Muscle In Health And Disease Flashcards
What happens when potassium is low in muscles
Muscle Cramps
Is skeletal under UMN or LMN control
LMN
Where are LMNs found
Ventral horn of spinal cord
Cranial nerve nuclei
Motor unit
motor neuron and all of the skeletal muscle fibers innervated by the neuron’s axon terminals
What happens to a muscle fibre when it loses innervation
Atrophies and becomes angulated
How are deinnervated muscle fibres reinnervated
Axons sprout from other motor neurones to innervate more fibres
Target fibre
Re innervated muscle fibre that looks like a target due to central nuclei
What determines whypich type of fibre a muscle fibre is
Primary motor neurone
Why can muscle fibres switch between fast and slow when they are deinnervated and reinnervated
Fibre type determined by mtooor neurone
Group atrophy
All fibres in a motor unit degenerate
Muscle structure in infantile hypotonia
Most fibres small and round with a few massively hypertrophic fibres
By what age are all symptoms of infantile hypotonia usually gone by
2 yrs
2 forms of infantile hypotonia
Large type 1 fibres + small type 2 fibres
Small type 1 fibres + normal/large type 2 fibres
Infantile hypotonia
abnormal limpness when an infant is born, affecting limbs, trunk, and head
Sarcopenia/cachexia
Age related gradual loss of muscle mass, strength and function
Are type 1 or type 2 muscle fibres more effected by sarcopenia
Type 2
Why does sarcopenia not cause decrease in body part size
Muscle replaced by fat
What causes muscle loss in sarcopenia
Pro inflammatory cytokines
General muscle disorder symptoms
Pain
Weakness
Twitching
Cramps
Muscle atrophy
Contractures
Drug exposure
Endocrine disorders
How can muscle disorders be diagnosed
Biopsy
EMG
Difference between polymyositis and dermatomyositis
Same condition but pt has skin rash in dermatomyositis
Polymyositis/dermatomyositis
Inflammatory myopathy causing chronic muscle inflammation, weakness, and pain (+ rash in dermatomyositis) from lymphocytes infiltrating CT around muscle fibres
What type of disease are inflammatory myopathies
Autoimmune
Rash characteristics in dermatomyositis
Red/purple
spotty/streaky
Hyperpigmentation in photodistribution pattern
Heliotrope rash over eyelids
Periorbital oedema
Hyperkeratotic papules on hands
Is myosotis symmetrical
Yes
How does myosotis effect serum creatine kinase
Incr
EMG in myositis
Irritable
Biopsy in myositis
Variation in fibre size
Central nuclei
Necrosis and regeneration
Infiltration of inflam cells
Hyperkeratotic papules
Epidermis thickens and keratinises
Dermatomyositis
Subcutaneous calcifications
Calcification in muscle and skin caused by autoimmune CT disease
First step of subcutaneous calcification
Mucin deposition
Myositis treatment
High dose corticosteroids
Azathioprine
Methotrexate
Rituximab
Most common muscle disease in elderly
Inclusion body myositis
Inclusion body myositis signs and symptoms
slowly progressive weakness and wasting of muscles
Associated polyneuropathy
Loss of quadriceps reflex
Dysphagia
Which muscle are most effected by inclusion body myositis
Finger and wrist flexors
Knee extensors
Why does inclusion body myositis cause loss of quadriceps reflex
Quadriceps atrophy
Inclusion body myositis biopsy
Empty vacuoles in muscle fibres
clumps of cellular material in fibres - beta amyloid, hyperphosphorylated TAU, apolipoprotein E
How does inclusion body myositis cause muscle atrophy
Muscle can’t contract properly due to vacuoles and cellular material so rip selves apart
Muscular dystrophies
Progressive genetically linked degenerative myopathies
X linked muscular dystrophies
Duchenne MD
Becker MD
limb girdle MD
emery-Dreyfus MD
Autosomal recessive muscular dystrophies
Limb girdle MD
emery dreifuss MD
Autosomal dominant muscular dystrophies
Facioscapulohumeral MD
limb girdle MD
emery dreifuss MD
oculopharyngeal MD
Most common MD
duchenne MD
Duchenne MD progression
Proximal muscle weakness in first 2 yrs
Continuous slow decline
Unable to walk by 7-12yrs
Death in early 30s
Difference between duchenne and Becker MDs
Duchenne has no dystrophin
Becker has some dystrophin
What causes duchenne and Becker MD
No/ lack of dystrophin
What is the gower manoeuvre and What condition is it associated with
child gets on hands-and-knees then walks hands up legs to stand
Duchenne MD
Why is creatine kinase elevated in duchenne MD
Muscle fibres rip self apart and repair continuously
Dystrophin
Protein between myofibres and sarcolemma that acts as a membrane stabilizer during muscle contraction to prevent contraction-induced damage
Duchenne MD biopsy
Fibre size variability
Endomysial fibrosis
Degenerating muscle fibres undergoing myophagocytosis
Thickened Perimetrium
Increased fibrotic material and fat
Atrophy and fibre death
What are dead muscle fibres replaced with in duchenne MD
Fibrotic material
Fat
What drugs can induce myopathies
Corticosteroids
Statins
Alcohol
Hydroxychloroquine
Fibromyalgia
chronic disorder characterized by widespread pain and other symptoms such as fatigue, muscle stiffness, and insomnia
Which antibodies are associated with fibromyalgia
Anti polymer antibodies
How many of 18 specific points need to be tender when pressure applied for fibromyalgia diagnosis
11
Fibromyalgia treatment
Tricyclic antidepressants - Amitryptyline
SSRIs - fluoxetine
Exercise
Massage, therapy, yoga
