Summary of the Fiber Composition of Peripheral Nerves

I. Nerve Fibers and the Locations of their Nerve Cells of Origin

The peripheral nervous system is made up of all parts of the nervous system except the brain and spinal cord, which make up the central nervous system. The peripheral nervous system consists of 1) the cranial nerves, 2) the spinal nerves, 3) the autonomic nervous system. In the PNS all of the nerve fibers come from nerve cells in only four different general locations. They are as follows:

1. Ganglia on cranial and spinal nerves- source of AFFERENT (sensory fibers). [Afferent= conducting toward the CNS] 2. The ventral gray column and equivalent nuclei in the brain- source of EFFERENT (motor) FIBERS TO SKELETAL MUSCLE. [Efferent= conducting away from the CNS]. 3. The Intermediolateral cell column and cranial and sacral equivalents- source of PREGANGLIONIC EFFERENT fibers to autonomic ganglia. 4. Autonomic ganglia- source of POSTGANGLIONIC EFFERENT fibers to smooth muscle, cardiac muscle, and glands.

Therefore, there are basically only four different types of nerve fibers in the peripheral nervous system, one afferent and three efferent. Although some of these four basic types can be subdivided, using such terms as special and general, somatic and visceral, we will not do so here. Because of their atypical nature, cranial nerves I and II are omitted from the following discussion of fiber types.

A. AFFERENT FIBERS- cells are located in ganglia on cranial and spinal nerves. Excluding cranial nerves I and II, all afferent fibers in the PNS come from one of the following ganglia:

Nerves Containing afferent fibers Location of cell bodies V. Trigeminal Trigeminal Ganglion Mesencephalic Nucleus of V (proprioceptive of muscles of mastication) VII. Facial Geniculate ganglion VIII. Vestibulocochlear Vestibular Ganglion Spiral Ganglion IX. Glossopharyngeal Superior Ganglion Inferior Ganglion X. Vagus Superior (Jugular) ganglion Inferior (Nodose) ganglion All spinal nerves Dorsal Root Ganglia

B. EFFERENT FIBERS TO SKELETAL MUSCLE- cells are located in the ventral gray column of the spinal cord and in equivalent nuclei (collections of nerve cells) in the brainstem. All efferent fibers to skeletal muscle come from one of the following places:

1 Nerve Containing Efferent Fibers to Location of Cell Bodies- Nuclei Skeletal Muscle III. Oculomotor Oculomotor Nucleus IV. Trochlear Trochlear Nucleus V. Trigeminal Motor Nucleus of the Trigeminal Nerve VI. Abducens Abducens Nucleus VII. Facial Facial Nucleus IX. Glossopharyngeal Nucleus Ambiguus X. Vagus Nucleus Ambiguus XI. Accessory Spinal Nucleus of Accessory Nerve XII. Hypoglossal Hypoglossal Nucleus Spinal nerves Ventral Gray Column of spinal cord

Location of Cell Bodies Peripheral Termination Oculomotor Nucleus Levator palpebrae superioris, Superior rectus, medial rectus, inferior rectus, inferior oblique Trochlear Nucleus Superior oblique Motor Nucleus of Trigeminal Nerve Masseter, temporalis, lateral pterygoid, medial pterygoid, mylohyoid, anterior belly of digastric, tensor veli palatini, tensor tympani. Abducens Nucleus Lateral rectus Facial Nucleus Muscles of facial expression, stylohyoid, posterior belly of digastric, stapedius. Nucleus Ambiguus (IX) Stylopharyngeus Nucleus Ambiguus (X) Muscles of palate (except tensor), muscles of pharynx (except stylopharyngeus), muscles of larynx, upper esophagus. Spinal nucleus of XI Sternocleidomastoid, trapezius Hypoglossal Nucleus Intrinsic muscles of tongue, all glossus muscles except palatoglossus.

C. PREGANGLIONIC EFFERENT FIBERS- cells of origin are located in the Intermediolateral cell column of the thoracic and upper lumbar segments of the spinal cord and in equivalent nuclei in the brain stem and in the sacral spinal cord. All preganglionic efferent fibers come from one of the following places:

Nerve containing preganglionic efferent Location of Cell Bodies fibers III. Oculomotor Nucleus of Edinger-Westphal VII. Facial Superior Salivatory Nucleus IX. Glossopharyngeal Inferior Salivatory Nucleus X. Vagus Dorsal Motor Nucleus of Vagus T1-L2 Spinal Nerves Intermediolateral Cell Column S2-S4 Spinal Nerves Sacral autonomic nucleus (intermediate gray of the sacral spinal cord)

2 D. POSTGANGLIONIC EFFERENT FIBERS- cells of origin are located in autonomic ganglia. These cells all receive the terminations of preganglionic efferent fibers from cells in one of the locations listed in C) above. All postganglionic efferent fibers come from cells in one of the following ganglia:

Source of preganglionic Efferent fibers Name of ganglion containing cell bodies to ganglion of postganglionic efferent fibers Nucleus of Edinger-Westphal Ciliary Superior Salivatory Nucleus Pterygopalatine Superior Salivatory Nucleus Submandibular Inferior Salivatory Nucleus Otic Dorsal Motor Nucleus of Vagus Terminal (in organs of thorax and abdomen down to splenic flexure of colon) Intermediolateral Cell Column Sympathetic (ganglia of sympathetic trunk + collateral or Prevertebral ganglia) + cells in adrenal medulla Sacral autonomic nucleus Terminal (in organs of pelvis + descending colon)

Postganglionic efferent fibers terminate peripherally in smooth muscle, cardiac muscle, or glands. The peripheral terminations of postganglionic efferent fibers are as follows:

Locations of Cell Bodies Peripheral Termination *Ciliary Ganglion Ciliary muscle + sphincter pupillae *Pterygopalatine ganglion Lacrimal gland + glands of the nasal cavity and the palate *Submandibular Ganglion Submandibular gland + sublingual gland *Otic Ganglion Parotid Gland *Terminal Ganglia Cardiac muscle, smooth muscle of coronary arteries, smooth muscle of bronchi, smooth muscle and glands of alimentary canal down to splenic flexure Sympathetic Ganglia Dilator pupillae, smooth muscle in blood vessels, smooth muscle in hair follicles (arrector pili), sweat glands, cardiac muscle, smooth muscle of viscera (generally inhibitory except for sphincters) *Terminal Ganglia (sacral) Smooth muscle and glands in descending colon and pelvic viscera

* Note: The pre and postganglionic efferent fibers associated with the Ciliary, Pterygopalatine, Submandibular, otic, and terminal ganglia make up what is known as the parasympathetic division of the Autonomic nervous system. This division is also called the craniosacral division because of the preganglionic nerve cells are located in either the brainstem or the sacral spinal cord and their fibers are distributed through either cranial (III, VII, IX, X) or sacral (S2, S3, or S4) nerves. The sympathetic (thoracolumbar) division of the ANS is made up of the pre and postganglionic efferent fibers associated with the sympathetic ganglia.

3 II. Classification of Cranial Nerves

A. Afferent (sensory) 1. Olfactory (CN I) 2. Optic (CN II) 3. Vestibulocochlear (CN VIII)

B. Efferent (motor) 1. Oculomotor (CN III) 2. Trochlear (CN IV) 3. Abducens (CN VI) 4. Accessory (CN XI) 5. Hypoglossal (CN XII)

C. Mixed (sensory and motor) 1. Trigeminal (CN V) 2. Facial (CN VII) 3. Glossopharyngeal (CN IX) 4. Vagus (CN X)

III. Summary of Cranial Nerves

A.Olfactory (CN I)

Types of Fibers Location of Cell Bodies Peripheral Termination Afferent Olfactory mucosa Olfactory mucosa

B. Optic (CN II)- The optic nerve is a tract of the brain connecting the retina, which is embryologically an outgrowth of the brain. It is made up almost entirely of afferent fibers which arise from the ganglion cells in the retina.

C. Oculomotor (CNIII)

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Oculomotor Nucleus All extraocular muscles except superior oblique and lateral rectus Preganglionic Nucleus of Edinger-Westphal Ciliary Ganglion

D. Trochlear (CN IV)

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Trochlear nucleus Superior oblique Muscle

4 E. Trigeminal (CN V)- The trigeminal nerve is the nerve of the first branchial arch

Types of Fibers Location of Cell Bodies Peripheral Termination Afferent (general sensation) Trigeminal Ganglion Skin of face and anterior half of scalp, the orbit and eyeball, the mucosa of the nasal cavity, paranasal sinuses, and the oral cavity, including the body of the tongue (except for taste), upper and lower jaws, including teeth, cranial dura mater. Afferent (Proprioception) Mesencephalic Nucleus of V Muscles of mastication Efferent to skeletal muscle Motor nucleus of V Muscles of mastication, mylohyoid, anterior belly of digastric, tensor veli palatini, tensor tympani

F. Abducens (CN VI)

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Abducens nucleus Lateral rectus (abducts the eye)

G. Facial (CN VII)- The facial nerve is the nerve of the second gill arch

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Facial nucleus Muscles of facial expression, stylohyoid, posterior belly of digastric, stapedius Afferent Geniculate Ganglion Taste buds on anterior 2/3 of tongue, external acoustic meatus, soft palate and adjacent pharynx. Preganglionic Superior Salivatory Nucleus Pterygopalatine Ganglion, Submandibular Ganglion

H. Vestibulocochlear (CN VIII)

Types of Fibers Location of Cell Bodies Peripheral Termination Afferent Spiral Ganglion Hair Cells in Spiral Organ (of Corti) Afferent Vestibular Ganglion Hair cells in maculae of saccule and utricle and cristae of semicircular ducts

5 I. Glossopharyngeal (CN IX)- the glossopharyngeal nerve is the nerve of the third branchial arch

Types of Fibers Location of Cell Bodies Peripheral Termination Afferent Inferior Ganglion Taste buds on posterior 1/3 of tongue including the sulcus terminalis and the vallate papillae; mucosa of posterior 1/3 of tongue, oropharynx, and the soft palate; carotid sinus and carotid body Efferent to skeletal muscle Nucleus Ambiguus Stylopharyngeus Preganglionic efferent Inferior Salivatory Nucleus Otic Ganglion

J. Vagus (CN X)- The vagus nerve is the nerve of the fourth and sixth branchial arches.

Types of Fibers Location of Cell Bodies Peripheral Termination Afferent Superior Ganglion Skin of external acoustic meatus Afferent Inferior Ganglion Mucosa of larynx, epiglottis (taste buds), trachea, bronchi, lungs, alimentary canal down to left colic flexure. Preganglionic efferent Dorsal Motor Nucleus of Vagus Terminal ganglia in thoracic and abdominal viscera down to left colic flexure Efferent to skeletal muscle Nucleus Ambiguus Muscles of palate except tensor veli palatini, muscles of pharynx except stylopharyngeus; all muscles of larynx; upper esophagus

K. Accessory (CN XI)

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Spinal nucleus of accessory Sternocleidomastoid, Trapezius nerve

L. Hypoglossal (CN XII)

Types of Fibers Location of Cell Bodies Peripheral Termination Efferent to skeletal muscle Hypoglossal nucleus Intrinsic muscles of tongue, genioglossus, hyoglossus, styloglossus