Major Plexuses and Peripheral Nervous System Flashcards Preview

DPT 736 Neuroanatomy > Major Plexuses and Peripheral Nervous System > Flashcards

Flashcards in Major Plexuses and Peripheral Nervous System Deck (32)
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Peripheral Nervous System

-consists of cranial nerves and spinal nerves, which link CNS to peripheral tissues
-neurons contributing to peripheral nerves are partly contained in CNS
-12 cranial
-31 spinal
-p. 325 table 8.1


Spinal Nerves

-spinal nerve is approximately 1 cm long
-shortly after exiting the intervertebral foramen, the spinal nerve divides into anterior and posterior rami
-roots combine to make spinal nerve then make rami



-posterior rami: supplies erector spinae muscle and the overlying skin of trunk
-anterior rami: supplies muscle and skin of side and front of trunk as well as muscles of limbs-cervical, brachia, and lumbosacral plexi are all derived from anterior rami


Cervical Plexus C1-C4

-C3, C4, C5 combine to make phrenic nerve
-supplies diaphragm
-lesion above or at C3 unable to breathe on own
-lesion at C4/C5 may be able to breathe on own without ventilators for brief periods of time



-CAD=cervical acceleration and deceleration aka whiplash
-thoracic outlet syndrome: compression --> altered signaling up and down pathway impingement of brachial plexus


Cervical Parts of Sympathetic Trunk

-superior cervical ganglion
-middle cervical ganglion
-inferior cervical ganglion
-look up function


Brachial Plexus

-other impingements of brachial plexus: pec minor or first rib
-5 roots: anterior rami of C5-T1
-3 trunks
-6 divisions
-3 cords
-4 terminal nerves: MMRU


Brachial Plexus: Nerve Root Branches

-dorsoscapular is branch of C5 nerve root: supplies rhomboids and levator scapulae
-long thoracic is branch of C5, C6, C7 nerve roots: supplies serratus anterior


Brachial Plexus: Trunk Branches

-suprascapular is branch of superior trunk: supplies supraspinatus and infraspinatus


Brachial Plexus: Branches of Cords

-branches of medial cords...
-median pectoral comes from C8-T1 and supplies pec major and minor
-medial brachial cutaneous nerve comes from T1
-median antebrachial cutaneous nerve comes from C8-T1
-ulnar nerve comes from C7-T1
-lateral cord branches...
-lateral pectoral nerve supplies pec major and comes from C5-C7
-musculocutaneous nerve innervates biceps, coracobrachialis, and brachialis
-branches of posterior cord...
-STAR or ARTS pneumonic
-upper subscapular nerve C7, C8 supplies subscapularis
-lower subscapular nerve supplies teres major C5, C6
-thoracodorsal nerve supplies latissimus dorsi C6-C8
-axillary supplies teres minor and deltoid and does sensation to shoulder C5, C6
-radial nerve supplies triceps, brachioradialis, extensor carpi radialis ms, extensor and abductor muscles of thumb C5, C6


Radial Nerve

-C6, C7**, C8
-innervates triceps, brachioradialis, extensor carpi radialis, extensor and abductor muscles of thumb
-motor function


Median Nerve

-carpal tunnel CTS
-innervates pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis
-motor function


Ulnar Nerve

-cubital fossa
-innervates flexor carpi ulnaris, flexor digitorum profundus, interosseus muscle, lumbricals, flexor pollicis brevis
-motor function


Axillary Nerve

-C5 and C6
-innervates deltoid, teres minor
-motor function


Musculocutaneous Nerve

-innervates BBC: biceps, brachialis, coracobrachialis
-motor function


Three Nerves Acting on Thumb

-radial nerve: thumb abduction in plane of thumb
-ulnar nerve: adduction
-median nerve: opposition, flexion (FPL and FPB), and thumb abduction perpendicular to palm
-RUM mnemonic


Intrinsic Muscles of Hand

-intrinsic: C8-T1, ulnar nerve supplies all except lumbricals I and II, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis superficial head
-thenar eminence: opponens pollicis, abductor pollicis brevis, flexor pollicis brevis, adductor pollicis
-hypothenar eminence: opponens digiti minimi, abductor digiti minimi, flexor digiti minimi, lumbricals, interossei


Lumbrosacral Plexus

-lumbar: anterior rami of spinal nerves L1-L3 and part of L4
-sacral plexus: anterior rami of S1-S4 and lumbosacral trunk
-femoral, obturator, sciatic, tibial, peroneal


Femoral Nerve

-L2-L4 dorsal deviations
-course: passes beneath inguinal ligament into thigh divides into anterior and posterior divisions
-muscles: sartorius, rectus femoris, vastus lateralis, vastus medialis, articularis genu, pectineus


Obturator Nerve

-L2, L3 some L4
-course: leaves pelvis through superior obturator foramen-has anterior and posterior branches
-muscles: gracilis, adductor brevis, adductor longus, adductor magnus with tibial division of sciatic nerve


Sciatic Nerve

-L4-S3 some branches from sacral plexus
-course: passes through greater sciatic foramen deep to piriformis in 90% of cases; travels in posterior thigh deep to hamstrings and enters popliteal fossa where it divides into common peroneal nerve and tibial nerve
-injury to this nerve would see weakness of knee flexors, hip extensors, all muscles below knee paralyzed, foot drop, absent achilles DTR
-tibial division of sciatic: adductor magnus, biceps femoris, semitendinosus, semimembranosus


Straight Leg Raise

-used to test source of back and leg pain (stretch spinal cord, cauda equina, and/or sciatic nerve
-position: patient supine or seated
-technique: keeping patients lower extremity straight, slowly lift leg until pain or discomfort is felt, decrease angle slightly and dorsiflex ankle
-interpretation: determine if pain is hamstring or sciatic nerve related


Tibial Nerve

-course: travel deep in leg with posterior tibial artery then travels posterior to medial malleolus into foot and divides into medial and lateral plantar nerves
-muscles: gastroc, soleus, plantaris, tibialis posterior, popliteus, FDL, FHL


Common Peroneal (Fibular) Nerve

-course: travels laterally from popliteal fossa towards fibula, courses around fibular neck and then divides into deep and superficial peroneal nerves
-muscle: biceps femoris short head


Superficial and Deep Peroneal (Fibular) Nerves

-superficial peroneal L5-S2, muscles: peroneus longus, peroneus brevis
-deep peroneal L4-S1 muscles: tibialis anterior, EHL, EDL, peroneus tertius


Lateral and Medial Plantar Nerves

-lateral plantar nerve S2-S3 adductor hallucis, FDM, ADM, quadratus plantae, lumbricals 2-4, dorsal interossei, plantar interossei
-medial plantar S2-S3 abductor hallucis, FHB, FDB, 1st lumbrical


Superficial vs. Deep Tendon Reflexes

-superficial: UMN, controlled by CNS, require stimulation of skin, presence of superficial reflex indicates UMN integrity, absences indicates UMN lesion
-deep: LMN, mediated by ventral horn cell of spinal cord, require stimulation of tendon, CNS inhibits DTRs



-biceps: C5, C6
-brachioradialis: C6
-triceps: C7
-patellar: L4
-achilles: S1
-monosynaptic stretch reflex: provides rapid local feedback for motor control; reflex arc begins with specialized receptors called muscle spindles which detect amount and rate of stretch in muscles, info transmitted to distal processes of sensory neurons then conveyed to dorsal roots; in roots sensory neuron form multiple synapses including some direct onto LMNs in anterior horn; LMNs project via ventral roots out into muscle causing contraction
-afferent sensory neurons also form synapses onto excitatory and inhibitory interneurons which synapse onto LMNs


Superficial Abdominal Reflex

-sharp edge of reflex hammer stroke each quadrant of abdomen looking to see if it moves toward that point
-absent = UMN lesion


Superficial Cremasteri Reflex

-sharp edge of reflex hammer stroke the inner side of upper thigh looking to see if scrotum pulls upward to cremaster muscle
-absent bilaterally = UMN, absent unilaterally = LMN lesion L1-L2