pathways Flashcards
control of defecation
GVE LMN L1-L4/5
Spinal nerve -> ramus communicans -> lumbar longitudinal sympathetic trunk -> lumbar splanchnic nerves -> caudal mesenteric ganglion -> hypogastric nerve
=> activation of internal sphincter (α1) + inhibition of descending colon & rectum (β)
GSE LMN S1-S3
Spinal nerve -> sacral plexus -> pudendal nerve -> caudal rectal branch
=> *activation of striated external anal sphincter (N)
*
GVE LMN S1-S3
Spinal nerve -> pelvic nerve -> ganglions in the wall of descending colon & rectum
=> activation of descending colon & rectum (M)
Control of micturition
Pontine micturition centre -> reticulospinal tr.
GVE LMN L1-L4/5
Spinal nerve -> ramus communicans -> lumbar longitudinal sympathetic trunk > lumbar splanchnic nerves -> caudal mesenteric ganglion -> hypogastric nerve
=> activation of internal sphincter (α1) + inhibition of detrusor (β) + inhibition of pelvic plexus (α2)
GSE LMN S1-S3
Spinal nerve -> sacral plexus -> pudendal nerve
=> activation of striated urethralis muscle (N)
GVE LMN S1-S3
Spinal nerve -> pelvic nerve -> ganglions in the wall of bladder & pelvic plexus
=> activation of detrusor (M)
Control of urine storage
Aδ mechanoreceptor responding to stretch and distension in the bladder wall -> pelvic nerve ->spinal nerve => GVA S1-S3
Storage reflex
GVA S1-S3 -> activation of GVE LMN L1-L4/5 in response of bladder distension -> activation of GSE LMN S1-S3 in response of urethral distension
Perception
GVA S1-S3 -> pontine micturition centre + cerebellum + thalamic nucleus
Thalamic nucleus -> sensory cerebral cortex -> IC -> crus cerebri -> pontine micturition centre
Pupil dilation (UMN, LMN preganglionic)
GVE-UMN: hypothalamus -> brainstem -> lateral tectotegmentospinal system -> lateral gray horn T1-T2-T3
GVE-LMN preganglionic: cell bodies in LGH T1-T2-T3 -> ventral root -> segmental SN -> segmental ramus communicans -> thoracic sympathetic trunk ->
through middle cervical and cervicothoracic ganglia without synapsing -> cervical sympathetic trunk -> vagosympathetic trunk in carotid sheath -> cervical cranial ganglion (medial to digastricus origin & ventromedial to tympanic bulla)
Some GVE-LMN preganglionic axons will synapse on cervicothoracic ganglion. GVE-LMN ganglionic axons course then in the vertebral nerve to supply C6 to C2 with a ramus to the cervical SN at each intervertebral foramina.
Pupil dilation (LMN ganglionic)
GVE-LMN ganglionic: cell bodies in cranial cervical ganglion, then 2 routes:
Internal carotid nerve -> follow ICA as a plexus -> tympano-occipital fissure -> carotid canal -> foramen lacerum -> *ophthalmic nerve *-> orbital fissure
Note: one branch follow the cerebral arterial circle to join the internal ophthalmic artery and enter the orbital cavity through the optic canal with optic nerve
through tympanic cavity -> enter cranial cavity to the trigeminal ganglion
Dilatator pupillae, ciliary, and orbitalis muscles
Note: levator palpebral superioris: CN.III
Levator anguli oculi medialis: CN.VII in LA, via auriculopalpebral nerve
Withdrawal reflex
Thoracic limb
Dorsal digits -> radial nerve -> dorsal roots C7-C8-T1 -> dorsolateral fasciculus -> interneurons on substancia gelatinosa (2-3 SCS cranially and caudally) -> fasciculus proprius -> GSE-LMN-α of major flexors:
- Shoulder: axillary, radial
- Elbow: musculocutaneous
- Carpus: median, ulnar
Ventral digits: median/ulnar nerves (C8-T1-T2)
Autonomous zones:
- Radial: dorsal paw
- Ulnar: caudal antebrachium
- Musculocutaneous: medial antebrachium
acoustric startle reflex
spiral organ -> spiral ganglion -> cochlear nerve internal acoustic meatus -> cochlear nuclei
-> +/- trapezoid body -> lat lemniscus -> caud colliculi -> +/- rostral colliculi
-> medial tectospinal tract -> LMN BS and cerv SC
rost colliculi can be indirectly reached by med genic nucleus -> auditory cortex -> rostral colliculi
middle ear reflex
spiral organ -> spiral ganglion -> cochlear div of CN VIII -> dorsal + ventral cochlear nuclei -> +/- dorsal nucl trapezoid body
-> motor nucl of trigeminus (tensor tympani attached to malleus) and facial (stapedius attached to stapes)
Pathway of ventral spinocerebellar tract
Trunk, pelvic limbs spinal ganglion -> dorsal root
-> maj cross at ventral commissure
->ventral spinocerebellar tract in lat funiculi
-> rostral cerebellar peduncle
-> cross back in cerebellum
->vermal/paravermal lobules of cerebellum
cutaneous trunci reflex
dorsa branch L/T spinal nerve -> dorsal roots -> interneur in fasciculus proprius bilat -> lateral thoracic nerve (C8-T1) -> cutaneous trunci m
most dog until middle lumbar
