M3 - Spinal Cord Flashcards
Vertebral foramen
Opening in middle of vertebrae posterior to vertebral body
Spinal cord
Located in vertebral foramen
Intervertebral foramina
On each side between 2 vertebrae, where spinal nerves are located
Superior vertebra
Forms roof of each foramen
Inferior vertebra
Forms floor of each foramen
Superior articular process
Articulates w L5
Ventral (anterior) foramina
Ventral rami of sacral spinal nerves
Dorsal (posterior) foramina
Dorsal rami of sacral spinal nerves
Sacrum
Above coccyx
Coccyx
Below sacrum
Meninges
Cover brain and spinal cord to protect and support them
Pia mater
V thin, innermost layer of meninges
Denticulate ligaments
Anchor spinal cord laterally
Filum terminale
Anchor spinal cord to coccyx
Arachnoid mater
Middle layer, between arachnoid mater and pia mater is cerebrospinal fluid, lumbar punctures to remove CSF take from this region
Dura mater
Outermost layer, v thick and tough
White matter pathways
Columns that run vertically in anterior position
Posterior (dorsal column)
Contain cell bodies involved in processing incoming sensory info
Anterior (ventral) column
Contain cell bodies of somatic motor neurons
Lateral column
Contain cell bodies of visceral motor neurons, thoracic lvls only
Roots/rootlets
Branches closest to spinal cord
Ventral root
Carries outgoing motor info only from anterior horn
Dorsal root
Carries incoming sensory info to posterior horn
Dorsal root ganglion
Contains cell bodies of pseudounipolar neurons that carry efferent sensory info to spinal cord
Spinal nerve
Carries motor and nerve info
Ventral ramus
Sends branches to limbs and anterior trunk wall
Dorsal ramus
Sends info to posterior trunk wall or back
Spinal cord
Shorter than vertebral column, forms cauda equina
Anterior spinal artery
Single artery, supplies 2/3 of spinal cord
Posterior spinal artery
2 arteries, supplies posterior 1/3 of spinal cord
Sensory pathways
Sensory axons leave dorsal root ganglion in dorsal root, enter posterior horn; ascending
3rd order neuron
Tracts that end in cerebral cortex, last step in pathway, travels from thalamus to pathway’s destination in cerebral cortex
1st order neuron
First step in pathway, may originate in spinal cord or brainstem, synapses in either thalamus or cerebellum
Spinocerebellar pathways (dorsal and ventral)
Fxn - proprioceptive and muscle sense info
Receptor - muscle spindles, golgi tendon organs
1st order neuron - DRG
2nd order - synapse @ lvl of entry to spinal cord, ascend ipsilaterally or decussate and cross back
Decussation - all info stays ipsilateral
Dorsal column-medial lemniscus pathway
Fxn - discriminative touch, light pressure, vibration, highly localized
Receptor - specialized receptors in skin
1st order neuron - DRG, fibers enter posterior horn of spinal cord and ascend uncrosses in dorsal columns
Decussation - brainstem
Anterolateral (ALS) pathway (spinothalamic tracts)
Fxn - pain, temp, crude touch, deep pressure
Receptor - free nerve endings in skin
1st order neuron - DRG
2nd order - neurons in dorsal horn
Decussation - fibers cross midline at each spinal segment and ascend in anterolateral fasciculus
Motor pathways
Anterior horns contain cell bodies of outgoing somatic motor neurons, axons from cell bodies leave spinal cord in ventral root
Upper motor neuron
Cell body in cerebral cortex or brainstem nucleus, excites or inhibits activity of lower motor neuron, send motor info from primary motor cortex of brain to lower motor neurons in anterior horn of spinal cord
Lower motor neuron
Cell body in anterior horn of spinal cord or brainstem cranial nerve nucleus, always excitatory, axon connects directly to skeletal muscle fibers, send motor info from spinal cord to skeletal muscles
Corticospinal tracts
Fxn - execute and control voluntary motor activity
Decussation - 75-90% fibers cross midline at pyramidal decussation in brainstem
Lateral CST - mainly decussated fibers that project to interneurons or directly to lower motor neurons innervating limb muscles
Subcorticospinal pathways
Motor pathways running from brainstem or cerebellum to spinal cord, help regulate and control pattern of somatic motor activity thru indirect pathways, can excite or inhibit LMNs, may modulate spinal reflexes, regulate muscle tone and posture, control orienting reflexes
Amyotrophic lateral sclerosis (ALS)
Motor neuron disease, involves UMN and LMN, slow progression of weakness and atrophy w fasciculations
Proprioceptors
Location - skeletal muscles (muscle spindles), tendons (golgi tendon organs), joints (free nerve endings)
Fxn - monitor tension, pressure, movement @ joint, send input on body movements to CNS, sense of body position w sensory info from internal ear
Reflex arc
Rapid, automatic, involuntary rxns of muscles to stimulus
Includes - receptor, sensory neuron, integration area in spinal cord, motor neuron, muscle
Ipsilateral
Both receptor and effector organs are on same side
Contralateral
Sensory impulses from a receptor organ crossover thru spinal cord to activate effector organs on opposite limb
Monosynaptic reflex
Involves just one synapse in reflex arc
Muscle spindle + monosynaptic stretch reflex
When a stim results in stretching of a muscle, muscle reflexively contracts
Golgi tendon reflex
Nerve impulses signal interneurons in spinal cord, inhibit actions of motor neurons, prevent from lifting too heavy of things
Polysynaptic reflex
Painful stim, sensory info sent to spinal corde, interneurons receive sensory info, stim motor neurons to direct flexor muscles to contract, extensory muscles inhibited so body part is withdrawn
