Back Muscles and Spinal Cord Flashcards
Name the layers of the back and muscles associated with each layer
extrinsic superficial: trapezius and lats
extrinsic intermediate: levator scapulae, rhomboid major and minor, serratus posterior superior and inferior
superficial intrinsic: splenius capitis and splenius cervicis
intermediate intrinsic: erector spinae
Deep intrinsic: semispinalis capitis and cervicis, rotatores costarum, interspinales, intertransversales, multifidus
What are the most medial lumbar back muscles
multifidus
Describe the multifidi
slope upwards from the laminae and the mammillary processes to the spinous process of vertebrae 2 or 4 over their level, produce extension and lateral bending and are loaded with mechanoreceptors
Describe the intertrnasversarii
intertransversarii are divided into medial and lateral, only medial are considered true back muscles since they are innervated by dorsal rami where lateral is ventral
What is affected by folic acid deficiency during the 1st trimester
neural tube formation
What do the neural crest cells develop into (DAMESS)
Dorsal root ganglia Adrenal medulla Melanocytes, Macroglia, Meninges (arachoid and pia) Enteric ganglia Schwann cells Sympathetic ganglia
Microglia and dura mater are derived from the mesoderm
where does the spinal cord begin and end
begins at foramen magnum and ends at L1/2
What are the two regional enlargements of the spinal cord
Largest at C6 and lumbosacrial for the brachial
What is the dilated end of the spinal cord called
conus medullaris
What are the nerves that leave the end of the spinal cord called
cauda equina
what mater gives rise to the dentate ligaments
pia (innermost)
What level does the dural sac end
s2
Describe the parts of the filum terminale
filum terminal internum - extends from the conus medulla to the end of the dural sac at S2
filum terminal externum - is covered by a thin layer of dura and extends to the coccyx as the coccygeal ligament
Describe the spinal cord and its segments
31 segments that with ventral and dorsal roots that come together to for spinal nerves
What maters are continuous with the epineurium of the spinal nerves
the dura and arachnoid
Describe the white matter of the spinal cord
mylenated, organized into 3 bundles of funiculi: posterior, anterior, and lateral
What do fast-conducting myelinated axons form and what lies between them
fasciculi and glial cells (oligodendrocytes and astrocytes)
Which tracts carry vibration, fine touch (two-point discrimination) and joint position sense
posterior or dorsal columns
From the posterior or dorsal columns where do axons from the lower limp and upper limb synapse
Lower limb synapse in nucleus graciLis in the medulla
Upper limb synapse in nucleus cUneatus in the medulla
Which tract carries pain and temperature
lateral spinothalamic
which tract carries crude touch and pressure
ventral spinothalamic
Which tract plays a role in mediating autonomic responses to nociception
spinoreticular
Which tract plays a role in activating eye movements in response to tactile stimuli
spinotectal
What function do DESCENDING tracts have
Carry axons that control skeletal motor function, smooth muscles and secretory glands.
ALL descending tracts are motor EXCEPT raphespinal which modulates nociception
Describe the pathway of the dorsal column
1st order: Mechano-receptors vibration and fine touch
2nd order: Nuclei gracilis and cuneatus
Decussation: Medulla
3rd Order: VPL nucleus of thalamus
Describe the pathway of the spinothalamic
1st order: nociceptors, thermoreceptors, crude touch and pressure receptors
2nd order: lamina I and II in the dorsal horn of the gray matter
Decussation: spinal cord
3rd order: VPL nucleus of thalamus`
Describe the pathway of the dorsal spinocerebellar
1st order: unconscious proprioception from the ipsilateral lower limb
2nd order: Clarke’s nucleus (dorsal) found in the thoracic region
Decussation: Ipsilateral does not cross
3rd order: cerebellum via inferior cerebellar peduncle
Describe the pathway of the ventral spinocerebellar
1st order: unconscious proprioception from the both upper and lower limbs
2nd order: lamina VII
decussation: TWICE: first at the spinal cord and again at the pons
3rd order: cerebellum via superior cerebellar peduncle
Describe the pathway of the rubrospinal
1st order: red nucleus
decussation: midbrain
2nd order: laminae V-VIII
Describe the pathway of the tectospinal
1st order: tectum of midbrain
Decussation: midbrain
2nd order: laminae VI and VIII
Describe the pathway of the lateral corticospinal (AKA pyramidal tract)
1st order: pre-central gyrus
decussation: medullar
2nd: order laminae IV-IX
Describe the pathway of the ventral corticospinal
1st order: pre-central gyrus
decussation: spinal cord at the leel of exit
2nd order: laminae VI-IX
Describe the pathway of the reticulospinal
1st order: reticular formation
decussation various levels
2nd order: laminae VIII
Describe the pathway of the vestibulospinal
1st order: vestibulospinal
decussation: uncrossed
2nd order: Laminae Vi and VIII
Describe the pathway of the raphespinal
1st order: raphe nucleus
decussation: uncrossed
2nd order: laminae I, II, and V
Which descending tract has voluntary control of the muscles in the limbs
Lateral corticospinal
.
Which descending tract has voluntary control of the muscles in the head, neck, and trunk
ventral corticospinal
.
Which descending tract excites proximal flexors and inhibits extensors mainly in the upper limb
rubrospinal
.
Which descending tract restricts voluntary movements through gamma motor neurons
reticulospinal
.
Which descending tract coordinates head and eye turning in response to visual input
tectospinal
.
Which descending tract is involved in postural reflexes - neck muscles, extensors of back and limbs
vestibulospinal
.
Which descending tract inhibits nociception by releasing serotonin and acts on the c fibers
raphespinal
Describe the gray matter and horns
Arranged into 3 horns:
Dorsal - sensory
Ventral - motor
Lateral - sympathetic
What horn is only found in the thoracic party of the spinal cord at T1 to L2
lateral (interomediolateral)
Describe rexed laminae I
Then layer that lies beneath the dorsolateral fasciculus (of Lissauer)
Contains neurons which synapse with the first order neruons and send axons to the spinothalamic tracts on opposite sides
Describe R. Lamina II
AKA substantia gelatinosa of Rolando
Substance P is found in HIGH concentrations in lamina I and II
Describe laminae III and IV
Jointly referred to as the nucleus PROPius - their main input is from fibers that carry PROPrioception and light touch
Describe lamina V
Contains neurons that respond to both noxious and visceral afferent stimuli
Describe lamina VI
deepest layer of the dorsal horn and receives mechanical signals from skin and joints
Describe lamina VII
Contains the dorsal nucleus (Clarke’s column) and the intermediolateral horn
What kind of cell bodies does the intermediolateral horn and clarke’s column contain
intermediolateral horn: preganglionic sympathetic from T1 to L2
Clarke’s Column: carries unconscious proprioception from the legs in the dorsal spinocerebellar tract from T6 - L1
Describe lamina VIII
contains neurons linked with the vestibulospinal and reticulospinal tracts
Describe Lamina IX
contains alpha and gamma motor neuron groups in the ventral horn
Alpha: extrafusal skeletal muscle
Gamma: intrafusal fibers in the muscle spindles
Describe lamina X
Small area of grey matter surrounding the central canal
AKA grey commissure - function is unknown
What arteries supply the spinal cord
Segmental spinal arteries from: ascending cervical deep cervical posterior intercostal upper two lumbar
What doe segmental spinal arteries give rise to
radicular and segmental medullary arteries
Describe the segmental medullary arteries roles
Feed into the single anterior spinal artery and two posterior spinal arteries which originate from vertebral arteries
What is the name of the artery that supplies between the lower half to 2/3 of the spinal cord
A relatively large radicular artery called the Great Radicular artery of (Adamkiweicz)
Where does the Great radicular artery usually arise
On the left side (68-80%) as a branch of either the lower posterior intercostal or the upper lumbar arteries
What does the single anterior spinal artery supply
Approx. the anterior 2/3 of the spinal cord
What do the two combined posterior spinal arteries supply
the posterior 1/3 of the spinal cord
Describe the difference between an upper and lower motor neuron lesion
Upper: Reflexes: increased with clonus Tone: Spastic (increased) Atrophy: Absent Fasciculations: Absent Babinski sign: present (up going toe)
Lower: Reflexes: decreased or absent Tone: Flaccid Atrophy: present Fasciculations: present Babinski sign: absent (down going toe)