorsalis. * Where is it? What is it homologous to? Where is its nucleus? What does it receive? Where does it project?
“clark’s nucleus” C8-L3
homologous to the lateral (assessory) cuneate
nucleus in the medulla
receives muscle spindle information
projects ipsilaterally to the cerebellum as the dorsal spinocerebellar tract
Describe intermediolateral nucleus*
What is it the origin of?
Where is it found?
What functional component?
origin of preganglionic cholinergic sympathetic efferents.
Found at levels T1-L3
GVE
origin of sympathetics
At S2-S4 what does the sacral autonomic nucleus occupy and send out?
occupies lateral horn area and sends out preganglionic parasympathetic efferents.
Describe intermediomedial nucleus.
receives visceral afferents
projects to IML
found at all sc levels
Describe the medial and lateral motor nuclei.
- made up of large alpha motor neurons that innervate skeletal muscle (i.e. radial-triceps)
- phrenic nucleus that exists at C3-5 in the medial n.
- the spinal accessory n exists at C1-6 laterally
- motor nuclei are the largest in the cervical and lumbar enlargements.
lateral - control fingers, medial- shoulder/trunk
Be able to label nuclei (soft chalk).
Slide 50
Describe motor neurons (IX).
innervate skeletal muscle
are large alpha motor neurons
termed lower motor neurons and “the final common pathway”
Where is the phrenic nucleus found?
in cervical ventral horn (C3,4,5)…keeps diaphragm alive
Where is the spinal accessory nucleus found?
C1-C6 (high cervical)
Describe the sensory modalities/functional components.
GSA (general somatic afferent) exteroception- touch temp pain vibration GVA (general visceral afferent) interoception-gut stretch, ph, etc SVA (special visceral afferent) taste smell SSA (special sensory afferents) vision hearing balance
Describe the non-encapsulated sensory receptors.
free nerve endings
Merkel’s disc
hair receptors/ hair follicle
Describe the encapsulated sensory receptors.
Meissner's corpuscles Pacinian corpuscles Ruffini endings Joint receptor neuromuscular spindle golgi tendon organs
Describe free nerve endings.
pain and temp, skin and viscera, slow adapting
Describe Merkel’s disk
touch
distal extremities, lips, genitalia, nipples
slow adapting
Describe Meisner’s Corpuscle.
connective tissue sheath surrounding a stack of flattened epithelial cells
2 point discrimination
fingers toes hands feet lips tongue genitals joint capsules ligaments
rapidly adapting
Describe Pacinian corpuscle.
afferent nerve endings surrounded by concentric lamellae of flattened epithelial cells (3-4mm)
light pressure, stretch, and esp vibration
fast adapting
Describe the following other encapsulated receptors: Ruffini ending Joint receptor endings Neuromuscular spindle Golgi tendon organ
Ruffini ending- widespread in dermis, slow adapting to stretch, deep pressure
Joint receptor endings- free nerve endings, slow adapting, joint position and movement
Neuromuscular spindle - muscle length (stretch)
Golgi tendon organ- located at muscle tendon junction, slow adapting
What do muscle spindles detect?
What do golgi tendon organs detect?
What do joints have?
Muscle spindles are important…
Muscle spindles detect muscle length
golgi tendon organs detect muscle tension
joints have receptors
muscle spindles are important proprioceptors
Compare firing patterns of muscle spindles and GTO’s.
Muscle spindles fire in response to stretching of a muscle,–while GTO’s fire in response to an increase in muscle tension while performing an isometric contraction (lifting a car)——
What makes a muscle spindle fire?
Stretching the center or nuclear bag region of the spindle makes it fire
Describe muscle spindles in regards to exercise of touching toes.
Here—same thing—stretching to touch one’s toes causes the spindle to stretch which causes it to fire—which shortens the hamstrings to resist overstretching—which shortens the spindle—which is now in a state unresponsive to further stretching until gamma axon firing ‘resets” or shorten the spindle (nuclear bag region)
muscle spindle senses the muscle stretching …sensory nerve to spinal cord in cross section..motor nerve and muscle contracting in response to stretch which causes gamma motor neurons to fire and shorten or reset the spindle for the next hamstring stretch
Describe the stretch reflex or deep tendon reflex.
Tapping the patellar tendon stretches the quads, causes the spindle to “fire”, makes the quads reflexively shorten (contract), makes the spindle nuclear bag sag, and finally causes gamma fibers to fire and tense up or reset the spindle bag.
Describe how gamma fibers from the ventral horn reset after a muscle contracts.
Gamma fibers from the ventral horn reset the spindle after the “big” muscle contracts (shortens).
muscle stretch causes spindle la afferents to fire which cause alpha motor neurons to fire la gamma alpha…muscle shortens and spindle gets saggy…gamma motor neurons fire and spindle shortens/resets
What is the function of the following non-encapsulated receptors:
free nerve endings
Merke’ls Disk
Hair follicle
free nerve endings- pain temp (in deep skin, viscera)
Merkel’s disc- touch (feet hands genitalia lips)
hair follicle- touch (anywhere there is hair)
Describe the function of the following encapsulated receptors: Meissner's corpuscles Pacinian corpuscles Ruffini endings Joint receptor neuromuscular spindle golgi tendon organs
Meissner’s corpuscles- 2 point discrimination (hairless skin, fingertips, joints, ligaments)
Pacinian corpuscles- vibration (fingers toes palms mesenteries peritoneum)
Ruffini endings- stretch, pressure (dermis)
Joint receptor- joint position (joint capsules, ligaments)
neuromuscular spindle- limb muscle, stretch/length (muscles)
golgi tendon organs- muscle tension (muscle tension junction)
Describe the dorsal root afferents: Lateral division.
thin, lightly myelinated fibers
pain and temp, light touch, visceral afferents
Describe the dorsal root afferents: Medial division.
thick heavily myelinated fibers
2-point touch, limb position, muscle stretch
sends collaterals to medulla (muscle spindle info comes in here)
