section 5, chapter 11 cranial nerves and spinal nerves
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Transcript of section 5, chapter 11 cranial nerves and spinal nerves
section 5, chapter 11
Cranial and Spinal Nerves
ivyanatomy.com
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The PNS consists of
31 pairs of Spinal nerves arising from the spinal cord
Peripheral Nervous System
Sensory fibers relay information from receptors to CNS
Somatic (voluntary) fibers connecting to the skin and skeletal muscles
Autonomic fibers connecting to viscera (involuntary)
12 pairs of Cranial nerves arising from the brain
Structure of a Peripheral Nerve
Peripheral nerves consist of bundles of nerve fibers encased by connective tissue.
Connective Tissue Coverings1.Epineurium – outermost layer
2.Perineurium – Surrounds fasicles
3.Endoneurium – surrounds individual nerve fibers
Fasicle – organized bundle of nerve fibers.
Blood vessels pass through perineurium and epineurium. Capillaries within endoneurium provide oxygen and nutrients to the neurons.
Figure 11.24. Scanning electron micrograph of a peripheral
nerve. Nerve fibers are organized into bundles, called fascicles.
Structure of a Peripheral Nerve
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Nerve and Nerve Fiber Classification
• Sensory nerves - conduct impulses into brain or spinal cord
• Motor nerves - conduct impulses to muscles or glands
• Mixed (both sensory and motor) nerves• Contain both sensory nerve fibers and motor nerve fibers• Most nerves are mixed nerves• ALL spinal nerves are mixed nerves (except the first pair)
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Cranial Nerves (CN) I - IV
Olfactory nerves (CN I) transmit impulses associated with smell
Optic nerves (CN II) transmit impulses associated with vision
Oculomotor nerve (CN III) Motor impulses to muscles that move the eyes, the eyelids, iris, and the lens
Trochlear nerve (CN IV) Motor impulses to muscles that move the eyes (superior oblique)
Cranial Nerve V
Trigeminal nerve (CN V) - Motor to muscles of mastication (chewing)
3 BranchesOphthalmic branch – sensory around eyes
Maxillary branch – sensory of upper jaw & teeth
Mandibular branch – sensory of lower jaw & teeth
Cranial Nerves VI and VII
Abducens nerve (CN VI) - motor impulses to lateral rectus muscles of eye = eye movement
Facial nerve (CN VII) - sensory from taste receptors and motor to muscles of facial expression
Figure 11.27 the facial nerves are associated with taste receptors on the tongue and with
muscles of facial expression.
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Cranial Nerves VIII and IXVestibulocochlear nerve (CN VIII)
Vestibular branch - Sensory from equilibrium receptors of ear
Cochlear branch - Sensory from hearing receptors
Glossopharyngeal nerve (CN IX)Sensory of tongue - taste
Motor to salivary glands
Motor to pharynx - swallowing
Cranial Nerve X
• Vagus nerve (CN X) “Wandering”Mixed nerve
• Somatic motor to muscles of speech and swallowing
• Autonomic motor to viscera of thorax and abdomen
• Sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 11.28 the vagus nerves extend from medulla downward through thorax and abdomen to supply many organs
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Cranial Nerves XI and XII
Accessory nerve (CN XI)• Motor to muscles of soft palate, pharynx and larynx
•Motor to muscles of neck and back
Hypoglossal nerve (CN XII)• Motor to muscles of the tongue
Cranial NervesCranial Nerves
I. OlfactoryII. OpticIII. OculomotarIV. TrochlearV. TrigeminalVI. AbducensVII. FacialVIII.VestibulocochlearIX. GlossopharyngealX. VagusXI. AccessoryXII. Hypoglossal
I. OhII. Once III. One IV. Takes V. The VI. AnatomyVII. Final VIII.Very IX. Good X. Vacations XI. Are XII. Heavenly
Pneumonic Device for remembring the 12 pairs of cranial nerves
The 12 pairs of cranial nerves
Cranial NervesCranial Nerves
Spinal Nerves
• ALL are mixed nerves (except the first pair)
• 31 pairs of spinal nerves:
• 8 cervical nerves (C1 to C8)
• 12 thoracic nerves (T1 to T12)
• 5 lumbar nerves (L1 to L5)
• 5 sacral nerves (S1 to S5)
• 1 coccygeal nerve (Co or Cc)
Nerve Plexuses
A Nerve plexus is a complex network formed by anterior branches of spinal nerves• The fibers of various spinal nerves are sorted and recombined• There are three (3) nerve plexuses:
Cervical plexus• Formed by anterior branches of C1-C4 spinal nerves• Lies deep in the neck• Supply to muscles and skin of the neck• C3-C4-C5 nerve roots contribute to phrenic nerves bilaterally
Phrenic Nerves conduct motor impulses to the diaphragm
(C3,4, and 5 keep the diaphragm alive)
(2) Brachial plexusFormed by C5-T1 spinal nervesLies deep within shoulders
Branches include: 1. Radial Nerve • extensor muscles of forearm, wrist, and fingers• May be damaged with crutches
2. Ulnar Nerve • Intrinsic muscles of hand• Funny bone
3. Median Nerve • Flexor muscles of forearm, wrist, and fingers• Inflamed with carpal tunnel syndrome
Brachial Plexus
Figure 11.33 Nerves of the brachial plexusFigure 11.33 Nerves of the brachial plexus
Lumbosacral Plexus
• (3) Lumbosacral plexus• Formed by T12-S5
• Branches include: 1. Obturator nerve
• Supply motor impulses to adductors of thighs
2. Femoral nerve• Supply motor impulses to muscles of anterior thigh and sensory impulses from skin of thighs and legs
3. Sciatic nerve• Supply muscles and skin of thighs, legs and feet
Figure 11.34 Nerves of the lumbosacral plexus.
Figure 11.32. The ventral branches of spinal nerves give rise to three plexuses. In the thoracic region spinal nerves give rise to intercostal nerves.
The thoracic spinal nerves give rise to intercostal nerves
• Supply intercostal muscles
• Supply muscles of upper abdominal wall
• Receive sensory from skin of the thorax and abdomen
Thoracic Spinal Nerves
End of section 5, chapter 11