Peripheral Neuroanatomy.docx

Peripheral Neuroanatomy (ANAT 114-LEC 01) Dr. Hunter Cosgrove | [email protected] Lecture Credits: 3.0 Office Hours: M (9:20-11:00 & 12:00-2:00) Student Learning Outcomes: SLO 1: Spinal Nerves Discuss spinal nerves relative to their formation, branches, and relations to discs and IVF's Dis...

Peripheral Neuroanatomy (ANAT 114-LEC 01) Dr. Hunter Cosgrove | [email protected] Lecture Credits: 3.0 Office Hours: M (9:20-11:00 & 12:00-2:00) Student Learning Outcomes: SLO 1: Spinal Nerves Discuss spinal nerves relative to their formation, branches, and relations to discs and IVF's Discuss the specific sensory, motor, and reflex functions of the C5-T1, and L1-S2, and S2-4 spinal nerves SLO 2: Plexuses Discuss the significance of plexuses in the formation of peripheral nerves of the head/neck, upper and lower extremities.  Describe/illustrate the cervical, brachial, lumbar, and sacral plexuses, and identify the major peripheral nerve branches of each plexus SLO 3: Peripheral Nerves List the peripheral nerves which innervate the upper and lower extremities, and discuss their specific sensory, motor, and reflex functions. Identify common sites of potential entrapment/compression for each peripheral nerve and discuss their clinical consequences. SLO 4: Cranial Nerves Name the cranial nerves, identify the cranial foramen which each nerve traverses, and discuss the structures innervated. Discuss the specific functions of each nerve and the consequences of neural compromise. SLO 5: ANS Discuss the general structure and function of ANS, and the specific structure and functions of the sympathetic and parasympathetic divisions.  Trace the pathway from the CNS to the effector organ for any sympathetic or parasympathetic function indicating the origin, route and termination of the preganglionic neuron and post-ganglionic neuron. Discuss the clinical features of Horner's Syndrome Discuss the clinical features of Cauda Equina Syndrome Course Summary: DATE Midterm 1 X / 30 (25%) DATE Midterm 2 X / 30 (25%) DATE Final X / 60 (50%) Required Texts: PNS class notes (Canvas) Felton DL, O'Banion MK. Netter's Atlas of Neuroscience. 3rd ed. 2015 Recommended Texts: Warfel J. Extremities: Muscles and Motor Points, 6thed. 1993 Draw It To Know It, (online resource available via library site) Fitzgerald. Clinical Neuroanatomy and Neurosciences. 2016 (available Ebook via library website) Blumenfeld H. Neuroanatomy Through Clinical Cases. 2ned. 2010 Marieb EM. Human Anatomy & Physiology. 10th ed. 2015 Moore KL. Clinically Oriented Anatomy. 8th ed. 2017 Reference Texts: Strandring S. Gray’s Anatomy. 41th ed. 2015 Videos: Course Media Gallery Week 1: (4/4) Anatomical Position: FCM Anterior/Ventral: Seen from the front. Posterior/Dorsal: Seen from the back. Superior/Cephalad: Headward Inferior/Caudal: Tailward Medial: Toward midline of body OR center of a limb Lateral: Away from midline of body or limb Proximal: Closer to the trunk attachment Distal: Further from trunk attachment Body Movements: (relative to anatomical position) FCM Flexion: Closing of an angle/joint Extension: Opening of an angle/joint Abduction: Moving away from midline of body OR limb Adduction: Moving toward the midline of body OR limb Internal (Medial) Rotation: Rotating toward the front/midline of the body. External (Lateral) Rotation: Rotating away from the front/midline of body. Supination: Lateral rotation of the forearm to where the palms face forward Pronation: Medial rotation of the forearm to where the palms face away Inversion: Supination but specific to the foot/ankle Eversion: Pronation but specific to the foot/ankle ________ deviation: moving toward “_________” e.g. radial deviation. Lateral deviation Valgus: Distal portion of extremity moving laterally Varus: Distal portion of extremity moving medially. (4/6) What is the Peripheral Nervous System? Any nervous tissue not contained within the spinal cord or brain (cranial, spinal, & peripheral nerves—sensory (afferent) & motor (efferent) neurons The Somatic Nervous System: Comprised of motor neurons coming from the brain/spinal cord and going out to muscles for control & sensory neurons—specialized receptors sensitive to change in the environment (i.e., temperature, pain, various forms of touch, position sense) Sensory Receptors: (FCM) Hair Follicles; Meissner Corpuscle; Pacinian Corpuscle; Merkel Cell-Neurite Complex; Ruffini Corpuscle; C-fibre LTM; Mechano-Nociceptor; Polymodal nociceptor Central adaptation – when the brain stops carrying about a sensory signal (ex. you become desensitized to the smell of your room) Transmission to the CNS: *** Enters the spinal cord through the posterior & transmits up the cord to the thalamus found in the diencephalon. The thalamus acts as a major relay station sorting & directing info in & out of the brain. The thalamus makes sure that info goes to the corresponding part of the brain to be perceived & processed (general somatosensory is found in the parietal lobe, but more on that in the CNS) General Neuronal Anatomy: Dendrites receive; Cell body builds & recycles; Axons send—the axon hillock is where action potentials initiate from; axon terminals are where neurotransmitters release from Layers of a Nerve: (deep to superficial) Endoneurium wraps around individual neurons. Perineurium wraps around fascicles (bundles of neurons). Epineurium wraps around an entire nerve (bundles of fascicles). Is continuous with the dura mater of the spinal cord. Nerve Damage & Regeneration: Nerves are often damaged/thinned due to compression and/or traction. Initial damage to the distal axon is known as Wallerian degeneration. This causes the neuron to disintegrate. Following damage to the axon is swelling and release of substance from the cell body known as Chromatolysis (as it prepares regenerate the axon) Regeneration CAN occur in the PNS if: (1-4mm/day needed to save the nerve) The cell body is intact The Schwann cells are intact Regrowth occurs quick enough to reach the target tissue before it dies 1st Degree injury= Neuropraxia- leads to slowing (damages/thins the neurolemma—the outer region) 2nd Degree injury= Axonotmesis (damages/compresses the axon itself) Nerve Exits: Cervical nerves exit above the cervical vertebrae; thoraco-lumbar nerves exit below the same numbered vertebrae. Dermatomes: We’ve mapped general location of innervation—this is important in being a detective discovering what is the involved nerves in our patient’s presentation. A difference in dermatomes means you can be hypersensitive on one thumb or desensitized on the other. Levels of principle dermatomes: T4 (nipples); T7 (xiphoid process); T10 (umbilicus); S2, S3, S4 (perineum) Radiculopathy: Radiculopathy is a common presentation of symptoms related to a specific spinal nerve root The most common ways to affect a nerve root is compression either through a disc herniation or IVF stenosis (narrowing) among other possibilities. The most common disc herniations are posterior lateral which will often compromise 1 spinal nerve root. Due to the orientation/exiting of nerves: Cervical IVF and disc will affect the same nerve root e.g. C5 disc and C5-6 IVF will affect C6 nerve root Thoracic IVF and disc will affect the same nerve root e.g. T2 disc and T2-3 IVF will affect T2 Lumbar IVF will affect the level while discs will affect 1 level lower e.g. L3-4 IVF will affect L3, but an L3 disc will affect L4 Mackenzie protocol and disc pumping can heal the disc (4/11) LIC Rule Cervical disc herniations are very uncommon by age 30 because the nucleus pulposus disappears. Dermatome Descriptors: C5 – anterior shoulder C6 – lateral forearm thumb C7 – middle finger C8 – medial hand & forearm T1: medial arm T2-T12: following rib lines T4: nipple level T7: Xiphoid T10: umbilicus T12: inguinal ligament L1-3: anterior thigh L4: medial shin L5: lateral shin S1: lateral calf S2: medial calf S3-5: bull’s eye surrounding the perineum. (4/13) Brachial Plexus: (WE NEED TO BE ABLE TO DRAW THE BRACHIAL PLEXUS) The brachial plexus is comprised of the C5-T1 nerve roots; these roots mix to form various trunks, divisions, cords, and branches. C5-6 form the superior trunk. C7 remains alone for the middle. C8-T1 form the inferior trunk. The superior & middle trunks bifurcate into an anterior & posterior division while the inferior gives off a collateral to the posterior division. Divisions Cords: Cords are named for their orientation around the subclavian artery found between the clavicle & 1st rib. The posterior division become the posterior cord, while the two separate anterior divisions become the lateral and medial cords. Cords Branches: Each cord is responsible for 2 terminal branches. The lateral cord gives off the musculocutaneous nerve and ½ of the median nerve. The posterior cord gives off the axillary nerve and the radial nerve. The median cord gives off the ulnar nerve and the other ½ of the median nerve. Musculocutaneous Nerve: (Cutaneous = skin meaning sensory) Motor function to: Biceps Brachii=elbow flexion + supination Brachialis = elbow flexion Coracobrachialis=shoulder flexion Sensory to the lateral forearm via antebrachial cutaneous nerve (lateral antebrachial cutaneous nerve) Axillary Nerve: Motor: Deltoid: shoulder abduction; Teres Minor: external shoulder rotation Sensory: Over 2/3 of the shoulder Radial Nerve: Motor: Triceps (elbow extension); Finger extensors; wrist extensors; supinator Sensory: Posterior forearm, dorsum of hand, & first 3 & ½ digits Ulnar Nerve: Motor: (hypothenar muscles); medial two lumbricals; adductor pollicis; interossei of the hand; palmaris brevis; flexor carpi ulnaris Sensory: Ventral & dorsal medial hand including 5th & ½ of 4th digit Median Nerve: Motor: Flexor carpi radialis; flexor digitorum; abductor pollicis brevis; pronator quadratus + teres; flexor pollicis longus + brevis Sensory: anterior lateral hand digits 1-3 ½ of 4; tips of digits 1-3 ½ of 4 on dorsum of hand Thoracic Outlet Syndrome (Scalenes) Median Nerve: Carpal Tunnel v. Pronator Teres Syndrome Radial Nerve: Lover’s Palsy & Supinator Ulnar Nerve: Erb’s v. Klumpke’s Palsy (4/20) Thoracic Spinal Nerves: As all nerves do, thoracic nerves are comprised of an anterior ramus and a posterior ramus. The anterior ramus goes on to innervate: The skin (dermatomes) of the anterior trunk Intercostal muscles which follow along rib lines aiding in respiration The posterior ramus goes to innervate: The skin on the posterior trunk Deep muscles of the back Varicella/Herpes Zoster (Chicken Pox/Shingles): The thoracic spine (along with the trigeminal nerve CN V) are often the target of the Herpes Zoster virus. Active forms look like chicken pox, rash/blisters across our body. The virus often will lay dormant in the dorsal nerve root of the thoracic spine. Reactivation later in life is shingles which often presents with a singular band of blisters/lesions outlining a dermatomal pattern, indicating the nerve affected. Can also lead to post-herpetic neuralgia causing a hypersensitivity over that given area even if no visible signs of infection are active and present. Sympathetic Nervous System: (fight or flight) Sympathetic fibers mostly arise from T1-L2/3 It gives gas to those organs which help this and pumps the brakes on the organs which are not needed at the time. Sympathetic division: Blue: preganglionic neuron, releases Ach Red: postganglionic neuron, releases NE Parasympathetic Nervous System: (rest & digest) Derived from cranial nerves 3/7/9/10 & S2-4. Gives gas to the organs that perform this function & pumps the brakes on organs not needed at that time. Both sets of neurons utilize Ach in signaling. Somatomotor System: From the brain (1° motor cortex) to a muscle is only ever 2 neurons away These are known as upper motor neurons (UMN) and lower motor neurons (LMN) The UMN is found entirely within the CNS. The LMN extends from the spinal cord to form nerves to their target muscle. Action Potentials: Remember the ion concentrations: Na+, K+, Cl-, Ca2+* Ions want to follow their concentration gradient either in or out of the cell Action potentials begin at the axon hillock and travel down the axon Saltatory along a myelinated axon Upon reaching the axon terminal causes release of neurotransmitters to the next neuron or target organ The Neuromuscular Junction: (“don’t worry about this”) The LMN extends from the ventral gray horn (VGH) out to its muscle Remember our plexus, and how peripheral nerves can arise from any portion of R>T>D>C>B Long thoracic from roots C5-7 Musculocutaneous from Lateral cord When these nerves reach their target muscle they from another chemical synapse Utilizing Ach; Recreating an AP on the muscle surface; Leading to muscular contraction Agonist: Neurotransmitters Agonist: a compound that mimics the action of a neurotransmitter Direct-acting binds directly to & activates NT receptors (Nicotine – ACH) Indirect-acting releases or enhances the action of a NT (Neostigmine – ACH) Antagonist: Neurotransmitters Antagonist: a compound that blocks or inhibits the action of a neurotransmitter Direct-acting binds directly to & inactivates NT receptors (Atropine – ACH) Indirect-acting reduces the action of a NT (Curare – ACH) NMJ Disorders: (ALL LEAD TO MUSCLE WEAKNESS/PARALYSIS) Lambert-Eaton Syndrome (LEMS): Autoimmune + pre-synaptic Affects Ca2+ channels, which is required to release Ach (inhibits Ach release) Not enough ACh = no new action potential on the muscle. Improves with activity/repetitive use. Myasthenia Gravis (MG): Autoimmune + post-synaptic Anti-bodies attack/block Ach gates Na channels along the muscle cells Inhibits action potential recreation in the muscle. Leads to muscle weakness & Diplopia (2x vision) Worsens throughout the day due to finite amounts of Ach Botulism: (bacterial toxin) Not Autoimmune + pre-synaptic Will degrade the vesicle or block binding to the membrane. Inhibits release of Ach = no Ach = no muscle contraction Curare: (poison dart frog toxin) Not Autoimmune + post-synaptic Direct antagonist of Ach on the muscular surface No Ach = no Na influx = no muscle contraction MIDTERM REVIEW Identify the major locations involved in the sympathetic and parasympathetic nervous systems Know their effects on a given organ based on if it helps fight/flight Know the NT involved in the pre-/post-ganglionic junctions Know the organization (nerve roots or cranial nerves involved and if they are long or short) What constitutes the CNS vs the PNS? CNS: brain & spinal cord PNS: cranial, spinal & peripheral nerves (efferent & afferent) Know which sensation is distinguished by which touch receptor. Hair Follicle: light brushing/movement Meissner Corpuscle: dynamic deformation; skin motion, slipping Pacinian Corpuscle: vibration Ruffini Corpuscle: stretch Merkel-Cell (N) Complex: indentation depth/fine tactile discrimination C-Fibre LTM: pleasant contact Mechano (Polymodal) injurious forces Nociceptor Understand the layers of a nerve from superficial to deep. Endoneurium: (wraps individual neuron)—deepest Perineurium: (wraps fascicles—nerve bundles) Epineurium: (wraps fascicle bundles—entire nerve) Know the different components of a neuron found within the PNS. Dendrites: receive (NT). Cell Body: builds & recycles. Axon Hillock: generates action potentials. Axon: sends Axon Terminals: release (NT). Know the levels of nerve injury as well as the steps involved in regeneration. Causes of injury: traction and/or compression Initial damage (dist. axon) Wallerian degeneration 1st Degree: neuropraxia—damages neurolemma (outer region); leads to slowing 2nd Degree: Axonotmesis—damages/compresses the neuron itself Regeneration (1st step) Chromatolysis—axon swells + cell body releases substance 3 Conditions: Cell body intact Schwann cells intact Regrowth occurs quickly enough Know where each spinal nerve exits in relation to its vertebra & disc Further understand which IVF or disc would cause a radiculopathy for the given nerve root. Know the general regions of each spinal root’s dermatome *REMEMBER* focus on where charts AGREE not where they disagree. If I want to test C7, go where C7 is agreed to always control (the middle finger) For the brachial plexus, know the roots involved, tracing their deviations, and ultimately knowing which terminal peripheral nerves come from which locations For peripheral nerves, know which muscles, and by extension motor functions are they responsible for, as well as patches of skin innervated. Musculocutaneous controls muscles of the arm and sensory to the lateral forearm. Largely in control of elbow flexion. So a compromised musculocutaneous n. Will lead to weakness of elbow flexion and pain/numbness/tingling down the lateral forearm By overlapping and comparing dermatomal patterns and peripheral nerves, be able to identify and differentiate if a problem is more likely arising from a spinal nerve root (due to radiculopathy, refer to #6.a) or peripheral nerve entrapment. Identify the major locations involved in the sympathetic and parasympathetic nervous systems Know their effects on a given organ based on if it helps fight/flight Know the NT involved in the pre-/post-ganglionic junctions Know the organization (nerve roots or cranial nerves involved and if they are long or short) Be able to identify the neuromuscular junction disorder based on descriptive symptom or described pathology Which one is autoimmune destruction of the post-synaptic ACh gated channels THIS IS WHERE MIDTERM 1 INFORMATION ENDS Motor Neuron Lesions (5/4): Upper vs. Lower motor neuron (UMN/LMN): The UMN is entirely found within the CNS. It arises from the brain or brainstem & travels down the spinal cord to its target. UMN often regulate/modulate motor activity (This ensures we don’t go 100% every moment) If we remove UMN inhibition, things will get *HYPER* (related to gamma motor neurons) LMN originate from the spinal cord & project to their target muscles. They are the *GAS* to the muscle. If we cut the gas line, we lose power and we go *HYPO* Square-Rectangle Analogy: ALL MOTOR NEURONS DO MOTOR; BUT NOT ALL THINGS THAT HAVE MOTOR FUNCTION ARE MOTOR NEURONS Motor = initiation & execution of motor activity; Basal ganglia can affect motor function UMN v. LMN Lesion Signs: UMN: LMN: Hypertonic Hypotonic Spastic Paralysis Flaccid Paralysis Hyperreflexia (reflex reaction) Hyporeflexia Atrophy/Weakness (disuse/often after time) Wasting atrophy/weakness Pathologic Reflexes Fasciculations (involuntary muscle twitching) Can be widespread Small area of involvement Pathologic reflexes are reversions to primitive responses (baby reflexes) & indicate loss of cortical inhibition (GABA inhibitory interneurons selectively reduce the effect of the activity of other neurons in the cortex). Wasting atrophy—if you cut off the innervation to the muscle completely, you will never get that function back Fasciculations—not spasms; twitching similar to when a fly twitches when it dies Pathologies: UMNL: LMNL: Stroke Peripheral neuropathy Multiple Sclerosis Ventral Grey Horn Pathologies Traumatic Brain Injury (TBI) Radiculopathy ALS (Lou Gehrigs) Plexus Compression Spinal Cord Injury How Do We Keep Track of Our Muscles: We need to be aware of our muscles length, tension, rate of change We have subcortical (involuntary) processes to protect our muscles from building too much tension, or changing length too much too quick. Muscles have local sensors that help us self-regulate—doesn’t require the message to travel all the way to the brain & back. Muscle Composition/Innervation: EXTRAfusal fibers = the outside of the muscle (alpha motor neuron) Function: generating force INTRAfusal fibers = deep regulatory fibers (gamma motor neuron) These are sensitive to stretch/length and rate of change Intrafusal Fibers: Muscle spindles (specifically excitatory) Bags & Chains—function to measure static change & dynamic rate of change. The combination of info from these 2 domains allows the local regulatory systems to ‘decide’ if the motion is too much too fast (leads to change or shutting down) Static track absolute value/length % of stretch Type Ia (annulospiral) – sensory neuron II neuron (flower spray) – does not tell rate at all – sensory neuron Dynamic track rate of change Type Ia Static & dynamic info combine to sense if we are overstretching or going too fast All intrafusal fibers are innervated by ɣ-motor fibers (gamma), this maintains sensitivity at all amounts of muscle length (the coactivate alongside the alpha fibers) Muscle Stretch Reflex: Muscle spindles sense excess/quick stretch (amount & rate of change) of the muscle To protect from excessive stretch, they stimulate the a-motor neuron to the same muscle, gamma to themselves and inhibit the antagonist muscle Reciprocal Inhibition: when you fire a muscle (primary mover/agonist), your body will simultaneously send an inhibitory signal to the antagonist to prevent your body from fighting itself (ex. w/bicep flexion, triceps are inhibited) Golgi Tendon Reflex: Golgi TENDON organs reside in/near the tendinous insertions of each muscle innervated by 1b fibers Sensitive to load/tension to identify when approaching dangerous amounts. When excessive load is sensed they autogenically inhibit the original muscles forcing relaxation Ex. Your body sits (quads turn off AND your hamstrings turn on) when your squat weight is too much Week 7: Lumbo-Sacral Plexus Iliohypogastric T12-L1: Sensory: Posterolateral gluteal region, inguinal canal/lower abdominals Muscle: Internal oblique & transverse abdominals Ilioinguinal L1: Sensory: Ant. Genitals (scrotum/labia); lower abdominals Muscle: Internal oblique & transverse abdominals Genitofemoral L1-L2: Sensory: Genital branch & femoral branch Motor: Cremasteric muscle Lateral Femoral Cutaneous L2-L3: Sensory: lateral thigh Tight jean syndrome (neuralgia parastheitca) Femoral L2-L4: Sensory: Ant. femoral cutaneous cutaneous, medial shin via Saphenous n. Muscle: Iliacus, Pectineus, Sartorius (hip flexors); Quadriceps femoris (knee extensor) Obturator L2-L4: Sensory: proximal inner thigh Motor: adductors (longus, brevis, gracilis) + ext. hip rotation (obturator externus***) Nerve Roots: Muscle: Psoas (hip flexor), Quadratus lumborum (stabilizer & gross side-bending), lumbar intertransverse, finetuned lat. flex Sacral Plexus L4-S4: Often described with the lumbar plexus as “Lumbosacral plexus” due to the shared nerve roots of L4-5 to sacral nerves. Dermatomes (Agreed Upon): L1-L3: Anterior thigh to knee; L4: Medial shin to medial foot; L5: top of foot & lateral shin S1: lateral calf & thigh; S2: medial calf & thigh; S3-S5 perineal bull’s eye Superior Gluteal L4-S1: Pure Motor Gluteus Medius (hip/thigh ABduction) Gluteus minimus (hip/thigh ABduction) Tensor fasciae latae (hip/thigh ABduction) through connection of the Iliotibial (IT) band Inferior Gluteal L5-S2: Motor: Gluteus Maximus (hip extension) Posterior Femoral Cutaneous S1-S3: Sensory: Inferior cluneal n. (lower buttocks) Perineal branch- scrotum/labia Perforating Cutaneous S2-S3: Sensory: skin over glute max Side Bar—External Hip Rotators: 6 deep external hip rotators: (PGOGOQ) Piriformis, Gemellus superior, obturator internus, gemellus inferior, obturator externus, quadratus femoris Remember that Obturator externus is innervated by the obturator n. the rest come from the sacral plexus. Direct Branches: Piriformis S1-2- piriformis muscle (external hip rotation) Obturator internus L5-S2 – Obturator internus and Superior gemellus muscles (ext. Hip rot) Quadratus Femoris L4-S1- quatdraus femoris and inferior gemellus muscles (ext Hip rot) Sciatic L4-S3: Motor: Hamstrings (Semitendinosus, Semimembranosus, Biceps femoris) & Adductor magnus KNEE FLEXION, ADDUCTION, EXT. HIP ROTATION Sensory: divided into Tibial and fibular/peroneal portions Common Fibular L4-S2: Superficial fibular/peroneal Motor: Fibularis/peroneus longus & brevis (EVERSION) Sensory: Medial & intermediate dorsal cutaneous + sensory over medial foot (1st-3rd toes) Common Fibular L4-S2: Deep fibular/peroneal Motor: Tibialis ant. (dorsiflexion & inversion), ext. Digitorum longus, Ext. digit. Brevis, Ext. hallucis longus (hallux=big toe), Ext. hallucis brevis, Fibularis/peroneus tertius (evert) Sensory: Lateral cutaneous; Intermediate dorsal cutaneous; Webbing of toes Tibial Nerve L4-S3: Motor: (PLANTAR FLEXION) Triceps surae (gastrocnemius & soleus)-plantar flexion Popliteus (rotatoes femur/tibia while walking) Plantaris- ankle plantar flexion knee flexion Tibialis posterior- plantar flexion Flexor digitorum longus Flexor hallucis longus Sensory Medial sural cutaneous Medial calcaneal Lateral dorsal cutaneous Medial Plantar (off the tibial nerve): Motor: FLEX TOES & ABDUCT HALLUX ABductor hallucis Flexor digitorum brevis Flexor hallucis brevis Lumbricals Sensory: BOTTOM OF FOOT Proper plantar digital Lateral Plantar (off the tibial nerve): Motor: ADDUCT HALLUX & ABDUCT PINKY TOE Flexor hallucis brevis Quadratus plantae Abductor digiti minimi Flexor digiti minimi Lumbricals Plantar interossei Dorsal interossei Adductor hallucis Sensory: BOTTOM OF FOOT Proper plantar digital Pudendal S2-S4 & Coccygeal S5-Co1: Pudendal Motor: Pelvic floor muscles Sensory: Inferior rectal, Perineal Coccygeal Motor: Coccygeus- pelvic floor Sensory: Anococcygeal-skin over coccyx Week 8: Cervical Plexus Cervical Plexus: Arises from C1-C5 Sensory generally to the head and neck Motor of neck muscles and diaphragm Ansa cervicalis C1-3: Motor: (Strap Muscles) Thyrohyoid Sternohyoid Sternothyroid Omohyoid (shoulder hyoid) Movement of thyroid & hyoiD during speaking, chewing, swallowing Phrenic Nerve C3-5: Motor: Diaphragm- ventilation of lungs Sensory: Pleura & Pericardium Segmental Roots: Motor: C1-C4: Anterior & middle scalenes; lift rib & laterally flex neck. C3-C4: Levator scapulae; elevates scapulae Head & neck pain referral from muscles Cutaneous: Sensory: Greater occipital C2 (back/top of skull) Lesser occipital C2 (base of skull) Great auricular C2-3 (around actual ear) Transverse cervical C2-3 (all of throat) Supraclavicular C3-4 (above clavicle)