Chap 20: PNS – Snow College Anatomy
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What are cranial nerves?
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Nerves that extend from the brain.
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How many cranial nerves are there?
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12 pairs
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What is the name and number of the first cranial nerve?
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I Olfactory
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What is the function of the first cranial nerve?
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Sensory function: olfaction
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What openings in the skull transmit the first cranial nerve?
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Foramina of the cribriform plate of the ethmoid
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What cranial nerve is transmitted by the foramina of cribriform plate of the ethmoid?
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first cranial nerve I Olfactory
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What is the name and number of the second cranial nerve?
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II Optic
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What is the function of the second cranial nerve?
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Sensory function: vision
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What opening in the skull transmits the second cranial nerve?
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Optic foramen
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What is the name and number of the third cranial nerve?
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III Oculomotor
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What is the function of the third cranial nerve?
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Somatic motor function: Supplies four extrinsic eye muscles (superior rectus, inferior rectus, medial rectus, inferior oblique), which move the eyeball, and the levator palpebrae superioris, which elevates the upper eyelid Parasympathetic motor: Innervates sphincter pupillae (pupil constrictor) muscle in eye to make pupil constrict; contracts ciliary muscles to make lens of eye more puffy (thicker, as needed for vision)
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What opening in the skull transmits the third cranial nerve?
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Superior orbital fissure
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What is the name and number of the fourth cranial nerve?
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IV Trochlear
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What is the function of the fourth cranial nerve?
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Somatic motor function: Supplies one extrinsic eye muscle (superior oblique) to move the eyeball inferiorly and laterally.
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What opening in the skull transmits the fourth cranial nerve?
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Superior orbital fissure
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What is the name and number of the fifth cranial nerve?
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V Trigeminal
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What are the three branches of the fifth cranial nerve?
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Ophthalmic branch (V1) Maxillary branch (V2) Mandibular branch (V3)
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What is the first branch of the fifth cranial nerve? What are its functions?
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The ophthalmic branch conducts sensory impulses from the cornea, nose, forehead and anterior scalp.
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What is the second branch of the fifth cranial nerve? What are its functions?
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The maxillary branch conducts sensory impulses from nasal mucosa, palate, gums, and cheek.
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What is the third branch of the fifth cranial nerve? What are its functions?
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The mandibular branch conducts sensory impulses from the anterior two-thirds of the tongue, skin of the chin, lower jaw, lower teeth, and one third of the sensory fibers of the auricle of the ear. Somatic motor function: Innervates muscles of mastication and other muscles of the lower facial region.
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What openings in the skull transmit the ophthalmic branch of the fifth cranial nerve?
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Superior orbital fissure
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What openings in the skull transmit the maxillary branch of the fifth cranial nerve?
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Foramen rotundum
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What openings in the skull transmit the mandibular branch of the fifth cranial nerve?
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Foramen ovale
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What is the name and number of the sixth cranial nerve?
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VI Abducens
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What is the function of the sixth cranial nerve?
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Somatic motor function: Innervates one extrinsic eye muscle (lateral rectus) for abduction of the eyeball.
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What opening in the skull transmits the sixth cranial nerve?
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Superior orbital fissure
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What is the name and number of the seventh cranial nerve?
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VII Facial
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What are the functions of the seventh cranial nerve?
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Sensory function: Taste from the anterior two-thirds of the tongue. Somatic motor function: Innervates the muscles of facial expression and other muscles of the facial region. Parasympathetic motor function: Innervates the lacrimal gland and the submandibular and sublingual salivary glands.
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What openings in the skull transmit the seventh cranial nerve?
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Internal auditory canal and stylomastoid foramen
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What is the name and number of the eighth cranial nerve?
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VIII Vestibulocochlear
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What are the functions of the eighth cranial nerve?
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Sensory function: Conducts impulses of hearing and equilibrium from the inner ear.
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What opening in the skull transmits the eighth cranial nerve?
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Internal auditory canal
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What is the name and number of the ninth cranial nerve?
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IX Glossopharyngeal
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What are the functions of the ninth cranial nerve?
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Sensory function: General sensation and taste from the posterior third of the tongue. Conducts sensory information on blood pressure and blood chemistry from the carotid sinuses. Somatic motor function: Innervates a pharyngeal muscle. Parasympathetic motor function: Innervates the parotid salivary gland.
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What opening in the skull transmits the ninth cranial nerve?
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Jugular foramen
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What is the name and number of the tenth cranial nerve?
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X Vagus
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What are the functions of the tenth cranial nerve?
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Sensory function: Innervates the pharynx, larynx, and thoracic and abdominal viscera, as well as the external auditory canal, eardrum, and pharynx. Somatic motor function: Innervates most pharyngeal and laryngeal muscles. Parasympathetic motor function: Innervates myocardium and the smooth muscle and glands of the thoracic and abdominal viscera.
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What opening in the skull transmits the tenth cranial nerve?
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Jugular foramen
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What is the name and number of the eleventh cranial nerve?
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XI Accessory
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What are the functions of the eleventh cranial nerve?
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Somatic motor function: Cranial root - Travels with CN X fibers to the pharynx. Spinal root — Innervates the trapezius and sternocleidomastoid.
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What opening in the skull transmits the eleventh cranial nerve?
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Jugular foramen
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What is the name and number of the twelfth cranial nerve?
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Hypoglossal
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What are the functions of the twelfth cranial nerve?
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Somatic motor function: Innervates intrinsic and extrinsic tongue muscles.
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What opening in the skull transmits the twelfth cranial nerve?
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Hypoglossal canal
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What are the two functions of the spinal cord?
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Pathway for sensory and motor impulses Spinal reflexes
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What is the general shape of the spinal cord in cross-section?
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Oval (AP compression)
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What depressions lie on the anterior and posterior surface of the spinal cord?
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Posterior median sulcus Anterior median sulcus
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Where does the spinal cord begin and end in an adult?
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In an adult the spinal cord extends from the foramen magnum to the first lumbar vertebra (L1). Although the spinal cord stops at L1, the lower portions are named for lower segments of the spinal column. This is so because the spinal cord extends the full length of the vertebral canal at birth. The spine, however, grows more than the spinal cord leaving the cord shorter.
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List the regions of the spinal cord.
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Cervical region Thoracic region Lumbar region Sacral region Coccygeal region
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What is the cauda equina?
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Spinal nerves extend from the end of the spinal cord to the end of the vertebral canal. A pair of them exits the canal at each of the lower levels. This collection of nerves resembles a horse's tail and thus is called the cauda equina.
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How many pairs of spinal nerves are there?
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31
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List the regions of the spinal cord and the spinal nerves associated with each region.
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Cervical region: C1-C8 Thoracic region: T1-T12 Lumbar region: L1-L5 Sacral region: S1-S5 Coccygeal region: Co
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From superficial to deep beginning with a vertebra, list the structures and spaces surrounding the spinal cord.
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Vertebra Epidural space Dura mater Subdural space Arachnoid Subarachnoid space Pia mater
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How does the dura mater within the vertebral canal different from the dura within the cranial cavity?
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It consists of one layer rather than two.
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What portion of the spinal cord is composed of dendrites and cell bodies of neurons and glial cells and unmyelinated axons?
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Gray matter
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What portion of the spinal cord is composed of myelinated axons?
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White matter
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Within the spinal cord where is gray matter located and how is it shaped?
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Centrally H-shaped or butterfly-shaped
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Within the spinal cord what are the anterior masses of gray matter that contain the cell bodies of somatic motor neurons?
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Anterior horns
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Within the spinal cord from T1-L2 what structures contain the cell bodies of autonomic motor neurons?
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Lateral horns
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Within the spinal cord what are the posterior masses of gray matter that contain the axons of sensory neurons and the cell bodies of interneurons?
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Posterior horns
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What horizontal bar of gray matter surrounds the central canal within the spinal cord?
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Gray commissure
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One of the characteristics of the phylum chordata is a dorsal-hollow nerve cord. This nerve chord is the spinal cord. Its hollowness is created by what structure?
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The central canal
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What fills the central canal of the spinal cord?
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Cerebrospinal fluid
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Within the regions of the spinal cord's gray matter, what are the various functional groups of neuron cell bodies?
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Nuclei
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Where does the white matter of the spinal cord lie in relation to the gray matter?
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External
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The white matter of the spinal cord is partitioned into three regions. What each called?
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Posterior funiculus Lateral funiculus Anterior funiculus
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Anteriorly and posteriorly what are the small attachments of a spinal nerve to the spinal cord?
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Rootlets
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The numerous small attachments of a spinal nerve to the spinal cord converge to form what structures?
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Anterior (ventral) root Posterior (dorsal) root
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The cell bodies of sensory neurons associated with the spinal cord are found in what structures?
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Posterior root ganglion
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The cell bodies of motor neurons within the spinal cord are found in what structures?
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Anterior horn
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Spinal nerves are formed by the convergence of what structures within what structure?
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Anterior and posterior roots within the intervertebral foramen
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What are the two main branches of a spinal nerve?
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Posterior (dorsal) ramus Anterior (ventral) ramus
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What branches of a spinal nerve are associated with the autonomic nervous system?
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Rami communicantes (communicating rami)
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What is a specific segment of skin supplied by a single spinal nerve?
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A dermatome
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What is a network of interweaving anterior rami of spinal nerves?
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Nerve plexuses
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The anterior rami of T1-T11 travel in intercostals spaces. What are these nerves called?
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Intercostal nerves
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What term is used to refer to T12 because it lies below the ribs rather than between them?
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Subcostal nerve
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In general, what do intercostals nerves innervate?
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Intercostal muscles Skin of the anterior and lateral thoracic wall Cervical Plexuses
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The cervical plexus arises from what spinal nerves?
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C1-C4
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Where is the cervical plexus located?
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Deep on the lateral side of the neck
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What regions of the body does the cervical plexus innervate?
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Anterior neck muscles Skin of the neck and portions of the head and shoulders Diaphragm
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What branch of the cervical plexus innervates the diaphragm?
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Phrenic nerve
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The brachial plexus arises from what spinal nerves?
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C5- T1
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Where is the brachial plexus located?
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Lateral neck & axilla
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What regions of the body does the brachial plexus innervate?
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Pectoral girdle and upper extremity
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List the five nerves that innervate the upper extremity.
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Axillary nerve Median nerve Musculocutaneous nerve Radial nerve Ulnar nerve
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What is the motor innervation of the axillary nerve?
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Deltoid Teres minor
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What is the cutaneous innervation of the axillary nerve?
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Superolateral portion of the arm
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What is the motor innervation of the median nerve?
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Anterior forearm muscles Thenar muscles Two lateral lumbricals
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What is the cutaneous innervation of the median nerve?
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Palmar side of the lateral 3 1/2 fingers and the lateral one-half of the ring finger and from the dorsal tips of the same fingers
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Carpal tunnel syndrome results in nocturnal hand paresthesia (a sensation of pricking, tingling, or creeping on the skin that has no objective cause) and pain, and sometimes sensory loss and wasting in the hand. The lateral palmar side of the hand and the thenar group are affected. What nerve is involved?
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Median nerve
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What is the motor innervation of the musculocutaneous nerve?
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Anterior muscles of the brachium
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What is the cutaneous innervation of the musculocutaneous nerve?
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Lateral surface of the forearm
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What is the motor innervation of the radial nerve?
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Posterior arm muscles Posterior forearm muscles
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What is the cutaneous innervation of the radial nerve?
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Posterior arm and forearm surface and the dorsolateral side of the hand
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What is the motor innervation of the ulnar nerve?
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Some of the anterior forearm muscles Intrinsic muscles of the hand (hypothenar muscles, palmar and dorsal interossei, and the medial two lumbricals
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What is the cutaneous innervation of the ulnar nerve?
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Dorsal and palmar aspects of the medial 1 1/2 fingers
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The lumbar plexus arises from the anterior rami of what spinal nerves?
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L1-L4
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What is the main nerve of the posterior division of the lumbar plexus?
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Femoral nerve
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What is the motor innervation of the femoral nerve?
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Anterior thigh muscles
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What is the cutaneous innervation of the femoral nerve?
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Anterior and inferomedial thigh Medial aspect of the leg
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What is the main nerve of the anterior division of the lumbar plexus?
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Obturator nerve
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What is the motor innervation of the obturator nerve?
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Medial thigh muscles
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What is the cutaneous innervation of the obturator nerve?
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Superomedial skin of the thigh
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What other regions of the body do small branches of the lumbar plexus innervate?
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Abdominal wall The scrotum and the labia Interior portions of the abdominal muscles Sacral Plexus
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The anterior rami of what spinal nerves form the sacral plexus?
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L4-S4
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Nerves emerging from the sacral plexus innervate what portions of the body?
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Gluteal region Pelvis Perineum Posterior thigh Almost all of the leg and foot
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What are the two main divisions of the sacral plexus?
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Anterior Posterior
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Nerves of the sacral plexus arising from the anterior division tend to innervate what muscles?
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Muscles that flex (or plantar flex) parts of the lower limb
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Nerves of the sacral plexus arising from the posterior division tend to innervate what muscles?
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Muscles that extends (or dorsiflex) part of the lower limb
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What is the largest and longest nerve in the body? It arises from the sacral plexus.
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Sciatic nerve
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What nerve is formed from the anterior divisions of the sciatic nerve?
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Tibial nerve
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What division of what nerve innervates the hamstrings?
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Tibial division of the sciatic nerve
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Within the leg what nerve innervates the plantar flexors of the foot and the flexors of the toes?
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Tibial nerve
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What is the cutaneous innervation of the tibial nerve?
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Plantar surface of the foot
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What nerve is formed from the posterior division of the sciatic nerve?
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Common fibular nerve
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What division of what nerve innervates the short head of the biceps femoris?
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Common fibular division of the sciatic nerve
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What are the two main divisions of the common fibular nerve?
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Deep fibular nerve Superficial fibular nerve
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What is the motor innervation of the deep fibular nerve?
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Anterior leg muscles Muscles of the dorsum of the foot
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What is the cutaneous innervation of the deep fibular nerve?
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Skin between the first and second toes on the dorsum of the foot
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What is the motor innervation of the superficial fibular nerve?
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Muscles of the lateral compartment
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What is the cutaneous innervation of the superficial fibular nerve?
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Anteroinferior part of the leg Most of the dorsum of the foot
