WEEK 2: Review of cranial nerves

Question 1

Outline the 12 cranial nerves according to their order.

Answer 1

Cranial nerve I – Olfactory nerve
Cranial nerve II – Optic nerve
Cranial nerve III – Oculomotor nerve
Cranial nerve IV – Trochlear nerve
Cranial nerve V – Trigeminal nerve
Cranial nerve VI – Abducens nerve
Cranial nerve VII – Facial nerve
Cranial nerve VIII – Vestibulocochlear nerve
Cranial nerve IX – Glossopharyngeal nerve
Cranial nerve X – Vagus nerve
Cranial nerve XI – Spinal accessory nerve
Cranial nerve XII – Hypoglossal nerve

Question 2

State the functions of the following.

Sensory (afferent) neurons

*General sensory (general somatic afferent) neurons.
*Special sensory (special visceral afferent) neurons.
*Visceral sensory (general visceral afferent) neurons.

Answer 2

Sensory (afferent) neurons.Carry information from the body tissues to the CNS.

*General sensory (general somatic afferent) neurons.Transmit sensory information (e.g., pain, temperature, and touch), carried mainly by CN V but also by CNN VII, IX, and X.

*Special sensory (special visceral afferent) neurons.Include special sensory neurons (e.g., smell, vision, taste, hearing, and equilibrium) that are carried by CNN I, II, VII, VIII, IX, and X.

*Visceral sensory (general visceral afferent) neurons.Transmit visceral sensory information (e.g., stretch and baroreceptors) from the heart, lungs, GI tract, carotid body, and carotid sinus mainly within CNN IX and X.

Question 3

Describe the function of the following:

Motor (efferent) neurons

*Somatic motor (general somatic efferent) neurons.

*Branchial motor (special visceral efferent) neurons.

Answer 3

Motor (efferent) neurons.Carry information from the CNS to body tissues.

*Somatic motor (general somatic efferent) neurons.
Innervate skeletal muscles derived from somites, including the extraocular and tongue muscles.

Innervation is accomplished via CNN III, IV, VI, and XII.

*Branchial motor (special visceral efferent) neurons.
Innervate skeletal muscles derived from the branchial arches, including the muscles of mastication and facial expression, and the palatal, pharyngeal, laryngeal, trapezius, and sternocleidomastoid muscles.

Innervation is accomplished via CNN V, VII, IX, X, and XI.

*Visceral motor (general visceral efferent) neurons.
Innervate involuntary (smooth) muscles or glands, including visceral motor neurons that constitute the cranial outflow of the parasympathetic division of the autonomic nervous system.

The preganglionic neurons originate in the brainstem and synapse outside the brain in parasympathetic ganglia.

The postganglionic neurons innervate smooth muscles and glands via CNN III, VII, IX, and X.