Module 08 Lab Worksheet: Peripheral Nervous System INTRODUCTION This week’s lab will focus on the peripheral nervous system, the cranial nerves and testing these components of the nervous system. OBJECTIVES Objectives for this week’s lab include: 1) Identify the components of the peripheral nervous system, 2) Identify the cranial nerves, and 3) Differentiate upper versus lower motor neurons and lesions. OVERVIEW The peripheral nervous system (PNS) consists of all the neural structures outside of the central nervous system (CNS) including the peripheral nerves, sensory receptors, ganglia and efferent motor endings. The PNS is divided into a sensory (also referred to as afferent) division and a motor (also referred to as efferent) division. The sensory division transmits neural information from the body, including the internal organs, to the CNS and the motor division transmits neural information from the CNS to the body. A peripheral nerve is a bundle of individual axons of neurons. One peripheral nerve can literally have hundreds and even thousands of axons of sensory and motor neurons. Peripheral nerves originate from one of the 31 pairs of spinal nerves and form nerve plexuses- a complex network of spinal nerves joining together. Nerve plexuses occur in the cervical, brachial, lumbar and sacral regions of the body. The 12 pairs of cranial nerves (CN) originate from the brain and brain stem, unlike the 31 pairs of spinal nerves which originate from the spinal cord. The cranial nerves are considered a portion of the PNS due to the fact their axons extend beyond the brain. The only exception is with cranial nerve II (optic nerve), it is technically considered part of the diencephalon. The CN have specific functions within the body, mainly in the head region such as movement of the eyes, muscles of the face, the tongue and so forth but CN X (vagus nerve) has strong parasympathetic stimulation throughout the majority of organs in the thoracic and abdominal cavities. Part of the neurological testing within this lab will assess the CN. A dermatome refers to a specific area of skin that is innervated by a branch of a single spinal nerve. A dermatome map of the body is demonstrated in “Appendix A”. You can determine the area of damage to the spinal cord and/or specific spinal nerve by testing the dermatomes. Reflexes can be classified as inborn or learned but both are developed to help maintain homeostasis to varying degrees. Inborn or intrinsic reflexes are extremely fast, controlled and predictable motor responses to a stimulus. Intrinsic reflexes have very specific neural pathways called reflex arcs and technically have five components to them. Reflexes will create an expected response upon a specific stimulus and is executed prior to conscious perception. Upper motor neurons (UMN) are neurons that originate in the cerebral cortex or brainstem and travel to the body via a few different motor spinal tracts. These motor neurons ultimately stimulate skeletal muscle movement. Lower motor neurons (LMN) connect the UMN to the skeletal muscles and are found outside of the CNS. A lesion, or damage, to either a UMN or LMN will cause specific characteristics to muscle tone, reflexes, muscle strength and voluntary/involuntary muscle movements. Please see “Appendix C” regarding these characteristic differences. Performing a neurological test will help differentiate between an UMN lesion and a LMN lesion. MATERIALS · Reflex hammer · Pen light · Tongue depressors PRE-LAB EVALUATION QUESTIONS The pre-lab evaluation questions must be answered prior to lab and demonstrated to your lab instructor. You must read through the assigned chapter readings, lab introduction, objectives, overview and procedure to answer these questions. Please cite your work for any reference source you utilize in answering these questions. 1. In your own words, please describe the characteristics of a peripheral nerve. 2. The cranial nerves have a number of different roles but none as diverse and unique as cranial nerve X, the vagus nerve. What makes the vagus nerve so unique and what is its role in the autonomic nervous system? 3. Identify the components of the reflex arc and briefly describe the overall process? 4. In your own words, explain what a dermatome is and the clinical significance of it? 5. What is peripheral neuropathy? Describe at least two different causes and the complications of this condition? How is it treated? Part 01 Procedure: Deep Tendon Reflexes (Stretch Reflexes) 1. Assess the deep tendon reflexes on two different lab partners. Please follow the instructions for each reflex and utilize Appendix A in providing the appropriate assessment. 2. While assessing the upper extremity, have the patient make a fist with one hand while the opposite extremity is tested. Assessing the lower extremity, utilize the “Jendrassik maneuver”; have the patient hook their fingers together and try to pull them apart. These maneuvers help “distract” the patient to ensure a proper reflex assessment. A) Biceps Reflex (C5, C6) Forearm should be supported with the arm midway between flexion and extension (elbow at 90 degrees). Place your thumb on the distal end of the bicep’s tendon and tap the reflex hammer briskly; using the triangular shaped side on your thumb. You should note flexion at the elbow. Patient 01 Right: _________ Patient 02 Right: _________ Patient 01 Left: _________ Patient 02 Left: _________ B) Brachioradialis Reflex (C6) The arm should be supported. Identify the brachioradialis tendon near the wrist. It inserts at the base of the styloid process of the radius. Once identified, use the blunt side of the reflex hammer to briskly tap the tendon. Flexion of the forearm/wrist should be noticed. Patient 01 Right: _________ Patient 02 Right: _________ Patient 01 Left: _________ Patient 02 Left: _________ C) Triceps Reflex (C7) Support the patient’s arm while it is midway between flexion and extension. Identify the triceps tendon at its insertion on the olecranon. Using the blunt side of the reflex hammer, tap just above the insertion. You should note extension at the elbow. Patient 01 Right: _________ Patient 02 Right: _________ Patient 01 Left: _________ Patient 02 Left: _________ D) Patellar Reflex (L4) Let the patient’s legs hang freely as he/she is sitting. Locate the quadriceps tendon inferior to the patella. Using the blunt end of the reflex hammer, briskly tap the quadriceps tendon.You should note extension of the knee. If there is no response, utilize the Jendrassik maneuver. Patient 01 Right: _________ Patient 02 Right: _________ Patient 01 Left: _________ Patient 02 Left: _________ E) Achilles Reflex (S1) With the patient sitting and legs hanging freely, place one hand underneath the sole and dorsiflex the foot slightly. Utilizing the blunt side of the reflex hammer, tap on the Achilles tendon just above its insertion on the calcaneus. You should note plantarflexion of the foot. Patient 01 Right: _________ Patient 02 Right: _________ Patient 01 Left: _________ Patient 02 Left: _________ F) Babinski’s Reflex (Optional) The foot must be cleared of shoes and socks. Use a blunt instrument such as the end of the reflex hammer and clean it off with alcohol wipes before and after use. Stroke the lateral side of the foot starting at the calcaneus and curve up to the big toe. A negative Babinski’s test occurs when: The toes curve downward and the foot everts. A positive Babinski’s test occurs when: The toes fan outward and even upward. Babinski’s sign: _______________ Part 02 Procedure: Dermatome Testing 1. Test the sensory perception of a few major dermatome spinal nerve root levels: C5, C6, C7, C8, L4 L5, S1. Utilizing Appendix B, note where each of these dermatomes are located. 2. For each dermatome level being tested, you should utilize a pen or two similar objects. Have the patient close his/her eyes and slide a pen along a specific dermatome of the left and right side of the body at the same time. Patient should note that he/she feels the sensation the same on each side of the body. Please note your observations below for each dermatome.For the best test results, the object should touch the skin directly. C5: same on both sides, more sensation on left, or more sensation on right C6: same on both sides, more sensation on left, or more sensation on right C7: same on both sides, more sensation on left, or more sensation on right C8: same on both sides, more sensation on left, or more sensation on right L4: same on both sides, more sensation on left, or more sensation on right L5: same on both sides, more sensation on left, or more sensation on right S1: same on both sides, more sensation on left, or more sensation on right Part 03 Procedure: Cranial Nerve Testing 1. Perform a general and quick cranial nerve test utilizing Appendix C. Please skip CN VIII, as these tests will be analyzed in more detail in a future lab. 2. Please note any observations below: CN I: CN II: CN III, IV, VI: CN V: CN VII: CN VIII: (Skip these hearing tests) CN IX: CN X: CN XI: CN XII: Part 04 Procedure: Peripheral Nerve Observation 1. Obtain the appropriate dissection equipment including gloves, dissection kit and tray. Locate and remove your pig specimen from its storage container. 2. Follow the instructions in the “Rasmussen Dissection Guide – Peripheral Nervous System Unit” and utilize the pictures to complete your dissections. Follow any specific instructions your lab instructor may have and if you have any questions or concerns, please contact your lab instructor right away. 3. When completed with the dissection, proper storage of your pig specimen is needed to prevent the pig from drying out or becoming contaminated with mold and/or bacteria. Refer any questions to your lab instructor. Part 05 Procedure: PNS Mini Case Studies 1. Utilizing the case studies handed out in the lab session, please determine and describe the type of condition presented in each case. Appendix D may be a helpful resource in determining your answers. Case Study A: Case Study B: Case Study C: POST-LAB EVALUATION QUESTIONS The post lab evaluation questions must be completed prior to your submission of the lab. Answers for these questions will be derived from the lab protocol, the weekly concepts associated with the lab and possibly research content from the book and/or online resources. Please cite your work for any reference source you utilize in answering these questions. 1. Compare and contrast the sympathetic and parasympathetic nervous systems. 2. With your knowledge of the central nervous system and the peripheral nervous system, please describe the situation of a quadriplegic and paraplegic using appropriate terminology. 3. How does the concept of referred pain associate with the peripheral nervous system and spinal nerves? What is an example of referred pain? 4. Both multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) can cause skeletal muscle contraction dysfunction. Explain the difference of each condition’s pathophysiology of how they can cause skeletal muscle contraction dysfunction. Focus on the peripheral nervous system within your answer. 5. Spinal stenosis, degenerative disc disease and herniated discs are three common conditions that can cause chronic back pain. Explain how these three conditions can cause the dysfunction and the symptomology that they do. Include the concept of spinal nerves and their innervation. Appendix A Deep tendon reflexes, often referred to as stretch reflexes, give a practitioner an opportunity to assess the integrity of the CNS and PNS. You probably recognize this test as the knee-jerk test performed with a reflex hammer. Grading of the reflexes is typically performed on a 0-4 scale, though there are some references that utilize a 0-5 scale. For our purposes, we will utilize the 0-4 scale. The goal of the deep tendon reflex is to stimulate a contraction of a muscle in response to stretching its muscle spindles by applying a quick force onto the tendon of that muscle. The reflex arc of a particular muscle will correspond to a specific spinal nerve root level. For example, the triceps reflex is primarily assessing the nerve root level of C7- location of the spinal nerves at C7 within the neck. Primary Spinal Nerve Root Level of the Deep Tendon Reflexes · Biceps reflex (C5, C6) · Brachioradialis reflex (C6,) · Triceps reflex (C7) · Patellar reflex (L4) · Achilles reflex (S1) Grading (measuring) Stretch Reflexes When assessing reflexes, they are measured on a scale from 0-4 with 2/4 as normal. Normal will vary from one individual to another. Clonus is a repetitive series of muscle contractions and relaxations that are involuntary. Grade Description 0 Absent/No reflex present; always abnormal 1 or + Hypoactive; slight response; may or may not be normal 2 or ++ A brisk response; normal 3 or +++ Hyperactive; a very brisk response; may or may not be normal 4 or ++++ Hyperactive; elicits a repeating reflex (clonus), always abnormal Hyporeflexia is an absent or diminished response to tapping. It usually indicates a disease that involves one or more of the components of the two-neuron reflex arc itself; typically peripheral nervous damage. Hyperreflexia refers to hyperactive or repeating (clonic) reflexes. These usually indicate an interruption of corticospinal and/or other spinal tract pathways that influence the reflex arc or possibly the cerebral cortex; typically central nervous system damage. Appendix B A dermatome refers to a specific area of skin that is innervated by a branch of a single spinal nerve. You can determine the area of damage to the spinal cord and/or specific spinal nerve by testing the dermatomes. Listed below is a dermatome map of the body. You will test the sensory awareness of a few major dermatomes on your lab partner: C5, C6, C7, C8, L4 L5, S1. Please note how these dermatome levels associate with the deep tendon reflex spinal nerve root levels. .jpg” alt=”HDTV:Users:jeremybarthels:Desktop:10_16_00.jpg”> Appendix C Cranial Nerve Number Name Sensory, Motor, or Both General Function I Olfactory Sensory Sense of smell II Optic Sensory Sense of vision III Oculomotor Motor Movement of the eye, pupil constriction IV Trochlear Motor Movement of the eye V Trigeminal Both Sensation from the face and innervates muscles of mastication VI Abducens Motor Movement of the eye VII Facial Both Innervates muscles involved in facial expression, taste from anterior 2/3 of tongue, innervation to salivary glands VIII Vestibulocochlear Sensory Sense of sound and equilibrium IX Glossopharyngeal Both Taste from the posterior 1/3 of tongue, and innervation to salivary glands X Vagus Both A number of functions but generally controls muscles for voice and swallowing, provides parasympathetic innervation to thoracic and abdominal viscera XI Accessory Motor Innervates the sternocleidomastoid and trapezius muscle XII Hypoglossal Motor Innervates muscles of the tongue Cranial Nerve Characteristics Appendix C(continued) Testing The Cranial Nerves (a simplified version) CN I: Test if patient can recognize various smells with each nostril CN II: Test visual acuity with Snelling eye chart, the peripheral visual fields and the pupillary light reflex CN III, IV, VI: Inspect for ptosis and nystagmus. Test ocular movements by having the patient following the examiners finger moved in the shape of an “H”. Test accommodation reflex by moving finger towards bridge of nose. CN V: Touch recognition within the 3 divisions of the Trigeminal nerve. Test muscles of mastication. CN VII: Test for motor control of facial muscles; have patient raise eyebrows, frown, smile, puff out cheeks and shut eyes as tight as possible. If accessible, test anterior portion of tongue for taste. CN VIII: Rinne and Webber hearing tests along with Romberg’s test. CN IX, X: Gag response and articulation of “KA” and “GO”. CN XI: Test if patient can shrug shoulders and turn head side to side. CN XII: Inspect tongue movement and symmetry on protrusion from mouth. Areas UMN Lesion LMN Lesion Location of Lesion CNS- Cerebral cortex, Brainstem, Spinal cord tracts including corticospinal tracts, and Spinal cord PNS- Peripheral nerves and spinal nerve roots, Spinal cord: anterior horn cell, Diagnosis/ Pathology Paralysis, Cerebral Palsy, Palsy, Stroke, Multiple Sclerosis Peripheral nerve injury, Peripheral neuropathy, Radiculopathy, Polio, Multiple Sclerosis Muscle Tone Increased: Hypertonia Decreased or absent: Hypotonia, flaccidity Reflexes Increased: Hyperreflexia, clonus, exaggerated cutaneous and autonomic reflexes, + Babinski Decreased or absent: Hyporeflexia, cutaneous reflexes decreased or absent Involuntary movements Muscle spasms: Flexors or extensors, velocity dependent With denervation: Fasciculations (muscle twitches) Voluntary Movements Impaired or absent Weak or absent if nerve interrupted Appendix D Comparison of Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN) Lesion Characteristics
