1. 1 Nervous System Subdivisions

2. 2 11.6: Peripheral Nervous System Cranial nerves arising from the brain Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera Spinal nerves arising from the spinal cord Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera

3. 3 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)

4. 4 Nerve Fiber Classification General somatic efferent (GSE) fibers Carry motor impulses from CNS to skeletal muscles Stimulate the muscles to contract General visceral efferent (GVE) fibers Carry motor impulses away from CNS to smooth muscles and glands General somatic afferent (GSA) fibers Carry sensory impulses to CNS from skin and skeletal muscles General visceral afferent (GVA) fibers Carry sensory impulses to CNS from blood vessels and internal organs

5. 5 Nerve Fiber Classification Special somatic efferent (SSE) fibers Carry motor impulses from brain to muscles used in chewing, swallowing, speaking and forming facial expressions Special visceral afferent (SVA) fibers Carry sensory impulses to brain from olfactory and taste receptors Special somatic afferent (SSA) fibers Carry sensory impulses to brain from receptors of sight, hearing and equilibrium

6. 6 Cranial Nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Olfactory bulb Hypoglossal (XII) Optic tract Olfactory tract Olfactory (I) Optic (II) Oculomotor (III) Abducens (VI) Facial (VII) Glossopharyngeal (IX) Accessory (XI) Trochlear (IV) Trigeminal (V) Vestibulocochlear (VIII) Vagus (X)

8. 8 Functions of Cranial Nerves

9. 9 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) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cauda equina C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 L1 L2 L3 L4 L5 S2 S3 S4 S1 S5 Co Posterior view Cervical nerves Thoracic nerves Lumbar nerves Sacral nerves Coccygeal nerve

10. 10 Spinal Nerves Dorsal root (aka posterior root) Sensory root Axons of sensory neurons are in the dorsal root ganglion Dorsal root ganglion Aka DRG Cell bodies of sensory neurons whose axons conduct impulses inward from peripheral body parts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral horn Ventral root(a) (b) Dorsal root Spinal nerve Dorsal root ganglion Posterior median sulcus Posterior horn Anterior horn Central canal Anterior median fissure Dorsal branch of spinal nerve Ventral branch of spinal nerve Visceral branch of spinal nerve Paravertebral ganglion Ventral branch of spinal nerve (ventral ramus) Dorsal branch of spinal nerve (dorsal ramus) Paravertebral ganglion Visceral branch of spinal nerve Ventral root

11. 11 Spinal Nerves Ventral root (aka anterior root) Motor root Axons of motor neurons whose cell bodies are in the spinal cord in the gray matter Supplies nerves to muscles and skin on the front & sides of the trunk & limbs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral horn Ventral root(a) (b) Dorsal root Spinal nerve Dorsal root ganglion Posterior median sulcus Posterior horn Anterior horn Central canal Anterior median fissure Dorsal branch of spinal nerve Ventral branch of spinal nerve Visceral branch of spinal nerve Paravertebral ganglion Ventral branch of spinal nerve (ventral ramus) Dorsal branch of spinal nerve (dorsal ramus) Paravertebral ganglion Visceral branch of spinal nerve Ventral root

12. 12 Spinal Nerves Spinal nerve Union of ventral root and dorsal roots Hence we now have a “mixed” nerve A posterior branch of a spinal nerve supplies the muscles and skin of the back Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral horn Ventral root(a) (b) Dorsal root Spinal nerve Dorsal root ganglion Posterior median sulcus Posterior horn Anterior horn Central canal Anterior median fissure Dorsal branch of spinal nerve Ventral branch of spinal nerve Visceral branch of spinal nerve Paravertebral ganglion Ventral branch of spinal nerve (ventral ramus) Dorsal branch of spinal nerve (dorsal ramus) Paravertebral ganglion Visceral branch of spinal nerve Ventral root

13. 13 Plexuses C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T8 T9 T10 T11 T12 L1 L2 L3 L4 L5 S2 S3 S4 S5 Co Posterior view Cervical plexus (C1–C4) Lumbosacral plexus (T12–S5) Sciatic nerve Brachial plexus (C5–T1) Obturator nerve Phrenic nerve Ulnar nerve Median nerve Radial nerve Axillary nerve T7 S1 Cauda equina Musculocutaneous nerve Femoral nerve Intercostal nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14. 14 Nerve Plexuses Nerve plexus Complex networks formed by anterior branches (ventral rami) of spinal nerves The fibers of various spinal nerves are sorted and recombined There are three (3) nerve plexuses: (1) Cervical plexus Formed by anterior branches of C1-C4 spinal nerves Lies deep in the neck on either side. Fibers supply the muscles and skin of the neck

15. 15 Brachial Plexus (2) Brachial plexus Formed by anterior branches C5-T1 Lies deep within shoulders between the neck and axilliae There are five (5) branches: 1. Musculocutaneous nerve Supply muscles of anterior arms and skin of forearms 2. Ulnar and 3. Median nerves Supply muscles of forearms and hands Supply skin of hands 4. Radial nerve Supply posterior muscles of arms and skin of forearms and hands 5. Axillary nerve Supply muscles and skin of superior, lateral, and posterior arms Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Musculocutaneous n. Humerus Thoracodorsal n. Lower subscapular n. Suprascapular n. Lateral pectoral n. Medial pectoral n. Axillary n. Radial n. Radius Ulna Ulnar n. Median n. C5 C6 C7 C8 T1 (a) (b) Ventral rami: C5, C6, C7, C8, T1 Anterior divisions Posterior divisions Trunks: upper, middle, lower Dorsal scapular n. 78

16. 16 Lumbosacral Plexus (3) Lumbosacral plexus Formed by the anterior branches of L1-S5 roots Can be a lumbar (L1-L5) plexus and a sacral (S1-S5) plexus Extends from lumbar region into pelvic cavity Obturator nerve Supply motor impulses to adductors of thighs Femoral nerve Supply motor impulses to muscles of anterior thigh and sensory impulses from skin of thighs and legs Sciatic nerve Supply muscles and skin of thighs, legs and feet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sciatic n. Saphenous n. Femoral n. Obturator n. Tibial n. Pudendal n. (b)(c)(a) Femoral n. Obturator n. Pudendal n. Sciatic n. L1 L2 L3 L4 L5 S1 S2 S3 S4 S5 Ventral rami Anterior divisions Posterior divisions Lateral femoral cutaneous n. Superior gluteal n. Inferior gluteal n. Superior gluteal n. Inferior gluteal n. Sacral plexus Common fibular (peroneal) n. Posterior cutaneous n. Common fibular (peroneal) n. Tibial n.

17. 17 11.7: Autonomic Nervous System Functions without conscious effort Controls visceral activities Regulates smooth muscle, cardiac muscle, and glands Efferent fibers typically lead to ganglia outside of the CNS Two autonomic divisions regulate: Sympathetic division (speeds up) Prepares body for ‘fight or flight’ situations Parasympathetic division (slows down) Prepares body for ‘resting and digesting’ activities