Spinal Tracts Flashcards
Cervical enlargement
Cervical swelling
Due to the emergence of the nerves of the brachial plexus
Extra inputs and outputs for the arms
Lumbar enlargement
Lumbar swelling
Due to emergence of nerves of the lumbar plexus
Extra inputs and outputs for the legs
Conus medullaris
At level L2
Spinal cord terminates by tapering to a conus medullaris
Below L2 is filled with the nerves roots from the lumbosacral spine
Filum terminale internum
Thin connective tissue
Anchors the spinal cord
Sensory pathways
Information from sensory receptors to the brain
Conscious - reach cerebral cortex
Unconscious - dont reach cerebral cortex, Proprioception information, delivered to cerebellum
Sensory receptors: free nerve endings
Widespread, especially in epithelia and connective tissues
Pain
Heat
Cold
Sensory receptors: tactile discs (merkel)
Stratum basale of epidermis
Light touch
Texture
Edges
Shapes
Sensory receptors: hair receptors (hair cell plexus)
Around hair follicle
Movement of hair
Sensory receptors: tactile corpuscles (meissner’s)
Dermal papillae of fingertips, palms, eyelids, lips, tongue, nipples, genital
Light touch
Texture
Sensory receptors: Krause end bulbs
Mucous membrane
Similar to tactile corpuscles
Light touch
Texture
Sensory receptors: lamellated corpuscles (pacinian)
Dermis, joint capsules, breasts, genitals, some visceral
Deep pressure
Stretch
Tickle
Vibration
Sensory receptors: Ruffini corpuscles
Dermis, subcutaneous tissue, joint capsules
Heavy touch
Pressure
Stretching of skin
Joint movement
Sensory receptors: muscle spindles
Skeletal muscle near tendon
Muscle stretch (Proprioception)
Sensory receptors: Golgi tendon organ
Tendons
Tension on tendons (Proprioception)
Sensory receptors: kinaesthetic receptors
Position and movement of muscles and joints
Generic sensory pathway: first order neurone
Connects sensory receptors to spinal cord via posterior (dorsal) nerve roots
Cell bodies lie in the posterior (dorsal) root ganglia of the spinal nerves
Generic sensory pathway: second order neurone
Connects spinal cord to the to the thalmus
Cell bodies lie in the dorsal horn/grey matter of spinal cord
Generic sensory pathway: third order neurone
Connects the thalamus to the ipsilateral portion of the somatosensory cortex
Cell bodies lie in the thalamus
Spinothalemic pathway (direct): first order neurone
Connects sensory receptors to spinal cord via posterior (dorsal) nerve roots
Cell bodies lie in the posterior (dorsal) root ganglia of the spinal nerves
Spinothalemic pathway (direct): second order neurone
Connects spinal cord to the thalamus
Cell bodies lie in the dorsal horn/grey matter of the spinal cord
Decussate in the spinal cord across the midline
Spinothalemic pathway (direct): third order neurone
Connects the thalamus to the ipsilateral portion of the somatosensory cortex
Cell bodies lie in the thalamus
Ventral spinothalemic
Crude touch
Lateral spinothalemic
Pain
Temperature
Spinothalemic damage
Life side spinal cord injury causes loss of sense of - touch, pain, warmth/cold in the right leg/side
Sensory loss in the controlateral side
Spinothalemic pathway (indirect)
Autonomic processes and unconscious
Synapses at - reticular formation, hypothalamus, limbic system, periaqueductal grey
Dorsal white column
Column of fibres found posteriorly
Dorsal column pathway: first order neurone
Connects sensory receptors to the spinal cord via posterior (dorsal) nerve roots
Cell bodies lie in the posterior (dorsal) root ganglia of spinal nerves
Dorsal column pathway: second order neurone
Decussation in medulla oblongata - crosses over to Contralateral side
Cell bodies lie in the medulla oblongata
Dorsal column pathway: third order neurone
Connects thalamus to the ipsilateral portion of the somatosensory cortex
Cell bodies lie in the thalamus
Fasciculus cuneatus
Dorsal column
Columns of nerves to the upper limbs
Fasciculus gracalis
Dorsal column
Columns of nerves to the lower limbs
Dorsal column damage
Left side spinal cord injury causes loss of sense of - touch, Proprioception, vibration in left leg
Sensory loss in the ipsilateral side
Spinocerebellar pathway
From body to spine then to cerebellum
Doesn’t go to somatosensory cortex
Cerebellum not consciously aware of information
Two neurones
Stay on ipsilateral side
Spinocerebellar pathway: first order neurone
Connects sensory receptors to spinal cord via posterior (dorsal) nerve roots
Cell bodies lie in the posterior (dorsal) root ganglia of spinal nerves
Spinocerebellar pathway: second order neurone
From the Frey matter of the spinal cord through the medulla to the cerebellum
Cell bodies lie in the spinal cord
Spinocerebellar tract damage
Cerebellar ataxia
Clumsy movements
Wide-based, reeling gait
Acute use - enhance GABA (inhibitory) suppress glutamate (excitatory)
Lack of coordination
Generic motor pathways: upper motor neurone
Originate in cerebral cortex/motor centres of brainstem
Some decussate in brain stem
Descend down spinal cord until it reaches lower motor neurone or interneurone
Generic motor pathways: lower motor neurone
From spinal cord via ventral roots to innervate skeletal muscles
Cell bodies lie in the ventral grey matter of spinal cord
Pyramidal pathways
Direct
Conscious
From cerebral cortex to skeletal muscle
Voluntary movement
UMN (cortical cell body in motor cortex) -> interneurone -> LMN (ventral horn/root)
Corticospinal pyramidal pathway: upper motor neurone
From cerebral cortex to form pyramids of the medulla oblongata
90% - decussate at medulla oblongata and travel in the lateral and anterior white column of the spinal cord, control limbs
10% - decussate at segmental level, control muscles of back/trunk
Corticospinal pyramidal pathway: lower motor neurone
Exit spinal cord via ventral spinal roots
Travel to muscle that control limbs or back
Corticospinal pyramidal pathway: Lateral fibres
Control fine movements
Corticospinal pyramidal pathway: anterior/ventral fibres
Control larger movements
Corticobulbar pyramidal pathway
Controls the upper neck and face
Corticobulbar pyramidal pathway: upper motor neurone
From the motor cortex for the face and tongue to the pons (brainstem)
Corticobulbar pyramidal pathway: lower motor neurone
Cranial nerves
Extrapyramidal pathways
Indirect
Subconscious/unconscious e.g. balance
Indirect tracts from brainstem to various effects causing involuntary movement
No connection from higher cortical areas
UMN in brain stem
Modifies movements - modulators action on LMN
Rubrospinal tract (extrapyramidal)
Upper limbs - fine motor coordination
Activation facilitates flexors and inhibits extensors
Rubrospinal tract (extrapyramidal): upper motor neurone
Originate in red nucleus (mid brain)
Decussate in the brainstem
Descends to terminate in the grey matter of spinal cord
Rubrospinal tract (extrapyramidal): lower motor neurone
Exit in spinal nerves of cervical spine
Travel to muscles that control the distal portion of the limbs
Tectospinal tract (extrapyramidal)
Relays motor impulses to muscles of the head and trunk in response to visual or auditory stimulation
Controlling neck muscles
Head eye coordination
Visual/auditory feedback
Tectospinal tract (extrapyramidal): upper motor neurone
Originate in superior colliculus (mid brain)
Decussate in the mid brain
Descends to terminate in the grey matter of cervical spinal cord
Tectospinal tract (extrapyramidal): lower motor neurone
Travel to the muscles that control the head, neck and back
Vestibulospinal tract (extrapyramidal)
Maintaining upright posture and balance
Extensors of lower limb
Projects ipsilaterally
Vestibulospinal tract (extrapyramidal): upper motor neurone
Descends from vestibular nucleus (information from inner ear about gravity, pressure and balance)
Terminated in the grey matter of spinal cord
Vestibulospinal tract (extrapyramidal): lower motor neurone
Travel to the muscles that control the trunk and proximal portions of the limbs
Reticulospinal tract (extrapyramidal)
Maintaining posture when the body is in motion
Motor function
Autonomic functions e.g. cardiac output, respiratory function
Suppression of spinal reflexes
Adjust voluntary movements
Pain modulation
Reticular formation - filtering system, locomotion, posture, sensory information
