Peripheral Nervous System I- Spinal Nerves PDF

Peripheral Nervous System: Spinal Nerves Course Objectives Nervous: Describe how the body communicates with itself by identifying anatomical structures and tracing pathways of the nervous system in order to aid in medical diagnoses when these systems are...

Peripheral Nervous System: Spinal Nerves Course Objectives Nervous: Describe how the body communicates with itself by identifying anatomical structures and tracing pathways of the nervous system in order to aid in medical diagnoses when these systems are compromised.  Lecture Learning Objectives 1. Describe the differences between posterior and 6. Draw out the brachial plexus (roots, trunks, anterior roots AND rami, identifying what they divisions, cords, peripheral nerves) in order to innervate a. Identify each component 2. Visually identify the gross anatomical structures b. Recall the spinal nerve contributions for the of spinal nerves and roots brachial plexus trunks and nerves c. Identify their innervation (cutaneous and motor) 3. Explain the 4 functional categorizations of spinal nerves, focusing on the type of 7. Take a deep breath information they carry and associated category 8. List the branches of the lumbar and sacral of neuron plexuses and recognize their cutaneous and 4. Link dermatomes to associated spinal nerve motor innervation segment (CN, cervical, thoracic, lumbar, sacral, 9. Define myotatic reflexes and explain their coccygeal) and describe the embryological clinical use process that produces this pattern 5. For the cervical plexus 10. Recognize where various regions of the spinal cord can be tested using myotatic reflexes a. List the nerves that comprise it and what they innervate b. Visually identify the branches indicated in the manual Spinal Nerve Intro  LO 1 Introduction: Spinal Nerves and Nerve Roots Spinal nerves arise from the spinal cord as rootlets Roots- converged rootlets Anterior (ventral) root Motor fibers to effector organs Nerve cell bodies in the anterior horn Posterior (dorsal ) root Sensory fibers extend from sensory endings and centrally to posterior horn of spinal cord Cell bodies in posterior/dorsal root ganglia Clinically Oriented Anatomy, Moore at el., 2018  LO 1 Introduction: Spinal Nerves and Nerve Roots Spinal nerve Convergence of anterior and posterior nerve roots Divides into posterior and anterior rami with mixed motor and sensory fibers Motor or sensory nerves are named from the majority of fiber types within Gray’s Basic Anatomy, Drake et al., 2018  LO 2 Gross Anatomy: Spinal Nerves and Nerve Roots All 1. Anterior rootlets 2 4 2. Posterior rootlets 5 3. Anterior root 1 4. Posterior root 5. Posterior root ganglion 3 6 a 6. Spinal nerve b a) Dorsal ramus (rami) b) Ventral ramus  LO 1 Introduction: Rami Posterior rami of spinal nerves Supply joints of vertebral column, epaxial muscles, and overlying skin Do not separate to form nerve plexuses Segmental nerve innervation/distribution Anterior rami of spinal nerves Supply remaining area: skin, hypaxial muscles Trunk- nerves remain separate Limbs- nerves form somatic nerve plexuses Peripheral nerve innervation/ distribution Clinically Oriented Anatomy, Moore at el., 2018  LO 3 Functional Categorization of Spinal Nerves Somatic motor Impulses to voluntary skeletal muscle from CNS Somatic motor fibers are processes of ______________ neurons Visceral motor Transmits impulses to involuntary smooth muscle and glandular tissue Synapse in ganglia, presynaptic and post synaptic fibers Clinically Oriented Anatomy, Moore at el., 2018  LO 3 Functional Categorization of Spinal Nerves Somatic (general) sensory Sensation from the body to CNS Exteroceptive- pain, temperature, touch and pressure from skin Proprioceptive- subconscious, information about position and tension in muscles and tendons Somatic sensory fibers are processes of _______________ neurons Visceral sensory Transmit pain or subconscious visceral reflex sensation from hollow organs and blood vessels to CNS Ex., distension, blood, gas, blood pressure levels Clinically Oriented Anatomy, Moore at el., 2018 Dermatomes and Myotomes LO 4 Segment of skin or muscle(s) supplied by a single spinal nerve Can indicate potential damage to one or more spinal nerves Experience referred visceral pain- pain in an organ is referred to a segment of the dermatome E.x., appendix and referred pain to T10 dermatome Area of Innervation/Area Tested Spinal Nerves/Nerve Damage Face and scalp CN V- Trigeminal nerve Neck, shoulders/superior thorax, Cervical majority of upper limb Middle and inferior thorax, medial Thoracic KenHub arm and forearm, abdomen Pelvis, gluteal region, lower limb Lumbar, sacral, coccygeal Gray’s Basic Anatomy, Drake et al., 2018  Development of the Dermatomes and Myotome Patterns LO 4 Somites from paraxial mesoderm form dermamyotome Axons from future spinal nerves enter dermamyotome; are pulled along during migration of future muscles and skin Segmental distribution of dermatomes and myotomes results from this migration Gray’s Basic Anatomy, Drake et al., 2018 Nerve Plexuses  LO 4 Nerve Plexuses (braid) LO 5-8 Network of interweaving anterior rami of spinal nerves Anterior rami of spinal nerves Supply hypaxial muscles and skin (except back) In trunk rami remain separate Intercostal nerves Limbs- form somatic nerve plexuses Cervical plexus - C1-C5 Brachial plexus- C5- T1 Lumbar plexus - L1- L4 Sacral plexus- L4- S4 Gray’s Basic Anatomy, Drake et al., 2018  Clinical Connection What is the benefit of having a plexus of nerves? Organized so axons from each anterior ramus extend to body structures through several different branches Each terminal branch of the plexus carries axons from several different spinal nerves  LO 5 Cervical Plexus Irregular series of nerve loops CN XI and their branches CN XII C1 Anterior rami of C1- C5 C2 C3 Somatic motor branches (red in image→) C4 Ansa cervicalis n.- (C1 -C4) C5 Geniohyoid, infrahyoid muscles Why is the geniohyoid muscle part of this group? Phrenic n. - (C3 - C5) Diaphragm C3, C4, C5 keeps the diaphragm alive!  LO 9 Ventral Axial Muscles- Hypaxial Division a. Cervical myotomes form muscles of the neck Scalenes Prevertebral Infrahyoid muscles Geniohyoid b. Thoracic myotomes form Epaxial anterolateral axial muscles Lateral and ventral flexors of Hypaxial the vertebral column c. Lumbar myotomes Quadratus lumborum d. Sacrococcygeal myotome Pelvic diaphragm  LO 5 Cervical Plexus CN XI 1 CN XII C1 Cutaneous (somatic sensory) branches C2 2 1. Greater auricular n. C3 Skin on ear 3 2. Lesser occipital n. C4 4 Skin of scalp superior and C5 posterior to ear 3. Transverse cervical n. Skin on anterior part of neck 4. Supraclavicular n. Skin on superior part of chest and shoulder Gary Loves Track Stars  LO 6 Brachial Plexus Cutaneous (somatic sensory) and motor innervation to pectoral girdle and upper limb Spinal nerves C5, C6, C7, C8, T1 Traverse under clavicle, over first rib, through axilla  LO 6a,b Brachial Plexus Anterior rami/roots Trunk Superior (C5-C6) Middle (C7) Inferior (C8-T1) Divisions Anterior (anterior upper limb) Posterior (posterior upper limb) Cords (named in reference to axillary artery) Posterior Lateral Medial Peripheral nerves Musculocutaneous n. (C5-C7) Median n. (C5-T1) Ulnar n. (C8-T1) Axillary n. (C5-C7) Radial n. (C5-T1) Clinically Oriented Anatomy, Moore at el., 2018  LO 6a,b Anterior rami Brachial Plexus Superior trunk Middle trunk C5 Inferior trunk C6 Anterior division C7 Posterior division C8 Lateral cord T1 Posterior cord Medial cord Terminal branches Musculocutaneous Median Ulnar Axillary Radial  LO 6c Brachial Plexus Peripheral Nerves 1. Axillary n. Through axilla posterior to surgical neck of humerus 1 Motor: deltoid and teres minor 2 4 Sensory: Skin over deltoid 5 2. Musculocutaneous n. 3 Motor: anterior arm muscles What are these? Sensory: Lateral forearm 3. Radial n. “Runs away” Motor: posterior arm and forearm muscles What do these muscles do as a group? Sensory: Skin over posterior arm, forearm, and hand  LO 6c Brachial Plexus Peripheral Nerves 3 4. Median n. Travels along midline of upper limb Motor: most of anterior forearm, thenar muscles, and lumbricals for digits 2 and 3 What do these muscles do as a compartment? 4 Sensory: Medial skin on medial wrist, hand, and 5 digits 2, 3, and ¼ of 4 5. Ulnar n. “Funny bone” Motor: flexor carpi ulnaris, medial ½ of flexor digitorum profundus, all other hand muscles Sensory: Anterior and posterior aspect of medial wrist, hand, digit 5 and ½ of digit 4  Brachial Plexus Peripheral LO 6c Nerves 1. Axillary n. Motor: deltoid and teres minor Sensory: over deltoid 2. Musculocutaneous n. Anterior Motor: anterior arm muscles Sensory: Lateral forearm 3. Median n. Motor: anterior forearm and thenar muscles Sensory: Lateral palmar surface of hand 4. Ulnar n. Motor: some anterior forearm muscles most hand muscles Sensory: Medial hand Posterior 5. Radial n. Motor: posterior arm and forearm muscles Sensory: Posterior arm, forearm, and hand C5 C6 C7  LO 7 Lumbosacral Plexus Anterior rami of L1-S4 Located in posterior abdominal wall deep to the psoas muscle Divided into an anterior and posterior division  LO 8 A C Lumbar Plexus- L1 Anterior Division B L2 L1-L4 L3 Sensory and motor innervation to inferior abdomen and pelvis L4 A. Iliohypogastric n. L5 B. Ilioinguinal n. 1 C. Genitofemoral n. 2 Genital branch Femoral branch 3 Sensory and motor to lower limb 1. Lateral femoral cutaneous n. 2. Femoral nerve n. 3. Obturator nerve n.  LO 8 Lumbar Plexus Peripheral Nerves Femoral n. (L2-L4) Motor: anterior thigh (knee extensors, hip flexors) Sensory: Anteromedial thigh, leg, and foot Obturator n. (L2-L4) Motor: medial thigh muscles (adductors of thigh) Sensory: medial thigh Femoral nerve cutaneous Obturator nerve cutaneous  Sacral Plexus- LO 8 Posterior Division Anterior rami of L1-S4 5 nerves that innervate gluteal region, pelvis, perineum, posterior thigh, all leg 4 Motor and sensory to gluteal region and perineum 1. Superior gluteal n. 2. Inferior gluteal n. 3. Nerve to piriformis B A Muscles of the posterior thigh and all leg 4. Sciatic n. (L4- S3) A. Tibial n. B. Common fibular n. 5. Posterior femoral cutaneous n.  LO 8 Branches of Posterior Division Posterior femoral cutaneous n. Sensory only Sciatic nerve Sciatic n. Motor: Muscles of posterior thigh (hip Sciatic nerve extensors, knee flexors) Sensory: Lateral and posterior leg, foot Sciatic nerve  LO 8 Sacral Plexus Branches of Posterior Division Tibial n. Motor: Posterior leg m. (plantar flex foot, flex knee) Plantar foot m.  LO 8 Sacral Plexus Branches of Posterior Division Common fibular (peroneal) n. Deep fibular n. Superficial fibular n. Motor: Anterior and lateral leg muscles (dorsiflex foot, extend toes, evert foot)  LO 8 Sacral Plexus Nerve Injury Gluteal nerves- poorly placed intramuscular injection in gluteal region Sciatic nerve- herniated intervertebral disc Sciatica- extreme pain down posterior leg  LO 9 Reflexes Rapid, automatic, involuntary reaction of muscles or glands to a stimulus Survival mechanism that allows for quick response without waiting for the brain to process the information Clinically Oriented Anatomy, Moore at el., 2018  LO 9 Reflexes Clinical use Myotatic reflex: movement after a muscle stretch is produced by tapping a tendon 1. Stimulus activates sensory receptor 2. Nerve impulse travels through sensory neuron to CNS 3. Sensory neuron synapses directly on motor neuron in spinal cord’s anterior horn 4. Motor neuron transmits nerve impulse to effector organ 5. Effector organ responds  LO 10 Reflexes Cervical spinal nerves Biceps reflex: Biceps brachii Triceps reflex: Triceps brachii Thoracic spinal nerves Abdominal reflex: Anterolateral abdominal wall muscles Lumbosacral spinal nerves Patellar reflex: Patellar ligament Ankle reflex (Achilles): Calcaneal tendon Plantar reflex: plantar flexors