Cranial nerves
Encased in skull
Most are believed to be homologous with
spinal nerves
No distinct dorsal or ventral root
Numbered by present position, not homology
first few cranial nerves reside outside the skull (occipitospinal nerves in cyclostomes)
12 pairs in all tetrapods and crossopterygians
Living amphibians secondarily lost 2 pairs
Cranial Nerves
*Terminal nerve (0)
Believed to be remnant from lost visceral arch (support for Composite theory)
Sensory and motor fibers to/from olfactory epithelium & associated blood vessels
Present in all gnathostomes except birds
Olfactory nerve (I)
Sensory from olfactory sac
Olfactory Epithelium
Optic nerve (II)
Not really a nerve! Actually brain outgrowth
Integrates visual information from retinas
Optic Chiasma-where sensory information crosses over
No visual perception occurs at point of attachment to retina
Cranial Nerves
Oculomotor nerve (III)
Motor for some of the extrinsic eye muscles (superior rectus, medial rectus, inferior rectus, inferior oblique) and some visceral fibers to intrinsic eye muscles (iris, ciliary body)
Trochlear nerve (IV)
Motor nerve to superior oblique extrinsic eye muscle
Cranial Nerves
Trigeminal nerve (V)
Usually the largest of the cranial nerves
3 major branches
Deep ophthalmic (V1) - to lost first arch?
Most often fused with other two branches
Maxillary (V2) - upper jaw, roof of mouth and pharynx, sensory
etc.
Mandibular (V3) - lower jaw and floor or
mouth and pharynx, motor and sensory
-tongue tactile cues, lower teeth, chin skin, mastication muscles etc.
Cranial Nerves
Abducens (VI)
Motor nerve to lateral rectus
(another extrinsic eye muscle)
Facial (VII)
Sensory fibers from lateral line of head (fishes, amphibians) and taste buds
Motor fibers to hyoid arch
Primary motor nerves of face
Salivary glands, lacrimal glands
Some taste buds
Five major branches
Temporal
Zygomatic
Buccal
Mandibular
Cervical
Cranial Nerves
Auditory (VIII)
(acoustic, vestibulocochlear, or statoacoustic)
Sensory fibers from inner ear
hearing and balance
Glossopharyngeal (IX)
Sensory fibers from taste buds, first gill slit and adjacent pharyngeal lining, lateral line
Swallowing and gag reflex
Motor fibers to third branchial arch
Cranial Nerves
Vagus (X)
The "wanderer" - mouth, pharynx, much
of viscera
Only cranial nerve to extend beyond head and neck region
formed by fusion of C1, C2 and cranial
nerve
Most Parasympathetic efferents
Regulates heart rate
Breathing rate
Digestive system activity
Transmits sensory impulses from thoracic and abdominal viscera
Proprioreceptors of larynx, taste buds, motor nerves of larynx and pharynx
Cranial Nerves
Spinal accessory (XI)
Formed by branch of vagus + several
occipitospinal nerves
(dorsal and ventral roots)
Motor to derivatives of cucullaris (cleidomastoid, sternomastoid, trapezius) - all derivatives of branchiomeric musculature
Also portions with vagus to pharynx, larynx,
maybe heart
Hypoglossal (XII)
Motor nerve to hyoid and tongue muscles
Lateral Line Nerves
Vagus and Facial nerves
Anterior and Posterior
Evolution of Cranial Nerves
Derived from Pharyngeal Arches?
Dorsal and ventral roots of spinal nerves have fused or become lost
Some nerves are persisting dorsal roots
Sensory afferent (terminal, facial, glossopharyngeal, vagus, accessory nerves
Ventral roots -oculomotor, trochlear and abducens
Quiz 12
5. How does a female placental mammal reproductive tract differ from a marsupial?
6. Write "internal fertilizer" or "external fertilizer" next to each characteristic
simple