Presentation on theme: "Chapter 36 Disorders of Neuromuscular Function"— Presentation transcript:
1 Chapter 36 Disorders of Neuromuscular Function Essentials of PathophysiologyChapter 36 Disorders of Neuromuscular Function
2 Pre lecture quiz (True / false) Paralysis refers to weakness or incomplete loss of muscle function. Carpal tunnel syndrome is an example of a polyneuropathy.All levels of spinal cord injury will require assistance to maintain breathing.Autonomic dysreflexia represents an acute episode of exaggerated sympathetic reflex responses that occur in persons with some types of spinal cord injuries.The pathophysiology of multiple sclerosis involves the demyelination and subsequent degeneration of nerve fibers in the central nervous system.FT
3 Pre lecture quiz Acetylcholine Fibers Ganglia Tic Weakness Myasthenia gravis, an autoimmune disorder, is caused by an antibody-mediated destruction of ______________________ receptors in the neuromuscular junction.Guillain-Barré syndrome is characterized by progressive ascending muscle _____________________ of the limbs, producing a symmetric flaccid paralysis.Parkinson disease is a degenerative disorder of the basal ___________________ that results in variable combinations of tremor, rigidity, and bradykinesia.A __________________ is a an irregularly occurring, brief, repetitive movement such as winking, grimacing, or shoulder shrugging.Muscular dystrophy is a term applied to a number of genetic disorders that produce progressive degeneration and necrosis of skeletal muscle __________________, which are eventually replaced with fat and connective tissue.AcetylcholineFibersGangliaTicWeakness
4 Upper Motor Neurons Are in the Brain and Spinal Cord Upper motor neuron cell bodies are in the motor cortexThey send their axons down through the internal capsuleThe axons then run down the white matter of the spinal cord
5 Two Motor Systems Extrapyramidal Pyramidal Most go to same side of bodyPyramidalMost cross to other side of bodyMotor cortex neuronsInternal capsulePonsExtrapyramidalPyramidal systemsystem
6 Lower motor neuron’s axon running through peripheral nerves Motor UnitLower motor neuronLower motor neuron’s axon running through peripheral nervesThe muscles it innervatesUpper motor neuronsSend axons downspinal cord tractsLower motorneurons in spinalcordPeripheral nervesMuscles
7 QuestionWhich motor neurons are damaged in patients who have neuromuscular disorders that directly affect skeletal muscle?UpperLowerBoth upper and lowerNeither upper nor lower
8 AnswerLowerRationale: The axons of lower motor neurons pass through peripheral nerves to effector tissue in skeletal muscle. Upper motor neurons’ axons travel down the spinal cord.
9 Muscle Tone Muscle stretches Afferent neuron carries impulse to spinal cordMotoneurons cause muscle to contract
10 Alterations in Muscle Tone HypotoniaHypertoniaRigidityClonus
11 Terms to Describe Motor Dysfunction -plegia = stroke or paralysisParalysis = loss of movement-paresis = weaknessMono- = one limbHemi- = both limbs on one sideDi- or para- = both upper limbs or both lower limbsQuadri- or tetra- = all four limbs
12 Discussion What would be the terms for the following? A defect causing weakness in both armsA weakness in the right arm and legInability to move one leg
13 Upper vs. Lower Motor Neurons Upper motor neuronsIn the brain and spinal cordLower motor neuronsSend axons out of the spinal cordUpper motor neuronsSend axons downspinal cord tractsLower motorneurons in spinalcordPeripheral nervesMuscles
14 Upper Motor Neuron Damage Weakness and loss of voluntary motionSpinal reflexes remain intact but cannot be modulated by the brainIncreased muscle toneHyperreflexiaSpasticity
15 Lower Motor Neuron Damage Neurons directly innervating muscles are affectedIrritated neuronsSpontaneous muscle contractions: fasciculationsDeath of neuronsSpinal reflexes are lostFlaccid paralysisDenervation atrophy of muscles
16 The Motor Unit One lower motor neuron (motoneuron) The neuromuscular junctionThe muscle fibers it innervates
17 QuestionTell whether the following statement is true or false. To increase the strength of a contraction, more motor neurons must be recruited.
18 AnswerTrue Rationale: A motor unit consists of branches of a neuron and the skeletal muscle fibers that they innervate. For stronger contractions, more motor units are required.
19 Possible Problems With the Motor Unit Lower motor neuron lesions or infections; peripheral nerve injuryNeuromuscular junction disordersMuscle atrophy or dystrophy
20 Skeletal Muscle Problems Disuse atrophyDenervation atrophyMuscular dystrophyContractile proteins not properly attached to cytoskeleton of muscle cellProtein movement does not effectively contract muscle cell
21 Neuromuscular Junction Problems Decreased acetylcholine releaseBotulismDecreased acetylcholine effects on muscle cellCurareMyasthenia gravisDecreased acetylcholinesterase activity; acetylcholine has a stronger effect on the muscle cellOrganophosphates
22 QuestionTell whether the following statement is true or false. Acetylcholinesterase stimulates the release of acetylcholine (ACh).
23 AnswerFalse Rationale: Acetylcholinesterase breaks down ACh, resulting in relaxation of the skeletal muscle.
24 Myasthenia Gravis Autoimmune disease Gradual development of weakness Gradual destruction of acetylcholine receptorsAssociated with thymus tumor or hyperplasiaGradual development of weaknessFrom proximal to distal portions of bodyMyasthenia crisis: respiration compromised
25 Peripheral Nerve Injuries Damage to LMN cell bodies in the spinal cordDamage to axons in the spinal or peripheral nervesDamage to myelin sheath (demyelination)
26 Peripheral Nerve Injuries (cont.) MononeuropathiesDamage to one peripheral nerveE.g., carpal tunnel syndromePolyneuropathiesDamage to many peripheral nervesE.g., Guillain-Barré syndrome
27 Back Pain Peripheral nerve injury at the spinal nerve roots Often due to compression of nerve root by vertebrae or vertebral disk
28 Motor Impulses Are Modulated by the Basal Ganglia Upper motor neuron cell bodies are in the motor cortexThey send their axons down through the internal capsuleThe basal ganglia inhibit and modulate movement patterns
29 Basal Ganglia Dysfunction Can Increase Patterned Movement TremorsTicsHyperkinesiaChoreiform: jerky movementsAthetoid: continuous twisting movementsBallismus: violent flinging movementsDystonia: rigidity
30 QuestionWhich disease is a result of basal ganglia dysfunction?Myasthenia gravisMultiple sclerosisPolioTourette syndrome
31 AnswerTourette syndromeRationale: The tics and hyperkinesia that often accompany Tourette syndrome are typical of basal ganglia dysfunction (the function of the basal ganglia is movement control).
32 Parkinsonism Tremor Rigidity Bradykinesia (slow movement) Loss of postural reflexesAutonomic system dysfunctionDementia
33 Cerebellum Damage Vestibulocerebellar disorders Difficulty maintaining postureCerebellar ataxiaMovements divided into separate componentsCerebellar tremor
34 Amyotrophic Lateral Sclerosis Damages both upper and lower motor neuronsUMN damage weakness, lack of motor controlLoss of control over spinal reflexes stiffness, spasticityLMN damageIrritation fasciculationsDecreased neuron firing weakness, denervation atrophy, hyporeflexia
35 Multiple SclerosisDestruction of myelin coating on axonsDemyelinated or sclerotic patches develop through white matter of CNSDecreased conduction velocity
36 QuestionWhich disorder causes damage to both upper and lower motor neurons?ALSMSMyasthenia gravisParkinson disease
37 AnswerALSRationale: Also known as Lou Gehrig disease, ALS destroys both upper and lower motor neurons. Typical S/S include weakness, lack of motor control, denervation atrophy, and hyporeflexia.
38 Spinal Cord Injury Immediate damage causes: Spinal cord shock Temporary complete loss of function below injuryPrimary neurologic injuryIrreversible damage to neurons
39 Secondary Injury to the Spinal Cord Neurons and white matter in area of initial damage are affectedPossible causes include:Damage to blood vessels supplying the areaDecreased vasomotor tone decreasing blood supplyLocal release of substances that cause vasospasmRelease of digestive enzymes from damaged cells
40 Partial Spinal Cord Injury Central cord syndrome: damage to axons near the gray matterArms more affected than legsAnterior cord syndrome: damage to anterior section of cordMotor functions affected; touch sensation not affectedBrown-Séquard syndrome: damage to one side of cordMotor function lost on that side; pain/temperature sensation lost from other side
41 Complete Spinal Cord Injury To upper motor neurons (T12 and above)Spinal reflexes still workNo longer modulated by brainHypertonia, spastic paralysisTo lower motor neurons (T12 and below)Cells in spinal reflex arcs damagedFlaccid paralysis