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69 Cards in this Set
- Front
- Back
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Cervical Plexus
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innervates anterior neck m. and diaphragm
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Phrenic Nerve
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most important branch from the cervical plexus- it's the main sensory n for the diaphragm
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Brachial plexus
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innervate the entire upper limb
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Lumbar plexus
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innervates skin and m of the anterior middle thigh
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Scral plexus
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innervates the posterior thigh and most of the leg and food
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Sacral plexus contains what type of axons?
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Parasympathetic
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Peripheral nn consist of
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parallel bundles of axons surrounded by 3 consecutive tissue sheaths
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Endoneurium
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separates individual axons of peripheral nn
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Perineurium
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surrounds bundles of axons of peripheral nn
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Epineurium
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encloses entire n trunk of peripheral nn
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Large myelinated axons
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part of the Aalpha efferent axon group & innervates extrafusal m fibers
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Medium myelinated axons
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part of the Ay efferent axon group & innervates intrafusal m fibers
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Small myelinated axons
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part of the Ad or C afferent axon group & convey sensory info perceived as pain and temp
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Unmyelinated axons
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part of the Ia afferent axon group & convey sensory info perceived as touch and pressure
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Neuromuscular junction
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where motor axons synapse with muscle fibers
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Signs of peripheral n damage include..
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sensory, autonomic and motor changes
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Sensory changes for peripheral nn include
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decreased or lost sensation and/or abnormal sensations: hyperalgesia, dyesthesia, paresthesia, and allodynia
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Hyperalgesia
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excessive sensitivity to painful stimuli
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Dyesthesia
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Painful abnormal sensation
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Allodynia
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pain in response to normally non-painful stimuli
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Paresthesia
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nonpainful abnormal sensation, often described as prickling & tingling
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Autonomic changes for a single n
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only observed if the n is completely severed: lack of sweating and loss of sympathetic control of smooth m
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Autonomic changes for multiple nn
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difficulty regulating BP, HR, sweating, and bowel and bladder fxns
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Motor changes for peripheral nn
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paresis or paralysis
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Fibrillation
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brief contraction of a single m fiber, not visible on the surface of the skin
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Fasiculation
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a quick twitch of m fibers in a single motor unit, which is visible on the surface of the skin
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Fractination
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ability to activate individual mm independently of other mm
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If m is denervated due to motor changes...
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muscle atrophy progresses rapidly; m fibers develop sensitivity to ACh and fibrillation ensues
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Trophic Changes happens when..
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n supply is interrupted
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Examples of Trophic Changes
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m atrophy, shiny skin, brittle nails, thickening of subcutaneous tissues, poor wound healing, infections
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Peripheral neuropathy can involve...
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a single n, several n, or many n
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Mononeuropathy
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neuropathy involving 1 nerve; with several nn it's multiple neuropathy
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Polyneuropathy
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neuropathy involving multiple nn
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Polyneuropathy occurs due to..
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complications of diabetes or autoimmune disorder; pathology- metabolic or inflammatory;
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Truamatic injuries to peripheral nn categories
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Traumatic myelinopathy, traumatic axonopathy, severance
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Traumatic Mylinopathy
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loss of myelin limited to the site of the injury
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Peripheral myelinopathies interfere with..
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the fxn of large-diameter axons, producing motor, discriminative touch, proprioceptive and phasic stretch reflex deficits and cause neuropathic pain; unless injury is severe, autonomic fxn is intaxt and the axons are not damaged
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Recovery from traumatic myelinopathny
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tends to be complete because remyelination can occur rapidly, before irreversal changes occur
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Cause of traumatic myelinopathy
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focal compression- caused by repeated mechanical stimuli (ex. stretch, vibration, friction, excessive pressure
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Sequence of events producing traumatic myelinopathy
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1) N. compression causing decreased blood flow & axonal transport
2) decreased blood flow causes edema 3) edema further restricts blood and axoplasmic flow, interfering with axon fxn 4) Myelin damage occurs, leading to decreased n conduction velocity 5) decreased n conduction results in impaired discriminative touch, proprioception & mvmts. |
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n. entrapment
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mechanical constriction of a n within an anatomic canal- can cause traumatic myelinopathy
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n. entrapment is most common in what nn?
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Median (Carpal tunnel), ulnar (ulnar groove), radial (spiral groove), peroneal (fibular head)
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what can compress nn?
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pressure from casts, crutches or sustained positions (sitting with knees crossed)
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Compression
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temporarily interferes with blood supply or may cause local demyelination (as is the case with prolonged compression)
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What is a common sign of carpal tunnel syndrome?
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Thenar eminence atrophy
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Traumatic Axonopathy
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disrupts axons and wallerian degeneration (myelin sheath pulls away from segment, causing degeneration and death of the entire distal segment pg 74) occurs distal to the lesion
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Traumatic axonopathy occurs from
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crushing of the n secondary to dislocations or closed fractures
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Traumatic axonopathy affects
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all sizes of axons, so reflexes, somatosensation, and motor function are reduced or absent
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Severance
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occurs when nn are physically divided, by excessive stretch or laceration causing immediate loss of sensation and/or m paralysis in the area supplied
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Multiple mononeuropathy occurs commonly from..
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ischemia of the nn, either from diabetes or vasiculitis- due this restricting flood flow, producing asymmetrical, random presentation of signs
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Vasiculitis
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inflammation of blood vessels
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Polyneuropathy is symmetrical or asymmetrical
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symmetrical, progressing from distal to proximal, involving sensory, motor, and autonomic fibers
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Polyneuropathy symptoms typically begin
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in the feet and then appear in the hands, areas of the body supplied by the longest axons
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Polyneuropathy etiology
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toxic, metabolic, or autoimmune
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Most common cause of polyneuropathy
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diabetes, nutritional deficiencies secondary to alcoholism, and autoimmune diseases
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Charcot-Marie-Tooth disease
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paresis of mm distal to the knee with resulting foot drop, a steppage gait, frequently tripping and m atrophy; decreased ability to sense heat, cold, and pain; onset occurs at a young age; hereditary
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Hereditary Motor and Sensory Neuropathy (HMSN) is also known as...
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Charcot-Marie-Tooth disease
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Guillain-Barre syndrome
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A polyneuropathy; rapid onset, progressive paralysis, often requires ventilator
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Diabetic polyneuropathy results in..
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the stocking/glove distribution of sensory impairment (pg 291)
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2 dysfunctions of the neuromuscualar junction
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1) Myasthenia Gracis
2) botulinum |
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Myasthenia Gravis
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autoimmune disease damaging ACh receptors at the NM junction- repeated use of a m leads to increasing weakness
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Botulinum
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Interferes with the release of ACh from the motor axon producing acute, progressive weakness, with loss of stretch reflexes; sensation remains intact
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How can you get botulinum?
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Ingesting the botulinum toxin from improperly stored foods (think of cans and jars with the tab popped up, that shows that the toxin is present)
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Myopathy
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Muscle disorder that doesnt affect the nervous system therefore sensation and autonomic function remain intact
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Do myopathies affect sensation and autonomic function?
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NO
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What do myopathies affect?
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Coordination, muscle tone, and reflexes (only when m atrophy becomes so severe that m activity cannot be elicited)
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What disorder is an example of a myopathy?
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Muscular Dystrophy
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Botox interferes with the release of..
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ACh
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Clinical signs that detect peripheral neuropathy:
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absence of ankle jerk reflex despite facilitation, impaired vibration, and impaired position sense of the great toe
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