Animal Form & Function III - Nervous System

Dogfish-Shark Cranial Nerves

In the head region of vertebrates there is present a special series of varied nerves which are at least superficially quite different from the spinal nerves. The cranial nerves were first studied in man and were named and numbered based on their functions and positions.

Twelve cranial nerves are usually listed as follows:

Nerve Origin Termination Function
I Olfactory olfactory lobe nasal capsule sensory
II Optic beneath optic lobe retina or eye sensory
III Oculomotor optic lobe eye muscles motor
IV Trochlear between optic lobe and cerebellum superior oblique eye muscle motor
V Trigeminal lateral surface of medulla skin and muscles and snout mixed
VI Abducens ventral surface of medulla posterior rectus eye muscle motor
VII Facial common with trigeminal lateral head region mixed
VIII Auditory medulla inner ear sensory
IX Glosso-pharyngeal medulla branches to gills and roof to mouth mixed
X Vagus medulla many parts of body including viscera mixed
XI Accessory medulla accessory to the vagus motor
XII Hypoglossal medulla tongue muscles motor

We will only hold you responsible for those highlighted in the table above:

Examine the dogfish Brain and locate the above nerves