Spinal Cord and Motor Tracts Flashcards
(25 cards)
Spinal cord enlargement
Cervical enlargement: C5-T1
Brachial plexus = innervates arms and hand
Lumbosacral enlargement = L2 -S3
Lumbosacral plexus = innervates legs, pelvis and lower abdomen
Pia vs arachnoid vs dura matter in spinal cord
Pia matter = inner most
- Forms denticulate ligament, which anchors spinal cord to dura
- Forms filum terminale, which anchors spinal cord to coccyx
Arachnoid matter= in between pia and dura
Dura matter = outer most layer
Subarachnoid vs sub dural vs epidural space
Sub arachnoid space: contains the CSF and is between the arachnoid and pia
Subdural space is between the dura and arachnoid matter
- This is tight to dura so it only becomes a space when there is a haemorrage
Epidural space: between dura and vertebrae, contains fat
Epidural anesthesia goes here
Grey vs white matter content
Grey
- Contains neuronal cell bodies, dendrites and synpases
- Processes signals
- Organized in horns
- Anterior = motor, posterior = sensory
White
- Contains mainly axons and glial cells
- Organized in collumns
- Ascending = sensory, descending = motor
- More white matter in cervical spine as there are ascending and descending tracts
In lumbar there is more grey as nerves have reached their target muscl
Descending tract function
- transmit motor commands from brain to spinal cord
- Motor system integrates sensory feedback, muscle groups and adapts to force
- Manage voluntary movements, reflexive responses and balance adjustments
Corticospinal tract
- Voluntary control of movement
- Limb movement, posture, balance- Motor fibres travel anteriorly in spinal cord and brainstem
- Two neurons
- One in upper cortex: UMN
§ Does not reach muscle - One in spinal cord : LMN
§ Directs signal to muscle via gamma motor neuron - Synapse in anterior horn in spinal cord
- One in upper cortex: UMN
Lateral vs anterior CST
- Lateral corticospinal tract
- Responsible for dexterity
- Innervation of limbs for skilled movement
- Crosses over (decussated) at the medulla- Anterior corticospinal tract
- Posture and stability
- Innervation of proximal muscles (shoulders, hips) for posture and balance
Stays on same side (mostly)
- Anterior corticospinal tract
Organization of white vs grey matter in spinal cord
White organization
- More medial is arms
- More. Lateralis legs and lower trunk
Grey matter
- Anterior is more extensors vs. posterior is flexors
Medial is proximal muscles vs lateral is distal muscles
UMN lesion
UMN lesion = damage to motor pathway in brain, brain stem or spinal cord above anterior horn of spinal cord
- Weakness
- Spasticity
- Hyperreflexia
- Babinksi sign
- No muscle atrophy
- Weak and stiff muscle but muscle itself is not affected so does not atrophy
No fasciculation (muscle fibres trying to contracT
LMN lesion
LMN lesion = damage to motor neuron located in anterior horn or in spinal root
- Wekannes
- Flaccidity (decreased tone)
- Hyporeflexia/areflexia
- Muscle atrophy
Fasiculation (twitching)
Reticulospinal tract
Plays a role in posture, locomotion and modulating reflexes
UMN starts in brainstem (reticular formation) and ends on interneuron
LMN continues in spine
Mainly ipsilateral
Function
○ Mediates automatic postural adjustments
○ Modulates reflexes
Voluntary and involuntary
Tectospinal tract
Plays a role in eye and head coordination so vision is clear when moving head
UMN starts in brain stem (midbrain specifically tectum)
Contralateral control
Function
○ Directs eye and head movement
○ Connects to neck muscle
Voluntary and involuntary
Vestibulospinal tract
Plays a role in neck (medial) and limb (lateral) stabilization
UMN starts in brain stem (vestibular nuclei)
a. Medial tract
i. Goes bilaterally to neck muscles
ii. Stabilizes head and ensures steady vision
b. Lateral tract
i. To limbs and activates extensors and inhibits flexors
ii. Maintains posture
Ipsilateral
Muscle tone and how
It is controlled
Continuous low level contraction for readiness of muscle at rest
- Via gamma neurons
○ Small LMN that innervate and contract intrafusal fibres within muscle spindles
○ innervation allows muscle spindles to detect muscle stretch and trigger stretch reflex to maintain tone
- Controlled by reticulospinal and vestibulospinal tract
- UMN lesion. –> spasticity
LMN lesion –> floppiness
How does a reflex work
- Receptor detects stimulus
- Sensory neruons sends signal to spinal cord
- Integration center: processes signal
○ Can have 0 inter neurons (monosynaptic)
○ Can have 1+ interneurons (polynspactic) - Motor neuron: send command to muscle
Effector: performs response
Pathology of reflexes
- Hyporeflexia: LMN lesion or peripheral nerve damage
Hyperreflexia: UMN or CNS dysfunction
CPGs
neural circuit that produces rythmic patterned movement without rythmic input
- Product walking by coordinating repetitive limb movement
- Activation requieres supraspinal input in humans
Location: spinal cord (walking) or brainstem (breathing, chewing)
UMN lesion affect on weakness, atrophy, reflexes and tone
Weakness, no atrophy, increased reflexes, increased tone
LMN lesion affect on weakness, atrophy, reflexes and tone
Weakness, atrophy, decreased reflexes, decreased tone
Spinal levels of sympathetic nervous system
Lateral horn at T1 - L2
Parasympathetic key spinal levels
CN III, VIII, X in the brainstem and S2-S4 lateral horn
Phase 1 bladder control
Filling
- Sympathetic control (T11 - L2) via hypogastric nerves
- Detrusor relaxes and internal sphincters contracts/closes
bladder gradually stretches
Phase 2 bladder control
Emptying
- Parasympathetic control (S2-S4) via pelvic nerves
- stretch receptors send fullness signals to spinal cord and brain
- Detrusor contracts, internal sphincter relaxes
Reflex/involuntary
Somatic control of bladder
(S2-S4) via pudendal nerve
- External sphincter relaxes
Voluntary and causes urine expelling
