Exam 4 Review:  Chapter 13:  Peripheral Nerve Terminology

 

cranial nerves - The 12 pairs of nerves (some pure sensory, some motor (with proprioception), and some mixed) which arise from the base of the brain and serve various regions of the head and neck, and, in the case of the Vagus, nerve X, organs and tissues in the thoracic and abdominopelvic cavities.

 

spinal nerves  - The 31 pairs of mixed (motor and sensory) nerves which arise from the various spinal segments of the spinal cord, which originate as dorsal and ventral roots which combine the in the region of the intervertebral foramen and shortly thereafter branch into various rami to innervate various regions of the body.

 

ramus / rami   - A general anatomical term for a branch which may be applied to a nerve, a blood vessel, or a region of a bone.

 

dorsal ramus - One of the first three branches of each spinal nerve, this small branch supplies the skeletal muscles and skin of the posterior portion of the neck or trunk of the body.

 

ventral ramus - One of the first three branches of each spinal nerve, this thick branch supplies the skeletal muscles and skin of the lateral and anterior portions of the neck or trunk of the body.

 

meningeal branch / ramus - One of the first three branches of each spinal nerve, this smallest branch turns back through the intervertebral foramen to supply the spinal meninges and the blood vessels of the spinal meninges.

 

 

rami communicantes - A fourth branch of the thoracic region spinal nerves, this branch, which is joined to the base of the ventral ramus, contains autonomic (visceral motor) fibers which innervate certain of the thoracic or abdominal organs.

 

 

nerve plexuses - Interlacing networks of nerve fibers which originate from the ventral rami of spinal nerves (except those in the region T2 - T12) in which individual nerve processes from individual spinal segments become redistributed to that (1) each resulting branch of the plexus contains fibers from several spinal nerves and (2) fibers from each ventral ramus travel to the periphery of the body by several routes; this arrangement permits each skeletal muscle in a limb to be innervated by motor (afferent) fibers from more than one spinal segment -- as a result, an injury to a single spinal segment or spinal motor (ventral) root cannot completely paralyze any limb muscle.

 

 

cervical plexus  - The most superior of the four pairs of plexuses  (interlacing branches of the ventral rami of spinal nerves), which provide cutaneous nerves to the skin of the neck, the region of the ear, the back of the head and the shoulder and motor nerves to muscles of the anterior neck and to the diaphragm, is formed from the ventral rami of C1-4.

 

 

brachial plexus - The large plexus  (interlacing branches of the ventral rami of spinal nerves), located in the neck and the axilla, which provides essentially all the innervation to the upper limb, is formed from the ventral rami of C4-5-C8 and T1-2.

 

 

lumbar plexus - The large plexus  (interlacing branches of the ventral rami of spinal nerves), located in the hip, superior and anterior to the ilium within the psoas muscle, which provides the innervation to the abdominal wall muscles, the psoas muscle, and the muscles of the anterior and medial thigh as well as cutaneous sensation from anterior thigh and the medial surface of the lower leg, is formed from the ventral rami of L1-4.

 

 

sacral plexus - The most inferior of the four pairs of plexuses (interlacing branches of the ventral rami of spinal nerves), located immediately inferior to the lumbar plexus, which provides the innervation to the buttock and lower leg, the pelvic structures and the perineum, is formed from the ventral rami of L4 and S1-4.

 

 

intercostal nerves - The major branch of each of the ventral rami from spinal nerves T1 - T12, which provides mixed (sensory and motor) innervation to the intercostal muscles between the ribs and the muscles and skin of the anteriolateral thorax and most of the abdominal wall.

 

dermatome - (1) anatomy - The area of skin innervated by the cutaneous branches of a single spinal nerve (this same area of skin will receive some additional innervation from branches of both the spinal nerve of the segment above and the segment below.  (2)  embryology - The portion of somite mesoderm which forms the dermis of the skin.

 

 

myotome - embryology - The portion of somite mesoderm which forms the skeletal muscles of the neck, trunk of the body, and via their limb buds, the muscles of the limbs.

 

List:

3. For each of the twelve Cranial Nerves, list:

    a.  number, name
    b.  general region(s) served
    c.  main functional role(s)
    d.  modality (sensory, motor, or mixed) 

Number Name General Region(s) Served Main Functional Role(s) Modality (sensory, motor*, or mixed)
I Olfactory olfactory epithelium in nasal cavity transmit olfactory information sensory
II Optic retina in the eyeball transmit visual information sensory
III Oculomotor extrinsic eye muscles control rotation of the eyeball motor*
IV Trochlear extrinsic eye muscles control rotation of the eyeball motor*
V Trigeminal face, oral cavity, jaws transmit general sensory information from the face, oral cavity, jaws; control of some of the jaw muscles for chewing mixed
VI Abducens extrinsic eye muscles control rotation of the eyeball motor*
VII Facial face, oral cavity transmit taste (gustatory) information from anterior portion of tongue; autonomic control of lacrimal and salivary glands, control facial muscles for expression mixed
VIII Vestibulocochlear inner ear = membranous labyrinth transmit hearing and static and dynamic equilibrium information sensory
IX Glossopharyngeal throat transmit general sensory information from the throat and transmit taste (gustatory) information from posterior portion of tongue; autonomic control of parotid salivary glands, control throat muscles involved in swallowing mixed
X Vagus thoracic and abdominal organs transmit general sensory and visceral sensory information from heart, blood vessels, lungs and abdominal organs; autonomic control of heart, lungs and abdominal organs mixed
XI Accessory throat control muscles of larynx, pharynx, and palate for swallowing, and speaking, controls muscles of neck and shoulders for head and neck movements motor*
XII Hypoglossal tongue control tongue movements for chewing, swallowing, and speaking motor*
*Note:  Cranial nerves identified as "motor" do carry proprioceptive sensory information from the skeletal muscles which they innervate.

 

Click here for a PowerPoint review of the twelve cranial nerves.

 

Explain:

1.  The relationship of the dermatomes to the spinal nerves.

          Each dermatome is a mapped area of skin innervated by the cutaneous branches of a single spinal nerve (this same area of skin will receive some additional innervation from branches of both the spinal nerrve of the segment above and the segment below.