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Peripheral Nervous system (PNS)by Annie Burke-Doe, PT, MPT, PhDPracticing physical therapist and associate professor at the university of St. Augustine for health and wellness Sciences in san Diego, CaliforniaSlide 1: Peripheral Nervous device (PNS)
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Hello. Welcome to neuroanatomy and physical therapy. I"m Dr. Annie Burke-Doe, a practicing physical therapist and also an associate professor in ~ the college of St. Augustine for wellness Science in mountain Diego, California.This lecture collection has been emerged for physics therapists embarking ~ above the study of neurology. Neuroanatomy is the research of the anatomical company of the brain, and also it is also considered a branch the neuroscience, which encounters the research of gross framework of the mind and the worried system. The peripheral nervous mechanism (PNS) is written of devoted clusters the neurons and also peripheral nerves. The peripheral nervous system relays details to the central nervous system and executes motor commands generated in the mind and spinal cord. Us will begin with the pistol anatomy and discuss clinical obstacle of nerves, nerve roots, and nerve plexus.Slide 2: Spinal Cord

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In our previous topics, we disputed the key motor and also sensory pathways, and also we will currently follow this pathways come the peripheral nervous system. Mental that follow me the size of the spinal cord, there is a sport in size and also shape. The white matter, which is consisted of of longitudinal tracts, pictured here, is thickest in the cervical levels, where many ascending fibers have already entered the cord and also most to decrease fibers have actually not however terminated on their targets, if the sacral cord is mainly gray matter.

The quantity of gray matter is best in the segment of the spinal cord devoted to the sensory and motor regulate of the extremities. This segments space expanded, forming enlargements the the spinal cord. The cervical enlargement gives nerves come the shoulder and also upper limbs, when the lumbosacral enlargement provides enervation to the frameworks of the pelvis and lower limbs. Inferior to the lumbar enlargement, the spinal cord becomes tapered and conical. This region is the conus medullaris. The filum terminale is a slim strand that fibrous organization that extends native the inferior guideline of the conus medullaris. It continues along the size of the vertebral canal as far as the 2nd sacral vertebra, where it offers support come the spinal cord as a component of the coccygeal ligament.

You are watching: The spinal cord continues to elongate until about age

Slide 3: regions of the Spinal Cord
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When looking in ~ the areas of the spinal cord here on on slide 3, there room 31 segments, each called according come the level they exit the bony vertebral bodies. In the cervical region, the first pair that spinal nerves, C1, passes between the skull and the very first cervical vertebra. Every cervical nerve takes its name from the vertebra instantly inferior to it. So, in other words, cervical nerve C2 precedes vertebra C2 and the same system is used for the rest of the cervical series. In the thoracic region, a change for the numbering device occurs between the last cervical vertebra and the an initial thoracic vertebra. The spinal nerve in ~ this ar is C8. Each spinal nerve worse to the very first thoracic vertebra takes its name from the vertebra automatically superior come it. The spinal nerve T1 emerges instantly inferior come vertebra T1, spinal nerve T2 complies with vertebra T2, and also so forth.

Note the the cord chin is no as lengthy as the vertebra column due to the fact that during breakthrough the bony vertebral canal increases in length much faster than the spinal cord. The spinal cord proceeds to enlarge and also elongate until an individual is about 4 year old. Up to that time, enlargement of the spinal cord keeps speed with expansion of the vertebral column. Throughout this period, the ventral and dorsal root are really short, and they go into the intervertebral foramina immediately surrounding to their spinal segments. After age 4, the vertebral column continues to elongate, yet the spinal cord walk not. This vertebral growth moves the intervertebral foramina, and also thus the spinal nerves, farther and farther native their original position family member to the spinal cord. Since the adult spinal cord extends only to the level that the very first or second lumbar vertebra, the dorsal and also ventral roots of spinal segments L2 v S5 extend inferiorly, past the inferior pointer of the conus medullaris. When seen in pistol dissection, the filum terminale and also the long ventral and also dorsal roots resemble a horse"s tail and also are called the cauda equina.

Slide 4: Spinal Cord and also Peripheral nervous System
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Every spinal segment is connected with a pair the dorsal source ganglia, situated near the spinal cord. These ganglia, pictured here, save on computer the cell bodies of sensory neurons. The axons that the neurons form the dorsal roots, which carry sensory details into the spinal cord. Over there is also a pair that ventral root containing the axons of motor neurons that extend into the perimeter to manage somatic and also visceral effectors. Top top both sides, the dorsal and also the ventral roots of each segment pass between the vertebral canal and also the periphery at the intervertebral foramen between successive vertebrae. Distal come the dorsal root ganglion, the sensory and motor roots room bound together into a solitary spinal nerve. Spinal nerves are classified as mixed nerves; that is, castle contain both afferent or sensory information and efferent or motor fibers.

Slide 5: Vertebral Bones
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You can see here, on slide 5, the vertebral bones role as a central mechanical assistance for the body and as security for the spinal cord. Every bone has actually a cylindrical vertebral body located anteriorly. The bodies room separated native each other by one intervertebral disc consist of of a nucleus pulposus surrounding by a capsule referred to as the annulus fibrosus. Posteriorly, the neural elements are surrounded by one arched bone formed by the pedicles, transverse process, laminae, and also spinous process. The superior and also inferior articular process, or facet joints, kind additional clues of mechanical contact between nearby vertebrae. Avoid here and identify every landmark.

Slide 6: company of Spinal Nerves
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The spinal cord runs v the spinal canal and is surrounded by the spinal meninges. The spinal meninges consists of 3 layers: the pia, arachnoid, and dura mater. As the dura exits the skull at the foramen magnum, the inner layer continues, and the external layer becomes indistinguishable from the periosteum. Unlike the cranium, there is a class of epidural fat between the dura and the periosteum in the spinal canal, which is a useful landmark ~ above MRI scans. Bacterial or famous infections can reason meningitis or inflammation the the meningial membranes. Meningitis is dangerous since it deserve to disrupt the normal circulatory and cerebrospinal liquid supplies, damaging or killing neurons or neuroglia in influenced areas. The nerve roots exit the spinal canal via the neural foramina.

Slide 7: connection of Cervical and Lumbar Nerve root to Intervertebral Discs
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Pictured here once more, we can see the necessary relationship that the cervical and also lumbar nerve roots to the intervertebral discs. We see that the cervical nerve root exit over the matching vertebral bone, except for C8, which has actually no equivalent vertebral bone and exits in between C7 and T1. Cervical nerve roots have actually a fairly horizontal course as they emerge from the dura or thecal sac near the intervertebral disc and also exit v the intervertebral foramina. Cervical discs room usually constrained through the posterior longitudinal ligament, i m sorry is no pictured here, and will herniate laterally towards the nerve root fairly than centrally toward the spinal cord. Thus, in the cervical cord, the nerve source involvement usually coincides to the reduced vertebral bone that the bowl space.

Unlike cervical roots, lumbar and also sacral roots need to travel down number of levels prior to they exit the spinal canal. In addition, the intervertebral foramina of the lumbosacral spine are such that the nerve roots departure some distance over the intervertebral discs. Together they are about to exit, the nerve roots move right into the lateral recesses that the spinal canal, and also it is in ~ this allude that they space closest to the disc. Thus, posterolateral disc herniation in the lumbosacral spine generally impinges ~ above nerve root on their means to exit beneath the next lower vertebral bone, which corresponds to the number of the nerve source involved.

Slide 8: Herniation
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Disc herniations are most usual at the cervical and also lumbosacral levels, which space pictured here. An knowledge of the anatomy of the nerve roots and also discs must make clean the following necessary rule: for both cervical and lumbosacral disc herniation, the nerve root connected usually synchronizes to the lower of the surrounding two vertebrae. Because that example, a L5/S1 disc generally produces the S1 radiculopathy. The dominion is various for cervical versus lumbosacral discs, as debated earlier. A posterior lateral bowl herniation in the lumbosacral spine usually impinges ~ above the nerve root on their means to departure beneath the next lower vertebral bone, which synchronizes to the variety of the nerve root involved. Much lateral lumbosacral disc herniation affects the nerve root exiting the level, and main lumbosacral disc herniation can reason cauda equina syndrome.

Slide 9: Dermatomes
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The sensory region of the skin innervated by a nerve source is referred to as a dermatome. Dermatome maps regularly vary from resource to resource. This sport is likely due to distinctions in both the approaches of testing and also individual patients gift studied. Being familiar with places of dermatomes will assist you as a clinician in determination of the exactly neurologic level that involvement with injuries.

Sensation for the face is listed by the trigeminal nerve, while most of the remainder that the head is detailed by C2. C5 is represented at the shoulder, C6 in the lateral arm and the very first two digits, C7 in the center digit, and C8 the fourth and also fifth digits. The L4 depiction extends end the anteromedial shin, L5 extends under the anterior lateral shin and also dorsum of the foot to the large toe, and also S1 is in the little toe, lateral foot, sole, and also calf. S2, 3, and 4 innervate the perianal area in a saddle-like distribution.

Note that there is a significant amount the overlap between adjacent dermatomes. So, lesions the a single nerve root ordinarily reason a decrease but not a complete loss of emotion in a offered dermatome. There may be less overlap for smaller sized fibers, therefore pinprick is a more sensitive test because that dermatomal sensory loss 보다 touch.

Slide 10: Myotomes
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Patients through frontal lobe dysfunction may have actually a particular difficulty changing from one action to the following when performing a repetitive sequence of action, together as illustration a pattern. At times, the patient might perseverate or get stuck top top one facet of the task. The Luria hands-on sequencing task might be helpful in identify perseveration. Extr support for frontal lobe pathology originates from the existence of frontal release signs, such together the understand reflex.

Slide 11: Myotomes
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Slide 12: Myotomes
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Slide 13: Myotomes
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Slide 14: Myotomes
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Slide 15: Disorders
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A variety of obstacle can impact the peripheral nervous device at lot of levels. Disorders of the peripheral nervous system can often be differentiated from main nervous mechanism dysfunction by an anatomical pattern of sensory or motor deficits. In addition, the visibility of lower motor neuron signs consisting of atrophy, fasciculations, decreased tone, and hyperreflexia suggests peripheral nervous device dysfunction as perform paresthesias in peripheral nerve distributions.

Slide 16: Disorders
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Neuropathy is a basic term an interpretation nerve disorder. The site of pathology can be in axons, myelin, or both and also can affect huge diameter fibers, small diameter fibers, or both. Usually, neuropathies impact both sensory and motor fibers in the nerve, although one or the other may be preferentially involved. Damage may be reversible or permanent. The location of the neuropathy can be focal, together in a mononeuropathy; multifocal in mononeuropathy multiplex; or generalized in polyneuropathy.

Remember, favor neuropathies, engine neuron obstacle can likewise cause lower motor neuron-type weakness, yet motor neuron disorders perform not reason sensory involvement.

Etiologies such together diabetic neuropathy due to diabetes, mechanical compression, traction, laceration, or entrapment that a peripheral nerve, or syndromes, such as acute inflammation demyelinating polyneuropathy, can also lead to peripheral nerve damage. A selection of obstacle can influence the peripheral nervous system at many levels. Disorders of the peripheral nervous system can frequently be identified from central nervous mechanism dysfunction by one anatomical pattern of sensory or engine deficits. In addition, the presence of reduced motor neuron signs including atrophy, fasciculations, decreased tone, and also hyperreflexia suggest peripheral nervous device dysfunction, as perform paresthesias in peripheral worried distributions.

Slide 17: Disorders
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Another disorder might be impaired neuromuscular transmission, which leader to engine weakness without sensory deficits. Examples of impaired neuromuscular junction disorders include myasthenia gravis, Lambert-Eaton myasthenic syndrome, and botulism poisoning.

Slide 18: Disorders
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Myopathies, or muscle disorders, create weakness that is typically an ext severe in proximal musculature than in distal musculature and also without lose of sensation or reflexes. Myopathies can be discovered in thyroid disorders, polymyositis, and Duchenne muscular dystrophy.

Slide 19: back Pain
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Back pain is one of the most usual reasons that human being seek medical attention and also can have countless causes, as detailed here on on slide 19.

Slide 20: Radiculopathy
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Back pains can also cause a neuropathy influence spinal nerve roots, i beg your pardon is called radiculopathy and causes a sensory or motor dysfunction. Radiculopathy is often connected with burning, study abroad pain the radiates or shoots down a body in a dermatome that the effected nerve root. There may be a ns of reflexes and also motor toughness in a radicular distribution as well. Chronic radiculopathy can an outcome in atrophy and also fasciculations. Sensations may be decreased if a solitary dermatome is involved, but because of overlap from nearby dermatomes, emotion is usually not absent.

Slide 21: vital Nerve root of Arm
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Clinically, the is very important come be acquainted with reflexes, motor and also sensory functions connected with the top extremity, particularly C5, C6, and C7. When evaluating patients, the is advantageous to have memorized at least one muscle the gets its significant innervation from every of these three nerve roots. Below pictured, you deserve to see C5 is associated with shoulder abduction, C5/6 is connected with elbow flexion and the bicep tendon reflex, and C7 is connected with elbow extension and also the triceps tendon reflex. That is additionally helpful to understand that C8 radiculopathy account for around 6% of cervical radiculopathies and is brought about by C7-T1 disc herniation. It"s likewise associated through weakness that the intrinsic hand muscles and decreased sensation over the fourth and also fifth digits of the medial forearm. About 20% of every cervical radiculopathies involve 2 or an ext cervical levels.

Slide 22: essential Nerve roots of Leg
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One must additionally be familiar with reflexes, motor and also sensory functions linked with the lower extremities, especially L4, L5, and S1. Together pictured, L4 mediates leg expansion at the knee and also the patellar tendon reflex. L5 mediates dorsiflexion in ~ the fish eye and an excellent toe extension, and S1 mediates plantar flexion at the ankle and the Achilles tendon reflex.

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Slide 23: instance 1
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The following clinical instances have been arisen for your review. Lock contain subject issue that is clinically related and also will reinforce lecture slide content. The questions for the instance follow the development of the case slide, and the conversation for the situation is in the on slide notes. I recommend not searching for the answers in the discussion notes until you have attempted come answer the questions on her own, using the on slide content. Great luck, and also I will see you in the next topic.

Slide 24: instance 1: Questions
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Slide 25: situation 2
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Slide 26: case 2: Questions
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Slide 27: References
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