The Notion of Mixed Spinal Segmental Nerves and their Equivalents in Cranial Nerves Flashcards
2 variants of peripheral nerve
- Spinal/segmental
- Cranial
Why are axons of nerve bundles said to be “mixed”?
- Some are myelinated and some not
- Different directions of impulses conducted by nerve fibres
4 general classes of spinal nerve fibres
- General somatic afferents (GSA)
- General visceral afferents (GVA)
- General somatic efferents (GSE)
- General autonomic efferents (GVE)
What do each of the classes of spinal nerve fibres provide?
- GSA = general sensation
- GVA = visceral sensation
- GSE = supply skeletal muscle
- GVE = autonomic fibres innervating visceral structures
How do spinal nerves exit the vertebral column?
Through inter-vertebral foramina
Where is a spinal nerve “fully mixed”?
As it emerges through the inter-vertebral foramen
2 branches of spinal nerve as it emerges from inter-vertebral foramen
- Dorsal ramus (posterior)
- Ventral ramus (anterior)
Relative sizes of ventral and dorsal rami
Dorsal is smaller, ventral is larger
What does the dorsal ramus further branch into?
- Medial branch
- Lateral branch
What does the dorsal ramus supply?
Tissues of the back of the body (incl. skin, muscles, blood vessels, sweat glands)
What does the ventral ramus supply?
Tissues of the front of the body (incl. skin, muscles, blood vessels, sweat glands)
What supplies the spinal meninges?
Meningeal ramus
Classes of cranial nerve fibres
- Same 4 as spinal
- Special visceral efferents
- Special somatic afferents
- Special visceral afferents
What do each of the classes of cranial nerves provide?
- SVE = supply muscles derived from branchial arches
- SSA = equilibration, hearing, sight
- SVA = taste
The 12 cranial nerves
- CNI = olfactory
- CNII = optic
- CNIII = oculomotor
- CNIV = trochlear
- CNV = trigeminal
- CNVI = abducent
- CNVII = facial
- CNVIII = vestibulocochlear
- CNIX = glossopharyngeal
- CNX = vagus
- CNXI = accessory
- CNXII = hypoglossal
