Endoneurium. Perineurium. Epineurium. Parasympathetic division (b) Figure Frontal lobe. Temporal lobe

Transcription

1 Peripheral Nervous System (PNS) The Nervous System Cranial and spinal Nerves All neural structures outside the brain and spinal cord Sensory receptors Peripheral and associated ganglia Motor neuron endings Constitutes a pathway between CNS and outlying structures 12 pairs of cranial 31 pairs of spinal Endoneurium Axon Myelin sheath Perineurium Central nervous system (CNS) Peripheral nervous system (PNS) Epineurium Sensory (afferent) division Motor (efferent) division Somatic nervous Autonomic nervous system system (ANS) Fascicle Blood vessels Sympathetic division Parasympathetic division (b) Figure 13.1 Figure 13.3b Cranial Nerves 12 pairs of Associated with the brain Do not decussate May continue in tracts that do Typically see ipsilateral functional deficits with brain injury Function may be sensory, motor, or both Most are at least partially mixed Each is identified by Number (I through XII) Name Frontal lobe Temporal lobe Infundibulum Facial (VII) Vestibulocochlear (VIII) Glossopharyngeal (IX) Vagus (X) Accessory (XI) Hypoglossal (XII) (a) Filaments of olfactory (I) Olfactory bulb Olfactory tract Optic (II) Optic chiasma Optic tract Oculomotor (III) Trochlear (IV) Trigeminal (V) Abducens (VI) Cerebellum Medulla oblongata Figure 13.5 (a) 1

2 1/17/2016 Cranial I VI Sensory function Motor function PS* fibers I Olfactory (smell) II Optic III Oculomotor (vision) IV Trochlear V Trigeminal (general sensation) VI Abducens Cranial VII XII VII Facial VIII Vestibulocochlear Sensory function Motor function MANY mnemonics to help you remember name, order, and function Google at your own risk A few possibilities PS* fibers (taste) (hearing and balance) Some IX Glossopharyngeal (taste) X Vagus (taste) XI Accessory XII Hypoglossal (b) Cranial Nerves *PS = parasympathetic Figure 13.5 (b) Loss of function casues ptosis, external strabismus ( down and out ) Trochlear Nerve Palsy 2

3 1/17/2016 Testing function Trigeminal neuralgia Loss of function causes internal strabismus Vestibulocochlear Nerve Test 3

4 1/17/2016 Accessory Nerve Testing Functions of the cranial Hypoglossal testing Spinal Nerves Cervical plexus Brachial plexus 31 pairs of mixed named according to their point of issue from the spinal cord 8 cervical (C1 ) 12 thoracic (T1 T12) 5 Lumbar (L1 ) 5 Sacral ( S5) 1 Coccygeal (C0) Cervical enlargement Intercostal Cervical C1 te: only 7 cervical vertebrae Thoracic T1 T12 Lumbar enlargement Lumbar plexus Sacral plexus Cauda equina Lumbar L1 Sacral S5 Coccygeal Co1 Figure

5 Spinal Nerve Organization Spinal connects to the spinal cord via two roots Ventral roots Contain motor (efferent) fibers from the ventral horn motor neurons Fibers innervate skeletal muscles Dorsal roots Contain sensory (afferent) fibers from sensory neurons in the dorsal root ganglia Conduct impulses from peripheral receptors Dorsal and ventral roots unite to form spinal Emerge from vertebral column via the intervertebral foramina Snack at 1AM Coccygeal (1) Afferent Dorsal root (sensory) Dorsal root ganglion Dorsal horn (interneurons) Somatic sensory neuron Visceral sensory neuron Visceral motor Spinal neuron Ventral horn Ventral root (motor neurons) Somatic (motor) motor neuron Interneurons receiving input from somatic sensory neurons Efferent Interneurons receiving input from visceral sensory neurons Spinal Nerve Organization Rami Each spinal branches into mixed rami Dorsal ramus Ventral ramus Rami communicantes branch off of ventral ramus Involved in ANS signaling pathways Meningeal branch Reenters the vertebral canal and innervates the meninges and blood vessels within Visceral motor (autonomic) neurons Somatic motor neurons Figure Dorsal root ganglion Dorsal ramus of spinal Ventral ramus of spinal Spinal Rami communicantes Sympathetic trunk ganglion Gray matter White matter Ventral root Dorsal root Dorsal and ventral rootlets of spinal Anterior view showing spinal cord, associated, and vertebrae. The dorsal and ventral roots arise medially as rootlets and join laterally to form the spinal. Figure 13.7 (a) 5

6 Spinal Nerve Organization Dorsal ramus Innervates Deep back muscles surface of trunk (skin and muscle) Ventral ramus Innervates Superficial back muscles Limbs Lateral and anterior surfaces of trunk (skin and muscle on side, chest, ribs, abdominal wall) Dorsal ramus Ventral ramus Spinal Rami communicantes Sympathetic trunk ganglion Intercostal Dorsal root ganglion Dorsal root Ventral root Branches of intercostal Lateral Anterior Sternum (b) Cross section of thorax showing the main roots and branches of a spinal. Figure 13.7 (b) Distribution of Spinal Nerves Dermatome Area of skin innervated by the branches of a single spinal All spinal except C 1 participate in dermatomes Most dermatomes overlap T2 L1 L2 L3 C4 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 S2 S3 L1 L2 C2 C3 L3 T2 L2 S2 C2 C3 C4 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 S2 S3 S4 S5 L1 L2 S2 T11 T12 L1 L3 L3 Anterior view (b) view Figure All ventral rami form interlacing networks 4 plexuses Cervical, brachial, lumbar, and sacral Fibers from the rami branch and become redistributed Each exiting the plexus has fibers from several spinal Advantage? Exception: ventral rami of T 2 T 12 Do not form a plexus Form intercostal Cervical plexus Brachial plexus Cervical enlargement Intercostal Lumbar enlargement Lumbar plexus Sacral plexus Cauda equina Cervical C 1 C 8 Thoracic T 1 T 12 Lumbar L 1 L 5 Sacral S 1 S 5 Coccygeal Co 1 Figure

7 Ventral rami Cervical plexus Formed by ventral rami of C 1 C 4 Innervates skin & muscles of the neck, ear, back of head, and shoulders Hypoglossal (XII) Lesser occipital Greater auricular Transverse cervical Ansa cervicalis Accessory (XI) Phrenic Supraclavicular Segmental branches Ventral rami: C 1 C 2 C 3 C 4 C 5 Figure 13.8 Phrenic Major motor and sensory of the diaphragm Critical for breathing Receives fibers from C 3 C 5 Therefore receives innervation from both the cervical plexus and the brachial plexus Brachial plexus Formed by ventral rami of C 4 T 1 Gives rise to the that innervate the upper limb Median Ulnar Axillary Radial Musculo Cords Lateral Medial Axillary Musculo Radial Median Ulnar Anterior Dorsal scapular Nerve to subclavius Suprascapular (a) Roots (rami C 5 T 1), trunks,, and cords Trunks Roots Roots (ventral rami): C 4 C 5 C 6 C 7 C 8 Upper Middle Lower Trunks T 1 Long thoracic Medial pectoral Lateral pectoral Upper subscapular Lower subscapular Thoracodorsal Medial of the arm and forearm Axillary Anterior Humerus Radial Musculo Ulna Radius Ulnar Median Radial (superficial branch) Dorsal branch of ulnar Superficial branch of ulnar Digital branch of ulnar Muscular branch Median Digital branch (c) The major of the upper limb Trunks Roots Figure 13.9 (a) Figure 13.9 (c) 7

8 Injuries Radial damage causes the fingers, wrist, or hand to be in the chronically flexed position Crutch paralysis caused when crutches are improperly adjusted Saturday night paralysis caused by falling asleep with the arm hanging over the armrest of a chair Honeymoon paralysis caused by someone else sleeping on and compressing the arm Injuries Radial damage causes the fingers, wrist, or hand to be in the chronically flexed position Radial is constantly pushed against the humerus, and cannot innervate extensor muscles Improves quickly with therapy Injuries Ulnar is the largest in the body that is not protected by muscle or bone Injury is common Funny bone Weakness in flexion of the hand at wrist, inability to cross fingers Claw hand at rest Injuries Carpal tunnel Caused when the median is compressed as it travels through the wrist Pain, numbness, tingling in the hand, forearm, and shoulder Caused by anything that applies pressure to the median Esp. cumulative trauma caused by repetitive motion If untreated may cause wasting on muscles at the base of the thumb Lumbar plexus Arises from L 1 L 5 (some T 12 ) Innervates thigh, abdominal wall, external genitalia, leg & foot Femoral Innervates quadriceps, skin of anterior thigh & medial surface of leg Functions in extending the knee; sensory function in skin on front and inner sides of thigh, shin, and arch of foot Obturator Passes through obturator foramen Innervates adductor muscles; sensory function in skin on medial aspect of thigh Ventral rami Iliohypogastric Ilioinguinal Genitofemoral Lateral femoral Obturator Ventral rami: Iliohypogastric L 1 Ilioinguinal Femoral L 2 Lateral femoral Obturator L 3 Anterior femoral L 4 Saphenous Femoral L 5 Lumbosacral trunk (a) Ventral rami and major branches of the lumbar plexus (b) Distribution of the major from the lumbar plexus to the lower limb Figure

9 Sacral plexus Arises from L 4 S 4 Serves the buttock, lower limb, pelvic structures & perineum Gives rise to sciatic Longest and thickest of the body Innervates Muscles of the leg and foot Skin on the leg and foot Superior gluteal Lumbosacral trunk Inferior gluteal Common fibular Tibial femoral Pudendal Sciatic Ventral rami Ventral rami: L 4 L 5 S 1 S 2 S 3 S 4 S 5 Co 1 Ventral rami and major branches of the sacral plexus Figure (a) Superior gluteal Inferior gluteal Pudendal Sciatic femoral Common fibular Tibial Sural (cut) Deep fibular Superficial fibular Plantar branches (b) Distribution of the major from the sacral plexus to the lower limb Figure (b) 9